全文获取类型
收费全文 | 7029篇 |
免费 | 692篇 |
国内免费 | 741篇 |
专业分类
化学 | 828篇 |
晶体学 | 17篇 |
力学 | 381篇 |
综合类 | 169篇 |
数学 | 5340篇 |
物理学 | 1727篇 |
出版年
2024年 | 8篇 |
2023年 | 65篇 |
2022年 | 119篇 |
2021年 | 133篇 |
2020年 | 148篇 |
2019年 | 151篇 |
2018年 | 168篇 |
2017年 | 210篇 |
2016年 | 211篇 |
2015年 | 152篇 |
2014年 | 290篇 |
2013年 | 478篇 |
2012年 | 326篇 |
2011年 | 412篇 |
2010年 | 356篇 |
2009年 | 461篇 |
2008年 | 478篇 |
2007年 | 461篇 |
2006年 | 448篇 |
2005年 | 404篇 |
2004年 | 314篇 |
2003年 | 361篇 |
2002年 | 325篇 |
2001年 | 310篇 |
2000年 | 259篇 |
1999年 | 244篇 |
1998年 | 245篇 |
1997年 | 200篇 |
1996年 | 130篇 |
1995年 | 100篇 |
1994年 | 84篇 |
1993年 | 64篇 |
1992年 | 46篇 |
1991年 | 41篇 |
1990年 | 27篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 3篇 |
排序方式: 共有8462条查询结果,搜索用时 15 毫秒
81.
单循环赛赛程安排的一个图论方法 总被引:2,自引:0,他引:2
唐保祥 《数学的实践与认识》2004,34(5):120-125
利用图论的边着色理论建立了一个赛程安排的数学模型 .首先建立 n支球队与完全图 Kn的 n个顶点间的一一对应 ,把球队 Ai和 Aj间的比赛关系抽象成 Kn的顶点 i和 j间的边 ( i,j) .然后分别构造出了图K2 m- 1和 K2 m的正常 2 m-1边着色 .从而给出了各球队每两场比赛间得到的休整时间最均等 ,休整的间隔场次数达到上限值 n2 的一个赛程安排方案 相似文献
82.
Global existence and blow-up of solutions to a parabolic system with nonlocal sources and boundaries 总被引:2,自引:0,他引:2
Ling-hua KONG~ 《中国科学A辑(英文版)》2007,50(9):1251-1266
This paper deals with a semi-linear parabolic system with nonlinear nonlocal sources and nonlocal boundaries.By using super-and sub-solution techniques,we first give the sufficient conditions that the classical solution exists globally and blows up in a finite time respectively,and then give the necessary and sufficient conditions that two components u and v blow up simultaneously.Finally,the uniform blow-up profiles in the interior are presented. 相似文献
83.
We isolate several classes of stationary sets of [k]ωand investigate implications among them. Under a large cardinal assumption, we prove a structure theorem for stationary sets. 相似文献
84.
In apparel industry, manufacturers developed standard allowed minutes (SAMs) databases on various manufacturing operations in order to facilitate better scheduling, while effective production schedules ensure smoothness of downstream operations. As apparel manufacturing environment is fuzzy and dynamic, rigid production schedules based on SAMs become futile in the presence of any uncertainty. In this paper, a fuzzification scheme is proposed to fuzzify the static standard time so as to incorporate some uncertainties, in terms of both job-specific and human related factors, into the fabric-cutting scheduling problem. A genetic optimisation procedure is also proposed to search for fault-tolerant schedules using genetic algorithms, such that makespan and scheduling uncertainties are minimised. Two sets of real production data were collected to validate the proposed method. Experimental results indicate that the genetically optimised fault-tolerant schedules not only improve the operation performance but also minimise the scheduling risks. 相似文献
85.
Paul Howard 《Mathematical Logic Quarterly》2007,53(3):247-254
Two theorems are proved: First that the statement “there exists a field F such that for every vector space over F, every generating set contains a basis” implies the axiom of choice. This generalizes theorems of Halpern, Blass, and Keremedis. Secondly, we prove that the assertion that every vector space over ?2 has a basis implies that every well‐ordered collection of two‐element sets has a choice function. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
86.
Ding-kang WANG~ Yan ZHANG Key Laboratory of Mathematics Mechanization Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2007,50(10):1441-1450
We present an algorithm to decompose a polynomial system into a finite set of normal ascending sets such that the set of the zeros of the polynomial system is the union of the sets of the regular zeros of the normal ascending sets.If the polynomial system is zero dimensional,the set of the zeros of the polynomials is the union of the sets of the zeros of the normal ascending sets. 相似文献
87.
本文利用一个新的分片线性NCP函数提出一个新的可行的QP-free方法解非线性不等式约束优化问题.不同于其他的QP-free方法,这个方法只考虑在工作集中的约束函数,工作集是积极集的一个估计,因此子问题的维数不是满秩的.这个方法可行的并且不需假定严格互补条件、聚点的孤立性得到算法的全局收敛性,并且积极约束函数的梯度不要求线性独立的,其中由拟牛顿法得到的子矩阵不需要求一致正定性. 相似文献
88.
New variants of the generalized level method for minimization of convex nondifferentiable functions taking infinite values 总被引:1,自引:1,他引:0
N. A. Sokolov 《Computational Mathematics and Mathematical Physics》2007,47(12):1952-1969
New variants of the generalized level method for minimization of convex Lipschitz functions on a compact set with a nonempty interior are proposed. These variants include the well-known generalized and classical level methods. For the new variants, an estimate of the convergence rate is found, including the variants in which the auxiliary problems are solved approximately. 相似文献
89.
90.
Arthur W. Apter 《Mathematical Logic Quarterly》2006,52(5):457-463
We construct models for the level by level equivalence between strong compactness and supercompactness in which for κ the least supercompact cardinal and δ ≤ κ any cardinal which is either a strong cardinal or a measurable limit of strong cardinals, 2δ > δ + and δ is < 2δ supercompact. In these models, the structure of the class of supercompact cardinals can be arbitrary, and the size of the power set of κ can essentially be made as large as desired. This extends and generalizes [5, Theorem 2] and [4, Theorem 4]. We also sketch how our techniques can be used to establish a weak indestructibility result. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献