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   217233篇
  免费   1577篇
  国内免费   638篇
化学   118954篇
晶体学   3287篇
力学   8410篇
综合类   6篇
数学   23730篇
物理学   65061篇
  2020年   1984篇
  2019年   2272篇
  2018年   3213篇
  2017年   3126篇
  2016年   4280篇
  2015年   2387篇
  2014年   3838篇
  2013年   9357篇
  2012年   6936篇
  2011年   8486篇
  2010年   6109篇
  2009年   5967篇
  2008年   8201篇
  2007年   8267篇
  2006年   7707篇
  2005年   7011篇
  2004年   6217篇
  2003年   5700篇
  2002年   5541篇
  2001年   5984篇
  2000年   4728篇
  1999年   3495篇
  1998年   3046篇
  1997年   3069篇
  1996年   2865篇
  1995年   2345篇
  1994年   2453篇
  1993年   2477篇
  1992年   2626篇
  1991年   2681篇
  1990年   2576篇
  1989年   2554篇
  1988年   2484篇
  1987年   2455篇
  1986年   2368篇
  1985年   3072篇
  1984年   3230篇
  1983年   2592篇
  1982年   2854篇
  1981年   2722篇
  1980年   2546篇
  1979年   2737篇
  1978年   2866篇
  1977年   2891篇
  1976年   2858篇
  1975年   2706篇
  1974年   2699篇
  1973年   2840篇
  1972年   1895篇
  1967年   1840篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
61.
We construct commuting rank 2 formally self-adjoint ordinary differential operators corresponding to a curve of genus 2.  相似文献   
62.
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   
63.
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   
64.
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   
65.
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   
66.
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   
67.
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   
68.
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   
69.
70.
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