全文获取类型
收费全文 | 218篇 |
免费 | 3篇 |
国内免费 | 4篇 |
专业分类
大气科学 | 30篇 |
地球物理 | 48篇 |
地质学 | 79篇 |
海洋学 | 35篇 |
天文学 | 22篇 |
综合类 | 1篇 |
自然地理 | 10篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 19篇 |
2008年 | 10篇 |
2007年 | 14篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 15篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1961年 | 1篇 |
1953年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 31 毫秒
151.
Decadal Sahelian rainfall variability was mainly driven by sea surface temperatures (SSTs) during the twentieth century. At the same time SSTs showed a marked long-term global warming (GW) trend. Superimposed on this long-term trend decadal and multi-decadal variability patterns are observed like the Atlantic Multidecadal Oscillation (AMO) and the inter-decadal Pacific Oscillation (IPO). Using an atmospheric general circulation model we investigate the relative contribution of each component to the Sahelian precipitation variability. To take into account the uncertainty related to the use of different SST data sets, we perform the experiments using HadISST1 and ERSSTv3 reconstructed sets. The simulations show that all three SST signals have a significant impact over West Africa: the positive phases of the GW and the IPO lead to drought over the Sahel, while a positive AMO enhances Sahel rainfall. The tropical SST warming is the main cause for the GW impact on Sahel rainfall. Regarding the AMO, the pattern of anomalous precipitation is established by the SSTs in the Atlantic and Mediterranean basins. In turn, the tropical SST anomalies control the impact of the IPO component on West Africa. Our results suggest that the low-frequency evolution of Sahel rainfall can be interpreted as the competition of three factors: the effect of the GW, the AMO and the IPO. Following this interpretation, our results show that 50% of the SST-driven Sahel drought in the 1980s is explained by the change to a negative phase of the AMO, and that the GW contribution was 10%. In addition, the partial recovery of Sahel rainfall in recent years was mainly driven by the AMO. 相似文献
152.
Colloidal complexed silver and silver nanoparticles in extrapallial fluid of Mytilus edulis 总被引:1,自引:0,他引:1
Metal transport in mollusk extrapallial fluid (EPF) that acts as a "bridge" between soft tissues and shell has surprisingly received little attention until now. Using ultrafiltration and radiotracer techniques we determined silver concentrations and speciation in the EPF of the blue mussel Mytilus edulis after short-term uptake and depuration laboratory experiments. Radiolabelled silver ((11?m)Ag) was used in dissolved or nanoparticulate phases (AgNPs < 40 nm), with a similar low Ag concentration (total radioactive and cold Ag ~0.7 μg/L) in a way that mussels could uptake radiotracers only from seawater. Our results indicated that silver nanoparticles were transported to the EPF of blue mussels at a level similar to the Ag ionic form. Bulk activity of radiolabelled silver in the EPF represented only up to 7% of the bulk activity measured in the whole mussels. The EPF extracted from mussels exposed to both treatments exhibited an Ag colloidal complexed form based on EPF ultrafiltration through a 3 kDa filter. This original study brings new insights to internal circulation of nanoparticles in living organisms and contributes to the international effort in studying the potential impacts of engineered nanomaterials on marine bivalves which play an essential role in coastal ecosystems, and are important contributors to human food supply from the sea. 相似文献
153.
