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   73192篇
  免费   1131篇
  国内免费   535篇
测绘学   1627篇
大气科学   5003篇
地球物理   14350篇
地质学   25988篇
海洋学   6672篇
天文学   16518篇
综合类   152篇
自然地理   4548篇
  2021年   737篇
  2020年   808篇
  2019年   910篇
  2018年   1767篇
  2017年   1646篇
  2016年   1970篇
  2015年   1095篇
  2014年   1859篇
  2013年   3607篇
  2012年   2115篇
  2011年   2930篇
  2010年   2652篇
  2009年   3404篇
  2008年   2958篇
  2007年   3052篇
  2006年   2819篇
  2005年   2153篇
  2004年   2144篇
  2003年   2141篇
  2002年   2011篇
  2001年   1739篇
  2000年   1619篇
  1999年   1379篇
  1998年   1366篇
  1997年   1405篇
  1996年   1165篇
  1995年   1132篇
  1994年   1015篇
  1993年   944篇
  1992年   860篇
  1991年   853篇
  1990年   871篇
  1989年   824篇
  1988年   781篇
  1987年   878篇
  1986年   842篇
  1985年   1015篇
  1984年   1113篇
  1983年   1049篇
  1982年   969篇
  1981年   958篇
  1980年   841篇
  1979年   818篇
  1978年   753篇
  1977年   760篇
  1976年   682篇
  1975年   676篇
  1974年   668篇
  1973年   701篇
  1971年   420篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
91.
92.
Summary The geometry of the principal Upper High (near the Indian Occean) in the 300–100 mb layer appears to account for the Southern Oscillation (S.O.), and models of its behaviour are presented. Significant features of these models include the equatorial points of upper convergence (C) and divergence (D), a pressure discontinuity (CNDS) forming «arcs» and an «enclosure» around the high, and, lastly, encircling «crescents» both outside and inside the enclosure. The geography of the seasonal sucession can thus—in a qualitative manner—be interpreted in the light of known wind and contour patterns near the tropopause. With a few general principles, the established empirical rules of long-range forecasting then follow by deduction. The models and the terminology are useful likewise in the interpretation of solar-terrestrial relations and of climatic fluctuations.  相似文献   
93.
The paper deals with a numerical integrated procedure to calculate the effects of the interaction between sea waves and a tripod-type steel gravity platform. The main aspects to be taken into account for a reliable wave loading analysis of such a new type of platform are emphasized. Among them, the field perturbation effect due to the large bodies presence is analysed. Finally, some principal results in terms of structure global loads obtained by the numerical integrated procedure are presented.  相似文献   
94.
The fauna composition, ecological groups, and life forms of Harpacticoids of soft littoral grounds from 15 sites off the Karelian coast in Kandalaksha Bay of the White Sea were studied. Six types of harpacticoid taxocens with different sets of dominating species are described. On silty sands with clear signs of desalination, the Stenchelia palustris taxocen is common; medium-grained sands are characterized by the Heterolaophonte minuta, Paraleptastacus kliei — Huntemannia jadensis, and Amphiascoides nanus — Scottopsyllus minor taxocens; while on coarse sands, the Ameira parvula and Ameira scotti — Mesochra lilljeborgi taxocens have developed. The diversity of the taxocens is partly explained by the differences in the grain-size composition and salinity at different sites. In addition, groups of various taxocens dwelling on the same type of the sediments were found in different minor bights of the coastline.  相似文献   
95.
The results of a comprehensive field trial of nearly all commercially available directional wave measurement systems at the Edda field in the North Sea during winter 1985-86 are presented. The results summarize the accuracy of the principal engineering wave parameters from each system and the dependence on sea state. Limiting factors on system performance and operational problems are also included in the assessment. Overall experience has been good with systems utilizing widely different measurement principles returning consistent results.  相似文献   
96.
97.
The authors describe the effect of copper pollution on the mitochondria from various areas of the Torpedo marmorata central nervous system. A high percentage of swollen mitochondria has been observed in neurons from animals experimentally exposed to high level of copper (4 ppm). The correlation with age pigment granules is discussed.  相似文献   
98.
99.
100.
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