全文获取类型
收费全文 | 214篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 16篇 |
地球物理 | 64篇 |
地质学 | 79篇 |
海洋学 | 31篇 |
天文学 | 16篇 |
自然地理 | 20篇 |
出版年
2024年 | 1篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 18篇 |
2014年 | 12篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 306 毫秒
81.
Sin Chan Chou Andr de Arruda Lyra Jorge Lus Gomes Daniel Andrs Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lus Felipe Alves de Carvalho Jos Luiz Lima Onofre Idalcio Major Manuel Penhor Adrito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
82.
We present the preliminary results for a sample of 21 high luminosity ULIRGs (LIR > 1012.3 L⊙), selected from the 1Jy sample. Based on R band imaging we have performed an analysis of their morphologies. The main
result obtained is that about half of the host galaxies are represented by spheroids and in the other half an exponential
disk has been detected or they show still trace of a merging process going on. Regarding the relation between morphology and
nuclear activity it seems that more advanced mergers appear in the most active galaxies. Hence the data support the evolutionary
scheme proposed by Sanders 15 years ago that ULIRGs can be the earliest precursors of optical QSOs.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
83.
Maria Isabel Vélez Henry Hooghiemstra Sarah Metcalfe Ignacio Martínez Herman Mommersteeg 《第四纪科学杂志》2003,18(1):17-30
The late Pleistocene–Holocene ecological and limnological history of Lake Fúquene (2580 m a.s.l.), in the Colombian Andes, is reconstructed on the basis of diatom, pollen and sediment analyses of the upper 7 m of the core Fúquene‐7. Time control is provided by 11 accelerator mass spectrometry (AMS) 14C dates ranging from 19 670 ± 240 to 6040 ± 60 yr BP. In this paper we present the evolution of the lake and its surroundings. Glacial times were cold and dry, lake‐levels were low and the area was surrounded by paramo and subparamo vegetation. Late‐glacial conditions were warm and humid. The El Abra Stadial, a Younger Dryas equivalent, is reflected by a gap in the sedimentary record, a consequence of the cessation of deposition owing to a drop in lake‐level. The early Holocene was warm and humid; at this time the lake reached its maximum extension and was surrounded by Andean forest. The onset of the drier climate prevailing today took place in the middle Holocene, a process that is reflected earlier in the diatom and sediment records than in the pollen records. In the late Holocene human activity reduced the forest and transformed the landscape. Climate patterns from the Late‐glacial and throughout the Holocene, as represented in our record, are similar to other records from Colombia and northern South America (the Caribbean, Venezuela and Panama) and suggest that the changes in lake‐level were the result of precipitation variations driven by latitudinal shifts of the Intertropical Convergence Zone. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
84.
Isabel Márquez Josefa Masegosa Mariano Moles Jesús Varela Daniella Bettoni Giusseppe Galletta 《Astrophysics and Space Science》2003,284(2):711-714
We present the study of long slit spectra in the region ofHα emission line of a sample of 111 spiral galaxies with recognizable
and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive
interaction with satellites or companions. The form and properties of the rotation curves (RC) are considered as a function
of the isolation degree, morphological type, t, and luminosity. The line ratios are used to estimate the metallicity of all
the detected HII regions, thus producing a composite metallicity profile for different types of spirals. We have found that
isolated galaxies (ISO) tend to be of later types and lower luminosity than the interacting galaxies (INT). The outer parts
of the RC of ISO tend to be flatter than in INT, but they show similar relations between global parameters. The scatter of
the Tully-Fisher (TF) relation defined by ISO is significantly lower than that of INT. The [NII]/Hα ratios, used as a metallicity
indicator, show a clear trend between Z and t, with earlier spirals showing higher ratios; this trend is tighter when instead
of t the gradient of the inner RC, G, is used; no trend is found with the change in interaction status. The Z-gradient of
the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/Hα ratios measured
for disk HII regions of INT are higher than for normal/ISO objects, even if all the galaxy families present similar distributions
of Hα Equivalent Width.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
85.
A series of experiments was performed using artificial seawater samples of increasing complexity, in order to identify, qualitatively and quantitatively, the contribution of main seawater components on the buffer capacity for CO2.The results show that magnesium plays the most important role in the uptake, enhancing the capacity of the carbonate system alone by more than 100%. 相似文献
86.
