全文获取类型
收费全文 | 5452篇 |
免费 | 348篇 |
国内免费 | 508篇 |
专业分类
化学 | 415篇 |
晶体学 | 4篇 |
力学 | 319篇 |
综合类 | 121篇 |
数学 | 5082篇 |
物理学 | 367篇 |
出版年
2024年 | 6篇 |
2023年 | 62篇 |
2022年 | 84篇 |
2021年 | 104篇 |
2020年 | 117篇 |
2019年 | 116篇 |
2018年 | 138篇 |
2017年 | 134篇 |
2016年 | 141篇 |
2015年 | 115篇 |
2014年 | 215篇 |
2013年 | 379篇 |
2012年 | 237篇 |
2011年 | 310篇 |
2010年 | 273篇 |
2009年 | 374篇 |
2008年 | 362篇 |
2007年 | 367篇 |
2006年 | 352篇 |
2005年 | 270篇 |
2004年 | 235篇 |
2003年 | 275篇 |
2002年 | 230篇 |
2001年 | 208篇 |
2000年 | 177篇 |
1999年 | 171篇 |
1998年 | 177篇 |
1997年 | 154篇 |
1996年 | 91篇 |
1995年 | 69篇 |
1994年 | 55篇 |
1993年 | 49篇 |
1992年 | 38篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有6308条查询结果,搜索用时 0 毫秒
991.
林拜松 《应用数学和力学(英文版)》1984,5(4):1549-1555
In this paper, we proposed a new cr tenon or mixea-moae brittle fracture, i.e., the strain energy criterion, which can be stated as (KⅠ/KⅠc)2 +(KⅠ/KⅠc)2+(KⅡ/KⅡc)2=1. This criterion is shown to be in good agreement with known experimental data.In this paper, an experimental criterion:(KⅠ/KⅠc)m+(KⅡ/KⅡc)n=1, 1≤nm≤2.is also proposed. 相似文献
992.
993.
1IntroductionLetG=(VE)beaconnectedsimplegraph.AsubsetFofvertexsetViscalIedafeedbackvertexsetofGifthegraPhGFisaf0rest.ThecardinaIity0faminimumfeedbackvertexset0fGisdenotedbyf(G).AvertexsubsetJofvertexsetViscaJledallonseparatingindependentsetofG,ifJisanilldependentsetofVandGJisconnected.Thema-xiammcardinalityofnollseparatingindependelltsetofGisden0tedbyz(G)andiscalledthenonseparatingindepelldentnumberofG,AgraphGiscalledacactusifGisc0nnectedandanytwocyclesofGaredisjoint.Avertexvofacon… 相似文献
994.
The purpose of this paper is to provide a characterization result for the canonical basis of an arbitrary closure operator. This theorem strengthens the result of Burosch, Demetrovics and Katona, who propose a characterization of the generating system of a closure operator defined by the quasi-closed sets of the closure operator. 相似文献
995.
Hans L. Bodlaender Dimitrios M. Thilikos 《Journal of Algorithms in Cognition, Informatics and Logic》1999,32(2):167
In this paper we investigate both the structure of graphs with branchwidth at most three, as well as algorithms to recognise such graphs. We show that a graph has branchwidth at most three if and only if it has treewidth at most three and does not contain the three-dimensional binary cube graph as a minor. A set of four graphs is shown to be the obstruction set for the class of graphs with branchwidth at most three. Moreover, we give a safe and complete set of reduction rules for the graphs with branchwidth at most three. Using this set, a linear time algorithm is given that verifies if a given graph has branchwidth at most three, and, if so, outputs a minimum width branch decomposition. 相似文献
996.
N指标d维广义Wiener过程的极性 总被引:1,自引:0,他引:1
本文讨论了N指标d维广义Wiener过程的极性,并得到了一个集合为极集的充分必要条件. 相似文献
997.
Dulac函数的构造及其应用(Ⅰ) 总被引:3,自引:1,他引:2
本文研究(Ⅰ)和(Ⅱ)类系统Dulac函数的构造问题,作为应用,讨论此两类系统的极限环的不存在性问题,得到了一些新结果. 相似文献
998.
We describe a change of time technique for stochastic control problems with unbounded control set. We demonstrate the technique on a class of maximization problems that do not have optimal controls. Given such a problem, we introduce an extended problem which has the same value function as the original problem and for which there exist optimal controls that are expressible in simple terms. This device yields a natural sequence of suboptimal controls for the original problem. By this we mean a sequence of controls for which the payoff functions approach the value function. 相似文献
999.
Ralf-Dieter Schindler 《Mathematical Logic Quarterly》1999,45(3):361-369
We generalize results of [3] and [1] to hyperprojective sets of reals, viz. to more than finitely many strong cardinals being involved. We show, for example, that if every set of reals in Lω (?) is weakly homogeneously Souslin, then there is an inner model with an inaccessible limit of strong cardinals. 相似文献
1000.
Farzad Didehvar 《Mathematical Logic Quarterly》1999,45(4):467-470
We define a class of so-called ∑(n)-sets as a natural closure of recursively enumerable sets Wn under the relation “∈” and study its properties. 相似文献