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   270341篇
  免费   2236篇
  国内免费   987篇
化学   130971篇
晶体学   4022篇
力学   14347篇
综合类   4篇
数学   49554篇
物理学   74666篇
  2018年   11472篇
  2017年   11239篇
  2016年   8195篇
  2015年   2492篇
  2014年   2660篇
  2013年   8104篇
  2012年   8868篇
  2011年   16775篇
  2010年   9887篇
  2009年   10196篇
  2008年   12332篇
  2007年   14597篇
  2006年   6094篇
  2005年   6648篇
  2004年   6406篇
  2003年   6303篇
  2002年   5247篇
  2001年   5998篇
  2000年   4647篇
  1999年   3645篇
  1998年   2912篇
  1997年   2906篇
  1996年   2910篇
  1995年   2629篇
  1994年   2467篇
  1993年   2376篇
  1992年   2831篇
  1991年   2722篇
  1990年   2659篇
  1989年   2697篇
  1988年   2635篇
  1987年   2642篇
  1986年   2461篇
  1985年   3313篇
  1984年   3325篇
  1983年   2752篇
  1982年   2951篇
  1981年   2885篇
  1980年   2798篇
  1979年   2939篇
  1978年   3173篇
  1977年   2977篇
  1976年   2909篇
  1975年   2767篇
  1974年   2713篇
  1973年   2742篇
  1972年   1776篇
  1968年   1945篇
  1967年   2141篇
  1966年   1938篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
We consider the discretization in time of an inhomogeneous parabolicequation in a Banach space setting, using a representation ofthe solution as an integral along a smooth curve in the complexleft half-plane which, after transformation to a finite interval,is then evaluated to high accuracy by a quadrature rule. Thisreduces the problem to a finite set of elliptic equations withcomplex coefficients, which may be solved in parallel. The paperis a further development of earlier work by the authors, wherewe treated the homogeneous equation in a Hilbert space framework.Special attention is given here to the treatment of the forcingterm. The method is combined with finite-element discretizationin spatial variables.  相似文献   
94.
The fusion evaporation reaction 122Sn(14N, 4n)132La was used to populate the high-spin states of 132La at the beam energy of 60 MeV. A new band consisting of mostly E2 transitions has been discovered. This band has the interesting links to the ground state 2- and the isomeric state 6-. A new transition of energy 351 keV connecting the low-spin states of the positive-parity band based on the πh 11/2 ⊗ νh 11/2 particle configuration, has been found. This has played a very important role in resolving the existing ambiguities and inconsistencies in the spin assignment of the band head. Received: 12 August 2002 / Accepted: 18 March 2003 / Published online: 7 May 2003  相似文献   
95.
The results of a numerical study are described in which the interactions of a primary shock wave with a secondary diaphragm in expansion tubes are taken into account. The developing wave pattern in the interacting process of the shock with a secondary diaphragm are visualized by many kinds of figures (e.g., the time-distance diagrams of the wave phenomena on the axis, the acoustic impedance contours, and the time histories of the pitot pressure on the axis), and the influences of the shape and rupture process of the diaphragm on the quality of the test gas are explored.  相似文献   
96.
97.
In order to reduce infant mortality in the municipality of Rio de Janeiro it is desired to encourage all mothers-to-be to attend the appropriate health care facilities. A 3-level hierarchical prenatal–neonatal health care system is described together with a basic model for optimising accessibility to facilities. A genetic algorithm to solve the basic model is developed and some numerical experience reported. Extensions to the basic model and planned future research are briefly indicated.  相似文献   
98.
 We prove a precise inversion of adjunction formula for the log variety (ℂ d +1,X), where X is a non-degenerate hypersurface. As a corollary, the minimal log discrepancies of non-degenerate normal hypersurface singularities are bounded by dimension. Received: 17 September 2002 / Revised version: 22 November 2002 Published online: 14 February 2003 Current address: DPMMS, CMS, University of Cambridge, Wilberforce Road, Cambridge CB3 0WB, England. e-mail: f.ambro@dpmms.cam.ac.uk Mathematics Subject Classification (2000): Primary 14B05; Secondary 14M25, 52B20  相似文献   
99.
100.
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