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   667217篇
  免费   5040篇
  国内免费   1516篇
化学   327972篇
晶体学   9596篇
力学   35628篇
综合类   19篇
数学   95666篇
物理学   204892篇
  2021年   6212篇
  2020年   6719篇
  2019年   7688篇
  2018年   10508篇
  2017年   10737篇
  2016年   14663篇
  2015年   7724篇
  2014年   13312篇
  2013年   29116篇
  2012年   22866篇
  2011年   27060篇
  2010年   20718篇
  2009年   20635篇
  2008年   25725篇
  2007年   25542篇
  2006年   23316篇
  2005年   20744篇
  2004年   19378篇
  2003年   17582篇
  2002年   17540篇
  2001年   18234篇
  2000年   14209篇
  1999年   10994篇
  1998年   9758篇
  1997年   9530篇
  1996年   8894篇
  1995年   7930篇
  1994年   8018篇
  1993年   7805篇
  1992年   8107篇
  1991年   8656篇
  1990年   8371篇
  1989年   8266篇
  1988年   7972篇
  1987年   7820篇
  1986年   7402篇
  1985年   9309篇
  1984年   9833篇
  1983年   8293篇
  1982年   8645篇
  1981年   8087篇
  1980年   7624篇
  1979年   8381篇
  1978年   8585篇
  1977年   8627篇
  1976年   8626篇
  1975年   8231篇
  1974年   8045篇
  1973年   8271篇
  1972年   6348篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006.  相似文献   
153.
154.
    
Ohne Zusammenfassung  相似文献   
155.
A method for suppressing self-modulation in backward-wave tubes is proposed. Additional delay is introduced into the feedback circuit, owing to which the output signal amplitude affects the electron beam current that enters into the interaction space. Numerical simulations demonstrate that the operating current in the single-frequency oscillation mode may be increased roughly twofold.  相似文献   
156.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
157.
The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes.  相似文献   
158.
159.
Effects of a low molecular weight physically adsorbed polyethylene oxide (PEO) and the range of the electrostatic repulsion on the rheological behavior of silica dispersions (as a model system) has been investigated. Particular attention is given to the evolution of the rheological behavior with increasing the polymer concentration in the system and also effectiveness of the polymer as a dispersant under extreme conditions (high ionic strength). Results indicate that at small separation distances and low polymer coverage, the polymer chains are long enough to adsorb on the surface of two particles simultaneously causing bridging flocculation in the system and hence increasing the viscosity and linear viscoelastic functions of the dispersion. A significant increase was observed in the viscosity of the dispersion at salt concentrations high enough to eliminate electrostatics between the particles. Under these conditions,the viscosity of the system increased significantly when PEO was added to the dispersion showing that at high electrolyte concentrations, a neutral polymer such as PEO is not able to stabilize the system.  相似文献   
160.
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