NAUGOLNYKH Serge V.and JIN Jianhua 《《地质学报》英文版》2014,88(5):1341-1351
The Huadu flora of Guangdong Province, South China contains the lepidodendrid Lepidodendron shanyangense Wu et He, its putative rhizophore Stigmaria cf. ficoides (Brongniart) Sternberg; sphenophyte s.l. Archaeocalamites scrobiculatus (Brongniart) Stur; bowmanitid Sphenophyllum tenerrimum (Ettingshausen) Stur; pteridophyll Sphenopteris sp. of uncertain taxonomic position; undetermined ferns gen. et sp. nov.; lyginopterid pteridosperm Rhodeopteridium hsianghsiangense (Sze) Zhang, Zhao et Wu, a trigonocarpoid pteridosperm represented by fronds and isolated pinnules of Paripteris gigantea (Sternberg) Gothan, male fructifications of Potoniea sp., and seeds of Trigonocarpus sp. Ecologically, the Early Carboniferous (Visean) Huadu vegetation was divided into two neighboring communities: (1) a near-shore hydrophilous "community A" with predominating Archaeocalamites and Rhodeopteridium; and (2) a wet forest "community B" with predominating shrubby trigonocarpalean pteridosperm Paripteris gigantea (Sternberg) Gothan and tall tree-like lepidodendrid Lepidodendron shanyangense Wu et He. The Huadu vegetation was physiognomically similar to present-day low-latitude mangrove forest. 相似文献
154.
Application of regularised optimal fingerprinting to attribution. Part I: method, properties and idealised analysis 总被引:1,自引:0,他引:1
Optimal fingerprinting has been the most widely used method for climate change detection and attribution over the last decade. The implementation of optimal fingerprinting often involves projecting onto k leading empirical orthogonal functions in order to decrease the dimension of the data and improve the estimate of internal climate variability. However, results may be sensitive to k, and the choice of k remains at least partly arbitrary. One alternative, known as regularised optimal fingerprinting (ROF), has been recently proposed for detection. This is an extension of the optimal fingerprinting detection method, which avoids the projection step. Here, we first extend ROF to the attribution problem. This is done using both ordinary and total least square approaches. Internal variability is estimated from long control simulations. The residual consistency test is also adapted to this new method. We then show, via Monte Carlo simulations, that ROF is more accurate than the standard method, in a mean squared error sense. This result holds for both ordinary and total least square statistical models, whatever the chosen truncation k. Finally, ROF is applied to global near-surface temperatures in a perfect model framework. Improvements provided by this new method are illustrated by a detailed comparison with the results from the standard method. Our results support the conclusion that ROF provides a much more objective and somewhat more accurate implementation of optimal fingerprinting in detection and attribution studies. 相似文献
155.
Macrofossil analyses were used to reconstruct long-term vegetation successions within ombrotrophic peatlands (bogs) from the northern shorelines of the St. Lawrence Estuary (Baie-Comeau) and the Gulf of St. Lawrence (Havre-St-Pierre). Over the Holocene, the timing and the ecological context of peatland inception were similar in both regions and were mainly influenced by fluctuations in relative sea level. Peat accumulation started over deltaic sands after the withdrawal of the Goldthwait Sea from 7500 cal yr BP and above silt–clay deposits left by the Laurentian marine transgression after 4200 cal yr BP. In each region, the early vegetation communities were similar within these two edaphic contexts where poor fens with Cyperaceae and eastern larch (Larix laricina) established after land emergence. The rapid transitions to ombrotrophy in the peatlands of Baie-Comeau are associated with particularly high rates of peat accumulation during the early developmental stage. The results suggest that climate was more propitious to Sphagnum growth after land emergence in the Baie-Comeau area. Macrofossil data show that treeless Sphagnum-dominated bogs have persisted over millennia and that fires had few impacts on the vegetation dynamics. This study provides insight into peatland vegetation responses to climate in a poorly documented region of northeastern America. 相似文献
156.
