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   149836篇
  免费   11552篇
  国内免费   7810篇
化学   73450篇
晶体学   1514篇
力学   11353篇
综合类   566篇
数学   40321篇
物理学   41994篇
  2024年   248篇
  2023年   1497篇
  2022年   2513篇
  2021年   2586篇
  2020年   2818篇
  2019年   2693篇
  2018年   12264篇
  2017年   11904篇
  2016年   9010篇
  2015年   4226篇
  2014年   4255篇
  2013年   5618篇
  2012年   10001篇
  2011年   16531篇
  2010年   9797篇
  2009年   10098篇
  2008年   10868篇
  2007年   12545篇
  2006年   4070篇
  2005年   4620篇
  2004年   4170篇
  2003年   3964篇
  2002年   2830篇
  2001年   1874篇
  2000年   1804篇
  1999年   1809篇
  1998年   1560篇
  1997年   1358篇
  1996年   1459篇
  1995年   1227篇
  1994年   1096篇
  1993年   987篇
  1992年   843篇
  1991年   751篇
  1990年   620篇
  1989年   548篇
  1988年   449篇
  1987年   413篇
  1986年   371篇
  1985年   364篇
  1984年   260篇
  1983年   219篇
  1982年   198篇
  1981年   155篇
  1980年   134篇
  1979年   104篇
  1978年   98篇
  1977年   77篇
  1975年   81篇
  1973年   88篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
The semi‐iterative method (SIM) is applied to the hyper‐power (HP) iteration, and necessary and sufficient conditions are given for the convergence of the semi‐iterative–hyper‐power (SIM–HP) iteration. The root convergence rate is computed for both the HP and SIM–HP methods, and the quotient convergence rate is given for the HP iteration. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
182.
在本文中,给定一组有序空间数据点列及每个数据点的切矢向量,利用加权二次有理Bézier曲线对数据点作插值曲线,使该曲线具有C1连续性,并且权因子只是对相应顶点曲线附近产生影响,同调整两个相邻的权因子可以调整这两个相邻顶点之间的曲线和它的控制多边形.  相似文献   
183.
184.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
185.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc.  相似文献   
186.
We calculate the leptonic constant for the pseudoscalar ground state of the B c meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.  相似文献   
187.
We define analytic functions within Clifford Algebras CL, and study their trigonometric properties. We write the addition formulas when their arguments, A and B in CL, commute, this generalizes ordinary trigonometry. We examine in particular the case A2 = 1.   相似文献   
188.
In the present paper it is shown that if S1 and S2 are two Clifford topological semigroups satisfying certain conditions and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T maps S1 topologically isomorphically onto S2. Furthermore, T maps M l n(S1) (M(S1), respectively) isometrically isomorphically onto M l n(S2) (M(S2), respectively). Indeed, we have obtained a generalization of a well-known result of Ghahramani, Lau and Losert for locally compact groups to a more general setting of Clifford topological semigroups.  相似文献   
189.
We develop the three-step explicit and implicit schemes of exponential fitting methods. We use the three- step explicit exponential fitting scheme to predict an approximation, then use the three-step implicit exponential fitting scheme to correct this prediction. This combination is called the three-step predictor-corrector of exponential fitting method. The three-step predictor-corrector of exponential fitting method is applied to numerically compute the coupled nonlinear Schroedinger equation and the nonlinear Schroedinger equation with varying coefficients. The numerical results show that the scheme is highly accurate.  相似文献   
190.
This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area.  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