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   154585篇
  免费   1463篇
  国内免费   423篇
化学   85866篇
晶体学   2434篇
力学   6134篇
综合类   3篇
数学   14699篇
物理学   47335篇
  2021年   1077篇
  2020年   1258篇
  2019年   1321篇
  2018年   1686篇
  2017年   1737篇
  2016年   2686篇
  2015年   1700篇
  2014年   2464篇
  2013年   6286篇
  2012年   5077篇
  2011年   6250篇
  2010年   4361篇
  2009年   4393篇
  2008年   6010篇
  2007年   5802篇
  2006年   5647篇
  2005年   5239篇
  2004年   4728篇
  2003年   4343篇
  2002年   4209篇
  2001年   5656篇
  2000年   4078篇
  1999年   3184篇
  1998年   2216篇
  1997年   2332篇
  1996年   2197篇
  1995年   2041篇
  1994年   2021篇
  1993年   1846篇
  1992年   2320篇
  1991年   2400篇
  1990年   2220篇
  1989年   2209篇
  1988年   2194篇
  1987年   2189篇
  1986年   2023篇
  1985年   2507篇
  1984年   2497篇
  1983年   2018篇
  1982年   2025篇
  1981年   1855篇
  1980年   1846篇
  1979年   2124篇
  1978年   2191篇
  1977年   2132篇
  1976年   2058篇
  1975年   1922篇
  1974年   1937篇
  1973年   1960篇
  1972年   1291篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
A general nonlinear programming problem with interval functions is considered. Two reductions of this problem to the deterministic nonlinear programming problem are proposed, and illustrative examples are discussed.  相似文献   
32.
The nonlinear theory of thermally stimulated depolarization currents is developed. The theory explains the processes of hetero- and homocharge relaxation in complex crystals with hydrogen bonds and allows the relaxation oscillator parameters to be calculated using the quadratic approximation for the external electric field.  相似文献   
33.
The equilibrium geometry and hyperfine interaction constants of the nearest and next-to-nearest neighbor atoms are calculated for a negatively charged silicon vacancy in the high-spin state in cubic SiC. The calculations are performed within the cluster approach in terms of the density-functional theory (DFT). It is shown that the results of calculations with the use of a 70-atom cluster are in good agreement with experimental data. A detailed consideration is given to spin polarization in the electron subsystem and the applicability of a simple LCAO model that is commonly used in the interpretation of the electron paramagnetic resonance data for semiconductors. The spin density distribution for the defect under investigation is analyzed in terms of localized orbitals.  相似文献   
34.
The European Physical Journal A - The ω-meson photoproduction, γ + p→p + ω, is studied in the framework of a model, containing π-meson exchange in t-channel and...  相似文献   
35.
The time-independent radiative transfer problem in a scattering and absorbing planar random medium with general boundary conditions and internal energy source is considered. The medium is assumed to consist of two randomly mixed immiscible fluids, with the mixing statistics described as a two-state homogeneous Markov process. The problem is solved in terms of the solution of the corresponding free-source problem with simple boundary conditions which is solved using Pomraning-Eddington approximation in the deterministic case. A formalism, developed to treat radiative transfer in statistical mixtures, is used to obtain the ensemble-averaged solution. The average partial heat fluxes are calculated in terms of the albedoes of the source-free problem. Results are obtained for isotropic and anisotropic scattering for specular and diffused reflecting boundaries.  相似文献   
36.
The properties of Skyrmions in finite nuclei are considered. The deformation effect is taken into account through the external-field-induced distortion of the profile function of a chiral field. The masses of classical Skyrmions and the distribution of their baryon number versus the Skyrmion position within a nucleus are discussed.  相似文献   
37.
The European Physical Journal E - The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D2O) in a mesoporous silica glass (CPG-10-75) of...  相似文献   
38.
We investigate the dynamics of the Λ system driven by two resonant laser fields in presence of dissipation for coupling strengths where the rotating‐wave approximation starts to break down. This regime is characterised by Rabi frequencies being approximately equal or smaller than the field frequencies. A systematic procedure to obtain an expansion for the solution of the Bloch evolution equations of the system is presented. The lowest contribution results to be the well‐known rotating‐wave approximation. The method is based on a semi‐classical treatment of the problem, and its predictions are interpreted fully quantum mechanically. The theory is illustrated by a detailed study of the disappearance of coherent population trapping as the intensities of the fields increase.  相似文献   
39.
40.

The accuracy of determination of the optical constants of smooth copper surfaces produced by different technologies is analyzed, with particular attention paid to the consideration of the influence of scattered radiation (which is ignored by many authors) on the retrieval of the optical constants of copper surfaces from reflected radiation. The neglect of scattered radiation can lead to errors as high as 50% in determining the optical constants for bulk copper. For thin films, the errors are much lower. The influence of surface oxidation during measurements in air and surface features of studied objects on the parameters to be determined is analyzed as well. It is shown that errors in determination of the constants are maximal in the plasma resonance region of copper.

  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