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   21093篇
  免费   3323篇
  国内免费   2357篇
化学   15531篇
晶体学   321篇
力学   1178篇
综合类   153篇
数学   2500篇
物理学   7090篇
  2024年   83篇
  2023年   496篇
  2022年   888篇
  2021年   892篇
  2020年   1042篇
  2019年   926篇
  2018年   784篇
  2017年   749篇
  2016年   1051篇
  2015年   1096篇
  2014年   1226篇
  2013年   1648篇
  2012年   1860篇
  2011年   1842篇
  2010年   1254篇
  2009年   1241篇
  2008年   1397篇
  2007年   1200篇
  2006年   1074篇
  2005年   943篇
  2004年   716篇
  2003年   545篇
  2002年   587篇
  2001年   470篇
  2000年   409篇
  1999年   379篇
  1998年   257篇
  1997年   189篇
  1996年   232篇
  1995年   187篇
  1994年   168篇
  1993年   137篇
  1992年   112篇
  1991年   104篇
  1990年   102篇
  1989年   73篇
  1988年   67篇
  1987年   53篇
  1986年   42篇
  1985年   49篇
  1984年   40篇
  1983年   20篇
  1982年   18篇
  1981年   22篇
  1980年   12篇
  1979年   9篇
  1977年   7篇
  1976年   11篇
  1975年   12篇
  1971年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The paper is devoted to a posteriori quantitative analysis for errors caused by linearization of non-linear elliptic boundary value problems and their finite element realizations. We employ duality theory in convex analysis to derive computable bounds on the difference between the solution of a non-linear problem and the solution of the linearized problem, by using the solution of the linearized problem only. We also derive computable bounds on differences between finite element solutions of the nonlinear problem and finite element solutions of the linearized problem, by using finite element solutions of the linearized problem only. Numerical experiments show that our a posteriori error bounds are efficient.  相似文献   
72.
微腔激光器的发展与应用   总被引:1,自引:0,他引:1  
韩艳玲  王宏 《物理与工程》2002,12(6):33-35,45
本文探讨了微腔激光器的分类、基本原理及特点,并简单介绍了目前几种微型激光器的发展及应用。  相似文献   
73.
A uniqueness theorem for two distinct non-constant meromorphic functions that share three values of finite weights is proved, which generalizes two previous results by H.X. Yi, and X.M. Li and H.X. Yi. As applications of it, many known results by H.X. Yi and P. Li, etc. could be improved. Furthermore, with the concept of finite-weight sharing, extensions on Osgood-Yang's conjecture and Mues' conjecture, and a generalization of some prevenient results by M. Ozawa and H. Ueda, ect. could be obtained.  相似文献   
74.
对LD端抽运平直腔Nd:YVO4固态激光器输出功率特性受激光器内在诸因素(热透镜效应、腔长、激活孔径等)的制约关系进行了研究.并用传播圆-变换圆图解分析方法给出了合理的解释,同时,对进一步提高其输出功率特性指出了方向. 关键词: 固体激光器 热透镜 变换圆 平直腔  相似文献   
75.
Frozen Landweber Iteration for Nonlinear Ill-Posed Problems   总被引:1,自引:0,他引:1  
In this paper we propose a modification of the Landweber iteration termed frozen Landweberiteration for nonlinear ill-posed problems.A convergence analysis for this iteration is presented.The numericalperformance of this frozen Landweber iteration for a nonlinear Hammerstein integral equation is compared withthat of the Landweber iteration.We obtain a shorter running time of the frozen Landweber iteration based onthe same convergence accuracy.  相似文献   
76.
In this paper, we find some new explicit examples of Hamiltonian minimal Lagrangian submanifolds among the Lagrangian isometric immersions of a real space form in a complex space form.  相似文献   
77.
郭锐  郭弘 《量子光学学报》2006,12(B08):30-30
In this talk, the interaction of a single photon injected to a single atom is studied, for which initially the photon is uncorrelated with the atom. The spontaneous emitted photon will then evolve to be entangled with the atom on their continuous kinetic variables (momentum) in the process of resonant scattering. We find the relations between the entanglement and their physical control parameters (such as the linewidth of the injected photon wave packet, and that of the atomic wave packet, etc. ), which indicates that high entanglement can be reached by broadening the scale of the atomic wave or squeezing the linewidth of the incident single-photon pulse.  相似文献   
78.
首先引述了红外探测器两点法进行图像非均匀校正的原理,给出了基于DSP+FPGA的图像处理系统硬件模块整体实现框图,以及其非均匀校正模块的硬件结构。然后对其非均匀校正模块硬件实现中的芯片选择,工作流程以及实现作了详细的阐述。最后给出了非均匀校正试验的结果。  相似文献   
79.
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels.  相似文献   
80.
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