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   52216篇
  免费   3973篇
  国内免费   3657篇
化学   25074篇
晶体学   407篇
力学   3784篇
综合类   504篇
数学   10527篇
物理学   19550篇
  2024年   54篇
  2023年   418篇
  2022年   760篇
  2021年   1052篇
  2020年   1149篇
  2019年   1172篇
  2018年   1032篇
  2017年   1228篇
  2016年   1393篇
  2015年   1391篇
  2014年   1992篇
  2013年   3413篇
  2012年   2303篇
  2011年   2522篇
  2010年   2083篇
  2009年   3135篇
  2008年   3404篇
  2007年   3742篇
  2006年   3150篇
  2005年   2506篇
  2004年   2153篇
  2003年   2374篇
  2002年   2644篇
  2001年   1978篇
  2000年   1859篇
  1999年   1578篇
  1998年   1519篇
  1997年   876篇
  1996年   831篇
  1995年   726篇
  1994年   783篇
  1993年   571篇
  1992年   653篇
  1991年   427篇
  1990年   409篇
  1989年   312篇
  1988年   266篇
  1987年   263篇
  1986年   231篇
  1985年   210篇
  1984年   217篇
  1983年   126篇
  1982年   173篇
  1981年   167篇
  1980年   107篇
  1979年   134篇
  1978年   100篇
  1977年   85篇
  1976年   39篇
  1973年   34篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
101.
The purpose of this paper is to investigate the asymptotic properties of the least squares estimates (L 2-estimates) and the least absolute deviation estimates (L 1-estimates) of the parameters of a nonlinear regression model subject to a set of equality and inequality restrictions, which has a long-range dependent stationary process as its stochastic errors. Then we will compare the asymptotic relative efficiencies of the above estimators.  相似文献   
102.
Summary This article provides a glimpse of some of the highlights of the joint work of Endre Csáki and Pál Révész since 1979. The topics of this short exploration of the rich stochastic milieu of this inspiring collaboration revolve around Brownian motion, random walks and their long excursions, local times and additive functionals, iterated processes, almost sure local and global central limit theorems, integral functionals of geometric stochastic processes, favourite sites--favourite values and jump sizes for random walk and Brownian motion, random walking in a random scenery, and large void zones and occupation times for coalescing random walks.  相似文献   
103.
104.
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   
105.
该文讨论了一类非线性抛物型方程组解的性质,利用微分方程上、下解方法证明了初值适当小时,方程存在整体解;初值适当大时,解在有限时间上爆破,推广了文献[1]的结果.  相似文献   
106.
The general stability of single-layer cylindrical grids is studied in linear and nonlinear formulations. Dependence of the general buckling load on the geometry and stiffness parameters of a grid is established in an analytical form. Such grids are numerically analyzed for stability. It is established that the general buckling load is much less than the local buckling load. Typical general buckling modes are found. It is shown that such grids are weakly sensitive to imperfections  相似文献   
107.
Amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers consisting of one polystyrene block and two poly(N‐isopropylacrylamide) blocks were prepared by the “arm‐first” method in which RAFT polymerization and nonconvalent ligand–metal complexation were employed. The prepared amphiphilic star‐shaped metallopolymers are able to form micelles in water. The size and distribution of the micelles were studied by dynamic light scattering and transmission electron microscopy techniques. Preliminary studies indicate that the polymer concentration and the hydrophilic poly(N‐isopropylacrylamide) block length can affect the morphologies of the formed metal‐interfaced core–shell micelles in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4204–4210, 2007  相似文献   
108.
109.
分形介质的传热与传质分析(综述)   总被引:9,自引:0,他引:9  
本文论述了分形介质的分形理论和数学基础,并简要综述了用分形理论和方法研究分形介质的传热与传质特性(如多孔介质的渗透率、热导率以及池核态沸腾换热)方面目前所取得的研究进展,最后扼要展望了用分形理论和方法进一步研究分形介质的传热与传质的可能的若干课题和方向。  相似文献   
110.
This paper derives the optimal trajectories in a general fluid network with server control. The stationary optimal policy in the complete state space is constructed. The optimal policy is constant on polyhedral convex cones. An algorithm is derived that computes these cones and the optimal policy. Generalized Klimov indices are introduced, they are used for characterizing myopic and time-uniformly optimal policies.Received: November 2004 / Revised: February 2005The research of this author has been supported by the project ‘‘Stochastic Networks’’ of the Netherlands Organisation for Scientific Research NWO.  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