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   2779篇
  免费   235篇
  国内免费   270篇
化学   298篇
晶体学   17篇
力学   260篇
综合类   73篇
数学   2022篇
物理学   614篇
  2024年   2篇
  2023年   26篇
  2022年   37篇
  2021年   35篇
  2020年   59篇
  2019年   66篇
  2018年   57篇
  2017年   66篇
  2016年   78篇
  2015年   63篇
  2014年   107篇
  2013年   199篇
  2012年   110篇
  2011年   111篇
  2010年   158篇
  2009年   195篇
  2008年   180篇
  2007年   214篇
  2006年   152篇
  2005年   158篇
  2004年   150篇
  2003年   130篇
  2002年   137篇
  2001年   115篇
  2000年   118篇
  1999年   85篇
  1998年   94篇
  1997年   74篇
  1996年   65篇
  1995年   43篇
  1994年   55篇
  1993年   19篇
  1992年   24篇
  1991年   14篇
  1990年   16篇
  1989年   9篇
  1988年   5篇
  1987年   7篇
  1986年   2篇
  1985年   5篇
  1984年   8篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   8篇
  1979年   6篇
  1978年   6篇
  1977年   2篇
  1975年   1篇
  1936年   1篇
排序方式: 共有3284条查询结果,搜索用时 0 毫秒
221.
A result from 1988 on the square-free integers represented by a positive definite ternary quadratic form with integral coefficients is made uniform in the determinant of the form.  相似文献   
222.
A method is described for obtaining conjunctive normal forms for logics using Gentzen-style rules possessing a special kind of strong invertibility. This method is then applied to a number of prominent fuzzy logics using hypersequent rules adapted from calculi defined in the literature. In particular, a normal form with simple McNaughton functions as literals is generated for ?ukasiewicz logic, and normal forms with simple implicational formulas as literals are obtained for Gödel logic, Product logic, and Cancellative hoop logic.  相似文献   
223.
We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition region at intermediate Q2. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large x, we calculate QCD moments of the pion structure function over a range of Q2, and quantify the role of higher twist corrections. Using a parameterization of the pion elastic form factor and phenomenological models for the π↦ρ transition form factor, we further test the extent to which local duality may be valid for the pion. Received: 10 February 2003 / Accepted: 12 March 2003 / Published online: 27 May 2003  相似文献   
224.
We consider the strongly elliptic operator A of order 2m in the divergence form with bounded measurable coefficients and assume that the coefficients of top order are uniformly continuous. For 1<p<∞, A is a bounded linear operator from the Lp Sobolev space Hm,p into Hm,p. We will prove that (Aλ)−1 exists in Hm,p for some λ and estimate its operator norm.  相似文献   
225.
In 1941 Hyers solved the well-known Ulam stability problem for linear mappings. In 1951 Bourgin was the second author to treat this problem for additive mappings. In 1982-1998 Rassias established the Hyers-Ulam stability of linear and nonlinear mappings. In 1983 Skof was the first author to solve the same problem on a restricted domain. In 1998 Jung investigated the Hyers-Ulam stability of more general mappings on restricted domains. In this paper we introduce additive mappings of two forms: of “Jensen” and “Jensen type,” and achieve the Ulam stability of these mappings on restricted domains. Finally, we apply our results to the asymptotic behavior of the functional equations of these types.  相似文献   
226.
本文介绍数学中“不变性”思想,讨论了线性代数中某种条件下秩数不变、特征多项式、特征值不变;对称性、半正定、正定性不变;以及度量性不变.以初等变换为首要方法,解决线性代数中一类重要问题.阐述了矩阵或线性方程组线性变换的本质  相似文献   
227.
By means of the theory of modular forms the formulas for a number of representations of positive integers by two positive quaternary quadratic forms of steps 36 and 60 and by all positive diagonal quadratic forms with seven variables of step 8 are obtain.  相似文献   
228.
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativistic constituent quark model. However its calculation results of GnE agree poorly with the new experimental data. The electromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculation results have good agreement with the new experimental data of GnE after considering the contribution of the quark structure term. This treatment seems to be able to improve the fit to experimental data of Gep/GMp, /Q2F2p/kpF1p,and Gen/GMn as well.  相似文献   
229.
A queueing network consisting of multiserver nodes with different sources of customers is considered. We investigate stationary probability distributions of network states. Their invariance with respect to the functional form of distributions of input and service processes is established under fixed expectations of these distributions and service discipline when any entering customer has a preemptive resume discipline.  相似文献   
230.
本文刻划了本质正规算子模的近似酉等价,并且改进了Carry和Pincus在[1]中的一些结果。  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