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   54499篇
  免费   2253篇
  国内免费   73篇
化学   33457篇
晶体学   250篇
力学   1690篇
数学   8209篇
物理学   10807篇
无线电   2412篇
  2023年   437篇
  2022年   340篇
  2021年   613篇
  2020年   731篇
  2019年   690篇
  2018年   1172篇
  2017年   949篇
  2016年   1705篇
  2015年   1528篇
  2014年   1565篇
  2013年   3206篇
  2012年   3732篇
  2011年   3805篇
  2010年   2326篇
  2009年   1955篇
  2008年   3234篇
  2007年   3259篇
  2006年   2840篇
  2005年   2760篇
  2004年   2359篇
  2003年   1917篇
  2002年   1664篇
  2001年   998篇
  2000年   847篇
  1999年   597篇
  1998年   462篇
  1997年   430篇
  1996年   522篇
  1995年   343篇
  1994年   404篇
  1993年   384篇
  1992年   415篇
  1991年   369篇
  1990年   350篇
  1989年   336篇
  1988年   276篇
  1987年   285篇
  1986年   255篇
  1985年   423篇
  1984年   387篇
  1983年   275篇
  1982年   361篇
  1981年   351篇
  1980年   303篇
  1979年   287篇
  1978年   275篇
  1976年   288篇
  1975年   262篇
  1974年   283篇
  1973年   270篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
This paper attempts to develop a theory of sufficiency in the setting of non-commutative algebras parallel to the ideas in classical mathematical statistics. Sufficiency of a coarse-graining means that all information is extracted about the mutual relation of a given family of states. In the paper sufficient coarse-grainings are characterized in several equivalent ways and the non-commutative analogue of the factorization theorem is obtained. As an application we discuss exponential families. Our factorization theorem also implies two further important results, previously known only in finite Hilbert space dimension, but proved here in generality: the Koashi-Imoto theorem on maps leaving a family of states invariant, and the characterization of the general form of states in the equality case of strong subadditivity. Supported by the EU Research Training Network Quantum Probability with Applications to Physics, Information Theory and Biology and Center of Excellence SAS Physics of Information I/2/2005. Supported by the Hungarian grant OTKA T032662  相似文献   
62.
We give an upper bound on the growth rate of the Schrödinger group on Zhidkov spaces. In dimension 1, we prove that this bound is sharp. To cite this article: C. Gallo, C. R. Acad. Sci. Paris, Ser. I 342 (2006).  相似文献   
63.
64.
We study the asymptotic properties of the Bayes estimator in models differentiable in quadratic mean (DQM) in the case of independent and identically distributed observations. The goal is to define weak assumptions on the model under which this estimator is asymptotically efficient, regular, and asymptotically of minimal risk. The results of the paper are applied to models based on a mixture distribution, the Cauchy distribution with location and scale parameter, and the Weibull distribution. Bibliography: 10 titles. Published in Zapiski Nauchnykh Seminarov POMI, Vol. 328, 2005, pp. 114–146.  相似文献   
65.
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters.  相似文献   
66.
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform.  相似文献   
67.
68.
In this Note, we study a 2×2 system of evolution equations with some codimension 3 crossing. We derive two conditions of non-degeneracy. We focus on one of them and reduce our system to some Landau–Zener's type system. Using this reduction, we describe the energy transfer at the crossing by Landau–Zener formula for 2-scales semi-classical measures. To cite this article: C. Fermanian Kammerer, P. Gérard, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 915–920.  相似文献   
69.
70.
Regioselective demethylation of 3,4-dihydropapaveraldine (2a) at 7 and 3' positions affords a properly substituted diphenolic key intermidiate (2d) for the synthesis of reticuline and N-norreticuline.  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