全文获取类型
收费全文 | 2825篇 |
免费 | 126篇 |
国内免费 | 248篇 |
专业分类
化学 | 220篇 |
晶体学 | 1篇 |
力学 | 50篇 |
综合类 | 30篇 |
数学 | 2671篇 |
物理学 | 227篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 36篇 |
2021年 | 32篇 |
2020年 | 41篇 |
2019年 | 61篇 |
2018年 | 57篇 |
2017年 | 53篇 |
2016年 | 67篇 |
2015年 | 58篇 |
2014年 | 125篇 |
2013年 | 182篇 |
2012年 | 108篇 |
2011年 | 149篇 |
2010年 | 124篇 |
2009年 | 201篇 |
2008年 | 227篇 |
2007年 | 177篇 |
2006年 | 161篇 |
2005年 | 151篇 |
2004年 | 108篇 |
2003年 | 112篇 |
2002年 | 105篇 |
2001年 | 97篇 |
2000年 | 94篇 |
1999年 | 91篇 |
1998年 | 88篇 |
1997年 | 77篇 |
1996年 | 59篇 |
1995年 | 36篇 |
1994年 | 32篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 27篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1969年 | 2篇 |
排序方式: 共有3199条查询结果,搜索用时 15 毫秒
111.
On Clique-Transversals and Clique-Independent Sets 总被引:1,自引:0,他引:1
Guillermo Durán Min Chih Lin Jayme L. Szwarcfiter 《Annals of Operations Research》2002,116(1-4):71-77
A clique-transversal of a graph G is a subset of vertices intersecting all the cliques of G. A clique-independent set is a subset of pairwise disjoint cliques of G. Denote by
C
(G) and
C
(G) the cardinalities of the minimum clique-transversal and maximum clique-independent set of G, respectively. Say that G is clique-perfect when
C
(H)=
C
(H), for every induced subgraph H of G. In this paper, we prove that every graph not containing a 4-wheel nor a 3-fan as induced subgraphs and such that every odd cycle of length greater than 3 has a short chord is clique-perfect. The proof leads to polynomial time algorithms for finding the parameters
C
(G) and
C
(G), for graphs belonging to this class. In addition, we prove that to decide whether or not a given subset of vertices of a graph is a clique-transversal is Co-NP-Complete. The complexity of this problem has been mentioned as unknown in the literature. Finally, we describe a family of highly clique-imperfect graphs, that is, a family of graphs G whose difference
C
(G)–
C
(G) is arbitrarily large. 相似文献
112.
Given a precompact subset of a type Banach space , where , we prove that for every and all
holds, where is the absolutely convex hull of and denotes the dyadic entropy number. With this inequality we show in particular that for given and with for all the inequality holds true for all . We also prove that this estimate is asymptotically optimal whenever has no better type than . For this answers a question raised by Carl, Kyrezi, and Pajor which has been solved up to now only for the Hilbert space case by F. Gao.
holds, where is the absolutely convex hull of and denotes the dyadic entropy number. With this inequality we show in particular that for given and with for all the inequality holds true for all . We also prove that this estimate is asymptotically optimal whenever has no better type than . For this answers a question raised by Carl, Kyrezi, and Pajor which has been solved up to now only for the Hilbert space case by F. Gao.
113.
Tero Kilpelä inen Xiao Zhong 《Proceedings of the American Mathematical Society》2002,130(6):1681-1688
We show that sets of Hausdorff measure zero are removable for -Hölder continuous solutions to quasilinear elliptic equations similar to the -Laplacian. The result is optimal. We also treat larger sets in terms of a growth condition. In particular, our results apply to quasiregular mappings.
114.
Jacek Cichon Andrzej Jasinski Anastasis Kamburelis Przemyslaw Szczepaniak 《Proceedings of the American Mathematical Society》2002,130(6):1833-1842
In this paper we discuss various questions connected with translations of subsets of the real line. Most of these questions originate from W. Sierpinski. We discuss the number of translations a single subset of the reals may have. Later we discuss almost invariant subsets of Abelian groups.
115.
Paul J. Szeptycki 《Proceedings of the American Mathematical Society》2002,130(12):3713-3717
An almost disjoint family is said to be soft if there is an infinite set that meets each in a nonempty but finite set. We consider the associated cardinal invariant defined to be the minimal cardinality of an almost disjoint family that is not soft. We show that this cardinal coincides with J. Brendle's cardinal .
116.
117.
A subset of the -dimensional torus is called a set of uniqueness, or -set, if every multiple trigonometric series spherically converging to outside vanishes identically. We show that all countable sets are -sets and also that sets are -sets for every . In particular, , where is the Cantor set, is an set and hence a -set. We will say that is a -set if every multiple trigonometric series spherically Abel summable to outside and having certain growth restrictions on its coefficients vanishes identically. The above-mentioned results hold also for sets. In addition, every -set has measure , and a countable union of closed -sets is a -set.
118.
We show that there do not exist computable functions f 1(e, i), f 2(e, i), g 1(e, i), g 2(e, i) such that for all e, i ∈ ω, (1) $ {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (2) $ {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)} \leqslant _{{\rm T}} {\left( {W_{e} - W_{i} } \right)}; $ (3) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)} \oplus {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}; $ (4) $ {\left( {W_{e} - W_{i} } \right)} \not\leqslant _{{\rm T}} {\left( {W_{{f_{1} {\left( {e,i} \right)}}} - W_{{f_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset};{\text{and}} $ (5) $ {\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\left( {W_{{g_{1} {\left( {e,i} \right)}}} - W_{{g_{2} {\left( {e,i} \right)}}} } \right)}{\text{unless}}{\left( {W_{e} - W_{i} } \right)} \leqslant _{{\rm T}} {\emptyset}. $ It follows that the splitting theorems of Sacks and Cooper cannot be combined uniformly. 相似文献
119.
Decision-making in an environment of uncertainty and imprecision for real-world problems is a complex task. In this paper it is introduced general finite state fuzzy Markov chains that have a finite convergence to a stationary (may be periodic) solution. The Cesaro average and the -potential for fuzzy Markov chains are defined, then it is shown that the relationship between them corresponds to the Blackwell formula in the classical theory of Markov decision processes. Furthermore, it is pointed out that recurrency does not necessarily imply ergodicity. However, if a fuzzy Markov chain is ergodic, then the rows of its ergodic projection equal the greatest eigen fuzzy set of the transition matrix. Then, the fuzzy Markov chain is shown to be a robust system with respect to small perturbations of the transition matrix, which is not the case for the classical probabilistic Markov chains. Fuzzy Markov decision processes are finally introduced and discussed. 相似文献
120.
Our main aim from this work is to see which theorems in classical probability theory are still valid in fuzzy probability theory. Following Gudder's approach [Demonestratio Mathematica 31(3), 1998, 235–254; Foundations of Physics, 30, 1663–1678] to fuzzy probability theory, the basic concepts of the theory, that is of fuzzy probability measures and fuzzy random variables (observables), are presented. We show that fuzzy random variables extend the usual ones. Moreover, we prove that for any separable metrizable space, the crisp observables coincide with random variables. Then we prove the existence of a joint observable for any collection of observables, and we prove the weak law of large numbers and the central limit theorem in the fuzzy context. We construct a new definition of almost everywhere convergence. After proving that Gudder's definition implies ours and presenting an example that indicates that the converse is not true, we prove the strong law of large numbers according to this definition. 相似文献