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   2265篇
  免费   165篇
  国内免费   245篇
化学   75篇
晶体学   1篇
力学   106篇
综合类   42篇
数学   2039篇
物理学   412篇
  2024年   4篇
  2023年   31篇
  2022年   26篇
  2021年   56篇
  2020年   52篇
  2019年   60篇
  2018年   51篇
  2017年   63篇
  2016年   71篇
  2015年   69篇
  2014年   97篇
  2013年   137篇
  2012年   104篇
  2011年   107篇
  2010年   89篇
  2009年   136篇
  2008年   201篇
  2007年   145篇
  2006年   136篇
  2005年   128篇
  2004年   100篇
  2003年   109篇
  2002年   101篇
  2001年   74篇
  2000年   87篇
  1999年   67篇
  1998年   71篇
  1997年   60篇
  1996年   52篇
  1995年   30篇
  1994年   28篇
  1993年   23篇
  1992年   12篇
  1991年   12篇
  1990年   9篇
  1989年   6篇
  1988年   7篇
  1987年   5篇
  1986年   3篇
  1985年   9篇
  1984年   5篇
  1983年   2篇
  1982年   6篇
  1981年   6篇
  1980年   12篇
  1979年   4篇
  1978年   4篇
  1977年   4篇
  1976年   1篇
  1936年   3篇
排序方式: 共有2675条查询结果,搜索用时 20 毫秒
991.
基于联系数的属性权重未知的区间数多属性决策研究   总被引:1,自引:0,他引:1  
针对一类属性权重未知且属性值用区间数表示的不确定多属性决策问题,把区间数表示的属性值转换为二元联系数,并改写成三角函数,按决策方案属性值方差确定属性权重,根据各方案属性加权综合值确定方案初排序,再通过不确定性分析方法做出最终排序.实例应用表明上述方法简明实用有效,而且能方便地开展方案排序的不确定分析.  相似文献   
992.
993.
An operator convex function on (0,∞)(0,) which satisfies the symmetry condition k(x−1)=xk(x)k(x1)=xk(x) can be used to define a type of non-commutative multiplication by a positive definite matrix (or its inverse) using the primitive concepts of left and right multiplication and the functional calculus. The operators for the inverse can be used to define quadratic forms associated with Riemannian metrics which contract under the action of completely positive trace-preserving maps.  相似文献   
994.
Trapezoidal intuitionistic fuzzy numbers (TrIFNs) is a special intuitionistic fuzzy set on a real number set. TrIFNs are useful to deal with ill-known quantities in decision data and decision making problems themselves. The focus of this paper is on multi-attribute group decision making (MAGDM) problems in which the attribute values are expressed with TrIFNs, which are solved by developing a new decision method based on power average operators of TrIFNs. The new operation laws for TrIFNs are given. From a viewpoint of Hausdorff metric, the Hamming and Euclidean distances between TrIFNs are defined. Hereby the power average operator of real numbers is extended to four kinds of power average operators of TrIFNs, involving the power average operator of TrIFNs, the weighted power average operator of TrIFNs, the power ordered weighted average operator of TrIFNs, and the power hybrid average operator of TrIFNs. In the proposed group decision method, the individual overall evaluation values of alternatives are generated by using the power average operator of TrIFNs. Applying the hybrid average operator of TrIFNs, the individual overall evaluation values of alternatives are then integrated into the collective ones, which are used to rank the alternatives. The example analysis shows the practicality and effectiveness of the proposed method.  相似文献   
995.
The goal of the present paper is to investigate some new HUR-stability results by applying the alternative fixed point of generalized quartic functional equationin β-Banach modules on Banach algebras. The concept of Ulam-Hyers-Rassias stability (briefly, HUR-stability) originated from Th. M. Rassias stability theorem that appeared in his paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978), 297-300.  相似文献   
996.
In this paper, we prove some fixed point theorems for generalized contractions in the setting of G-metric spaces. Our results extend a result of Edelstein [M. Edelstein, On fixed and periodic points under contractive mappings, J. London Math. Soc., 37 (1962), 74–79] and a result of Suzuki [T. Suzuki, A new type of fixed point theorem in metric spaces, Nonlinear Anal., 71 (2009), 5313–5317]. We prove, also, a fixed point theorem in the setting of G-cone metric spaces.  相似文献   
997.
We discuss a class of discrete dynamic systems in a complete metric space (M, d) defined by mappings which satisfy various types of contractive type conditions. Their variants in ordered Banach space are investigated and applied to solve the global asymptotic stability of the equilibriums of some discrete dynamic systems.  相似文献   
998.
999.
Given a pair (metric g, symmetric 2-covariant tensor field H though as a Rayleigh dissipation) on a path space (manifold M, semispray S), the family of nonlinear connections N such that H equals the dynamical derivative of g with respect to (S,N) is determined by using the Obata tensors. In this way, we generalize the case of metric nonlinear connections as well as that of recurrent metrics. As applications, we treat firstly the case of Finslerian (α,β)-metrics finding all nonlinear connections for which the associated Finsler-Sasaki metric is exactly the dynamical derivative of the Riemannian-Sasaki metric. Secondly, we apply our results for the case of Beil metrics used in Relativity and field theories.  相似文献   
1000.
The half-Apollonian metric is a generalization of the hyperbolic metric, similar to the Apollonian metric. It can be defined in arbitrary domains in the euclidean space and has the advantages of being easy to calculate and estimate. We show that the half-Apollonian metric has many geodesics and use this fact to show that in most domains all the isometries of the metric are similarity mappings.  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