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   2373篇
  免费   317篇
  国内免费   787篇
化学   5篇
力学   90篇
综合类   3篇
数学   3303篇
物理学   76篇
  2017年   19篇
  2016年   15篇
  2015年   25篇
  2014年   45篇
  2013年   78篇
  2012年   93篇
  2011年   138篇
  2010年   99篇
  2009年   71篇
  2008年   82篇
  2007年   221篇
  2006年   268篇
  2005年   243篇
  2004年   193篇
  2003年   185篇
  2002年   163篇
  2001年   151篇
  2000年   155篇
  1999年   129篇
  1998年   93篇
  1997年   88篇
  1996年   97篇
  1995年   104篇
  1994年   83篇
  1993年   81篇
  1992年   57篇
  1991年   35篇
  1990年   18篇
  1989年   19篇
  1988年   15篇
  1986年   10篇
  1985年   11篇
  1978年   13篇
  1977年   11篇
  1976年   10篇
  1975年   11篇
  1972年   9篇
  1967年   31篇
  1966年   15篇
  1965年   30篇
  1964年   29篇
  1963年   13篇
  1962年   31篇
  1961年   15篇
  1960年   17篇
  1959年   19篇
  1958年   15篇
  1957年   9篇
  1955年   8篇
  1954年   8篇
排序方式: 共有3477条查询结果,搜索用时 14 毫秒
31.
In this paper,we are concerned with the existence of positive solutions to an m-point boundary value problem with p-Laplacian of nonlinear fractional differential equation.By means of Krasnosel'skii fixed-point theorem on a convex cone and Leggett-Williams fixed-point theorem,the existence results of solutions are obtained.  相似文献   
32.
An initial boundary value problem of semilinear nonlocal reaction diffusion equations is considered.Under some suitable conditions,using the asymptotic theory,the existence and asymptotic behavior of the interior layer solution to the initial boundary value problem are studied.  相似文献   
33.
This paper considers the synchronization of two coupled Hindmarsh-Rose neurons by a pacemaker.Based on the stability theory of differential equations,the complete synchronization of this pacemaker neuron model is reached.Moreover,we also show that pacemaker can enhance or induce synchronization.Numerical simulations are given to illustrate the main results.  相似文献   
34.
In this paper, we employ qualitative analysis and methods of bifurcation theory to study the maximum number of limit cycles for a polynomial system with center in global bifurcation.  相似文献   
35.
The existence of positive solutions to a singular sublinear semipositone Neumann boundary value problem is considered. In this paper,the nonlinearity term is not necessary to be bounded from below and the function q(t) is allowed to be singular at t = 0 and t = 1.  相似文献   
36.
In this paper, an SIR epidemic model with vaccination for both the newborns and susceptibles is investigated, where it is assumed that the vaccinated individuals have the temporary immunity. The basic reproduction number determining the extinction or persistence of the infection is found. By constructing a Lyapunov function, it is proved that the disease free equilibrium is globally stable when the basic reproduction number is less than or equal to one, and that the endemic equilibrium is globally stable wh...  相似文献   
37.
We prove a general archimedean positivstellensatz for hermitian operator-valued polynomials and show that it implies the multivariate Fejer-Riesz theorem of Dritschel-Rovnyak and positivstellensätze of Ambrozie-Vasilescu and Scherer-Hol. We also obtain several generalizations of these and related results. The proof of the main result depends on an extension of the abstract archimedean positivstellensatz for ?-algebras that is interesting in its own right.  相似文献   
38.
In this paper, we extend some results of D.Dolzan on finite rings to profinite rings, a complete classification of profinite commutative rings with a monothetic group of units is given. We also prove the metrizability of commutative profinite rings with monothetic group of units and without nonzero Boolean ideals. Using a property of Mersenne numbers, we construct a family of power 2ℵ0 commutative non-isomorphic profinite semiprimitive rings with monothetic group of units.  相似文献   
39.
In this paper we propose numerical treatment for singular integral equations. The methods are developed by means of the Sinc approximation with smoothing transformations. Such approximation is an effective technique against the singularities of the equations, and achieves exponential convergence. Therefore the methods improve conventional results where only polynomial convergence have been reported. The resulting algebraic system is solved by least squares approximation and leap frog algorithm. Estimation of errors of the approximate solution is presented. Some experimental tests are presented to show the efficient of the proposed methods.  相似文献   
40.
Let G be a finite group. The prime graph ??(G) of G is defined as follows. The vertices of ??(G) are the primes dividing the order of G and two distinct vertices p, p?? are joined by an edge if G has an element of order pp??. Let L=L n (2) or U n (2), where n?R17. We prove that L is quasirecognizable by prime graph, i.e. if G is a finite group such that ??(G)=??(L), then G has a unique nonabelian composition factor isomorphic to L. As a consequence of our result we give a new proof for the recognition by element orders of L n (2). Also we conclude that the simple group U n (2) is quasirecognizable by element orders.  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