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   4525篇
  免费   486篇
  国内免费   1001篇
化学   2838篇
晶体学   173篇
力学   87篇
综合类   1篇
数学   1264篇
物理学   1649篇
  2024年   1篇
  2023年   86篇
  2022年   101篇
  2021年   107篇
  2020年   104篇
  2019年   76篇
  2018年   48篇
  2017年   78篇
  2016年   93篇
  2015年   152篇
  2014年   253篇
  2013年   307篇
  2012年   416篇
  2011年   488篇
  2010年   367篇
  2009年   419篇
  2008年   338篇
  2007年   403篇
  2006年   379篇
  2005年   293篇
  2004年   232篇
  2003年   170篇
  2002年   201篇
  2001年   180篇
  2000年   135篇
  1999年   139篇
  1998年   125篇
  1997年   84篇
  1996年   53篇
  1995年   43篇
  1994年   38篇
  1993年   35篇
  1992年   25篇
  1991年   25篇
  1990年   7篇
  1989年   1篇
  1986年   8篇
  1976年   2篇
排序方式: 共有6012条查询结果,搜索用时 31 毫秒
1.
兰玉婷  张宁 《数学学报》2019,62(4):591-604
受Peng-中心极限定理的启发,本文主要应用G-正态分布的概念,放宽Peng-中心极限定理的条件,在次线性期望下得到形式更为一般的中心极限定理.首先,将均值条件E[X_n]=ε[X_n]=0放宽为|E[X_n]|+|ε[X_n]|=O(1/n);其次,应用随机变量截断的方法,放宽随机变量的2阶矩与2+δ阶矩条件;最后,将该定理的Peng-独立性条件进行放宽,得到卷积独立随机变量的中心极限定理.  相似文献   
2.
We define the notion of basic set data for finite groups (building on the notion of basic set, but including an order on the irreducible characters as part of the structure), and we prove that the Springer correspondence provides basic set data for Weyl groups. Then we use this to determine explicitly the modular Springer correspondence for classical types (defined over a base field of odd characteristic p, and with coefficients in a field of odd characteristic ?p): the modular case is obtained as a restriction of the ordinary case to a basic set. In order to do so, we compare the order on bipartitions introduced by Dipper and James with the order induced by the Springer correspondence. We provide a quick proof, by sorting characters according to the dimension of the corresponding Springer fibre, an invariant which is directly computable from symbols.  相似文献   
3.
Multicomponent binary metal oxide-involved hybrid structures with unique physicochemical properties have received extensive attention due to their fascinating electrochemical performance. Herein, a flexible strategy, which involves the preparation of dual-functional heterometallic Fe2M clusters and their subsequent sintering treatment, is developed to engineer novel 3D hierarchical porous structures assembled with MFe2O4(M = Co, Mn, Ni and Zn) nanoparticles confi...  相似文献   
4.
The paper examines the model problem of high-frequency diffraction by a convex surface consisting of two parts. One is soft, the other is hard. The incident wave falls at a small angle to the line which separates soft and hard parts of the surface. The change in the boundary condition provokes the field in the Fock zone to have a rapid transverse variation. This causes a special boundary-layer to be formed. The boundary value problem for the three dimensional parabolic equation is reduced to the Riemann problem solved by the factorization in the form of infinite products containing the zeros of the Airy function and zeros of its derivative. the results of this factorization appear under the sign of double Fourier integral in the representation of the field. Both numerical and asymptotic analysis of this representation is carried out and illustrates the effects of high-frequency diffraction caused by the line of the boundary condition discontinuity.  相似文献   
5.
6.
Mono‐ and octa‐azobenzene‐functionalized cage silsesquioxanes were easily synthesized by the reaction of 4‐bromoazobenzene with monovinyl‐substituted octasilsesquioxane and cubic octavinylsilsesquioxane through the Heck coupling reaction. Excited‐state energies obtained from time‐dependent density functional theory (TDDFT) and the CAM‐B3LYP functional correlate very well with experimental trans–cis photoisomerization results from UV/Vis spectroscopy. These azobenzene‐functionalized cages exhibit good thermal stability and are fluorescent with maximum emission at approximately 400 nm, making them potential materials for blue‐light emission.  相似文献   
7.
8.
9.
10.
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