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   108948篇
  免费   6743篇
  国内免费   5774篇
化学   63049篇
晶体学   1442篇
力学   6233篇
综合类   386篇
数学   13085篇
物理学   37270篇
  2023年   975篇
  2022年   2069篇
  2021年   2482篇
  2020年   2697篇
  2019年   2882篇
  2018年   3238篇
  2017年   3169篇
  2016年   3944篇
  2015年   2864篇
  2014年   3991篇
  2013年   5646篇
  2012年   5848篇
  2011年   6230篇
  2010年   4846篇
  2009年   4805篇
  2008年   5139篇
  2007年   4742篇
  2006年   4325篇
  2005年   3760篇
  2004年   3373篇
  2003年   2964篇
  2002年   3110篇
  2001年   2736篇
  2000年   2180篇
  1999年   1839篇
  1998年   1706篇
  1997年   1453篇
  1996年   1429篇
  1995年   1207篇
  1994年   1249篇
  1993年   1197篇
  1992年   1148篇
  1991年   1207篇
  1990年   1192篇
  1989年   1097篇
  1988年   957篇
  1987年   950篇
  1986年   901篇
  1985年   951篇
  1984年   934篇
  1983年   835篇
  1982年   812篇
  1979年   804篇
  1978年   817篇
  1977年   807篇
  1976年   922篇
  1975年   815篇
  1974年   844篇
  1973年   849篇
  1972年   754篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Results of experimental investigations of the volt-brightness characteristics, frequency dependences of brightness, and the directional radiation pattern of electroluminescent MSDM, MSCM, and MSDCM emitters, where M stands for the first transparent and second nontransparent electrodes, S is a semiconductor, D is a thin-film dielectric, and C is a silicone-based composite liquid dielectric with a powdered segnetoelectric filler, developed on conventional “smooth” and rough glass substrates are presented. It is shown that electroluminescent structures on rough surfaces have a brightness approximately two times higher than that of similar structures developed on a “smooth” substrate. Ul’yanovsk State University, 42, L. Tolstoi St., Ul’yanovsk, 432700, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 507–512, July–August, 1997.  相似文献   
112.
A scheme for automated study of current-voltage characteristics of gyroresonance devices is developed. The effective emission spread at the cathodes of powerful gyrotrons is studied by analysis of current-voltage characteristics. Experimental data on the effective emission spread parameter for different modes are given. The permissible emission spread at the cathodes of powerful gyrotrons is estimated, and the dependence of the electron beam parameters on the cathode emission spread is presented. A complex measurement technique showing the contribution of different physical mechanisms to the cathode emission spread is proposed. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 4, pp. 506–516, April, 1997.  相似文献   
113.
114.
We consider the application of asymptotic methods of nonlinear mechanics (the Krylov-Bogolyubov-Mitropol'skii method) and the method of separation of motions in nonlinear systems for the construction of an approximate solution of a nonlinear equation that describes a nonstationary wave process. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 3, pp. 357–371, March, 1998.  相似文献   
115.
We construct the second approximation for random oscillations described by the Van der Pol equation which are under the action of a broadband random process. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 11, pp. 1517–1521, November, 1998.  相似文献   
116.
The electronic spectrum of an icosahedral quasicrystal with a central-atom decoration of the Amman-Mackay network is investigated in the tight-binding approximation. The quasicrystal is described as a structural limit of the optimal cubic approximants with increasing period. The electronic spectra for the first four optimal cubic approximants do not contain the hierarchical gap structure which is typical for the Cantor set of the spectrum of a one-dimensional quasicrystal. At the same time, as the order of the approximant increases, the spectrum becomes singular throughout the entire energy scale. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 557–562 (25 April 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.  相似文献   
117.
The anomalous proximity effect between a d-wave superconductor and a thin disordered normal layer is studied theoretically in the framework of Eilenberger equations. It is shown that disorder of the quasiparticle reflection from this thin layer leads to the formation of an s-wave component localized near the boundary. The angular and spatial structure of the pair potential near the interface is studied. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 478–483 (10 April 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.  相似文献   
118.
Space time-index plots for probing dynamical nonstationarity   总被引:3,自引:0,他引:3  
We propose a simple method to efficiently probe dynamical nonstationarity in observed time series. In a space time-index plot, the density distributions as a function of normalized time-index are V-shaped due to nonstationarity. We show that this method is workable for short data sets and typical examples are illustrated.  相似文献   
119.
介绍在细径内窥镜中GRIN透镜的应用原理及其设计方法。  相似文献   
120.
纳米硅量子线的发现与研究   总被引:5,自引:0,他引:5  
俞大鹏 《物理》1998,27(4):193-195
一维纳米材料是当今介观物理学研究的前沿领域.文章报道了一种利用脉冲激光成功地制备纯度高、直径分布均匀的纳米硅量子线(SiNWs)的方法,介绍了纳米量子线的形貌、显微结构、生长机理和物理性能研究的最新结果.纳米硅量子线的发现具有重要的科学意义和潜在的应用前景.  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