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   533195篇
  免费   4780篇
  国内免费   1494篇
化学   273716篇
晶体学   8382篇
力学   25273篇
综合类   16篇
数学   64623篇
物理学   167459篇
  2021年   4283篇
  2020年   4723篇
  2019年   5312篇
  2018年   7269篇
  2017年   7402篇
  2016年   10458篇
  2015年   6063篇
  2014年   10010篇
  2013年   23858篇
  2012年   18180篇
  2011年   22001篇
  2010年   16024篇
  2009年   15876篇
  2008年   20055篇
  2007年   20079篇
  2006年   18609篇
  2005年   16430篇
  2004年   15195篇
  2003年   13617篇
  2002年   13544篇
  2001年   15499篇
  2000年   11768篇
  1999年   9179篇
  1998年   7832篇
  1997年   7729篇
  1996年   7233篇
  1995年   6486篇
  1994年   6571篇
  1993年   6220篇
  1992年   6938篇
  1991年   7110篇
  1990年   6880篇
  1989年   6667篇
  1988年   6543篇
  1987年   6615篇
  1986年   6276篇
  1985年   8080篇
  1984年   8372篇
  1983年   6992篇
  1982年   7161篇
  1981年   6849篇
  1980年   6800篇
  1979年   7021篇
  1978年   7356篇
  1977年   7233篇
  1976年   7267篇
  1975年   6725篇
  1974年   6788篇
  1973年   6985篇
  1972年   4956篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
In this paper, we obtain a nonlinear Poisson structure and two first integrals in the problem of the plane motion of a circular cylinder and n point vortices in an ideal fluid. This problem is a priori not Hamiltonian; specifically, in the case n= 1 (i.e., in the problem of the interaction of a cylinder with a vortex) it is integrable.  相似文献   
183.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to attain the perpendicular orientation at monolayer coverage. Dedicated to Professor C N R Rao on his 70th birthday  相似文献   
184.
The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg3Si2O5(OH)4 filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes.  相似文献   
185.
We provide a rigorous derivation of an asymptotic formula for perturbations in the eigenvalues caused by the presence of a finite number of inhomogeneities of small diameter with conductivity different from the background conductivity. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
186.
 The Belavkin equation, describing the continuous measurement of the position of a quantum particle, is studied. A rigorous representation of its solution by means of an infinite dimensional oscillatory integral (Feynman path integral) defined on the complex Cameron-Martin space is given. Received: 7 January 2002 / Revised version: 20 June 2002 / Published online: 19 December 2002 Mathematics Subject Classification (2000): 81, 81S40, 60H15 Key words or phrases: Belavkin equation – Continuous measurement – Quantum theory – Oscillatory integrals – Feynman path integrals  相似文献   
187.
In this study, a novel stepwise extraction method has been examined. The guest molecules housed between the helices of the clathrate δ form of syndiotactic polystyrene can be removed completely with this method. A systematic study of the preparation of a solvent‐free mesophase (emptied clathrate) membrane, its helical and residual solvent contents, and its structural transformations has been performed. In this first attempt, an enhancement in the TTGG helical content has been observed in the extracted membrane, and a conceptual mechanism is proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 269–273, 2003  相似文献   
188.
189.
A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the 10B nucleus at low energy-momentum transfers as the first step of the research.  相似文献   
190.
The title compound is a centrosymmetric dimer with each cadmium in a distorted CdS5 square pyramidal geometry. The Cd–S bond distances range from 2.5626(11) to 2.8459(11) Å. Copyright © 2004 John Wiley & Sons, Ltd.  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