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   23498篇
  免费   849篇
  国内免费   410篇
化学   5966篇
晶体学   299篇
力学   635篇
综合类   51篇
数学   9511篇
物理学   8295篇
  2023年   100篇
  2022年   167篇
  2021年   118篇
  2020年   165篇
  2019年   495篇
  2018年   318篇
  2017年   305篇
  2016年   192篇
  2015年   175篇
  2014年   229篇
  2013年   1041篇
  2012年   491篇
  2011年   1023篇
  2010年   549篇
  2009年   844篇
  2008年   960篇
  2007年   957篇
  2006年   925篇
  2005年   631篇
  2004年   1020篇
  2003年   1162篇
  2002年   1754篇
  2001年   1775篇
  2000年   1630篇
  1999年   1786篇
  1998年   1531篇
  1997年   914篇
  1996年   455篇
  1995年   239篇
  1994年   203篇
  1993年   87篇
  1992年   89篇
  1991年   72篇
  1990年   162篇
  1989年   146篇
  1988年   97篇
  1987年   81篇
  1986年   126篇
  1985年   190篇
  1984年   175篇
  1983年   74篇
  1982年   137篇
  1981年   237篇
  1980年   230篇
  1979年   106篇
  1978年   168篇
  1977年   103篇
  1976年   71篇
  1975年   80篇
  1974年   74篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
31.
32.
Let K and S be locally compact Hausdorff spaces and let X be a strictly convex Banach space of finite dimension at least 2. In this paper, we prove that if there exists an isomorphism T from onto satisfying then K and S are homeomorphic. Here denotes the Schäffer constant of X. Even for the classical cases , and , this result is the X‐valued Banach–Stone theorem via isomorphism with the largest distortion that is known so far, namely . On the other hand, it is well known that this result is not true for , even though K and S are compact Hausdorff spaces.  相似文献   
33.
In this article, we study for the ‐realization of the vector‐valued Schrödinger operator . Using a noncommutative version of the Dore–Venni theorem due to Monniaux and Prüss, we prove that the ‐realization of , defined on the intersection of the natural domains of the differential and multiplication operators which form , generates a strongly continuous contraction semigroup on . We also study additional properties of the semigroup such as extension to L1, positivity, ultracontractivity and prove that the generator has compact resolvent.  相似文献   
34.
We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ).  相似文献   
35.
We consider systems of stochastic differential equations of the form d X t i = j = 1 d A i j ( X t ? ) d Z t j for i = 1 , ? , d with continuous, bounded and non‐degenerate coefficients. Here Z t 1 , ? , Z t d are independent one‐dimensional stable processes with α 1 , ? , α d ( 0 , 2 ) . In this article we research on uniqueness of weak solutions to such systems by studying the corresponding martingale problem. We prove the uniqueness of weak solutions in the case of diagonal coefficient matrices.  相似文献   
36.
We study a dynamic free-entry oligopoly with sluggish entry and exit of firms under general demand and cost functions. We show that the number of firms in a steady-state open-loop solution for a dynamic free-entry oligopoly is smaller than that at static equilibrium and that the number of firms in a steady-state memoryless closed-loop solution is larger than that in an open-loop solution.  相似文献   
37.
Let Fq be a finite field and n a positive integer. In this paper, we find a new combinatorial method to determine weight enumerators of reducible cyclic codes and their dual codes of length n over Fq, which just generalize results of Zhu et al. (2015); especially, we also give the weight enumerator of a cyclic code, which is viewed as a partial Melas code. Furthermore, weight enumerators obtained in this paper are all in the form of power of a polynomial.  相似文献   
38.
39.
Explicit and partly sharp estimates are given of integrals over the square of Bessel functions with an integrable weight which can be singular at the origin. They are uniform with respect to the order of the Bessel functions and provide explicit bounds for some smoothing estimates as well as for the L2 restrictions of Fourier transforms onto spheres in which are independent of the radius of the sphere. For more special weights these restrictions are shown to be Hölder continuous with a Hölder constant having this independence as well. To illustrate the use of these results a uniform resolvent estimate of the free Dirac operator with mass in dimensions is derived.  相似文献   
40.
Jordan operator algebras are norm‐closed spaces of operators on a Hilbert space with for all . In two recent papers by the authors and Neal, a theory for these spaces was developed. It was shown there that much of the theory of associative operator algebras, in particular, surprisingly much of the associative theory from several recent papers of the first author and coauthors, generalizes to Jordan operator algebras. In the present paper we complete this task, giving several results which generalize the associative case in these papers, relating to unitizations, real positivity, hereditary subalgebras, and a couple of other topics. We also solve one of the three open problems stated at the end of our earlier joint paper on Jordan operator algebras.  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