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   44927篇
  免费   353篇
  国内免费   278篇
测绘学   939篇
大气科学   2317篇
地球物理   8535篇
地质学   17398篇
海洋学   4285篇
天文学   10462篇
综合类   142篇
自然地理   1480篇
  2022年   531篇
  2021年   791篇
  2020年   826篇
  2019年   914篇
  2018年   1928篇
  2017年   1745篇
  2016年   1879篇
  2015年   742篇
  2014年   1651篇
  2013年   2439篇
  2012年   1866篇
  2011年   2243篇
  2010年   2077篇
  2009年   2391篇
  2008年   2106篇
  2007年   2320篇
  2006年   2008篇
  2005年   1146篇
  2004年   1067篇
  2003年   1029篇
  2002年   964篇
  2001年   939篇
  2000年   831篇
  1999年   561篇
  1998年   595篇
  1997年   619篇
  1996年   438篇
  1995年   468篇
  1994年   436篇
  1993年   366篇
  1992年   342篇
  1991年   368篇
  1990年   415篇
  1989年   335篇
  1988年   323篇
  1987年   352篇
  1986年   266篇
  1985年   395篇
  1984年   389篇
  1983年   391篇
  1982年   354篇
  1981年   325篇
  1980年   350篇
  1979年   283篇
  1978年   314篇
  1977年   270篇
  1976年   227篇
  1975年   242篇
  1974年   233篇
  1973年   264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
It is shown that the chronology of flare star discoveries in the Pleiades cluster and the Orion association can be described satisfactorily by various distribution functions (gamma, binomial, decreasing exponential, and delta) for the mean frequencies of stellar flares. However, it has been found that this is due to the uncertainty in the observationally derived distribution function for the mean frequency of stellar flares. The most likely function is that derived by Ambartsumian, which has a physical basis.Translated fromAstrofizika, Vol. 38, No. 1, pp. 25–32, January–March, 1995.  相似文献   
52.
53.
Izvestiya, Physics of the Solid Earth - Abstract—Granular media determine the dynamics of many natural systems including faults in the Earth’s crust. The paper addresses the laboratory...  相似文献   
54.
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   
55.
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   
56.
57.
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   
58.
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   
59.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied.  相似文献   
60.
The solubility of quartz in 2, 3, and 4 molal NaCl was measured at 350°C and pressures ranging from 180 to 500 bars. The molal solubility in each of the salt solutions is greater than that in pure water throughout the measured pressure range, with the ratio of solubility in NaCl solution to solubility in pure water decreasing as pressure is increased. The measured solubilities are significantly higher than solubilities calculated using a simple model in which the water activity in NaCl solutions decreases either in proportion to decreasing vapor pressure of the solution as salinity is increased or in proportion to decreasing mole fraction of water in the solvent.  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