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   1945篇
  免费   184篇
  国内免费   115篇
化学   269篇
晶体学   9篇
力学   103篇
综合类   58篇
数学   1194篇
物理学   611篇
  2024年   3篇
  2023年   30篇
  2022年   30篇
  2021年   48篇
  2020年   51篇
  2019年   54篇
  2018年   57篇
  2017年   86篇
  2016年   94篇
  2015年   59篇
  2014年   145篇
  2013年   142篇
  2012年   94篇
  2011年   101篇
  2010年   97篇
  2009年   127篇
  2008年   124篇
  2007年   117篇
  2006年   101篇
  2005年   89篇
  2004年   67篇
  2003年   65篇
  2002年   68篇
  2001年   54篇
  2000年   63篇
  1999年   58篇
  1998年   46篇
  1997年   29篇
  1996年   21篇
  1995年   11篇
  1994年   19篇
  1993年   16篇
  1992年   6篇
  1991年   15篇
  1990年   8篇
  1989年   3篇
  1988年   8篇
  1987年   2篇
  1986年   6篇
  1985年   8篇
  1984年   2篇
  1983年   2篇
  1982年   8篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1976年   1篇
  1973年   1篇
  1972年   1篇
  1936年   1篇
排序方式: 共有2244条查询结果,搜索用时 695 毫秒
91.
马玉梅 《数学学报》1936,63(4):329-334
本文推广Vogt定理到广义n-赋范空间,即证明了两个广义n-赋范空间之间的保持ρ-诱导距离映射是仿射的.  相似文献   
92.
The objective of this work is to determine the maximum stretch of the C–C bond before it misses the character of single bond, employing both the Atoms in Molecules (AIM) and Electron Localization Function (ELF) methods. It was concluded that C–C distances up to 2.0 Å could be considered single bonds.  相似文献   
93.
在一拥有辐射环状交通网络的城市工作区内,使用小车上下班的职员在通勤时的平均移动距离约为多少?本文基于一个较现实的模型对此进行了理论上的解析,所得结果,从城市规划的观点来看,具有一定的实际意义。  相似文献   
94.
A dual-frequency Nd: YAG laser which can output two frequencies with frequency difference of more than 5 gigaherz is developed. By inserting and moving an intracavity quartz crystal wedge in diode pumped Nd:YAG laser, It can be obtained and tuned frequency difference in a wide frequency range. The stabilization of frequency difference in free state is much better than that of birefringent dual-frequency He-Ne lasers at similar laboratory conditions. With such a large tunable frequency difference i.e. short synthetic wavelength, the laser may be used as the light source of absolute distance interferometers. In our experiment, the methods for tuning frequency difference by rotating and applying a tunable force on the intracavity quartz plate are also studied.  相似文献   
95.
96.
97.
In this paper we characterize John domains in terms of John domain decomposition property. In addition, we also show that a domain D in ℔ n is a John domain if and only if D\P is a John domain, where P is a subset of D containing finitely many points of D. The best possibility and an application of the second result are also discussed.  相似文献   
98.
It has been found that the amount of charge transfer between donor and acceptor molecules in four sets of hydrogen‐bonded complexes may be adequately described as an exponential function of the equilibrium distance between the hydrogen atom and the nearest atom of the acceptor molecule. The exponential factors of the transfer are of the same order but somewhat larger than the factors found otherwise in the investigations of dynamic electron transfer. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   
99.
Used digital speckle correlation method (DSCM) to realize orientation function of optical mouse is researched. The experiment is designed to obtain the dynamic speckle patterns which are shot by CCD, then the DSCM is used to process the sequential images and also the experiment is simulated. The experimental results show the DSCM can confirm orientation function of the optical mouse, and have a good agreement with the simulation results, and the resolution we obtained is higher than the resolution of mouse on the market.  相似文献   
100.
Point clouds are one of the most primitive and fundamental manifold representations. Popular sources of point clouds are three-dimensional shape acquisition devices such as laser range scanners. Another important field where point clouds are found is in the representation of high-dimensional manifolds by samples. With the increasing popularity and very broad applications of this source of data, it is natural and important to work directly with this representation, without having to go through the intermediate and sometimes impossible and distorting steps of surface reconstruction. A geometric framework for comparing manifolds given by point clouds is presented in this paper. The underlying theory is based on Gromov-Hausdorff distances, leading to isometry invariant and completely geometric comparisons. This theory is embedded in a probabilistic setting as derived from random sampling of manifolds, and then combined with results on matrices of pairwise geodesic distances to lead to a computational implementation of the framework. The theoretical and computational results presented here are complemented with experiments for real three-dimensional shapes.  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