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   538046篇
  免费   5796篇
  国内免费   1527篇
化学   289016篇
晶体学   7735篇
力学   23602篇
综合类   18篇
数学   62464篇
物理学   162534篇
  2021年   4397篇
  2020年   4918篇
  2019年   5285篇
  2018年   6798篇
  2017年   6657篇
  2016年   10355篇
  2015年   6544篇
  2014年   10044篇
  2013年   24393篇
  2012年   18711篇
  2011年   23104篇
  2010年   16142篇
  2009年   16024篇
  2008年   21161篇
  2007年   21123篇
  2006年   19680篇
  2005年   17715篇
  2004年   16300篇
  2003年   14310篇
  2002年   14224篇
  2001年   15986篇
  2000年   12147篇
  1999年   9501篇
  1998年   8024篇
  1997年   7704篇
  1996年   7414篇
  1995年   6691篇
  1994年   6646篇
  1993年   6365篇
  1992年   7167篇
  1991年   7268篇
  1990年   6897篇
  1989年   6730篇
  1988年   6754篇
  1987年   6595篇
  1986年   6241篇
  1985年   8070篇
  1984年   8305篇
  1983年   6683篇
  1982年   6882篇
  1981年   6758篇
  1980年   6315篇
  1979年   6847篇
  1978年   7073篇
  1977年   6867篇
  1976年   6863篇
  1975年   6417篇
  1974年   6459篇
  1973年   6397篇
  1972年   4493篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
The projection approach is applied to construct and investigate an operator-difference scheme for fluid dynamics in Lagrangean variables which has first-order local approximation in the axisymmetric case near the symmetry axis. The scheme also has operator properties that make it suitable for rederiving and substantiating previous results, methods, and algorithms.  相似文献   
133.
Journal of Nanoparticle Research - It was shown that the thermoelastic martensite transformation B2 ? B19 inside nanoparticles surrounded by amorphous matrix in Ni–Ti–Cu alloys as...  相似文献   
134.
135.
136.
The results of optical study and quantum-chemical simulation of a conjugated organic system, 2-cyclooctylamino-5-nitropyridine (COANP)-fullerene, performed to determine its potential for application as a limiter of visible and near-IR laser radiation and as a material for diffraction elements in systems for reversible recording of optical information, are presented. Complexation between a COANP molecule and fullerene is considered as one of the main mechanisms responsible for the corresponding properties of this system. For the first time, nonlinear optical characteristics of COANP-C60 and COANP-C70 systems are comparatively studied and the intermolecular interaction between a COANP molecule and fullerene is analyzed on the quantum-chemical level.  相似文献   
137.
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed.  相似文献   
138.
We prove new theorems on the justification of the averaging method for multifrequency oscillation systems with pulse influence at fixed times.  相似文献   
139.
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree.  相似文献   
140.
A precession mechanism of spin relaxation of conduction electrons in a square quantum well is analyzed. The dependence of the spin relaxation time on the width of a quantum well and the height of its barriers is calculated under the assumption that the electron-electron collisions dominate over other processes of carrier scattering.  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