全文获取类型
收费全文 | 194篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 27篇 |
地球物理 | 38篇 |
地质学 | 74篇 |
海洋学 | 25篇 |
天文学 | 25篇 |
综合类 | 2篇 |
自然地理 | 15篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 16篇 |
2012年 | 9篇 |
2011年 | 17篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有209条查询结果,搜索用时 15 毫秒
201.
A 520 year record of summer sunshine for the eastern European Alps based on stable carbon isotopes in larch tree rings 总被引:1,自引:1,他引:0
Polona Hafner Danny McCarroll Iain Robertson Neil J. Loader Mary Gagen Giles HF Young Roderick J. Bale Eloni Sonninen Tom Levanič 《Climate Dynamics》2014,43(3-4):971-980
A 520-year stable carbon isotope chronology from tree ring cellulose in high altitude larch trees (Larix decidua Mill.), from the eastern European Alps, correlates more strongly with summer temperature than with summer sunshine hours. However, when instrumental records of temperature and sunshine diverge after AD1980, the tree ring time series does not follow warming summer temperatures but more closely tracks summer sunshine trends. When the tree ring stable carbon isotope record is used to reconstruct summer temperature the reconstruction is not robust. Reconstructed temperatures prior to the twentieth century are higher than regional instrumental records, and the evolution of temperature conflicts with other regional temperature reconstructions. It is concluded that sunshine is the dominant control on carbon isotope fractionation in these trees, via the influence of photosynthetic rate on the internal partial pressure of CO2, and that high summer (July–August) sunshine hours is a suitable target for climate reconstruction. We thus present the first reconstruction of summer sunshine for the eastern Alps and compare it with the regional temperature evolution. 相似文献
202.
203.
Applying neighbourhood classification systems to natural hazards: a case study of Mt Vesuvius 总被引:1,自引:1,他引:0
Mt Vesuvius is regarded as one of the most deadly volcanoes on earth. With over 1 million people living on its flanks and in its periphery, there is little doubt that an eruption of sub-Plinian magnitude would be catastrophic to the livelihood and well being of contemporary Neopolitans. Such a large scale eruption would have wide ranging and differential effects on the surrounding population. Whereas previous studies of social vulnerability have focused on individual demographic factors (such as age, income or ethnicity), this research proposes the application of a general neighbourhood classification system to assess natural hazard vulnerability. In this study, Experian’s Mosaic Italy is used to classify and delineate the most vulnerable neighbourhood types around the province of Naples. Among the neighbourhoods considered most at risk, those areas with high proportions of elderly and low income families are deemed particularly vulnerable. With current evacuation plans deemed outdated and poorly communicated to the locals Rolandi (2010), Barberi et al. (2008), this methodology could prove to be a useful input to both town planners and civil protection agencies. A range of statistical measures and geophysical risk boundaries are employed here to assess the different areas of human resilience. 相似文献
204.
Saioa Suárez Hazel M. Prichard Francisco Velasco Peter C. Fisher Iain McDonald 《Mineralium Deposita》2010,45(4):331-350
The distribution, mineralogy and mobility of the platinum-group elements (PGE) in the surface environment are poorly understood.
This study of the lower, less altered and upper, more altered gossan, overlying the Aguablanca Ni–Cu-(PGE) magmatic deposit
(Spain), has shown that the platinum-group minerals (PGM) are progressively oxidised and dispersed into iron oxides that form
the gossan. A combination of the characterization of PGE in host PGM, using a scanning electron microscope, and measurement
of PGE at lower concentrations in host iron oxides, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS),
has for the first time allowed the total distribution of the PGE within a gossan to be documented. This study has revealed
a complete in situ alteration and dispersion sequence of the PGM including (1) breakdown of both the more stable Pt-arsenides,
Pt/Pd-tellurides and the less stable bismuthotellurides, (2) formation of partially oxidised PGM, (3) development of a wide
range of oxidised Pt- and Pd-bearing phases, (4) subsequent formation of Fe–PGE-oxides and PGE-hydroxides, (5) incorporation
of PGE into ferruginous supergene products and lastly (6) concentration of PGE at the edges of veins and iron oxides. Dispersion
of Pd is greater than for the other PGE with Pd being widely distributed throughout the iron oxides. This oxidising environment
produced PGE-oxides rather than PGE-alloys, also commonly found in the surface environment, especially in placers. These results
provide critical evidence for the stages of mineralogical change from PGE host mineralogy in magmatic ores to surface weathering
producing PGE-oxides. 相似文献
205.
206.
207.
