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   79878篇
  免费   782篇
  国内免费   1401篇
测绘学   2542篇
大气科学   5006篇
地球物理   15128篇
地质学   32175篇
海洋学   6319篇
天文学   15308篇
综合类   2290篇
自然地理   3293篇
  2022年   600篇
  2021年   896篇
  2020年   1014篇
  2019年   1077篇
  2018年   6742篇
  2017年   5859篇
  2016年   4758篇
  2015年   1201篇
  2014年   2097篇
  2013年   3152篇
  2012年   3179篇
  2011年   5331篇
  2010年   4441篇
  2009年   5164篇
  2008年   4418篇
  2007年   5041篇
  2006年   2589篇
  2005年   1657篇
  2004年   1754篇
  2003年   1670篇
  2002年   1503篇
  2001年   1254篇
  2000年   1120篇
  1999年   816篇
  1998年   867篇
  1997年   836篇
  1996年   667篇
  1995年   654篇
  1994年   656篇
  1993年   527篇
  1992年   525篇
  1991年   530篇
  1990年   602篇
  1989年   455篇
  1988年   443篇
  1987年   497篇
  1986年   374篇
  1985年   569篇
  1984年   547篇
  1983年   506篇
  1982年   519篇
  1981年   444篇
  1980年   480篇
  1979年   375篇
  1978年   425篇
  1977年   341篇
  1976年   329篇
  1975年   336篇
  1974年   314篇
  1973年   341篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Quasi-steady high-temperature current sheets are an energy source during the main or hot phase of solar flares. Such sheets are shown to be stabilized with respect to the tearing instability by a small transverse component of magnetic field existing in the sheets.  相似文献   
63.
64.
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   
65.
66.
In this paper the peculiarities of compiled oceanographic data sets, which consist primarily in the presence of some characteristic information as well as in the planned incomplete filling of the files with observations, are discussed. A number of special ways are suggested which essentially improve the packing density of computerized data without applying special archiving algorithms. The effectiveness of these methods has been tested by treating thein situ hydrological/chemical data file compiled in the Black Sea in 1988.Translated by Vladimir A. Puchkin.  相似文献   
67.
Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation. The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also controlled the offshore structural pattern.  相似文献   
68.
69.
70.
This study considers the influence of the effects of scattering due to Langmuir turbulent pulsations in the transfer of radiation in the spectral lines. The transfer equation of radiation in spectral lines, by taking into account scattering due to Langmuir turbulent pulsations, is written in a form convenient for application by numerical methods.The profile's intensity for a plane-parallel finite isothermal slab of a turbulent plasma in the case of complete redistribution of scattering by an atom are obtained. Numerical studies show that in this case with the broadening of spectral lines and the decreasing of self-reversal, the Langmuir frequency pe is of the same order as the electronic Doppler width De. Creation of the line satellites when pe is larger than the line width is shown with the aid of numerical methods.  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