首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   91815篇
  免费   1641篇
  国内免费   578篇
测绘学   2361篇
大气科学   7033篇
地球物理   18874篇
地质学   33473篇
海洋学   7400篇
天文学   19239篇
综合类   294篇
自然地理   5360篇
  2021年   428篇
  2020年   564篇
  2019年   564篇
  2018年   4014篇
  2017年   3839篇
  2016年   3152篇
  2015年   1296篇
  2014年   1630篇
  2013年   3497篇
  2012年   2784篇
  2011年   5030篇
  2010年   4661篇
  2009年   5595篇
  2008年   4657篇
  2007年   5007篇
  2006年   2585篇
  2005年   2696篇
  2004年   2651篇
  2003年   2558篇
  2002年   2241篇
  2001年   1857篇
  2000年   1843篇
  1999年   1542篇
  1998年   1541篇
  1997年   1524篇
  1996年   1300篇
  1995年   1254篇
  1994年   1153篇
  1993年   1029篇
  1992年   977篇
  1991年   833篇
  1990年   1039篇
  1989年   876篇
  1988年   777篇
  1987年   950篇
  1986年   844篇
  1985年   1056篇
  1984年   1212篇
  1983年   1152篇
  1982年   1055篇
  1981年   1022篇
  1980年   879篇
  1979年   847篇
  1978年   905篇
  1977年   819篇
  1976年   772篇
  1975年   726篇
  1974年   726篇
  1973年   746篇
  1972年   463篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets.  相似文献   
62.
63.
This paper proposes a multi‐level parallelized substructuring–frontal combined algorithm for the analysis of the problem of thermo/hydraulic/mechanical behaviour of unsaturated soil. Temperature, displacement, pore water pressure and pore air pressure are treated as the primary variables in a non‐linear analysis. Details are given firstly of the substructuring–frontal combined approach. The incorporation of the algorithm in a multi‐level parallel strategy is then discussed. The parallel processing can thus be carried out at different substructural levels. The method thus developed impacts, in a positive way, on both computer storage requirement and execution time. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
64.
65.
66.
67.
68.
We examine possible locations for the primordial disk of the Edgeworth-Kuiper Belt (EKB), using several subsets of the known objects as markers of the total mass distribution. Using a secular perturbation theory, we find that the primordial plane of the EKB could have remained thin enough to escape detection only if it is clustered very closely about the invariable plane of the Solar System.  相似文献   
69.
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K' band. The project's main scientific aims are the identification of galaxy clusters up to redshifts of unity and the selection of a large sample of field early-type galaxies up to z < 1.5 for evolutionary studies. We created a Large Scale Structure catalog, using a new structure finding technique specialized for photometric datasets, that we developed on the basis of a friends-of-friends algorithm. We tested the plausibility of the resulting galaxy group and cluster catalog with the help of Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
70.
We present the results of a radial-velocity study of eight Am stars (HD 341, 55822, 61250, 67317, 93991, 162950, 224890 and 225137) observed at Observatoire de Haute-Provence with the CORAVEL instrument. We find that these systems are single-line spectroscopic binaries whose orbital elements are determined for the first time.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号