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   7974篇
  免费   361篇
  国内免费   647篇
化学   653篇
晶体学   4篇
力学   363篇
综合类   48篇
数学   6787篇
物理学   1127篇
  2023年   80篇
  2022年   54篇
  2021年   78篇
  2020年   154篇
  2019年   163篇
  2018年   189篇
  2017年   196篇
  2016年   225篇
  2015年   142篇
  2014年   309篇
  2013年   557篇
  2012年   321篇
  2011年   354篇
  2010年   330篇
  2009年   505篇
  2008年   591篇
  2007年   528篇
  2006年   481篇
  2005年   422篇
  2004年   297篇
  2003年   377篇
  2002年   319篇
  2001年   230篇
  2000年   236篇
  1999年   253篇
  1998年   196篇
  1997年   223篇
  1996年   124篇
  1995年   114篇
  1994年   99篇
  1993年   69篇
  1992年   57篇
  1991年   61篇
  1990年   65篇
  1989年   49篇
  1988年   52篇
  1987年   38篇
  1986年   38篇
  1985年   50篇
  1984年   56篇
  1983年   18篇
  1982年   35篇
  1981年   32篇
  1980年   33篇
  1979年   25篇
  1978年   30篇
  1977年   38篇
  1976年   25篇
  1974年   14篇
  1973年   15篇
排序方式: 共有8982条查询结果,搜索用时 31 毫秒
1.
2.
In this paper, we define interval‐valued left‐sided and right‐sided generalized fractional double integrals. We establish inequalities of Hermite‐Hadamard like for coordinated interval‐valued convex functions by applying our newly defined integrals.  相似文献   
3.
This work is concerned with the extension of the Jacobi spectral Galerkin method to a class of nonlinear fractional pantograph differential equations. First, the fractional differential equation is converted to a nonlinear Volterra integral equation with weakly singular kernel. Second, we analyze the existence and uniqueness of solutions for the obtained integral equation. Then, the Galerkin method is used for solving the equivalent integral equation. The error estimates for the proposed method are also investigated. Finally, illustrative examples are presented to confirm our theoretical analysis.  相似文献   
4.
5.
6.
7.
As part of previous studies, we introduced a new type of basis function named Simplified Box Orbitals (SBOs) that belong to a class of spatially restricted functions which allow the zero differential overlap (ZDO) approximation to be applied with complete accuracy. The original SBOs and their Gaussian expansions SBO-3G form a minimal basis set, which was compared to the standard Slater-type orbital basis set (STO-3G). In the present paper, we have developed the SBO basis functions at double-zeta (DZ) level, and we have assessed the option of expanding the SBO-DZ as a combination of Gaussian functions. Finally, we have determined the quality of the new basis set by comparing the molecular properties calculated with SBO-nG with those achieved with some standard basis sets.  相似文献   
8.
Motivated by the well-established phase derivative embedded technique, this study devotes to sharper uncertainty principles related to the Lp-norm type of uncertainty product, giving rise to two kinds of uncertainty inequalities that improve the classical result through providing tighter lower bounds. The conditions that truly reach these better estimates are obtained. Examples and simulations are carried out to verify the correctness of the derived results, and finally, possible applications in time-frequency analysis are also given.  相似文献   
9.
It is shown in Li and Ying (2019) that a regular and local Dirichlet form on an interval can be represented by so-called effective intervals with scale functions. This paper focuses on how to operate on effective intervals to obtain regular Dirichlet subspaces. The first result is a complete characterization for a Dirichlet form to be a regular subspace of such a Dirichlet form in terms of effective intervals. Then we give an explicit road map how to obtain all regular Dirichlet subspaces from a local and regular Dirichlet form on an interval, by a series of intuitive operations on the effective intervals in the representation above. Finally applying previous results, we shall prove that every regular and local Dirichlet form has a special standard core generated by a continuous and strictly increasing function.  相似文献   
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