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   1449176篇
  免费   28300篇
  国内免费   9274篇
化学   747114篇
晶体学   20820篇
力学   76796篇
综合类   108篇
数学   249037篇
物理学   392875篇
  2021年   14073篇
  2020年   17011篇
  2019年   18007篇
  2018年   14771篇
  2017年   13207篇
  2016年   30190篇
  2015年   22432篇
  2014年   32185篇
  2013年   77079篇
  2012年   44139篇
  2011年   44209篇
  2010年   41053篇
  2009年   42673篇
  2008年   42387篇
  2007年   38306篇
  2006年   42213篇
  2005年   35488篇
  2004年   35553篇
  2003年   32683篇
  2002年   33636篇
  2001年   33811篇
  2000年   28386篇
  1999年   24080篇
  1998年   21668篇
  1997年   21509篇
  1996年   21548篇
  1995年   19496篇
  1994年   18990篇
  1993年   18604篇
  1992年   19136篇
  1991年   19238篇
  1990年   18466篇
  1989年   18452篇
  1988年   18034篇
  1987年   17925篇
  1986年   16897篇
  1985年   23242篇
  1984年   24237篇
  1983年   20286篇
  1982年   21851篇
  1981年   21076篇
  1980年   20399篇
  1979年   20863篇
  1978年   21961篇
  1977年   21656篇
  1976年   21389篇
  1975年   20148篇
  1974年   19789篇
  1973年   20202篇
  1972年   14704篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
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   
152.
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   
153.
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   
154.
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   
155.
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   
156.
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   
157.
158.
159.
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   
160.
The problem of the vector and axial-vector dominance of weak interactions within the framework of the quark model of superconductivity type is 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