全文获取类型
收费全文 | 34726篇 |
免费 | 7015篇 |
国内免费 | 7693篇 |
专业分类
测绘学 | 6290篇 |
大气科学 | 5117篇 |
地球物理 | 10099篇 |
地质学 | 15393篇 |
海洋学 | 4268篇 |
天文学 | 1553篇 |
综合类 | 2392篇 |
自然地理 | 4322篇 |
出版年
2024年 | 117篇 |
2023年 | 347篇 |
2022年 | 1034篇 |
2021年 | 1297篇 |
2020年 | 1465篇 |
2019年 | 1853篇 |
2018年 | 1726篇 |
2017年 | 2012篇 |
2016年 | 2104篇 |
2015年 | 2173篇 |
2014年 | 2408篇 |
2013年 | 2949篇 |
2012年 | 2484篇 |
2011年 | 2529篇 |
2010年 | 2006篇 |
2009年 | 2168篇 |
2008年 | 2313篇 |
2007年 | 2273篇 |
2006年 | 2203篇 |
2005年 | 1989篇 |
2004年 | 1736篇 |
2003年 | 1469篇 |
2002年 | 1371篇 |
2001年 | 1114篇 |
2000年 | 1042篇 |
1999年 | 849篇 |
1998年 | 784篇 |
1997年 | 646篇 |
1996年 | 527篇 |
1995年 | 498篇 |
1994年 | 459篇 |
1993年 | 393篇 |
1992年 | 251篇 |
1991年 | 209篇 |
1990年 | 155篇 |
1989年 | 104篇 |
1988年 | 113篇 |
1987年 | 66篇 |
1986年 | 40篇 |
1985年 | 36篇 |
1984年 | 22篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1954年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
71.
72.
Kenai, located on the west coast of the Kenai Peninsula, Alaska, subsided during the great earthquake of AD 1964. Regional land subsidence is recorded within the estuarine stratigraphy as peat overlain by tidal silt and clay. Reconstructions using quantitative diatom transfer functions estimate co‐seismic subsidence (relative sea‐level rise) between 0.28±0.28 m and 0.70±0.28 m followed by rapid post‐seismic recovery. Stratigraphy records an earlier co‐seismic event as a second peat‐silt couplet, dated to ~1500–1400 cal. yr BP with 1.14±0.28 m subsidence. Two decimetre‐scale relative sea‐level rises are more likely the result of glacio‐isostatic responses to late Holocene and Little Ice Age glacier expansions rather than to co‐seismic subsidence during great earthquakes. Comparison with other sites around Cook Inlet, at Girdwood and Ocean View, helps in constructing regional patterns of land‐level change associated with three great earthquakes, AD 1964, ~950–850 cal. yr BP and ~1500–1400 cal. yr BP. Each earthquake has a different spatial pattern of co‐seismic subsidence which indicates that assessment of seismic hazard in southern Alaska requires an understanding of multiple great earthquakes, not only the most recent. All three earthquakes show a pre‐seismic phase of gradual land subsidence that marked the end of relative land uplift caused by inter‐seismic strain accumulation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
73.
M. J. Carson J. C. Davies E. Daw R. J. Hollingworth V. A. Kudryavtsev T. B. Lawson P. K. Lightfoot J. E. McMillan B. Morgan S. M. Paling M. Robinson N. J. C. Spooner D. R. Tovey 《Astroparticle Physics》2004,21(6):667-687
Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10−9–10−10 pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector. 相似文献
74.
Geophysical data from Gerlache Strait, Croker Passage, Bismarck Strait and the adjacent continental shelf reveal streamlined subglacial bedforms that were produced at the bed of the Antarctic Peninsula Ice Sheet (APIS) during the last glaciation. The spatial arrangement and orientation of these bedforms record the former drainage pattern and flow dynamics of an APIS outlet up‐flow, and feeding into, a palaeo‐ice stream in the Western Bransfield Basin. Evidence suggests that together, they represent a single ice‐flow system that drained the APIS during the last glaciation. The ice‐sheet outlet flowed north/northeastwards through Gerlache Strait and Croker Passage and converged with a second, more easterly ice‐flow tributary on the middle shelf to form the main palaeo‐ice stream. The dominance of drumlins with low elongation ratios suggests that ice‐sheet outlet draining through Gerlache Strait was comparatively slower than the main palaeo‐ice stream in the Western Bransfield Basin, although the low elongation ratios may also partly reflect the lack of sediment. Progressive elongation of drumlins further down‐flow indicates that the ice sheet accelerated through Croker Passage and the western tributary trough, and fed into the main zone of streaming flow in the Western Bransfield Basin. Topography would have exerted a strong control on the development of the palaeo‐ice stream system but subglacial geology may also have been significant given the transition from crystalline bedrock to sedimentary strata on the inner–mid‐shelf. In the broader context, the APIS was drained by a number of major fast‐flowing outlets through cross‐shelf troughs to the outer continental shelf during the last glaciation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
75.
76.
This paper considers the problem of estimatingm, the number of components in a finite mixture of distributions from a parametric family. A step-up procedure using the bootstrap method is proposed. Some properties of the procedure are illustrated with simulation studies. An example of the method, applied to orientation of beach clasts, is given. 相似文献
77.
78.
A. P. M. Vaughan L. A. Dowling F. J. G. Mitchell S.‐E. Lauritzen A. M. McCabe P. Coxon 《第四纪科学杂志》2004,19(6):577-590
Organic‐rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic‐rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high‐energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium–thorium disequilibrium dating suggests that the organic‐rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post‐depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post‐Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
79.
Yanjun ZHANG Fenglong ZHANG Full QI Fuquan NI 《东北亚地学研究》2006,9(2):199-203
In view of the situation of excavation of open coal mine for the underground water disaster,we should carry out simulation studies for the numerical value of the water lowering project and improve the accuracy and the level of the water lowering project.On the basis of the hydrological geological conditions of certain open mine digging,a more reasonable seepage numerical model was built according to MODFLOW.It was simulated in advance that the process of the confined water level descending with the time,and combining with the actual observations to test the correctness of the model.The calculation showed that the results coincided well with the results of actual measurement.Based on this,different water lowering numerical simulations were built for the open coal mine digging.It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit,and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process,which provide an important basis for the actual water lowering project and the possible project disposal. 相似文献
80.
笔者曾对广西芒场锡多金属矿田的稳定同位素进行研究。本文根据硫、铅、氢、氧、碳等稳定同位素组成和锶的初始值提供的信息.探讨了矿床成因。并结合矿田矿床地质特征、控矿条件及有关统计参数,参考前人对矿床认识的基础上,修正提出了该矿田混合热液成矿模式,可供类似矿床研究和找矿的参考。 相似文献