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   342664篇
  免费   3255篇
  国内免费   1001篇
化学   172010篇
晶体学   5468篇
力学   15975篇
综合类   7篇
数学   40391篇
物理学   113069篇
  2021年   3238篇
  2020年   3481篇
  2019年   3859篇
  2018年   5296篇
  2017年   5527篇
  2016年   7545篇
  2015年   4322篇
  2014年   7250篇
  2013年   16379篇
  2012年   12858篇
  2011年   15436篇
  2010年   11366篇
  2009年   11223篇
  2008年   13756篇
  2007年   13774篇
  2006年   12697篇
  2005年   11103篇
  2004年   10319篇
  2003年   9064篇
  2002年   9035篇
  2001年   10715篇
  2000年   7994篇
  1999年   6156篇
  1998年   5140篇
  1997年   4975篇
  1996年   4698篇
  1995年   4072篇
  1994年   4018篇
  1993年   3935篇
  1992年   4303篇
  1991年   4503篇
  1990年   4251篇
  1989年   4174篇
  1988年   3966篇
  1987年   4090篇
  1986年   3815篇
  1985年   4803篇
  1984年   4854篇
  1983年   4020篇
  1982年   4134篇
  1981年   3839篇
  1980年   3788篇
  1979年   4048篇
  1978年   4049篇
  1977年   4017篇
  1976年   4006篇
  1975年   3776篇
  1974年   3727篇
  1973年   3745篇
  1972年   2660篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An arbitrary operator-valued function from the generalized Shur class is realized as the transfer function of a minimal optimal and minimal *-optimal dissipative scattering system with the Pontryagin state space. These results generalize Arov's results for the case of the Hilbert state space. Bibliography: 11 titles.  相似文献   
82.
83.
The ZnS:Cu,Al,Au (P22G) phosphor powder was bombarded by an electron beam in an O2 ambient, Ar ambient and other mixture of gases. These gases consisted of mixtures of O2 and COx, and O2, COx and Ar gas. Auger electron spectroscopy (AES) was used to monitor changes in the surface composition of the P22G phosphor during electron bombardment. When the P22G phosphor powder was exposed to the electron beam in a water-rich O2 ambient, a chemically limited ZnO layer was formed on the surface. The electron beam degradation of the P22G phosphor powder was also performed in a dry O2 ambient and a layer of ZnSO4 was formed on the surface. The ZnSO4 formation decayed exponentially with time and it is postulated that this was due to the diffusion of the charge reactants through the ZnSO4 film to the reaction interfaces. The P22G phosphor exposed to the electron beam in an Ar ambient and to the other gas mixtures degraded at a lower rate than in the case of the O2 ambient. This suggests that Ar and COx may suppress the degradation of the P22G phosphor powder.  相似文献   
84.
85.
86.
87.
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   
88.
89.
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   
90.
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   
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