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   37154篇
  免费   254篇
  国内免费   218篇
测绘学   721篇
大气科学   1705篇
地球物理   7050篇
地质学   14630篇
海洋学   3529篇
天文学   8795篇
综合类   99篇
自然地理   1097篇
  2022年   488篇
  2021年   708篇
  2020年   754篇
  2019年   826篇
  2018年   1696篇
  2017年   1545篇
  2016年   1638篇
  2015年   615篇
  2014年   1414篇
  2013年   2035篇
  2012年   1619篇
  2011年   1898篇
  2010年   1790篇
  2009年   1986篇
  2008年   1765篇
  2007年   1978篇
  2006年   1735篇
  2005年   898篇
  2004年   815篇
  2003年   808篇
  2002年   741篇
  2001年   764篇
  2000年   630篇
  1999年   417篇
  1998年   437篇
  1997年   474篇
  1996年   337篇
  1995年   358篇
  1994年   335篇
  1993年   281篇
  1992年   284篇
  1991年   290篇
  1990年   337篇
  1989年   272篇
  1988年   258篇
  1987年   260篇
  1986年   191篇
  1985年   301篇
  1984年   302篇
  1983年   295篇
  1982年   274篇
  1981年   248篇
  1980年   265篇
  1979年   203篇
  1978年   242篇
  1977年   204篇
  1976年   177篇
  1975年   184篇
  1974年   171篇
  1973年   206篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
This paper traces the theoretical development of the regional concept and the use of regionalization techniques in Soviet geography and seeks to compare this history with comparable trends in Western geography. It is severely critical of the major and rapid paradigm shifts noticed in post-war Western geographical science and relates these to shifts in the approach to global development issues.  相似文献   
73.
The causes of the high Mn concentration in the solid phase and pore solution of bottom sediments in the Mozhaisk Reservoir are discussed. Regularities are identified in variations the concentrations of Mn forms in reservoir deposits from its upper part to the dam.  相似文献   
74.
In July 2000, a transatlantic hydrographic section was made on board the Russian R/V Akademik Ioffe in the northern equatorial region at ~6.5° N on the WOCE (World Ocean Circulation Experiment) A06 line. A significant warming in the layers of intermediate and deep waters in the interior eastern basin is determined from comparison of the section temperature data and those obtained on the WOCE A06 line in 1993. This result, together with the results of the previous studies, indicates a substantial warming of intermediate and upper deep waters above 2800–3000 m in the eastern equatorial North Atlantic during the second half of the 20th century. In the 1000–2000 m layer, temperature has increased by 0.13–0.14°C since 1957.  相似文献   
75.
A special system of canonical variables is considered. An algorithm for expanding the principal functions of Keplerian motion in new elements is presented. The advantage of the proposed system is a relatively small number of terms in the classical expansions of the unperturbed two-body problem. A method for expanding the time derivatives of the rectangular coordinates is proposed. Some estimates of the number of terms in the presented expansions have been obtained through numerical experiments.  相似文献   
76.
This paper reports the results of the experimental determination of the coefficient of sorption of rare-earth elements and yttrium (REY) under conditions of acidic pH using several strains of heterotrophic bacteria (Microbacterium sp., Curtobacterium sp., Bacillus subtilis, Pseudomonas putida, and Bacillus pumilis) that are widespread in natural and technogenic waters of the Far East (Russia). Insignificant fractionation between heavy and light rare-earth elements, negative cerium and dysprosium anomalies, and a positive europium anomaly were revealed. The selectivity of REY biosorption by gram-positive and gram-negative bacteria, as well as inertia of the biosorption process under more acidic conditions of the medium, were shown.  相似文献   
77.
The results of the first study of the PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia) are presented here. The complex character of evolution of the PGE composition in the Deformed lherzolites is assumed to be the result of silicate metasomatism. At the first stage, growth in the amount of clinopyroxene and garnet in the rock is accompanied by a decrease in the concentration of the compatible PGE (Os, Ir). During the final stage, the rock is enriched with incompatible PGE (Pt, Pd) and Re possible due to precipitation of submicron-sized particles of sulfides in the interstitial space of these mantle rocks.  相似文献   
78.
Bumba  V.  Garcia  A.  Klvaňa  M. 《Solar physics》2000,197(1):175-202
The first small active regions of the last two new cycles seem to be formed, in its very first, preparatory stage, close to the equator with uncertain magnetic orientation, and as secondary products at the periphery of equatorial `magnetic bubbles' of the new magnetic flux still belonging to the old cycle. At the real beginning of the new cycle, at the periphery of its higher-latitude `magnetic bubbles', the opposite applies to the secondary regions of the ending cycle. It seems that two modes of magnetic flux supply the visible layers of the photosphere during the cycle transition phase: the emergence of the magnetic flux from the depth of the convective zone, and the mutual interaction of the earlier emerging fluxes, or the action of the `local dynamo', giving rise to the new local magnetic field concentrations.  相似文献   
79.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied.  相似文献   
80.
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