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   68271篇
  免费   841篇
  国内免费   439篇
测绘学   1432篇
大气科学   3938篇
地球物理   13422篇
地质学   25209篇
海洋学   6211篇
天文学   15890篇
综合类   174篇
自然地理   3275篇
  2022年   599篇
  2021年   924篇
  2020年   1036篇
  2019年   1162篇
  2018年   2246篇
  2017年   2122篇
  2016年   2322篇
  2015年   1084篇
  2014年   2163篇
  2013年   3475篇
  2012年   2439篇
  2011年   3098篇
  2010年   2804篇
  2009年   3328篇
  2008年   2992篇
  2007年   3170篇
  2006年   2873篇
  2005年   1801篇
  2004年   1725篇
  2003年   1779篇
  2002年   1603篇
  2001年   1507篇
  2000年   1318篇
  1999年   1060篇
  1998年   1082篇
  1997年   1121篇
  1996年   878篇
  1995年   874篇
  1994年   789篇
  1993年   698篇
  1992年   652篇
  1991年   687篇
  1990年   731篇
  1989年   634篇
  1988年   601篇
  1987年   640篇
  1986年   579篇
  1985年   776篇
  1984年   813篇
  1983年   802篇
  1982年   741篇
  1981年   680篇
  1980年   655篇
  1979年   590篇
  1978年   597篇
  1977年   574篇
  1976年   503篇
  1975年   514篇
  1974年   495篇
  1973年   554篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
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   
82.
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   
83.
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   
84.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied.  相似文献   
85.
The eleventh list of faint late M and carbon type stars detected on the plates of the First Byurakan Spectral Survey in zone -7° -3° and covering about 1000 square degrees is presented. From 126 detected stars, 88 are newly discovered objects: they are 6 carbon stars, 8 carbon star candidates, and 74 M-type stars; among the latter 38 (26 PSC + 12 FSC) are unclassified IRAS sources, and one object is an unclassified ROSAT source. Distances to the 6 newly discovered early-type carbon stars are estimated. Equatorial coordinates, red magnitudes, and spectral classes determined from the Palomar E-charts are provided. The lack of optical counterparts on Palomar O and E maps for two detected late M-type stars indicates a large variability in brightnesses of these objects (amplitude not smaller than 7.0 magnitude).  相似文献   
86.
87.
88.
89.
The neotectonic structures of the Lower Oka (Nizhneokskii) Region formed under different geodynamic conditions. This is attested by the morphology, orientation, internal structure, and jointing of the structures. The Oka-Tsna arc formed under the effect of tension from an inner source on the one hand and stress from the Alpian belt on the other hand. The latitudinally-oriented structures of the northwestern slope of the Tokmovo arc emerged as a result of uplift and widening. Both types of structure are combined within the limits of the Oka-Murom trough, which is a geodynamically active zone.  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