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   24481篇
  免费   3678篇
  国内免费   2009篇
化学   4884篇
晶体学   273篇
力学   4430篇
综合类   365篇
数学   11442篇
物理学   8774篇
  2024年   55篇
  2023年   233篇
  2022年   313篇
  2021年   430篇
  2020年   658篇
  2019年   566篇
  2018年   576篇
  2017年   691篇
  2016年   730篇
  2015年   590篇
  2014年   1114篇
  2013年   1663篇
  2012年   1344篇
  2011年   1566篇
  2010年   1407篇
  2009年   1512篇
  2008年   1650篇
  2007年   1751篇
  2006年   1517篇
  2005年   1435篇
  2004年   1296篇
  2003年   1296篇
  2002年   1064篇
  2001年   900篇
  2000年   801篇
  1999年   693篇
  1998年   651篇
  1997年   524篇
  1996年   443篇
  1995年   416篇
  1994年   332篇
  1993年   284篇
  1992年   262篇
  1991年   229篇
  1990年   181篇
  1989年   147篇
  1988年   133篇
  1987年   107篇
  1986年   91篇
  1985年   89篇
  1984年   77篇
  1983年   34篇
  1982年   85篇
  1981年   61篇
  1980年   41篇
  1979年   37篇
  1978年   20篇
  1977年   13篇
  1976年   13篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.  相似文献   
2.
3.
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution { u , p } of the Navier–Stokes equation such that | ? j u ( t , x ) | = O ( | x | 1 ? n ? j ) and | ? j p ( t , x ) | = O ( | x | ? n ? j ) ( j = 0 , 1 , ) uniformly in t R as | x | . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described.  相似文献   
4.
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR.  相似文献   
5.
6.
7.
Substantial progress in research on the recession of coastal cliffs composed of soft materials has been made in recent years and data with higher accuracy have been accumulated. This paper provides the state of the art review in the recession studies and highlights two new findings obtained from the reanalysis of existing data. The review topics are: episodic and localized nature of cliff recession; the development of cliffline; the relationship between cliff height and recession rate; mechanisms of cliff toe erosion by waves; a fundamental equation for wave-induced toe erosion; factors controlling toe erosion; and slope instabilities and mass movements. The findings are presented on (1) the temporal change in cliffline recession mode and (2) the effect of beach sediment at the cliff base on the cliff erosion.  相似文献   
8.
9.
This article explores the questions of long time orbital stability in high order Sobolev norms of plane wave solutions to the NLSE in the defocusing case.  相似文献   
10.
The zero dissipation limit of the one-dimensional non-isentropic micropolar equations is studied in this paper. If the given rarefaction wave which connects to vacuum at one side, a sequence of solution to the micropolar equations can be constructed which converge to the above rarefaction wave with vacuum as the viscosity and the heat conduction coefficient tend to zero. Moreover, the uniform convergence rate is obtained. The key point in our analysis is how to control the degeneracies in the vacuum region in the zero dissipation limit process.  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