全文获取类型
收费全文 | 52658篇 |
免费 | 9254篇 |
国内免费 | 10764篇 |
专业分类
测绘学 | 4074篇 |
大气科学 | 5896篇 |
地球物理 | 11591篇 |
地质学 | 27671篇 |
海洋学 | 8236篇 |
天文学 | 3461篇 |
综合类 | 3433篇 |
自然地理 | 8314篇 |
出版年
2024年 | 236篇 |
2023年 | 656篇 |
2022年 | 1633篇 |
2021年 | 2070篇 |
2020年 | 1976篇 |
2019年 | 2513篇 |
2018年 | 1868篇 |
2017年 | 2105篇 |
2016年 | 2081篇 |
2015年 | 2357篇 |
2014年 | 2982篇 |
2013年 | 3426篇 |
2012年 | 3072篇 |
2011年 | 3321篇 |
2010年 | 2919篇 |
2009年 | 3461篇 |
2008年 | 3514篇 |
2007年 | 3652篇 |
2006年 | 3608篇 |
2005年 | 3248篇 |
2004年 | 2920篇 |
2003年 | 2717篇 |
2002年 | 2349篇 |
2001年 | 2102篇 |
2000年 | 2038篇 |
1999年 | 1816篇 |
1998年 | 1545篇 |
1997年 | 1190篇 |
1996年 | 973篇 |
1995年 | 832篇 |
1994年 | 791篇 |
1993年 | 659篇 |
1992年 | 485篇 |
1991年 | 403篇 |
1990年 | 283篇 |
1989年 | 248篇 |
1988年 | 177篇 |
1987年 | 108篇 |
1986年 | 68篇 |
1985年 | 70篇 |
1984年 | 36篇 |
1983年 | 36篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 24篇 |
1977年 | 6篇 |
1971年 | 5篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
1 INTRODUCTIONThe South China Sea (SCS) is a semi-enclosedmarginal sea in western North Pacific Ocean withvery complex topography and is the important pas-sage connecting the Pacific and Indian Oceans. Ithas great impact to the global climate and a greatinterest of many oceanography researchers. Twodominant surface hydrographic and circulation fea-tures in the northern SCS are a strong fresh waterexpansion and a warm and high-salinity seawaterintrusion such as the SCS Diluted Water… 相似文献
102.
国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程.其总控系统下共包括8个既相互独立又互有关联的子系统.如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转,以及如何确保软件开发的可维护性、可持续性是研究重点. 相似文献
103.
104.
105.
V. Castellani S. Degl'Innocenti P. G. Prada Moroni 《Monthly notices of the Royal Astronomical Society》2001,320(1):66-72
We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able to account for an observed mismatch between theoretical predictions and observations of the coolest Hyades MS stars. Finally, we show that current theoretical models probably give too faint He burning luminosities unlike the case of less massive He burning models, with degenerate progenitors, which have been suggested to suffer the opposite discrepancy. 相似文献
106.
107.
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
108.
109.
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
110.
Sunetra Giridhar N. Kameswara Rao David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40
Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines
show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present
in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to
1992 相似文献