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   24723篇
  免费   523篇
  国内免费   100篇
化学   13754篇
晶体学   152篇
力学   759篇
综合类   9篇
数学   3437篇
物理学   7235篇
  2022年   190篇
  2021年   387篇
  2020年   356篇
  2019年   312篇
  2018年   402篇
  2017年   362篇
  2016年   624篇
  2015年   515篇
  2014年   596篇
  2013年   964篇
  2012年   1250篇
  2011年   1424篇
  2010年   790篇
  2009年   753篇
  2008年   1191篇
  2007年   1176篇
  2006年   1061篇
  2005年   1494篇
  2004年   1518篇
  2003年   1064篇
  2002年   709篇
  2001年   598篇
  2000年   553篇
  1999年   345篇
  1998年   290篇
  1997年   292篇
  1996年   358篇
  1995年   314篇
  1994年   307篇
  1993年   327篇
  1992年   320篇
  1991年   266篇
  1990年   216篇
  1989年   204篇
  1988年   181篇
  1987年   175篇
  1986年   174篇
  1985年   226篇
  1984年   213篇
  1983年   185篇
  1982年   189篇
  1981年   187篇
  1980年   172篇
  1979年   151篇
  1978年   178篇
  1977年   140篇
  1976年   140篇
  1975年   115篇
  1974年   133篇
  1973年   124篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
A new, very useful application of open-closed configurations to kinetic studies is reported. The multipeak recordings provided by the manifold used, which features a single conventional photometric detector, were used to calculate the rate constants and reaction orders of a chemical system, namely the ligand displacement reaction between the cobalt(II)-EGTA complex and PAR.  相似文献   
932.
The silicoaluminophosphate SAPO-37 as well as ZSM-20 zeolite have a faujaside-like structure and are potentially useful as catalysts. We report in this work different procedures to decompose the organic template occluded in SAPO-37. The texture of the final products was analyzed by means of nitrogen adsorption. The acid properties of SAPO-37 and ZSM-20 were also compared by IR measurements of adsorbed pyridine and related to the acidic properties of the presently commonly used cracking catalyst zeolite Y.
-37, ZSM-20 . , -37. . -37 ZSM-20 - . , .
  相似文献   
933.
A unified treatment is given for partially and totally asynchronous parallel successive overrelaxation (SOR) algorithms for the linear complementarity problem. Convergence conditions are established and compared to previous results. Convergence of the partially asynchronous method for the symmetric linear complementarity problem can be guaranteed if the relaxation factor is sufficiently small. Unlike previous results, this relaxation factor interval does not depend explicitly on problem size.This material is based on research supported by the Air Force Office of Scientific Research Grant No. AFOSR-89-0410.The author wishes to thank the referee for pointing out how to improve the bound (12). The same technique can be used to reduce the factorn in Ref. 5, p. 553, to .  相似文献   
934.
In this paper we deduce the general pattern of the potential surfaces for time-like geodesics in the Curzon metric. We find that for fairly small energies and orbital angular momenta, the time-like geodesics group into two sets; the geodesics of one set tend to thez-axis asR=(r2+z2)1/2 0,R=0 being a directional singularity, the others tend to ther-axis. At low energies these two sets are detached but they merge together as the energy increases. Stable circular motion is confined to thez = 0-plane and an energy threshold for stationary motion exists and is equal (per unit of rest-mass energy) to 0.945, a value almost indistinguishable from that in the Schwarzschild space-time.  相似文献   
935.
We are dealing with a numerical method for solving the problem of minimizing a difference of two convex functions (a d.c. function) over a closed convex set in n . This algorithm combines a new prismatic branch and bound technique with polyhedral outer approximation in such a way that only linear programming problems have to be solved.Parts of this research were accomplished while the third author was visiting the University of Trier, Germany, as a fellow of the Alexander von Humboldt foundation.  相似文献   
936.
937.
938.
939.
940.
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