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   457134篇
  免费   2927篇
  国内免费   882篇
化学   218100篇
晶体学   7140篇
力学   24410篇
综合类   7篇
数学   61461篇
物理学   149825篇
  2021年   4078篇
  2020年   4527篇
  2019年   5374篇
  2018年   7677篇
  2017年   7811篇
  2016年   10253篇
  2015年   5202篇
  2014年   9335篇
  2013年   19210篇
  2012年   15543篇
  2011年   18440篇
  2010年   14324篇
  2009年   14405篇
  2008年   17403篇
  2007年   17398篇
  2006年   15991篇
  2005年   14085篇
  2004年   13416篇
  2003年   12184篇
  2002年   12321篇
  2001年   12813篇
  2000年   10053篇
  1999年   7565篇
  1998年   6717篇
  1997年   6566篇
  1996年   5999篇
  1995年   5495篇
  1994年   5410篇
  1993年   5299篇
  1992年   5658篇
  1991年   6012篇
  1990年   5921篇
  1989年   5708篇
  1988年   5556篇
  1987年   5624篇
  1986年   5187篇
  1985年   6338篇
  1984年   6783篇
  1983年   5692篇
  1982年   6082篇
  1981年   5750篇
  1980年   5408篇
  1979年   5935篇
  1978年   6103篇
  1977年   6195篇
  1976年   6351篇
  1975年   5875篇
  1974年   5716篇
  1973年   6002篇
  1972年   4578篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
An analysis is made of the thermodynamic stability of the dislocation structure in polycrystalline samples of Fe-C, deformed under conditions of high rates and hydrostatic pressures, based on experimental and theoretical data concerning the internal energy and on diffractometer measurements of the broadening of x-ray lines. The method of deformation calorimetry was used to determine the internal energy in a wide range of deformations. A theoretical model is proposed for estimating the change in internal energy in deformed alloys. An investigation is made of the dependence of the interdislocation interaction parameter on the deformation rate for different stressed state-schemes and large plastic deformations. It is shown that the relative quantity δU/A is correlated in a wide range of deformations with the relative root-mean-square distortions of the crystal lattice of the deformed solid solution. The mechanisms for the accumulation of energy in deformed solid solutions having a body-centered cubic lattice are considered. Don State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 77–83.  相似文献   
23.
24.
We provide a characterization of the limit periodic sets for analytic families of vector fields under the hypothesis that the first jet is non-vanishing at any singular point. Also, applying the family desingularization method, we reduce the complexity of some of these sets.  相似文献   
25.
A simple method is proposed for increasing the accuracy of computation of the eigenvalues of elliptic operators, which does not require high-order accurate schemes.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 63, pp. 63–68, 1987.  相似文献   
26.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
27.
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex variables. Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61.  相似文献   
28.
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   
29.
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   
30.
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   
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