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   390742篇
  免费   2268篇
  国内免费   554篇
化学   182457篇
晶体学   5843篇
力学   22387篇
综合类   9篇
数学   56065篇
物理学   126803篇
  2020年   4162篇
  2019年   5055篇
  2018年   7448篇
  2017年   7610篇
  2016年   9529篇
  2015年   4427篇
  2014年   8436篇
  2013年   15848篇
  2012年   12898篇
  2011年   15125篇
  2010年   12612篇
  2009年   12806篇
  2008年   14587篇
  2007年   14379篇
  2006年   12883篇
  2005年   11205篇
  2004年   10841篇
  2003年   10027篇
  2002年   10335篇
  2001年   10476篇
  2000年   8117篇
  1999年   6190篇
  1998年   5689篇
  1997年   5480篇
  1996年   5010篇
  1995年   4464篇
  1994年   4505篇
  1993年   4507篇
  1992年   4586篇
  1991年   5074篇
  1990年   4999篇
  1989年   5048篇
  1988年   4695篇
  1987年   4773篇
  1986年   4461篇
  1985年   5353篇
  1984年   5548篇
  1983年   4724篇
  1982年   4972篇
  1981年   4633篇
  1980年   4286篇
  1979年   4924篇
  1978年   5103篇
  1977年   5296篇
  1976年   5450篇
  1975年   5057篇
  1974年   4887篇
  1973年   5132篇
  1972年   4303篇
  1971年   3944篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy.  相似文献   
142.
The simple relation between representations of the covering groups of SL2 and GL2 makes it possible to fuse and extend the recent metaplectic results of Shimura, Waldspurger, Flicker, and ourselves. By giving a new (purely local andL-function theoretic) treatment of the Waldspurger-Shintani correspondence, we also simplify some of Waldspurger’s original results.  相似文献   
143.
Estimates of a rate of convergence of orderO(n –1) are obtained for integral functionals of an empirical process.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 10–16, 1987.  相似文献   
144.
Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 84–92.  相似文献   
145.
A mixed boundary-value problem for the nonlinear Schrödinger equation and its generalization is studied by the method used for the inverse scattering problem. A connection is established between conservation laws and boundary conditions in integrable boundary-value problems for higher nonlinear Schrödinger equations. It is shown that the generalized boundary-value problem requires a joint consideration of regular and singular solutions for the nonlinear Schrödinger equation with repulsion.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 169, pp. 151–165, 1988.  相似文献   
146.
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented.  相似文献   
147.
148.
149.
150.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers.  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