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   1305798篇
  免费   29621篇
  国内免费   7667篇
化学   646699篇
晶体学   20229篇
力学   74125篇
综合类   102篇
数学   239621篇
物理学   362310篇
  2021年   13451篇
  2020年   15905篇
  2019年   16035篇
  2016年   27530篇
  2015年   20646篇
  2014年   30370篇
  2013年   74238篇
  2012年   36250篇
  2011年   31706篇
  2010年   36049篇
  2009年   38700篇
  2008年   31718篇
  2007年   26831篇
  2006年   33964篇
  2005年   26052篇
  2004年   27901篇
  2003年   26721篇
  2002年   27921篇
  2001年   26619篇
  2000年   23568篇
  1999年   21915篇
  1998年   20819篇
  1997年   20814篇
  1996年   21030篇
  1995年   19105篇
  1994年   18553篇
  1993年   18090篇
  1992年   17802篇
  1991年   18121篇
  1990年   17357篇
  1989年   17394篇
  1988年   16961篇
  1987年   16979篇
  1986年   15864篇
  1985年   22307篇
  1984年   23638篇
  1983年   19911篇
  1982年   21589篇
  1981年   20827篇
  1980年   20163篇
  1979年   20258篇
  1978年   21643篇
  1977年   21195篇
  1976年   20878篇
  1975年   19584篇
  1974年   19244篇
  1973年   19711篇
  1972年   14210篇
  1968年   12070篇
  1967年   12435篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
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   
962.
We consider the inverse problem for the identification of the coefficient in a parabolic equation. The model is applied to describe the functioning of a hierarchical structure [1]; it is also relevant for heat-conduction theory [2]. Unique solvability of the inverse problem is proved.  相似文献   
963.
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   
964.
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   
965.
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   
966.
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   
967.
968.
969.
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   
970.
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