全文获取类型
收费全文 | 6565篇 |
免费 | 553篇 |
国内免费 | 416篇 |
专业分类
化学 | 309篇 |
晶体学 | 4篇 |
力学 | 189篇 |
综合类 | 168篇 |
数学 | 6401篇 |
物理学 | 463篇 |
出版年
2024年 | 16篇 |
2023年 | 108篇 |
2022年 | 173篇 |
2021年 | 171篇 |
2020年 | 236篇 |
2019年 | 255篇 |
2018年 | 242篇 |
2017年 | 255篇 |
2016年 | 188篇 |
2015年 | 117篇 |
2014年 | 262篇 |
2013年 | 537篇 |
2012年 | 268篇 |
2011年 | 373篇 |
2010年 | 381篇 |
2009年 | 538篇 |
2008年 | 467篇 |
2007年 | 363篇 |
2006年 | 405篇 |
2005年 | 288篇 |
2004年 | 249篇 |
2003年 | 229篇 |
2002年 | 211篇 |
2001年 | 194篇 |
2000年 | 171篇 |
1999年 | 160篇 |
1998年 | 140篇 |
1997年 | 99篇 |
1996年 | 66篇 |
1995年 | 71篇 |
1994年 | 55篇 |
1993年 | 41篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有7534条查询结果,搜索用时 15 毫秒
101.
面对多样化的市场需求,企业的销售渠道也变得异常复杂,利用网络图可以简化实际问题,并能形象地描述它。本根据网络知识建立了产品分销模型,探求企业在市场需求固定和随机时的最优收益。最后,章还进行实例验算,并做出相应的结果分析。 相似文献
102.
Richard Arratia Bla Bollobs Gregory B. Sorkin 《Journal of Combinatorial Theory, Series B》2004,92(2):199-233
Motivated by circle graphs, and the enumeration of Euler circuits, we define a one-variable “interlace polynomial” for any graph. The polynomial satisfies a beautiful and unexpected reduction relation, quite different from the cut and fuse reduction characterizing the Tutte polynomial.It emerges that the interlace graph polynomial may be viewed as a special case of the Martin polynomial of an isotropic system, which underlies its connections with the circuit partition polynomial and the Kauffman brackets of a link diagram. The graph polynomial, in addition to being perhaps more broadly accessible than the Martin polynomial for isotropic systems, also has a two-variable generalization that is unknown for the Martin polynomial. We consider extremal properties of the interlace polynomial, its values for various special graphs, and evaluations which relate to basic graph properties such as the component and independence numbers. 相似文献
103.
104.
多指标区间决策的理想点贴近法 总被引:5,自引:0,他引:5
研究了指标的权重不能完全确定但知道其所在区域的条件下的多指标决策问题 ,给出了方案与理想解的贴近度及其算法 ,按贴近度的大小可以对方案进行排序 .它同传统的决策方法相比较 ,具有需要信息量少 ,简单可靠等特点 .最后用该决策方法分析了一个实际问题 . 相似文献
105.
106.
Michel Vasquez 《Journal of Heuristics》2004,10(4):407-413
For the Queens_n
2 graph coloring problems no chromatic numbers are available for n > 9 except where n is not a multiple of 2 or 3. In this paper we propose an exact algorithm that takes advantage of the particular structure of these graphs. The algorithm works on the independent sets of the graph rather than on the vertices to be colored. It combines branch and bound, for independent set assignment, with a clique based filtering procedure. A first experimentation of this approach provided the coloring number values ranging for n = 10 to n = 14. 相似文献
107.
This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests. 相似文献
108.
Ioan Tomescu 《Journal of Graph Theory》2003,43(3):210-222
In the set of graphs of order n and chromatic number k the following partial order relation is defined. One says that a graph G is less than a graph H if ci(G) ≤ ci(H) holds for every i, k ≤ i ≤ n and at least one inequality is strict, where ci(G) denotes the number of i‐color partitions of G. In this paper the first ? n/2 ? levels of the diagram of the partially ordered set of connected 3‐chromatic graphs of order n are described. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 210–222, 2003 相似文献
109.
JINJIANG YUAN 《运筹学学报》1998,(3)
1.IntroductionGraphsconsideredinthispaperarefiniteandsimple.FOragraphG,V(G)andE(G)denoteitssetofvenicesandedges,respectively.AbijectionwillbecalledalabellingofG.Letpbeapositiverealnumber.ForagivenlabellingTofagraphG,definethegndiscrepencya.(G,ac)ofTasTheobjectiveoftheminimum-p--sumproblemistofindalabelling7ofagraphGsuchthatac(G,T)isassmallaspossible.ThelabellingTminimizinga.(G,7)iscalledanoptimalHsumlabellingofG.Theminimumvalueiscalledtheminimum-psumofG.ItisshowninI31thattheminimum-… 相似文献
110.
关于k—消去图的若干新结果 总被引:2,自引:0,他引:2
汪长平 《数学物理学报(A辑)》1998,18(3):302-309
设G是一个图.k是自然数.图G的一个k-正则支撑子图称为G的一个k-因子.若对于G的每条边e.G—e都存在一个k-因子,则称G是一个k-消去图.该文得到了一个图是k-消去图的若干充分条件,推广了文[2—4]中有关结论. 相似文献