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   490075篇
  免费   1891篇
  国内免费   953篇
化学   252532篇
晶体学   9731篇
力学   20681篇
综合类   15篇
数学   56004篇
物理学   153956篇
  2020年   4602篇
  2019年   4920篇
  2018年   6104篇
  2017年   6236篇
  2016年   8820篇
  2015年   5530篇
  2014年   8311篇
  2013年   20078篇
  2012年   15124篇
  2011年   18419篇
  2010年   12915篇
  2009年   12478篇
  2008年   17460篇
  2007年   17504篇
  2006年   16324篇
  2005年   14730篇
  2004年   13251篇
  2003年   12130篇
  2002年   12187篇
  2001年   12852篇
  2000年   10260篇
  1999年   7956篇
  1998年   7057篇
  1997年   6923篇
  1996年   6566篇
  1995年   5790篇
  1994年   6024篇
  1993年   5835篇
  1992年   6378篇
  1991年   6301篇
  1990年   6236篇
  1989年   6115篇
  1988年   6121篇
  1987年   5952篇
  1986年   5739篇
  1985年   7547篇
  1984年   7844篇
  1983年   6582篇
  1982年   7005篇
  1981年   6834篇
  1980年   6546篇
  1979年   6728篇
  1978年   7156篇
  1977年   7012篇
  1976年   7075篇
  1975年   6634篇
  1974年   6671篇
  1973年   6962篇
  1972年   4893篇
  1971年   4229篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Russian Journal of General Chemistry -  相似文献   
52.
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   
53.
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   
54.
In the present paper, the notion of norm series with respect to the norm residue symbol is generalized to high-dimensional local fields. Necessary and sufficient conditions for the existence of norm series are obtained. Bibliography: 12 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 305, 2003, pp. 60–83.  相似文献   
55.
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   
56.
57.
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   
58.
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr2Fe1+x Mo1-x O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.  相似文献   
59.
Let F be a non-arithmetic distribution on the line , and W be the class of bounded functions w without discontinuity of the second kind such that
.In this paper, we show that the solution of the homogeneous renewal equation w = w F in the class W is a constant-function.  相似文献   
60.
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