Ian D. Howarth Richard J. Price Ian A. Crawford Isabel Hawkins 《Monthly notices of the Royal Astronomical Society》2002,335(2):267-274
We present observations of the Li i 6708 Å doublet in the ζ Oph sightline, obtained at a resolution of ∼106 and a signal-to-noise ratio of ∼1200, together with supplementary observations of K i λ 7699 and the Na i λ 3302 doublet. These observations marginally resolve the main '−15 km s−1 ' system into its two principal clouds; we model the data using standard physical assumptions, but in a statistically rigorous manner, taking fully into account the hyperfine, doublet and isotopic structure for each species, in each cloud, using a new code, vapid . The average 7 Li/6 Li ratio determined in this sightline is 1.12±0.20 dex (68 per cent confidence interval), in excellent agreement with the solar-system (meteoritic) value. The ratios in the individual clouds are determined with less precision, but are also consistent with the solar-system value, as is the total lithium abundance (with little evidence for depletion). The thermal and 'turbulent' broadening in the two clouds is discussed on the basis of observed line widths. 相似文献
87.
Trottini Mario Vigo Isabel Vargas-Alemañy Juan A. García-García David Fernández José 《Mathematical Geosciences》2021,53(8):1813-1840
Mathematical Geosciences - Two important issues characterize the design of bootstrap methods to construct confidence intervals for the correlation between two time series sampled (unevenly or... 相似文献
88.
The rip current hazard in Costa Rica 总被引:1,自引:1,他引:0
89.
Solar influence and hydrological variability during the Holocene from a speleothem annual record (Molinos Cave,NE Spain) 总被引:1,自引:0,他引:1 下载免费PDF全文
Arsenio Muñoz Miguel Bartolomé Alicia Muñoz Carlos Sancho Ana Moreno John C. Hellstrom Mª Cinta Osácar Isabel Cacho 《地学学报》2015,27(4):300-311
We present a multi‐proxy approach to reconstructing Holocene climate conditions in northeastern Spain based on an excellent correlation among the lamina thickness, colour parameters and isotope (δ18O and δ13C) variations recorded in a speleothem. An age model constructed from five U/Th dates and annual lamina counting suggests that the uppermost 14.7 cm of the MO‐7 stalagmite grew between 7.2 and 2.5 ka before present but experienced a growth hiatus from 4.9 to 4.3 ka. Three spectral analysis methods were applied to 11 time series. The results reveal common solar periodicities on decennial (Gleissberg cycle) and centennial (De Vries‐Suess cycle) scales. The onset of Holocene carbonate precipitation in the MO‐7 stalagmite appears to be associated with a cold, wet period, whereas the hiatus and the end of growth are related to warm, dry periods. This environmental trend fits well within the regional Holocene climate. 相似文献
90.
Jessica L. Oster Isabel P. Montañez Regina Mertz-Kraus Warren D. Sharp Greg M. Stock Howard J. Spero John Tinsley James C. Zachos 《Quaternary Research》2014
Dansgaard–Oeschger (D–O) cycles had far-reaching effects on Northern Hemisphere and tropical climate systems during the last glacial period, yet the climatic response to D–O cycles in western North America is controversial, especially prior to 55 ka. We document changes in precipitation along the western slope of the central Sierra Nevada during early Marine Oxygen Isotope Stages (MIS) 3 and 4 (55–67 ka) from a U-series dated speleothem record from McLean's Cave. The timing of our multi-proxy geochemical dataset is coeval with D–O interstadials (15–18) and stadials, including Heinrich Event 6. The McLean's Cave stalagmite indicates warmer and drier conditions during Greenland interstadials (GISs 15–18), signified by elevated δ18O, δ13C, reflectance, and trace element concentrations, and less radiogenic 87Sr/86Sr. Our record extends evidence of a strong linkage between high-latitude warming and reduced precipitation in western North America to early MIS 3 and MIS 4. This record shows that the linkage persists in diverse global climate states, and documents the nature of the climatic response in central California to Heinrich Event 6. 相似文献