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   1366943篇
  免费   36294篇
  国内免费   14805篇
化学   687357篇
晶体学   20559篇
力学   78252篇
综合类   410篇
数学   246047篇
物理学   385417篇
  2021年   15892篇
  2020年   18152篇
  2019年   18449篇
  2018年   13653篇
  2016年   30098篇
  2015年   23316篇
  2014年   33705篇
  2013年   78549篇
  2012年   42009篇
  2011年   37667篇
  2010年   39552篇
  2009年   42019篇
  2008年   35471篇
  2007年   30262篇
  2006年   37333篇
  2005年   28486篇
  2004年   29852篇
  2003年   28103篇
  2002年   29380篇
  2001年   27682篇
  2000年   24772篇
  1999年   23262篇
  1998年   21958篇
  1997年   21950篇
  1996年   22128篇
  1995年   20005篇
  1994年   19344篇
  1993年   18674篇
  1992年   18359篇
  1991年   18622篇
  1990年   17776篇
  1989年   17726篇
  1988年   17215篇
  1987年   17203篇
  1986年   16068篇
  1985年   22468篇
  1984年   23723篇
  1983年   19941篇
  1982年   21628篇
  1981年   20854篇
  1980年   20183篇
  1979年   20257篇
  1978年   21613篇
  1977年   21180篇
  1976年   20864篇
  1975年   19553篇
  1974年   19180篇
  1973年   19663篇
  1972年   14185篇
  1967年   12404篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
152.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed.  相似文献   
153.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
154.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters.  相似文献   
155.
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism. Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process may be useful for the various optoelectronic applications of photoconductive a-Se layers. Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001  相似文献   
156.
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy.  相似文献   
157.
The Al2O3−CdSe interface of a thin-film transistor is investigated in the frequency range 30 Hz-30 kHz under weak depletion and accumulation. The surface states are, most likely, located in the insulator Al2O3 with a concentration varying from 4·1018 to 1019 cm−3 eV−1. The surface states have a negligible influence on the thin-film transistor operation.  相似文献   
158.
159.
160.
The simple relation between representations of the covering groups of SL2 and GL2 makes it possible to fuse and extend the recent metaplectic results of Shimura, Waldspurger, Flicker, and ourselves. By giving a new (purely local andL-function theoretic) treatment of the Waldspurger-Shintani correspondence, we also simplify some of Waldspurger’s original results.  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