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   27345篇
  免费   651篇
  国内免费   126篇
化学   15552篇
晶体学   179篇
力学   853篇
综合类   9篇
数学   3894篇
物理学   7635篇
  2023年   138篇
  2022年   221篇
  2021年   450篇
  2020年   437篇
  2019年   389篇
  2018年   477篇
  2017年   420篇
  2016年   719篇
  2015年   604篇
  2014年   717篇
  2013年   1145篇
  2012年   1463篇
  2011年   1701篇
  2010年   934篇
  2009年   871篇
  2008年   1387篇
  2007年   1327篇
  2006年   1211篇
  2005年   1616篇
  2004年   1629篇
  2003年   1158篇
  2002年   784篇
  2001年   639篇
  2000年   576篇
  1999年   365篇
  1998年   304篇
  1997年   306篇
  1996年   374篇
  1995年   324篇
  1994年   313篇
  1993年   337篇
  1992年   331篇
  1991年   269篇
  1990年   219篇
  1989年   206篇
  1988年   181篇
  1987年   177篇
  1986年   177篇
  1985年   233篇
  1984年   214篇
  1983年   187篇
  1982年   190篇
  1981年   187篇
  1980年   170篇
  1979年   151篇
  1978年   183篇
  1977年   141篇
  1976年   138篇
  1974年   133篇
  1973年   125篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s…  相似文献   
52.
Affine Arithmetic: Concepts and Applications   总被引:2,自引:0,他引:2  
Affine arithmetic is a model for self-validated numerical computation that keeps track of first-order correlations between computed and input quantities. We explain the main concepts in affine arithmetic and how it handles the dependency problem in standard interval arithmetic. We also describe some of its applications.  相似文献   
53.
54.
55.
56.
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL.  相似文献   
57.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations.  相似文献   
58.
This article deals with stability and small linear oscillations of liquid bridges between fixed solid surfaces (parallel plates, spheres, ...) under zero gravity. A general investigation method for any kind of axisymmetric liquid bridge is exposed but the author focus his work on the spherical liquid bridge cases. In particular, he exposes a full theoretical study of spherical liquid bridges between two spheres, plates and cones.  相似文献   
59.
In this article the main theorem establishes the necessity and sufficiency of the Poincaré-Hopf inequalities in order for the Morse inequalities to hold. The convex hull of the collection of all Betti number vectors which satisfy the Morse inequalities for a pre-assigned index data determines a Morse polytope defined on the nonnegative orthant. Using results from network flow theory, a scheme is provided for constructing all possible Betti number vectors which satisfy the Morse inequalities for a pre-assigned index data. Geometrical properties of this polytope are described.

  相似文献   

60.
The errata concern mainly the last computations for the universality of the local statistics of eigenvalues at the edge of the spectrum in parts (iii) of Theorems 2.3 and 2.4.  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