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   24900篇
  免费   3177篇
  国内免费   2443篇
化学   4279篇
晶体学   78篇
力学   2015篇
综合类   523篇
数学   13874篇
物理学   9751篇
  2024年   38篇
  2023年   222篇
  2022年   460篇
  2021年   502篇
  2020年   584篇
  2019年   570篇
  2018年   580篇
  2017年   720篇
  2016年   809篇
  2015年   674篇
  2014年   1250篇
  2013年   1662篇
  2012年   1317篇
  2011年   1613篇
  2010年   1414篇
  2009年   1731篇
  2008年   1632篇
  2007年   1744篇
  2006年   1589篇
  2005年   1455篇
  2004年   1235篇
  2003年   1154篇
  2002年   1005篇
  2001年   890篇
  2000年   852篇
  1999年   722篇
  1998年   663篇
  1997年   557篇
  1996年   411篇
  1995年   351篇
  1994年   289篇
  1993年   228篇
  1992年   198篇
  1991年   159篇
  1990年   164篇
  1989年   117篇
  1988年   113篇
  1987年   90篇
  1986年   94篇
  1985年   98篇
  1984年   83篇
  1983年   52篇
  1982年   71篇
  1981年   71篇
  1980年   48篇
  1979年   42篇
  1978年   39篇
  1977年   35篇
  1976年   35篇
  1973年   23篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
This paper proves a result that if two entire functions f(z) and g(z) share four small functions aj(z) (j = 1,2,3,4) in the sense of Ek)(aj, f) = Ek)(aj,g), (j = 1,2,3,4) (k ≥ 11), then there exists f(z) = g(z).  相似文献   
112.
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions.  相似文献   
113.
In this paper, the author gives a characterization of atomic Hardy spaces associated to Schrodinger operators by using area functions, and hence gets the dual spaces of atomic Hardy spaces.  相似文献   
114.
Let X and Y be Banach spaces and ψ a continuous convex function on the unit interval [0,1] satisfying certain conditions. Let XψY be the direct sum of X and Y equipped with the associated norm with ψ. We show that XψY is uniformly convex if and only if X,Y are uniformly convex and ψ is strictly convex. As a corollary we obtain that the ?p,q-direct sum (not p=q=1 nor ∞), is uniformly convex if and only if X,Y are, where ?p,q is the Lorentz sequence space. These results extend the well-known fact for the ?p-sum . Some other examples are also presented.  相似文献   
115.
We prove some weighted estimates for certain Littlewood-Paley operators on the weighted Hardy spaces Hwp (0<p?1) and on the weighted Lp spaces. We also prove some weighted estimates for the Bochner-Riesz operators and the spherical means.  相似文献   
116.
Let Ω be a smoothly bounded pseudoconvex domain in and let be a point of finite type. We also assume that the Levi form of bΩ is comparable in a neighborhood of z0. Then we get a quantity which bounds from above and below the Bergman kernel function in a small constant and large constant sense.  相似文献   
117.
A covariant generalisation of Wigner function proposed by us some years ago is reviewed, and its remarkable and useful properties are elucidated; its being a natural solution to a relativistically covariant Liouville equation is also demonstrated.  相似文献   
118.
A result of Balas and Yu (1989) states that the number of maximal independent sets of a graph G is at most p+1, where is the number of pairs of vertices in G at distance 2, and p is the cardinality of a maximum induced matching in G. In this paper, we give an analogue of this result for hypergraphs and, more generally, for subsets of vectors in the product of n lattices =1××n, where the notion of an induced matching in G is replaced by a certain binary tree each internal node of which is mapped into . We show that our bounds may be nearly sharp for arbitrarily large hypergraphs and lattices. As an application, we prove that the number of maximal infeasible vectors x=1××n for a system of polymatroid inequalities does not exceed max{Q,logt/c(2Q,)}, where is the number of minimal feasible vectors for the system, , , and c(,) is the unique positive root of the equation 2c(c/log–1)=1. This bound is nearly sharp for the Boolean case ={0,1}n, and it allows for the efficient generation of all minimal feasible sets to a given system of polymatroid inequalities with quasi-polynomially bounded right-hand sides . This research was supported by the National Science Foundation (Grant IIS-0118635), and by the Office of Naval Research (Grant N00014-92-J-1375). The second and third authors are also grateful for the partial support by DIMACS, the National Science Foundation's Center for Discrete Mathematics and Theoretical Computer Science.Mathematics Subject Classification (2000):20E28, 20G40, 20C20  相似文献   
119.
An essential bounded function ? gives a continuous linear functional on the Hardy space H1 on the bitorus. In this paper, we consider extremal problems on H1 when ? is a rational function, ? is a product of one variable functions or ? = |f|/f for some outer function f in H1 such that f(z, w) has a good property with respect to w for a.e. z. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
120.
Let X 1 ,...,X n be a random sample drawn from distribution function F(x) with density function f(x) and suppose we want to estimate X(x). It is already shown that kernel estimator of F(x) is better than usual empirical distribution function in the sense of mean integrated squared error. In this paper we derive integrated squared error of kernel estimator and compare the error with that of the empirical distribution function. It is shown that the superiority of kernel estimators is not necessarily true in the sense of integrated squared error.  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