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   3145篇
  免费   269篇
  国内免费   335篇
化学   324篇
晶体学   2篇
力学   321篇
综合类   117篇
数学   2372篇
物理学   613篇
  2024年   6篇
  2023年   15篇
  2022年   44篇
  2021年   40篇
  2020年   62篇
  2019年   43篇
  2018年   59篇
  2017年   74篇
  2016年   102篇
  2015年   66篇
  2014年   129篇
  2013年   196篇
  2012年   176篇
  2011年   210篇
  2010年   190篇
  2009年   227篇
  2008年   223篇
  2007年   243篇
  2006年   216篇
  2005年   179篇
  2004年   150篇
  2003年   159篇
  2002年   120篇
  2001年   115篇
  2000年   93篇
  1999年   95篇
  1998年   100篇
  1997年   75篇
  1996年   62篇
  1995年   34篇
  1994年   37篇
  1993年   32篇
  1992年   33篇
  1991年   21篇
  1990年   10篇
  1989年   13篇
  1988年   10篇
  1987年   6篇
  1986年   9篇
  1985年   12篇
  1984年   9篇
  1983年   8篇
  1982年   12篇
  1981年   9篇
  1980年   10篇
  1979年   3篇
  1978年   3篇
  1977年   4篇
  1971年   1篇
  1936年   2篇
排序方式: 共有3749条查询结果,搜索用时 15 毫秒
61.
A problem in extremal quasiconformal extensions   总被引:2,自引:0,他引:2  
A constantK 0 (m) (h) is introduced for every quasisymmetric mappingh of the unit circle and every integerm≥4 which contains the constantK 0(h) (indicated by the change in module of the quadrilaterals with vertices on the circle) as a special case. A necessary and sufficient condition is established forK 0 (m) (h) =K 1(h). It is shown that there are infinitely many quasisymmetric mappings of the unit circle having the property thatK 0 (m) (h)<K 1(h), wherek 1(h) is the maximal dilatation ofh.  相似文献   
62.
63.
In this paper, we introduce and study a new system of nonlinear A-monotone multivalued variational inclusions in Hilbert spaces. By using the concept and properties of A-monotone mappings, and the resolvent operator technique associated with A-monotone mappings due to Verma, we construct a new iterative algorithm for solving this system of nonlinear multivalued variational inclusions associated with A-monotone mappings in Hilbert spaces. We also prove the existence of solutions for the nonlinear multivalued variational inclusions and the convergence of iterative sequences generated by the algorithm. Our results improve and generalize many known corresponding results.  相似文献   
64.
Aromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc.  相似文献   
65.
设T是m-增生算子,I是恒等映射.本文通过一个反例说明(T+λI)-1(λ>0)不一定是非扩张映射.  相似文献   
66.
A multiparameter boundary-value problem of fresh infiltration water seepage in a drained fringe above quiescent saline water is solved in the direct statement and studied in detail.  相似文献   
67.
研究函数族的正规性定则是复变函数论中的一个重要且有意义的工作.引进多元K-拟全纯函数的定义,并给出了多元K-拟全纯函数族的一个正规定则.  相似文献   
68.
Summary Some stability and convergence theorems of the modified Ishikawa iterative sequences with errors for asymptotically nonexpansive mapping in the intermediate sense and asymptotically pseudo contractive and uniformly Lipschitzian mappings in Banach spaces are obtained.  相似文献   
69.
We have been developing a new analytical transmission electron microscope (TEM), called a coincidence TEM, which in principle enables elemental mapping images to be observed at a high signal‐to‐noise (S/N) ratio under very low dose radiation conditions. In this paper, we report the development of a coincidence TEM with a digital waveform measuring system for obtaining a coincidence elemental mapping image. In this system, analog signals detected by a Si(Li) detector and a multianode, position‐sensitive photomultiplier (PSPM) are continuously converted into 12‐bit digital waveform data at a rate of 100 MHz, and transferred to a PC. From the transferred digital waveform data, information on X‐ray photon energy, electron incident position, and detection times of both X rays and electrons are calculated by digital waveform measurement, which lead to the observation of a successful coincidence elemental mapping image. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
70.
Various definitions of directional derivatives in topological vector spaces are compared. Directional derivatives in the sense of Gâteaux, Fréchet, and Hadamard are singled out from the general framework of -directional differentiability. It is pointed out that, in the case of finite-dimensional spaces and locally Lipschitz mappings, all these concepts of directional differentiability are equivalent. The chain rule for directional derivatives of a composite mapping is discussed.  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