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   89509篇
  免费   1748篇
  国内免费   785篇
测绘学   2141篇
大气科学   6675篇
地球物理   17959篇
地质学   30993篇
海洋学   8233篇
天文学   20249篇
综合类   190篇
自然地理   5602篇
  2021年   759篇
  2020年   938篇
  2019年   1008篇
  2018年   1940篇
  2017年   1861篇
  2016年   2367篇
  2015年   1455篇
  2014年   2316篇
  2013年   4668篇
  2012年   2470篇
  2011年   3446篇
  2010年   3048篇
  2009年   4131篇
  2008年   3717篇
  2007年   3539篇
  2006年   3491篇
  2005年   2669篇
  2004年   2724篇
  2003年   2532篇
  2002年   2462篇
  2001年   2245篇
  2000年   2159篇
  1999年   1839篇
  1998年   1823篇
  1997年   1786篇
  1996年   1565篇
  1995年   1470篇
  1994年   1367篇
  1993年   1219篇
  1992年   1171篇
  1991年   1020篇
  1990年   1253篇
  1989年   1016篇
  1988年   935篇
  1987年   1144篇
  1986年   976篇
  1985年   1260篇
  1984年   1393篇
  1983年   1320篇
  1982年   1227篇
  1981年   1131篇
  1980年   1015篇
  1979年   975篇
  1978年   1020篇
  1977年   916篇
  1976年   879篇
  1975年   823篇
  1974年   838篇
  1973年   855篇
  1972年   541篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
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   
162.
163.
Sediment successions in coastal cliffs around Mezen Bay, southeastern White Sea, record an unusually detailed history of former glaciations, interstadial marine and fluvial events from the Weichselian. A regional glaciation model for the Weichselian is based on new data from the Mezen Bay area and previously published data from adjacent areas. Following the Mikulinian (Eemian) interglacial a shelf‐centred glaciation in the Kara Sea is reflected in proglacial conditions at 100–90 ka. A local ice‐cap over the Timan ridge existed between 75 and 65 ka. Renewed glaciation in the Kara Sea spread southwestwards around 60 ka only, interrupted by a marine inundation, before it advanced to its maximum position at about 55–50 ka. After a prolonged ice‐free period, the Scandinavian ice‐sheet invaded the area from the west and terminated east of Mezen Bay about 17 ka. The previously published evidence of a large ice‐dammed lake in the central Arkhangelsk region, Lake Komi, finds no support in this study. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
164.
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   
165.
166.
Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric device MIDI. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
167.
168.
169.
170.
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