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   9648篇
  免费   996篇
  国内免费   803篇
化学   1374篇
晶体学   21篇
力学   724篇
综合类   177篇
数学   7252篇
物理学   1899篇
  2024年   18篇
  2023年   66篇
  2022年   91篇
  2021年   157篇
  2020年   169篇
  2019年   207篇
  2018年   202篇
  2017年   273篇
  2016年   316篇
  2015年   214篇
  2014年   408篇
  2013年   707篇
  2012年   486篇
  2011年   453篇
  2010年   439篇
  2009年   527篇
  2008年   602篇
  2007年   625篇
  2006年   567篇
  2005年   559篇
  2004年   464篇
  2003年   410篇
  2002年   448篇
  2001年   400篇
  2000年   357篇
  1999年   358篇
  1998年   278篇
  1997年   255篇
  1996年   211篇
  1995年   167篇
  1994年   137篇
  1993年   111篇
  1992年   103篇
  1991年   90篇
  1990年   68篇
  1989年   59篇
  1988年   48篇
  1987年   50篇
  1986年   44篇
  1985年   52篇
  1984年   59篇
  1983年   17篇
  1982年   37篇
  1981年   21篇
  1980年   22篇
  1979年   24篇
  1978年   13篇
  1977年   17篇
  1976年   11篇
  1974年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
In this paper, we consider questions related to the structure of inverse matrices of linear bounded operators acting in infinite-dimensional complex Banach spaces. We obtain specific estimates of elements of inverse matrices for bounded operators whose matrices have a special structure. Matrices are introduced as special operator-valued functions on an index set. The matrix structure is described by the behavior of the given function on elements of a special partition of the index set. The method used for deriving the estimates is based on an analysis of Fourier series of strongly continuous periodic functions.  相似文献   
62.
A natural criterion for dimensional full-valuedness of locally compact spaces with finitely generated local homology is given.  相似文献   
63.
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust against small external noise. The mechanism underlying this high control efficiency is intuitively explained. Received 15 January 2002 Published online 6 June 2002  相似文献   
64.
We determine all linear codes C containing the constant code E, for which there is a weight-preserving group of semilinear automorphisms which acts transitively on the set of nontrivial cosets of E in C. Michael Giudici - The author holds an Australian Postdoctoral Fellowship.  相似文献   
65.
Linear complexity and linear complexity profile are important characteristics of a sequence for applications in cryptography and Monte-Carlo methods. The nonlinear congruential method is an attractive alternative to the classical linear congruential method for pseudorandom number generation. Recently, a weak lower bound on the linear complexity profile of a general nonlinear congruential pseudorandom number generator was proven by Gutierrez, Shparlinski and the first author. For most nonlinear generators a much stronger lower bound is expected. Here, we obtain a much stronger lower bound on the linear complexity profile of nonlinear congruential pseudorandom number generators with Dickson polynomials.  相似文献   
66.
证明了线性规划的K uhn-Tucker条件蕴含着它的对偶问题,解释了L agrange乘子的意义.进而显示了K-T条件中的互补松驰性与对偶线性规划的互补松紧定理之间的联系.  相似文献   
67.
利用已知弹性函数级联上高非线性度多输出布尔函数的方法构造(n,m,t)弹性函数,其非线性度为2^n-1-2^n-l/2-1+2^l/2.nlmax(n-l,m,t),在相同条件下改进了Kurosawa的非线性度2^n-1-2^n-l/2-1.特别地,本文构造了两类具体的向量弹性函数,得到两个不同的非线性度.本文所得函数的非线性度在大多数情况下是比较好的.  相似文献   
68.
本文建立一个理论模型研究互联网互联结算的问题。文章利用多元线性回归法对互联网骨干网运营商(IBPs:Internet Backbone Providers)的网络价值进行评估,利用IBPs各自的网络价值对其交换速率进行加权,从而得出网络价值加权速率,依据这个速率进行结算既可以反映了每个网络对互联的贡献程度,又反映了在互联中对网络资源的被占用程度。  相似文献   
69.
This paper develops a mathematical model for project time compression problems in CPM/PERT type networks. It is noted this formulation of the problem will be an adequate approximation for solving the time compression problem with any continuous and non-increasing time-cost curve. The kind of this model is Mixed Integer Linear Program (MILP) with zero-one variables, and the Benders' decomposition procedure for analyzing this model has been developed. Then this paper proposes a new approach based on the surrogating method for solving these problems. In addition, the required computer programs have been prepared by the author to execute the algorithm. An illustrative example solved by the new algorithm, and two methods are compared by several numerical examples. Computational experience with these data shows the superiority of the new approach.  相似文献   
70.
The objective of this paper is to analyze under what well-known operations the class of quasipolyhedral convex functions, which can be regarded as an extension of that of polyhedral convex functions, is closed. The operations that will be considered are those that preserve polyhedral convexity, such that the image and the inverse image under linear transformations, right scalar multiplication (including the case where λ=0+) and pointwise addition.   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