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   641126篇
  免费   5840篇
  国内免费   1492篇
化学   323477篇
晶体学   9445篇
力学   31975篇
综合类   16篇
数学   85045篇
物理学   198500篇
  2021年   5796篇
  2020年   6425篇
  2019年   7247篇
  2018年   9955篇
  2017年   9900篇
  2016年   14066篇
  2015年   7937篇
  2014年   13174篇
  2013年   28529篇
  2012年   22471篇
  2011年   27069篇
  2010年   20257篇
  2009年   20332篇
  2008年   25486篇
  2007年   25080篇
  2006年   23032篇
  2005年   20367篇
  2004年   19123篇
  2003年   17087篇
  2002年   17257篇
  2001年   18524篇
  2000年   14322篇
  1999年   11050篇
  1998年   9556篇
  1997年   9212篇
  1996年   8712篇
  1995年   7864篇
  1994年   7822篇
  1993年   7602篇
  1992年   8188篇
  1991年   8554篇
  1990年   8280篇
  1989年   8119篇
  1988年   7916篇
  1987年   7868篇
  1986年   7388篇
  1985年   9288篇
  1984年   9520篇
  1983年   7763篇
  1982年   8005篇
  1981年   7710篇
  1980年   7212篇
  1979年   7919篇
  1978年   8125篇
  1977年   8128篇
  1976年   8119篇
  1975年   7505篇
  1974年   7361篇
  1973年   7474篇
  1972年   5721篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
151.
The nonprimary subgroups of the symmetric group S 9 are investigated. Embedding properties of these subgroups are listed in a table. Properties such as abnormality, pronormality, paranormality, weak normality, etc. were checked with the help of a computer. Algorithms and codes of the first author were used for this purpose. The research leans upon the technique of Burnside marks, as well as upon pertinent information on the table of marks of S 9 from the computer algebra package GAP. The subgroups were investigated up to conjugacy; the total number of conjugacy classes of nonprimary subgroups of S 9 is 432. Some subgroups were additionally checked by other programs based on the double coset method. Bibliography: 24 titles.  相似文献   
152.
153.
The thermal expansion coefficients and the thermal conductivity of Bridgman-grown crystals of CuGa1−x InxTe2 solid solutions are investigated. It is found that the thermal expansion coefficient varies with x linearly, while the thermal conductivity is minimal when x=0.5. The Debye temperature and the rms dynamic atomic displacements are calculated from experimental data. It is shown that the Debye temperature decreases and the rms displacements in the crystal lattice sharply increase as the In content in the solid solutions grows.  相似文献   
154.
155.
156.
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   
157.
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   
158.
    
  相似文献   
159.
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   
160.
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