Max Wisshak Matthias López Correa Serge Gofas Carmen Salas Marco Taviani Joachim Jakobsen André Freiwald 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(3):374-407
A conspicuous new deep-sea oyster, Neopycnodonte zibrowii sp. n., is described from the Azores Archipelago, where it thrives in 420 to >500 m water depth in high densities concealed underneath overhangs. The new species reaches a relatively large size, which may exceed 20 cm, and is characterised by a very unusual hinge line morphology, straight without a bulge of the resilium. It is compared to the extant Indo-Pacific Empressostrea kostini Huber and Lorenz, 2007 and to the cosmopolitan Neopycnodonte cochlear (Poli, 1791), which has a broadly sympatric distribution at shallower depths in the Azores and Bay of Biscay. Radiocarbon dating reveals that individuals reach an impressive lifespan of one to more than five centuries, placing them among the longest-lived molluscs known to date. They often grow on top of each other, forming stacks that resemble dish piles—an effective measure to optimise shell stability with minimal biomineralisation effort, but with the drawback of increased bioerosion ultimately leading to detachment.Three microstructure types are developed in N. zibrowii: (1) the cross-foliated, calcitic, dorsal to central endostracum and aragonitic ligostracum, (2) the porous vesicular structure of the calcitic ventral endostracum, and (3) the simple prismatic aragonitic myostracum. Foliated and vesicular shell portions show sub-millimetre-scale first-order increments delineated by conchiolin-rich growth breaks (interpreted as reproductive cyclicity), and less distinct second-order increments (interpreted as annual in nature). This pattern is clearly reflected by the elemental composition with the primary growth breaks lacking Ca and Sr but including Mg and S as organic matrix constituents. The second-order increments within the calcite are mirrored by moderately co-varying Mg/Ca and S/Ca fluctuations at stable Sr concentrations, reflecting varying proportions of organic matrix. Dorsal and central endostracum transects reveal a low inter-valve, but considerable inter-specimen variability with high Mg/Ca molar ratios and fluctuations (22.5±17.6 mmol/mol), low Sr/Ca values (0.2±0.1 mmol/mol), and a typical to high S/Ca content (6.9±2.2 mmol/mol), when compared to other calcitic bivalves.Unlike short-lived, shallow-water oysters, N. zibrowii thrives under very stable environmental conditions. Minimal temperature fluctuations and stable open marine salinity provide an optimal basis to recognise biological fractionation processes. Strong Mg/Ca fluctuations indicate a physiological control related to metabolism and biomineralisation, prohibiting the use of this ratio as a temperature or ocean chemistry proxy. Low Sr/Ca ratios indicate rather constant and low long-term accretion rates, while short-scale fluctuations may be attributed to short-term variations in growth rate and Mg incorporation. Oxygen isotopes yield a considerable spread of 1.8‰ with a mean of 2.0±0.3‰ δ18O V-PDB, and low correlation between different contemporaneous parts of the shell and between specimens. These values surprisingly exceed expected equilibrium conditions, calculated from in situ temperature data (annual mean 12.3±0.3 °C) and seawater isotopic composition (0.5±0.1‰ δ18O SMOW), by 0.5‰ on average. Such positively shifting vital effects, previously reported for limpets and barnacles, are often overlooked in high-temperature and high-amplitude settings and may be more common than is currently believed. Carbon isotopes range from 0.2 to 3.5‰ δ13C V-PDB (mean 1.8±0.7‰) and show an ontogenetic decrease, but may incorporate an environmental signal in adult portions, indicated by a strong correspondence of peaks between specimens. This signal is likely driven by a complex interplay of different factors, such as primary production, current-based food supply and metabolism. 相似文献
157.
Céline Déandreis Christian Pagé Pascale Braconnot Lars Bärring Edoardo Bucchignani Wim Som de Cerff Ronald Hutjes Sylvie Joussaume Constantin Mares Serge Planton Maarten Plieger 《Climatic change》2014,125(3-4):333-347
Future climate evolution is of primary importance for the societal, economical, political orientations and decision-making. It explains the increasing use of climate projections as input for quantitative impact studies, assessing vulnerability and defining adaptation strategies in different sectors. Here we analyse 17 national and representative use cases so as to identify the diversity of the demand for climate information depending on user profiles as well as the best practices, methods and tools that are needed to answer the different requests. A particular emphasis is put on the workflow that allows to translate climate data into suitable impact data, the way to deal with the different sources of uncertainty and to provide a suited product to users. We identified three complementary tools to close the gap between climate scientists and user needs: an efficient interface between users and providers; an optimized methodology to handle user requests and a portal to facilitate access to data and elaborated products. We detail in the paper how these three tools can limit the intervention of experts, educate users, and lead to the production of useful information. This work provides the basis on which the ENES (European Network for Earth System Modelling) Portal Interface for the Climate Impact Communities is built. 相似文献
158.
