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   554141篇
  免费   6107篇
  国内免费   1424篇
化学   290787篇
晶体学   8202篇
力学   26097篇
综合类   20篇
数学   66893篇
物理学   169673篇
  2021年   4861篇
  2020年   5314篇
  2019年   5936篇
  2018年   7952篇
  2017年   7960篇
  2016年   11404篇
  2015年   6700篇
  2014年   10824篇
  2013年   24787篇
  2012年   19192篇
  2011年   23408篇
  2010年   17083篇
  2009年   17085篇
  2008年   21728篇
  2007年   21567篇
  2006年   19892篇
  2005年   17754篇
  2004年   16573篇
  2003年   14699篇
  2002年   14707篇
  2001年   16624篇
  2000年   12518篇
  1999年   9812篇
  1998年   8295篇
  1997年   7945篇
  1996年   7613篇
  1995年   6892篇
  1994年   6802篇
  1993年   6632篇
  1992年   7199篇
  1991年   7539篇
  1990年   7194篇
  1989年   7077篇
  1988年   6974篇
  1987年   6863篇
  1986年   6520篇
  1985年   8410篇
  1984年   8498篇
  1983年   6866篇
  1982年   7022篇
  1981年   6912篇
  1980年   6394篇
  1979年   6994篇
  1978年   7226篇
  1977年   7219篇
  1976年   7232篇
  1975年   6664篇
  1974年   6631篇
  1973年   6758篇
  1972年   4942篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust.  相似文献   
902.
Journal of Statistical Physics - We study high-energy asymptotics of the steady velocity distributions for model kinetic equations describing various regimes in dilute granular flows. The main...  相似文献   
903.
The kinetics of formation and relaxation of transient holographic gratings recorded in a system of saturable three-level centers is studied. Distortions in the shape of the profile of recorded and decaying structures of population and of the refractive index are taken into account. The analysis of the time dependences of diffraction efficiencies of different orders is performed for phase (thermal) and amplitude (concentration) gratings.  相似文献   
904.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
905.
906.
In this paper we analyze the bottom of the energy-momentum spectrum of the translation invariant Nelson model, describing one electron linearly coupled to a second quantized massive scalar field. Our results are valid for all values of the coupling constant and include an HVZ theorem, non-degeneracy of ground states, existence of isolated groundstates in dimensions 1 and 2, non-existence of ground states embedded in the bottom of the essential spectrum in dimensions 3 and 4, (i.e., at total momenta where no isolated groundstate eigenvalue exists), and we study regularity and monotonicity properties of the bottom of the essential spectrum, as a function of total momentum. Communicated by Joel Feldman submitted 04/11/04, accepted 17/02/05  相似文献   
907.
908.
The structure of bis-(2,3-pentamethylene-3,4-dihydro-4-oxoquinazolinium) tetrachlorocuprate (II) sesquihydrate, (C13H15N2O)2[CuCl4]·1.5H2O, was determined by single crystal X-ray diffraction. In contrast to the previously studied analogs, the compound contains crystallization water molecules.Original Russian Text Copyright © 2004 by K. K. Turgunov, B. Tashkhodzhaev, L. V. Molchanov, and Kh. M. Shakhidoyatov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 955–959, September–October, 2004.  相似文献   
909.
Lígia M. Rodrigues 《Tetrahedron》2004,60(40):8929-8936
Tetrapeptides containing one of a set of four different α,α-dialkyl glycines at the C-terminus were synthesized by conventional methods in solution and their conformational behavior investigated by 1H NMR spectroscopy in connection with molecular mechanics calculations. The results were consistent with conformations stabilized by a γ-turn in the case of compounds with alkyl groups larger than methyl, while the corresponding Aib derivative did not exhibit intramolecular hydrogen bonding.  相似文献   
910.
Using radical chemistry novel highly condensed heterocycles have been synthesized. The mechanism for their formation 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