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   9944篇
  免费   982篇
  国内免费   753篇
化学   2014篇
晶体学   119篇
力学   906篇
综合类   227篇
数学   5971篇
物理学   2442篇
  2024年   117篇
  2023年   135篇
  2022年   231篇
  2021年   243篇
  2020年   282篇
  2019年   303篇
  2018年   296篇
  2017年   385篇
  2016年   419篇
  2015年   295篇
  2014年   561篇
  2013年   770篇
  2012年   537篇
  2011年   597篇
  2010年   485篇
  2009年   537篇
  2008年   581篇
  2007年   579篇
  2006年   508篇
  2005年   483篇
  2004年   411篇
  2003年   336篇
  2002年   371篇
  2001年   315篇
  2000年   294篇
  1999年   258篇
  1998年   227篇
  1997年   208篇
  1996年   148篇
  1995年   111篇
  1994年   90篇
  1993年   70篇
  1992年   45篇
  1991年   65篇
  1990年   35篇
  1989年   41篇
  1988年   36篇
  1987年   30篇
  1986年   22篇
  1985年   38篇
  1984年   32篇
  1983年   15篇
  1982年   25篇
  1981年   23篇
  1980年   17篇
  1979年   23篇
  1978年   15篇
  1977年   6篇
  1976年   7篇
  1959年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
对带端面负载的半无限带状各向异性弹性材料建立了Saint-Venant原理.应用能量方法确立了应力效应衰减率的下界,得出了用各向异性材料的弹性常量表示的估计显式.最后,为了说明所得结果,对带端面负载、纤维偏离主轴的石墨-环氧树脂的衰减率给出数值实例.  相似文献   
982.
The main theme of this paper is to consider a notion of 'approximately unital operator systems' including both C*-algebras and unital operator systems.The goals are to prove a version of the Choi-Effros theorem for these systems,to introduce a functorial process for forming an approximately unital operator systems from a given matrix ordered vector space with a proper approximate order unit,to study second duals of these objects and to prove that a C*-algebra can be characterized as an approximately unital ...  相似文献   
983.
利用分析中的解析函数方法和代数中的矩阵方法,得到了m阶常系数齐次线性递推数列通项公式的解析表达式,是对已有结果的完善和推广.  相似文献   
984.
For testing “univariate” binomial proportions, it has been proven that, under mild conditions, there exist group sequential designs which satisfy the pre-specified Type I error and power of the single-stage design while the sample size is bounded above by that of the single-stage design (Kepner and Chang, 2003). In this article, we extend this result and prove the existence of such group sequential designs for various decision rules in the space of bivariate binomial variables. We also demonstrate how to obtain the actual group sequential designs for detecting changes in bivariate binomial variables.  相似文献   
985.
In this paper, we present an application of some known generalizations of the Exp‐function method to the fifth‐order Burgers and to the seventh‐order Korteweg de Vries equations for the first time. The two examples show that the Exp‐function method can be an effective alternative tool for explicitly constructing rational and multi‐wave solutions with arbitrary parameters to higher order nonlinear evolution equations. Being straightforward and concise, as pointed out previously, this procedure does not require the bilinear representation of the equation considered. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
986.
Cauchy problems for a second order linear differential operator equation
in a Hilbert space H are studied. Equations of this kind arise for example in elasticity and hydrodynamics. It is assumed that A 0 is a uniformly positive operator and that A 0−1/2 DA 0−1/2 is a bounded accretive operator in H. The location of the spectrum of the corresponding semigroup generator is described and sufficient conditions for analyticity are given.  相似文献   
987.
In the present paper we provide a broad survey of the regularity theory for non-differentiable higher order parabolic systems of the type
Initially, we prove a partial regularity result with the method of A-polycaloric approximation, which is a parabolic analogue of the harmonic approximation lemma of De Giorgi. Moreover, we prove better estimates for the maximal parabolic Hausdorff-dimension of the singular set of weak solutions, using fractional parabolic Sobolev spaces. Thereby, we also consider different situations, which yield a better dimension reduction result, including the low dimensional case and coefficients A(z, D m u), independent of the lower order derivatives of u.   相似文献   
988.
In this paper, based on C3 quartic splines, a semi-discretization method containing two schemes is constructed to solve one-space-dimensional linear hyperbolic equations. It is shown that both schemes are unconditionally stable and their approximation orders are of O(k5+h4) and of O(k7+h4) with k and h being step sizes in time and space, respectively, which are much higher than those of other published schemes. A numerical example is presented and the results are compared with other published numerical results.  相似文献   
989.
990.
Satisfiability problems are of importance for many practical problems. They are NP-complete problems. However, some instances of the SAT problem can be solved efficiently. This paper reports on a study concerning the behaviour of a variety of algorithmic approaches to this problem tested on a set of problems collected at FAW. The results obtained give a lot of insight into the algorithms and problems, yet also show some general technical and methodological problems associated with such comparisons.  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