全文获取类型
收费全文 | 6507篇 |
免费 | 443篇 |
国内免费 | 656篇 |
专业分类
化学 | 866篇 |
晶体学 | 6篇 |
力学 | 358篇 |
综合类 | 171篇 |
数学 | 5714篇 |
物理学 | 491篇 |
出版年
2024年 | 7篇 |
2023年 | 65篇 |
2022年 | 99篇 |
2021年 | 139篇 |
2020年 | 134篇 |
2019年 | 157篇 |
2018年 | 161篇 |
2017年 | 170篇 |
2016年 | 185篇 |
2015年 | 139篇 |
2014年 | 276篇 |
2013年 | 442篇 |
2012年 | 287篇 |
2011年 | 348篇 |
2010年 | 322篇 |
2009年 | 422篇 |
2008年 | 419篇 |
2007年 | 404篇 |
2006年 | 398篇 |
2005年 | 326篇 |
2004年 | 288篇 |
2003年 | 346篇 |
2002年 | 283篇 |
2001年 | 252篇 |
2000年 | 222篇 |
1999年 | 213篇 |
1998年 | 215篇 |
1997年 | 187篇 |
1996年 | 116篇 |
1995年 | 97篇 |
1994年 | 82篇 |
1993年 | 64篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有7606条查询结果,搜索用时 31 毫秒
81.
利用集合在某点的相依切锥、法向锥和可行方向锥等研究向量优化问题的有效点、 弱有效点和真有效点的特征,对局部有效点、局部弱有效点和局部真有效点与集合的各 锥之间的关系作了刻画. 相似文献
82.
83.
Xin Tao YE Chong LI 《数学学报(英文版)》2007,23(1):65-76
The BCQ and the Abadie CQ for infinite systems of convex inequalities in Banach spaces are characterized in terms of the upper semi-continuity of the convex cones generated by the subdifferentials of active convex functions. Some relationships with other constraint qualifications such as the CPLV and the Slate condition are also studied. Applications in best approximation theory are provided. 相似文献
84.
In this article,the Hausdorff dimension and exact Hausdorff measure function of any random sub-self-similar set are obtained under some reasonable conditions.Several examples are given at the end. 相似文献
85.
John Ginsburg 《Order》1989,6(2):137-157
For a partially ordered setP and an elementx ofP, a subsetS ofP is called a cutset forx inP if every element ofS is noncomparable tox and every maximal chain ofP meets {x}∪S. We letc(P) denote the smallest integerk such that every elementx ofP has a cutsetS with ‖S‖?k: Ifc(P)?n we say thatP has then-cutset property. Our results bear on the following question: givenP, what is the smallestn such thatP can be embedded in a partially ordered set having then-cutset property? As usual, 2 n denotes the Boolean lattice of all subsets of ann-element set, andB n denotes the set of atoms and co-atoms of 2 n . We establish the following results: (i) a characterization, by means of forbidden configurations, of whichP can be embedded in a partially ordered set having the 1-cutset property; (ii) ifP contains a copy of 2 n , thenc(P)?2[n/2]?1; (iii) for everyn>3 there is a partially ordered setP containing 2 n such thatc(P)<c(2 n ); (iv) for every positive integern there is a positive integerN such that, ifB m is contained in a partially ordered set having then-cutset property, thenm?N. 相似文献
86.
A family of skew Hadamard difference sets 总被引:1,自引:0,他引:1
Cunsheng Ding 《Journal of Combinatorial Theory, Series A》2006,113(7):1526-1535
In 1933 a family of skew Hadamard difference sets was described by Paley using matrix language and was called the Paley-Hadamard difference sets in the literature. During the last 70 years, no new skew Hadamard difference sets were found. It was conjectured that there are no further examples of skew Hadamard difference sets. This conjecture was proved to be true for the cyclic case in 1954, and further progress in favor of this conjecture was made in the past 50 years. However, the conjecture remains open until today. In this paper, we present a family of new perfect nonlinear (also called planar) functions, and construct a family of skew Hadamard difference sets using these perfect nonlinear functions. We show that some of the skew Hadamard difference sets presented in this paper are inequivalent to the Paley-Hadamard difference sets. These new examples of skew Hadamard difference sets discovered 70 years after the Paley construction disprove the longstanding conjecture on skew Hadamard difference sets. The class of new perfect nonlinear functions has applications in cryptography, coding theory, and combinatorics. 相似文献
87.
In this paper we characterize the local maxima of a continuous global optimization formulation for finding the independence
number of a graph. Classical Karush-Kuhn-Tucker conditions and simple combinatorial arguments are found sufficient to deduce
several interesting properties of the local and global maxima. These properties can be utilized in developing new approaches
to the maximum independent set problem. 相似文献
88.
对于线性型多目标半定规划问题,引进加权中心路径的概念,并利用单目标半定规划的中心路径法,提出了求解多目标半定规划问题的加权中心路径法,先得型对一个叔向量的有效解,然后在此基础上,提出了通过一次迭代得到对应一定范围内其他任意权向量的有效解的一步修正方法. 相似文献
89.
Yu Jun ZHU Jin Lian ZHANG Lian Fa HE 《数学学报(英文版)》2006,22(5):1321-1328
In this paper, we consider the shadowing and the inverse shadowing properties for C^1 endomorphisms. We show that near a hyperbolic set a C^1 endomorphism has the shadowing property, and a hyperbolic endomorphism has the inverse shadowing property with respect to a class of continuous methods. Moreover, each of these shadowing properties is also "uniform" with respect to C^1 perturbation. 相似文献
90.
关于Ramsey数下界的部分结果 总被引:3,自引:1,他引:2
刘富贵 《数学的实践与认识》2002,32(1):97-99
本文得到 Ramsey数下界的一个计算公式 :R( l,s+ t-2 )≥ R( l,s) + R( l,t) -1 ,(式中 l、s、t≥ 3) .用此公式算得的 Ramsey数的下界比用其它公式算得的下界好 . 相似文献