Anne-Marie Bodergat Christophe Lécuyer François Martineau Atike Nazik Kemal Gürbüz Serge Legendre 《Journal of Paleolimnology》2014,52(1-2):43-59
The euryhaline ostracod Cyprideis torosa lives in Akyatan Lagoon, Turkey, which is exposed to large spatial and seasonal variations in water salinity, δ18O, and temperature. Hydrogen and oxygen isotope measurements of waters reveal that the large range of salinity (15–80 g L?1) in the lagoon results from a combination of evaporation and mixing between Mediterranean seawater and Seyhan River input. Round sieve-pore relative abundance in C. torosa provides a robust proxy for water salinity (S) from 15 to 80 g L?1, according to the equation: S = 161.41 (±4.52) * log10(% rounded pores) ? 94.04 (±3.44) (R2 = 0.937; p = 10?31). Seasonal sampling and isotope analysis of C. torosa in waters of known δ18O values (?4.7 to +6.9 ‰ V-PDB) and temperatures (15–35 °C) yielded a weak positive correlation (r = 0.71) between 1000 lnα(calcite–water) ‰ V-SMOW) and 103 * T?1. Specimens of C. torosa collected during the mild and warm seasons have oxygen isotope compositions close to those of inorganic calcite precipitated in equilibrium with ambient water. The large oxygen-isotope variability observed during any season of the year most likely results from shell calcification in water bodies of highly variable salinity, alkalinity, Mg/Ca and water saturation relative to calcite. Indeed, distinct water bodies in the Akyatan Lagoon are generated by mixing of fresh and marine waters, which are exposed to different evaporation rates at the seasonal scale. 相似文献
159.
Batrice Morel Hassan Bencherif Philippe Keckhut Serge Baldy Alain Hauchecorne 《Journal of Atmospheric and Solar》2002,64(18)
Systematic measurements of the middle-atmosphere temperature by a RAYLEIGH LIDAR located at La Réunion Island (20.8°S–55.5°E) has led to a preliminary study of the tidal effects in the height range of 30–70 km. Two analysis methods able to estimate the mean nighttime evolution of the temperature have been compared. Method 1 consists in averaging the temperature deviations from the nightly mean over several successive nights of measurement for given local solar times (LST); method 2 consists in averaging the raw data over the period of observation for given LST and in deriving afterwards the mean nighttime evolution of the temperature profiles. Some consistent LST-related structures have been observed with both methods, though better results have been obtained with method 1. One possible explanation for the differences between the two methods is the use of a series of data ranging from 4 to 8 h/night, depending on the meteorological conditions. In contrast to method 2, method 1 allows to correct the mean temperature for a given night, when the measurement window is different from night to night. Method 1 has been applied to two time series recorded in October and November 1995. The results clearly show the presence of tidal components with a downward phase propagation, specifically a warmer early night and a colder midnight in the stratosphere and the lower mesosphere. This behaviour is consistent with other LIDAR measurements made at similar latitudes in the Northern Hemisphere. In addition, a close comparison with the Global-Scale Wave Model (GSWM) tidal model predictions has also pointed out some similarities. Yet, large discrepancies in magnitude are also observed: as already reported in previous studies, the amplitudes predicted by GSWM are more than two times smaller compared to the corresponding values observed with the LIDAR. 相似文献
160.
To achieve high spatial resolution capability for IR solar observations, we suggest the use of a special mask placed before the entrance aperture of large conventional optical telescopes. Such a mask would match well the resolution of a non-redundant array and would provide safe operation of a large telescope used for solar observations. The proposed solution has the additional advantage of relatively low cost because already-existing optical telescopes are used. 相似文献