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   42933篇
  免费   467篇
  国内免费   293篇
测绘学   865篇
大气科学   2228篇
地球物理   8389篇
地质学   16712篇
海洋学   3970篇
天文学   9784篇
综合类   125篇
自然地理   1620篇
  2022年   524篇
  2021年   789篇
  2020年   846篇
  2019年   942篇
  2018年   1866篇
  2017年   1733篇
  2016年   1816篇
  2015年   775篇
  2014年   1635篇
  2013年   2351篇
  2012年   1847篇
  2011年   2220篇
  2010年   2039篇
  2009年   2307篇
  2008年   2034篇
  2007年   2210篇
  2006年   1959篇
  2005年   1102篇
  2004年   1030篇
  2003年   995篇
  2002年   920篇
  2001年   857篇
  2000年   736篇
  1999年   500篇
  1998年   539篇
  1997年   557篇
  1996年   415篇
  1995年   436篇
  1994年   397篇
  1993年   350篇
  1992年   336篇
  1991年   337篇
  1990年   383篇
  1989年   318篇
  1988年   311篇
  1987年   315篇
  1986年   241篇
  1985年   364篇
  1984年   374篇
  1983年   352篇
  1982年   335篇
  1981年   300篇
  1980年   314篇
  1979年   253篇
  1978年   291篇
  1977年   242篇
  1976年   214篇
  1975年   216篇
  1974年   204篇
  1973年   239篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The composition and nature of high-Cr minerals in lithic clasts from the carbonatites of the Veseloe occurrence, northern Transbaikalia, were considered. In order to determine their source, the Cr-bearing phases were compared with chromite, magnetite, and rutile from ultrabasic rocks, mantle xenoliths, and eclogites. It was suggested that the xenoclasts studied were formed at great depths, whereas the carbonatites were directly derived from the mantle rather than formed by the crustal differentiation of a silicate-carbonate melt.  相似文献   
82.
In this paper we report on the MEM power spectrum analysis of brightness temperature fluctuations observed at 2.8 GHz during the total solar eclipse of 16 February 1980. The observed periodicities range from 3.5 min to 64 min. These periodicities may arise due to spatial and/or temporal variations in the solar radio emission. The observed periodicities imply presence of scale sizes ranging from 70,000 to 600,000 km assuming that the brightness fluctuations arise because of spatial variation only. On the other hand, if these fluctuations are due to temporal variation, the observed periodicities correspond well to predicted modes of solar global oscillations.  相似文献   
83.
84.
Sattar  Ashim  Goswami  Ajanta  Kulkarni  Anil V. 《Natural Hazards》2019,98(2):817-817
Natural Hazards - The article was published with the citation “Worni et al. (2012)”. The author group of the article would like readers to know that this information should instead...  相似文献   
85.
This paper presents an integrated measurement technique based on DC methods (vertical electrical sounding, electrical resistivity tomography) which was used to identify faults and determine their geoelectric parameters in the western part of the Chuya basin. New information on the structure of the Chagan River valley located in the zone of the disastrous 27 September 2003 Chuya earthquake has been obtained from the results of these methods. Geoelectric cross-sections of the sedimentary sequence and the upper part of the basement were obtained from VES data, showing the block structure of the study area. Electrical resistivity tomography sections confirm the presence of a major fault between basement blocks of different heights and indicate the presence of faults bounding the valley on its right side and in the southwestern part.  相似文献   
86.
This work is based on the results of 2-D and 3-D surveys in the Tuapse Basin and field works in the Crimea-Caucasus region. Seven zones were outlined in the model of sedimentation starting from the eroded mountain structure of the Greater Caucasus down to deep water sediments of the Tuapse Basin. The slope and deep-water sediments of channels and fan complexes are characterized. Volume models of the sedimentation system in the Black Sea are shown for the first time.  相似文献   
87.
88.
Results of numerical simulations using the WRF-ARW nonhydrostatic model are presented for eight episodes of intense convection over European Russia in the summer of 2007. The calculations were performed on four nested grids with horizontal grid meshes of 27, 9, 3, and 1 km. Convection was parametrized on the first two grids and explicitly resolved on the other two. It has been found that simulations on finer grids with explicit calculation of convective flows make it possible to reproduce heavy rainfalls and strong-wind zones in the areas of intense convection. A preliminary verification of the short-range predictions of convective systems shows that the maximum 12-h precipitation totals and the maximum winds at 10 m are close, in the order of magnitude, to the observed values. Prediction of convection centers is the weakest point. Difficulties in the model verification associated with the absence of data with high space-time resolution are discussed.  相似文献   
89.
Marine disperse grounds from the shelf of the North Caspian Sea were studied using various test methods. The strain modulus and the coefficient of transverse strain were specified by triaxial compression and compression tests. Empirical correlations were found for the strain modulus as a result of both tests for different types of grounds.  相似文献   
90.
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