全文获取类型
收费全文 | 386篇 |
免费 | 20篇 |
国内免费 | 17篇 |
专业分类
化学 | 3篇 |
力学 | 8篇 |
综合类 | 3篇 |
数学 | 398篇 |
物理学 | 11篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 14篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 12篇 |
2009年 | 41篇 |
2008年 | 34篇 |
2007年 | 28篇 |
2006年 | 21篇 |
2005年 | 12篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有423条查询结果,搜索用时 156 毫秒
31.
Biembedding a Steiner Triple System With a Hamilton Cycle Decomposition of a Complete Graph 下载免费PDF全文
Thomas A. McCourt 《Journal of Graph Theory》2014,77(1):68-87
We construct a face two‐colourable, blue and green say, embedding of the complete graph in a nonorientable surface in which there are blue faces each of which have a hamilton cycle as their facial walk and green faces each of which have a triangle as their facial walk; equivalently a biembedding of a Steiner triple system of order n with a hamilton cycle decomposition of , for all and . Using a variant of this construction, we establish the minimum genus of nonorientable embeddings of the graph , for where and . 相似文献
32.
Daniel Horsley 《组合设计杂志》2014,22(8):343-365
It was proved in 2009 that any partial Steiner triple system of order u has an embedding of order v for each admissible . This result is best possible in the sense that, for each , there exists a partial Steiner triple system of order u that does not have an embedding of order v for any . Many partial Steiner triple systems do have embeddings of orders smaller than , but much less is known about when these embeddings exist. In this paper, we detail a method for constructing such embeddings. We use this method to show that each member of a wide class of partial Steiner triple systems has an embedding of order v for at least half (or nearly half) of the orders for which an embedding could exist. For some members of this class we are able to completely determine the set of all orders for which the member has an embedding. 相似文献
33.
Let n, k, and t be integers satisfying . A Steiner system with parameters t, k, and n is a k‐uniform hypergraph on n vertices in which every set of t distinct vertices is contained in exactly one edge. An outstanding problem in Design Theory is to determine whether a nontrivial Steiner system exists for . In this note we prove that for every and sufficiently large n, there exists an almost Steiner system with parameters t, k, and n; that is, there exists a k‐uniform hypergraph on n vertices such that every set of t distinct vertices is covered by either one or two edges. 相似文献
34.
A Steiner system is called a Steiner quintuple systems of order v. The smallest order for which the existence, or otherwise, of a Steiner quintuple system is unknown is 21. In this article, we prove that, if an S(4, 5, 21) exists, the order of its full automorphism group is 1, 2, 3, 4, 5, 6, 7, or 10. 相似文献
35.
Several authors have demonstrated how reductions can be used to improve the efficiency with which the Steiner Problem in Graphs can be solved. Previous reduction algorithms have been largely ad hoc in nature. This paper uses a theory of confluence to show that, in many cases, all maximal reduction sequences are equivalent, gaining insights into the design of reduction algorithms that obtain a maximum degree of reduction. 相似文献
36.
We describe Steiner loops of nilpotency class 2 and establish the classification of finite 3-generated nilpotent Steiner loops of nilpotency class 2. 相似文献
37.
A tight Heffter array is an matrix with nonzero entries from such that (i) the sum of the elements in each row and each column is 0, and (ii) no element from appears twice. We prove that exist if and only if both m and n are at least 3. If H has the property that all entries are integers of magnitude at most , every row and column sum is 0 over the integers, and H also satisfies ), we call H an integer Heffter array. We show integer Heffter arrays exist if and only if . Finally, an integer Heffter array is shiftable if each row and column contains the same number of positive and negative integers. We show that shiftable integer arrays exists exactly when both are even. 相似文献
38.
IntroductionInPartⅠofthisseries (see [1 ] )weproposeamethodtoextendanoperatorTdefinedinaspaceofcontinuousfunctionstoanoperatorT definedinaspaceofcontinuousset_valuedfunctions ,viaSteinerselections.Westudysomepropertiesofthisextensionandalsoweanalyzesomerel… 相似文献
39.
M.Düldül 《应用数学和力学(英文版)》2003,24(8):945-949
The Steiner formula and the mixture area formula given by M(U|¨)ller were expressed under the one-parameter closed planar homothetic motions in the complex sense . Also, using the generalization of Steiner formula, the result of Holditch theorem for homothetic motions is got. In the case of the homothetic scale h≡1 the results given by M(U|¨)ller are obtained as a special case. 相似文献
40.
A Steiner triple system of order v, STS(v), may be called equivalent to another STS(v) if one can be converted to the other by a sequence of three simple operations involving Pasch trades with a single negative block. It is conjectured that any two STS(v)s on the same base set are equivalent in this sense. We prove that the equivalence class containing a given system S on a base set V contains all the systems that can be obtained from S by any sequence of well over one hundred distinct trades, and that this equivalence class contains all isomorphic copies of S on V. We also show that there are trades which cannot be effected by means of Pasch trades with a single negative block. 相似文献