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   337997篇
  免费   2732篇
  国内免费   1001篇
化学   184582篇
晶体学   5288篇
力学   13882篇
综合类   9篇
数学   35656篇
物理学   102313篇
  2021年   2599篇
  2020年   2924篇
  2019年   3293篇
  2018年   4427篇
  2017年   4387篇
  2016年   6292篇
  2015年   3691篇
  2014年   5754篇
  2013年   14403篇
  2012年   10925篇
  2011年   13327篇
  2010年   9516篇
  2009年   9446篇
  2008年   12797篇
  2007年   12745篇
  2006年   12077篇
  2005年   10981篇
  2004年   9813篇
  2003年   9021篇
  2002年   8745篇
  2001年   10570篇
  2000年   8011篇
  1999年   6098篇
  1998年   4812篇
  1997年   4916篇
  1996年   4579篇
  1995年   3961篇
  1994年   4051篇
  1993年   3875篇
  1992年   4494篇
  1991年   4599篇
  1990年   4408篇
  1989年   4304篇
  1988年   4224篇
  1987年   4237篇
  1986年   3967篇
  1985年   5090篇
  1984年   5252篇
  1983年   4205篇
  1982年   4439篇
  1981年   4170篇
  1980年   3960篇
  1979年   4410篇
  1978年   4620篇
  1977年   4571篇
  1976年   4529篇
  1975年   4271篇
  1974年   4248篇
  1973年   4381篇
  1972年   2946篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Optics and Spectroscopy - The fluorescence of the nematic liquid crystal n-butyl-n′-methoxyazoxybenzene (BMAOB) in the form of a layer and in porous glasses with pores of different diameter...  相似文献   
92.
We construct commuting rank 2 formally self-adjoint ordinary differential operators corresponding to a curve of genus 2.  相似文献   
93.
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   
94.
A new quasi-hydrodynamic algorithm is proposed for numerical analysis of convective flows in the presence of a homogeneous external magnetic field. The Marangoni convection problem in a square cross-section cavity is solved.  相似文献   
95.
An invariant of a closed set that is equal to the sum of roots is introduced. For a closed subset in a root system, we describe symmetric and special parts and its stabilizer in the Weyl group by means of the sum of roots. We determine associated bases with respect to which the closed set has the simplest form. All possible values of the root sum are found. Bibliography: 9 titles.  相似文献   
96.
The integration procedure based on the generalized Darboux transform is suggested for the Ishimori magnet model. Exact solutions are constructed for the model on the background of spiral structures. The possibility of phase transition in the system is hypothesized.  相似文献   
97.
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   
98.
The kinetics of decay of a phase hologram in a semiconductor CdF2 crystal with bistable In centers is studied. Kinetic constants of the hologram decay are found, and the potential relief of the bistable center is plotted. The resolving power of the crystal is evaluated and recording of a transparency is demonstrated.  相似文献   
99.
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   
100.
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   
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