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   7425篇
  免费   584篇
  国内免费   743篇
化学   823篇
晶体学   6篇
力学   517篇
综合类   163篇
数学   6596篇
物理学   647篇
  2024年   9篇
  2023年   82篇
  2022年   122篇
  2021年   147篇
  2020年   176篇
  2019年   184篇
  2018年   178篇
  2017年   206篇
  2016年   217篇
  2015年   164篇
  2014年   308篇
  2013年   521篇
  2012年   321篇
  2011年   395篇
  2010年   356篇
  2009年   474篇
  2008年   475篇
  2007年   469篇
  2006年   470篇
  2005年   392篇
  2004年   328篇
  2003年   385篇
  2002年   350篇
  2001年   295篇
  2000年   266篇
  1999年   239篇
  1998年   246篇
  1997年   225篇
  1996年   142篇
  1995年   108篇
  1994年   79篇
  1993年   67篇
  1992年   52篇
  1991年   38篇
  1990年   28篇
  1989年   17篇
  1988年   15篇
  1987年   19篇
  1986年   13篇
  1985年   28篇
  1984年   33篇
  1983年   13篇
  1982年   26篇
  1981年   22篇
  1980年   25篇
  1979年   7篇
  1978年   7篇
  1977年   3篇
  1976年   5篇
  1974年   3篇
排序方式: 共有8752条查询结果,搜索用时 15 毫秒
61.
丁承杰  刘文安 《数学季刊》1992,7(4):106-110
In this paper,we research general Defective Cion Problem under the model S,i.e,the number d of Defective cions is not fixed. For d=O,1,or 2. we get some good results.  相似文献   
62.
本文综合应用因素空间、信息系统和重于关系的方法,讨论了概念的内涵表示及其他有关问题。特别是,对在描述概念问题中不同于内涵和外延的第三种方法,即典型示范表示做了进一步的分析。  相似文献   
63.
In this article, the inverse problem of the differential inclusion theory is studied. For a given ε>0 and a continuous set valued map tW(t), t∈[t0,θ], where W(t)⊂Rn is compact and convex for every t∈[t0,θ], it is required to define differential inclusion so that the Hausdorff distance between the attainable set of the differential inclusion at the time moment t with initial set (t0,W(t0)) and W(t) would be less than ε for every t∈[t0,θ].  相似文献   
64.
Existence of positive solutions for the nonlinear fractional differential equation Dsu(x)=f(x,u(x)), 0<s<1, has been studied (S. Zhang, J. Math. Anal. Appl. 252 (2000) 804-812), where Ds denotes Riemann-Liouville fractional derivative. In the present work we study existence of positive solutions in case of the nonlinear fractional differential equation:
L(D)u=f(x,u),u(0)=0,0<x<1,  相似文献   
65.
Let be a polynomial of degree . Assume that the set there is a sequence s.t. and is finite. We prove that the set of generalized critical values of (hence in particular the set of bifurcation points of ) has at most points. Moreover, We also compute the set effectively.

  相似文献   

66.
We show that there is a continuous map of the unit interval into itself of type which has a trajectory disjoint from the set of recurrent points of , but contained in the closure of . In particular, is not closed. A function of type , with nonclosed set of recurrent points, was found by H. Chu and J. Xiong [Proc. Amer. Math. Soc. 97 (1986), 361-366]. However, there is no trajectory contained in , since any point in is eventually mapped into . Moreover, our construction is simpler.

We use to show that there is a continuous map of the interval of type for which the set of recurrent points is not an set. This example disproves a conjecture of A. N. Sharkovsky et al., from 1989. We also provide another application of .

  相似文献   

67.
Let be domains in . Under very mild conditions on we show that there exist holomorphic functions , defined on with the property that is nowhere extendible across , while the graph of over is not complete pluripolar in . This refutes a conjecture of Levenberg, Martin and Poletsky (1992).

  相似文献   

68.
In this article we prove a strong law of large numbers for Borel measurable nonseparably valued random elements in the case of generalized random sets.

  相似文献   

69.
For a coanalytic-complete or -complete subspace of a Polish space we prove that there exists a continuous bijection of onto the Hilbert cube . This extends results of Pytkeev. As an application of our main theorem we give an answer to some questions of Arkhangelskii and Christensen.

Under the assumption of Projective Determinacy we also give some generalizations of these results to higher projective classes.

  相似文献   

70.
We consider the hyperbolic Hardy class , . It consists of holomorphic in the unit complex ball for which and


where denotes the hyperbolic distance of the unit disc. The hyperbolic version of the Littlewood-Paley type -function and the area function are defined in terms of the invariant gradient of , and membership of is expressed by the property of the functions. As an application, we can characterize the boundedness and the compactness of the composition operator , defined by , from the Bloch space into the Hardy space .

  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