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   1427篇
  免费   46篇
  国内免费   133篇
化学   92篇
晶体学   1篇
力学   32篇
综合类   10篇
数学   1268篇
物理学   203篇
  2024年   1篇
  2023年   11篇
  2022年   16篇
  2021年   17篇
  2020年   20篇
  2019年   31篇
  2018年   38篇
  2017年   28篇
  2016年   31篇
  2015年   19篇
  2014年   52篇
  2013年   151篇
  2012年   56篇
  2011年   61篇
  2010年   57篇
  2009年   100篇
  2008年   106篇
  2007年   92篇
  2006年   81篇
  2005年   64篇
  2004年   62篇
  2003年   64篇
  2002年   44篇
  2001年   62篇
  2000年   54篇
  1999年   42篇
  1998年   44篇
  1997年   33篇
  1996年   39篇
  1995年   11篇
  1994年   17篇
  1993年   16篇
  1992年   17篇
  1991年   12篇
  1990年   10篇
  1989年   3篇
  1988年   11篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   1篇
  1982年   4篇
  1981年   4篇
  1980年   5篇
  1979年   1篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
排序方式: 共有1606条查询结果,搜索用时 218 毫秒
991.
We characterize the O(N)-equivariant vortex solution for Ginzburg-Landau type equations in the N-dimensional Euclidean space and we prove its local energy minimality for the corresponding energy functional.  相似文献   
992.
Through a simple extension of Brézis-Browder principle to partially ordered spaces, a very general strong minimal point existence theorem on quasi ordered spaces, is proved. This theorem together with a generic quasi order and a new notion of strong approximate solution allow us to obtain two strong solution existence theorems, and three general Ekeland variational principles in optimization problems where the objective space is quasi ordered. Then, they are applied to prove strong minimal point existence results, generalizations of Bishop-Phelps lemma in linear spaces, and Ekeland variational principles in set-valued optimization problems through a set solution criterion.  相似文献   
993.
In the finite-dimensional case, we present a new approach to the theory of cones with a mapping cone symmetry, first introduced by Størmer. Our method is based on a definition of an inner product in the space of linear maps between two algebras of operators and the fact that the Jamio?kowski-Choi isomorphism is an isometry. We consider a slightly modified class of cones, although not substantially different from the original mapping cones by Størmer. Using the new approach, several known results are proved faster and often in more generality than before. For example, the dual of a mapping cone turns out to be a mapping cone as well, without any additional assumptions. The main result of the paper is a characterization of cones with a mapping cone symmetry, saying that a given map is an element of such cone if and only if the composition of the map with the conjugate of an arbitrary element in the dual cone is completely positive. A similar result was known in the case where the map goes from an algebra of operators into itself and the cone is a symmetric mapping cone. Our result is proved without the additional assumptions of symmetry and equality between the domain and the target space. We show how it gives a number of older results as a corollary, including an exemplary application.  相似文献   
994.
We address the enumeration of properly q-colored planar maps, or more precisely, the enumeration of rooted planar maps M weighted by their chromatic polynomial χM(q) and counted by the number of vertices and faces. We prove that the associated generating function is algebraic when q≠0,4 is of the form 2+2cos(jπ/m), for integers j and m. This includes the two integer values q=2 and q=3. We extend this to planar maps weighted by their Potts polynomial PM(q,ν), which counts all q-colorings (proper or not) by the number of monochromatic edges. We then prove similar results for planar triangulations, thus generalizing some results of Tutte which dealt with their proper q-colorings. In statistical physics terms, the problem we study consists in solving the Potts model on random planar lattices. From a technical viewpoint, this means solving non-linear equations with two “catalytic” variables. To our knowledge, this is the first time such equations are being solved since Tutte?s remarkable solution of properly q-colored triangulations.  相似文献   
995.
Some common fixed point theorems due to Abbas and Khan [M. Abbas, A.R. Khan, Common fixed points of generalized contractive hybrid pairs in symmetric spaces, Fixed Point Theor. Appl. 2009 (2009) 11, Article ID 869407, doi:10.1155/2009/869407], and Abbas and Rhoades [M. Abbas, B.E. Rhoades, Common fixed point theorems for hybrid pairs of occasionally weakly compatible mappings defined on symmetric spaces, Pan. Amer. Math. J. 18 (1) (2008) 55-62] are proved for two new classes of hybrid pair of mappings which contain occasionally weakly compatible hybrid pairs as a proper subclass. Consequently, some results proved by Hussain et al. [N. Hussain, M.A. Khamsi, A. Latif, Common fixed points for JH-operators and occasionally weakly biased pairs under relaxed conditions, Nonlinear Anal. 74 (2011) 2133-2140], Bhatt et al. [A. Bhatt, et al., Common fixed point theorems for occasionally weakly compatible mappings under relaxed conditions, Nonlinear Anal. 73 (2010) 176-182] and many others are extended to hybrid pair of mappings. Examples are also presented to support the concepts defined in the paper.  相似文献   
996.
997.
The bifurcations of orbit flip homoclinic loop with nonhyperbolic equilibria are investigated. By constructing local coordinate systems near the unperturbed homoclinic orbit, Poincaré maps for the new system are established. Then the existence of homoclinic orbit and the periodic orbit is studied for the system accompanied with transcritical bifurcation.  相似文献   
998.
令H为复数域C上的Hilbert空间,A为H上的标准算子代数.设δ:A→B(H)是线性映射.本文证明了,如果对任意A∈A成立δ(AA~*A)=δ(A)A~*A-Aδ(A~*)A+AA~*δ(A),则存在λ∈C及算子S,T∈B(H)满足S+T=λI,使得对所有的A∈A都有δ(A)=SA-AT.  相似文献   
999.
假定(X,‖.‖)为可分的Banach空间,X*为其对偶空间,X*可分。设(Ω,Φ,P)为完备的概率空间,{Φn,n≥1}为Φ的上升子σ-域族,且Φ=∨Φn本文首先讨论了集值Subpramart若干性质,在此基础上,给出了集值Subpramart的一类Riesz鞅逼近。  相似文献   
1000.
在实赋范空间X的所有非空有界闭子集构成的集类上,利用Hausdorff距离定义了集值模糊测度,其次,给出了伪零可加、伪零可减、伪自连续性、一致伪自连续性等的定义,进而研究了它们之间的蕴涵关系.  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