Matthew S. Huber Christian Koeberl Frank C. Smith Billy P. Glass Roland Mundil Iain McDonald 《Meteoritics & planetary science》2019,54(10):2254-2272
Samples from a single outcrop of the Graenseso spherule layer, Midternaes, South Greenland, consist of a spherule‐bearing dolomixtite with matrix‐supported intraclasts up to 1 m in size. In addition to field observations, we performed mineralogical and whole rock geochemical analysis, including electron microprobe, neutron activation analysis, X‐ray fluorescence, and mass spectrometry of the horizon and the overlying and underlying strata. We show that the spherules are petrographically similar to those in the Zaonega spherule layer, Karelia, Russia. Our petrographic and chemical results are consistent with the previous suggestion that the Grænsesø layer correlates with the Zaonega layer, and it is possible that both layers are related to the Vredefort impact event. The samples containing spherules, as well as the overlying rocks, have elevated REEs compared to the underlying pre‐impact layer, suggestive of a new continental source of sediment that may be coincident with the impact event. Zircons separated from the lower part of the Grænsesø spherule layer display complex age patterns suggesting that they have genetically different origins based on distinctly different Th/U ratios. Crystallization ages of all groups are ≥ 2.8 Ga, with ~2.8 Ga representing a time of major crustal growth globally. Therefore, we cannot conclusively determine in this study if the zircons are locally derived or if they are transported with the ejecta. The spherule layer was deposited by a high‐energy, subaqueous debris flow, an origin that is consistent with the hypothesis that the layer was deposited by impact‐induced waves and/or currents. 相似文献
208.
David Rissik Edward Ho Shon Brooke Newell Mark E. Baird Iain M. Suthers 《Estuarine, Coastal and Shelf Science》2009
After a prolonged summer dry period, the effects of a distinctive and continuing rainfall on the nutrients and plankton of an urban coastal lagoon were investigated over 2 months. The lagoon filled up over 5 weeks from <10% of its maximum volume until it broke open to the sea. Nutrients (ammonia and oxidised nitrogen) significantly increased the day after initial rainfall, before returning to pre-rainfall conditions within 5 days. Phytoplankton biomass grew 10 fold within a week after initial rainfall in the 25–30 °C water and declined to near initial levels 2 weeks later. The assemblage of phytoplankton and zooplankton changed dramatically after 1 day and again by 6 days later, gradually returning to the original community by 2 weeks after the initial rainfall. Zooplankton responded within a day with a two fold increase in the adult stages of the calanoid copepod Oithona sp., followed a week later by nauplii and adult Acartia bispinosa. The influx of adult Oithona indicates resting populations that were previously under sampled by our plankton net. The plankton community returned to the initial state by 2 weeks, to being dominated by a centric diatom and A. bispinosa after 5 weeks. Dilution of the lagoon reached a maximum of 0.25 d−1, while growth rates of the phytoplankton population reached a maximum of 1 d−1, and A. bispinosa nauplii growth of 2.5 d−1. Declines in chlorophyll biomass from the maximum 10 μg l−1, at a rate of approximately 10% d−1 are consistent with the modelled uptake by zooplankton. The nutrients from runoff, growth and the influx of new zooplankton into the water column, resulted in a depleted δ13C and δ15N stable isotope signature of A. bispinosa by 2–4 ppt within 1–2 weeks, consistent with diatom growth and the terrestrial supply of depleted nutrients. δ34S of A. bispinosa was enriched by 2 ppt for 1–2 weeks after rainfall, but unlike C and N, returned to pre-rainfall levels by the end of the study period. We suggest that plankton studies in coastal lakes with variable water levels that are not tidally driven, should account for the influence of changes in water levels to help explain data variability. 相似文献
209.
William R. Hyde Adam A. Garde Nynke Keulen Sebastian N. Malkki Steven J. Jaret Tod Waight Pierre Beck Iain McDonald Nicolaj K. Larsen 《Meteoritics & planetary science》2023,58(6):789-814
Impact melt rocks formed during hypervelocity impact events are ideal for studying impact structures. Here, we describe impact melt rock samples collected proximal to the 31 km wide 58 Ma Hiawatha impact structure, northwest Greenland, which is completely covered by the Greenland Ice Sheet. The melt rocks contain diagnostic shock indicators (e.g., planar deformation features [PDF] in quartz and shocked zircon) and form three groups based on melt textures and chemistry: (i) hypocrystalline, (ii) glassy, and (iii) carbonate-based melt rocks. The exposed foreland directly in front of the structure consists of metasedimentary successions and igneous plutons; however, the carbonate-based impactites indicate a mixed target sequence with a significant carbonate-rich component. Well-preserved organic material in some melt rocks indicates that North Greenland at the time of impact was host to abundant organic material, likely a dense high-latitude temperate forest. Geochemical signatures of platinum-group elements in selected samples indicate an extraterrestrial component and support previous identification of a highly fractionated iron impactor in glaciofluvial sand. Our results illustrate the possibility to study impact structures hidden beneath a thick ice sheet based on transported samples and this opens a new avenue for identifying other potential impact craters in Greenland and Antarctica. 相似文献