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   772368篇
  免费   9945篇
  国内免费   2605篇
化学   412376篇
晶体学   10874篇
力学   35132篇
综合类   37篇
数学   101898篇
物理学   224601篇
  2021年   5796篇
  2020年   6657篇
  2019年   7204篇
  2018年   10299篇
  2017年   10264篇
  2016年   14768篇
  2015年   9962篇
  2014年   14121篇
  2013年   34845篇
  2012年   29094篇
  2011年   34276篇
  2010年   23423篇
  2009年   22769篇
  2008年   30175篇
  2007年   30263篇
  2006年   28162篇
  2005年   28698篇
  2004年   26143篇
  2003年   22256篇
  2002年   20385篇
  2001年   21297篇
  2000年   16484篇
  1999年   12960篇
  1998年   10854篇
  1997年   10606篇
  1996年   10387篇
  1995年   9295篇
  1994年   9228篇
  1993年   8832篇
  1992年   10015篇
  1991年   9955篇
  1990年   9549篇
  1989年   9206篇
  1988年   9301篇
  1987年   9071篇
  1986年   8585篇
  1985年   11405篇
  1984年   11752篇
  1983年   9596篇
  1982年   9932篇
  1981年   9741篇
  1980年   9340篇
  1979年   9691篇
  1978年   10098篇
  1977年   9880篇
  1976年   9952篇
  1975年   9238篇
  1974年   9276篇
  1973年   9474篇
  1972年   6535篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
New lower bounds for probabilities of large deviations of tests and estimators are proposed. These bounds cover the cases of moderate and Cramér-type large deviations. Bibliography: 12 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 216, 1994, pp. 52–61. Translated by the author.  相似文献   
172.
173.
174.
175.
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday  相似文献   
176.
177.
The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co2+, Cu2+, Zn2+ and Fe3+. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co2+, Cu2+ and Fe3+ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu2+ and Cu2+. Interferences were studied.  相似文献   
178.
179.
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material.  相似文献   
180.
The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures is discussed. Zh. Tekh. Fiz. 67, 97–99 (December 1997)  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