全文获取类型
收费全文 | 3689篇 |
免费 | 187篇 |
国内免费 | 392篇 |
专业分类
化学 | 244篇 |
力学 | 39篇 |
综合类 | 31篇 |
数学 | 2302篇 |
物理学 | 146篇 |
综合类 | 1506篇 |
出版年
2024年 | 4篇 |
2023年 | 29篇 |
2022年 | 33篇 |
2021年 | 32篇 |
2020年 | 48篇 |
2019年 | 64篇 |
2018年 | 69篇 |
2017年 | 65篇 |
2016年 | 75篇 |
2015年 | 68篇 |
2014年 | 157篇 |
2013年 | 211篇 |
2012年 | 153篇 |
2011年 | 159篇 |
2010年 | 179篇 |
2009年 | 223篇 |
2008年 | 290篇 |
2007年 | 269篇 |
2006年 | 257篇 |
2005年 | 222篇 |
2004年 | 173篇 |
2003年 | 173篇 |
2002年 | 146篇 |
2001年 | 148篇 |
2000年 | 130篇 |
1999年 | 124篇 |
1998年 | 106篇 |
1997年 | 99篇 |
1996年 | 98篇 |
1995年 | 57篇 |
1994年 | 56篇 |
1993年 | 50篇 |
1992年 | 41篇 |
1991年 | 26篇 |
1990年 | 25篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 6篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1936年 | 2篇 |
排序方式: 共有4268条查询结果,搜索用时 15 毫秒
211.
Patrizio Cintioli 《Mathematical Logic Quarterly》2011,57(5):517-523
Given a reducibility ?r, we say that an infinite set A is r‐introimmune if A is not r‐reducible to any of its subsets B with |A\B| = ∞. We consider the many‐one reducibility ?m and we prove the existence of a low1 m‐introimmune set in Π01 and the existence of a low1 bi‐m‐introimmune set. 相似文献
212.
M. Smithson 《Mathematical Social Sciences》1984,7(3):231-251
The connectives ‘and’ and ‘or’ are potentially useful in multivariate analysis and theory construction. They are simple, logical ways to connect two or more variables together. However, until recently there has been no framework for operationalizing these connectives for continuous variables, and this lack has severely limited their use. Using fuzzy set theory as a basis for such a framework, this paper lays out the necessary tools and models to permit the use of ‘and’ and ‘or’ in multivariate analysis.Section 1 introduces conventional operators for ‘and’ and ‘or’, and Section 2 provides suitable extensions and generalizations of them. Section 3 sets out the required least-squares techniques for fitting these generalized operators to data, first in the context of ANOVA problems and then in regression contexts, for single-connective (three-variable) models. The theoretical developments and examples from real data-sets demonstrate the utility of ‘and’ and ‘or’ as a means to cell-specific interpretations of interaction effects which can also readily be translated into English. Section 4 extends these developments to multivariate, multiple-connective models and discusses issues of generalizability. The paper concludes (Section 5) with a brief discussion of remaining unsolved problems, future prospects for more sophisticated models, and computer programs. 相似文献
213.
214.
《Annals of Pure and Applied Logic》2022,173(8):103135
We further develop a forcing notion known as Coding with Perfect Trees and show that this poset preserves, in a strong sense, definable P-points, definable tight MAD families and definable selective independent families. As a result, we obtain a model in which , each of , , has a witness and there is a well-order of the reals. Note that both the complexity of the witnesses of the above combinatorial cardinal characteristics, as well as the complexity of the well-order are optimal. In addition, we show that the existence of a well-order of the reals is consistent with and each of the following: , , , where the smaller cardinal characteristics have co-analytic witnesses.Our methods allow the preservation of only sufficiently definable witnesses, which significantly differs from other preservation results of this type. 相似文献
215.
216.
217.
《Discrete Mathematics》2022,345(6):112832
An oriented hypergraph is an oriented incidence structure that extends the concepts of signed graphs, balanced hypergraphs, and balanced matrices. We introduce hypergraphic structures and techniques that generalize the circuit classification of the signed graphic frame matroid to any oriented hypergraphic incidence matrix via its locally-signed-graphic substructure. To achieve this, Camion's algorithm is applied to oriented hypergraphs to provide a generalization of reorientation sets and frustration that is only well-defined on balanceable oriented hypergraphs. A simple partial characterization of unbalanceable circuits extends the applications to representable matroids demonstrating that the difference between the Fano and non-Fano matroids is one of balance. 相似文献
218.
《Discrete Mathematics》2022,345(1):112659
In a recent paper, Gerbner, Patkós, Tuza and Vizer studied regular F-saturated graphs. One of the essential questions is given F, for which n does a regular n-vertex F-saturated graph exist. They proved that for all sufficiently large n, there is a regular -saturated graph with n vertices. We extend this result to both and and prove some partial results for larger complete graphs. Using a variation of sum-free sets from additive combinatorics, we prove that for all , there is a regular -saturated with n vertices for infinitely many n. Studying the sum-free sets that give rise to -saturated graphs is an interesting problem on its own and we state an open problem in this direction. 相似文献
219.
Supervised fuzzy pattern recognition 总被引:1,自引:0,他引:1
Boris Shukhat 《Fuzzy Sets and Systems》1998,100(1-3):257-265
This paper is devoted to the problem of supervised fuzzy pattern recognition. The cases with non-fuzzy and fuzzy labels are considered. Based on the properties of linearly separable fuzzy classes, some algorithms are proposed for building matching functions of these classes. All algorithms are computer oriented and can be implemented for the automatic recognition of fuzzy patterns. 相似文献
220.