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   216809篇
  免费   1622篇
  国内免费   633篇
化学   118989篇
晶体学   3279篇
力学   8360篇
综合类   6篇
数学   23440篇
物理学   64990篇
  2020年   1997篇
  2019年   2289篇
  2018年   3222篇
  2017年   3133篇
  2016年   4312篇
  2015年   2399篇
  2014年   3868篇
  2013年   9331篇
  2012年   6996篇
  2011年   8554篇
  2010年   6128篇
  2009年   5964篇
  2008年   8235篇
  2007年   8306篇
  2006年   7725篇
  2005年   7006篇
  2004年   6235篇
  2003年   5688篇
  2002年   5539篇
  2001年   5959篇
  2000年   4708篇
  1999年   3481篇
  1998年   3016篇
  1997年   3040篇
  1996年   2834篇
  1995年   2328篇
  1994年   2429篇
  1993年   2455篇
  1992年   2610篇
  1991年   2665篇
  1990年   2566篇
  1989年   2539篇
  1988年   2465篇
  1987年   2438篇
  1986年   2361篇
  1985年   3047篇
  1984年   3198篇
  1983年   2562篇
  1982年   2835篇
  1981年   2709篇
  1980年   2505篇
  1979年   2722篇
  1978年   2838篇
  1977年   2864篇
  1976年   2838篇
  1975年   2692篇
  1974年   2670篇
  1973年   2817篇
  1972年   1878篇
  1967年   1831篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
111.
We introduce the notions of δ-t-sets, δβ-t-sets, δ-B-continuity and δβ -B-continuity and obtain decompositions of continuity and complete continuity.  相似文献   
112.
E. J. S. Lage 《Physica A》1987,140(3):629-636
We study critical dynamics of general q-state Potts models on d-dimensional hypercubic lattices. The master equation is formulated according to a theory recently presented by the author. A simple bond moving technique, followed by decimation, is used to obtain the dynamical exponents. Although this approximation yields poor results for the static exponents, the dynamic behaviour is closer to Monte Carlo simulations. We compare our results with those obtained with a different formulation of dynamics. A final discussion is included.  相似文献   
113.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 613–618, October, 1991.  相似文献   
114.
The behavior of the edges of cuts in shallow shells with the symmetric combined action of tension and flexure is investigated. For shells of different curvature with one and two parallel or collinear cuts, the load region in which there is no contact of the cut edges in the course of shell deformation is determined.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 98–100, 1988.  相似文献   
115.
116.
117.
Results of an experimental observation of the voltage oscillations associated with a discrete tunneling of holes in porous silicon at room temperature are presented. The noise characteristics of diode structures with a porous silicon interlayer formed on heavily boron-doped silicon single crystals are studied. Peaks of excessive noise are observed at frequencies of ~1 MHz, at which single-electron oscillations should be expected. The peak noise power is found to increase with current according to the ~2.5 power law and, at a current density of 0.15 A/cm2, to exceed the noise power of the receiver by three to four orders of magnitude. The complex shape of the noise spectrum and its extension to the higher frequency region with increasing current are explained by the three-dimensionality of the system of nanometer-sized silicon grains embedded in insulating silicon dioxide of porous silicon.  相似文献   
118.
119.
The present paper deals with the well-posedness and regularity of one class of one-dimensional time-dependent boundary-value problems with global boundary conditions on the entire time interval. We establish conditions for the well-posedness of boundary-value problems for partial differential equations in the class of bounded differentiable functions. A criterion for the regularity of the problem under consideration is also obtained.  相似文献   
120.
Binding energy spectra of the valence electrons of the open shell molecule NO have been obtained up to 55 eV at azimuthal angles of 0° and 7° using binary (e, 2e) spectroscopy at an impact energy of 1200 eV. The momentum distribution has been obtained for the least tightly bound (unpaired) electron, removal of which leads to formation of the X 1Σ+ ground state of NO+. Momentum distributions have also been measured at 21.0 and 40.5 eV. The measured momentum distributions are compared with several literature wavefunctions of varying complexity. They are found to be in excellent agreement with those calculated using the natural spin orbital wavefunctions of Kouba and Ohrn.  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