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   87732篇
  免费   1105篇
  国内免费   1554篇
测绘学   3043篇
大气科学   6388篇
地球物理   17100篇
地质学   33512篇
海洋学   6926篇
天文学   16807篇
综合类   2301篇
自然地理   4314篇
  2022年   416篇
  2021年   685篇
  2020年   789篇
  2019年   886篇
  2018年   6334篇
  2017年   5500篇
  2016年   4505篇
  2015年   1327篇
  2014年   2005篇
  2013年   3406篇
  2012年   3042篇
  2011年   5227篇
  2010年   4348篇
  2009年   5334篇
  2008年   4574篇
  2007年   5050篇
  2006年   2729篇
  2005年   2036篇
  2004年   2208篇
  2003年   2100篇
  2002年   1983篇
  2001年   1609篇
  2000年   1506篇
  1999年   1268篇
  1998年   1288篇
  1997年   1236篇
  1996年   1038篇
  1995年   967篇
  1994年   928篇
  1993年   783篇
  1992年   715篇
  1991年   710篇
  1990年   741篇
  1989年   668篇
  1988年   619篇
  1987年   726篇
  1986年   631篇
  1985年   798篇
  1984年   886篇
  1983年   777篇
  1982年   776篇
  1981年   691篇
  1980年   662篇
  1979年   599篇
  1978年   612篇
  1977年   524篇
  1976年   492篇
  1975年   493篇
  1974年   472篇
  1973年   505篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
V. P. Singh 《水文研究》2001,15(4):671-706
The history of the kinematic wave theory and its applications in water resources are traced. It is shown that the theory has found its niche in water resources and its applications are so widespread that they may well constitute what may be termed ‘kinematic wave hydrology’. Few theories have been applied in hydrology and water resources as extensively as the kinematic wave theory. This theory, however, is not without limitations and when it is applied they must be so recognized. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
93.
94.
P. L. Bornmann 《Solar physics》1985,102(1-2):111-130
The light curves of soft X-ray lines, observed by the Flat Crystal Spectrometer on Solar Maximum Mission during eight solar flares are modeled to determine the plasma temperature and emission measure as functions of time using the method first presented by Bornmann (1985, Paper I), but modified to include a 2 search routine. With this modification the technique becomes more general, more accurate, and applicable throughout the gradual phase of the flare. The model reproduces the light curves of the soft X-ray lines throughout these flares. Model fits were repeated for each flare using five different sets of published line emissivity calculations. The emissivities of Mewe and Gronenschild (1981) consistenly gave the best fits to the observed light curves for each flare.  相似文献   
95.
96.
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   
97.
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   
98.
99.
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   
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