全文获取类型
收费全文 | 498篇 |
免费 | 7篇 |
国内免费 | 4篇 |
专业分类
化学 | 213篇 |
晶体学 | 1篇 |
力学 | 29篇 |
数学 | 150篇 |
物理学 | 116篇 |
出版年
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 22篇 |
2012年 | 17篇 |
2011年 | 25篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 32篇 |
2005年 | 11篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1971年 | 2篇 |
1969年 | 5篇 |
1940年 | 2篇 |
1939年 | 5篇 |
1936年 | 2篇 |
1930年 | 2篇 |
排序方式: 共有509条查询结果,搜索用时 15 毫秒
111.
A Structured Family of Clustering and Tree Construction Methods 总被引:1,自引:0,他引:1
A cluster A is an Apresjan cluster if every pair of objects within A is more similar than either is to any object outside A. The criterion is intuitive, compelling, but often too restrictive for applications in classification. We therefore explore extensions of Apresjan clustering to a family of related hierarchical clustering methods. The extensions are shown to be closely connected with the well-known single and average linkage tree constructions. A dual family of methods for classification by splits is also presented. Splits are partitions of the set of objects into two disjoint blocks and are widely used in domains such as phylogenetics. Both the cluster and split methods give rise to progressively refined tree representations. We exploit dualities and connections between the various methods, giving polynomial time construction algorithms for most of the constructions and NP-hardness results for the rest. 相似文献
112.
Kilby Seth Jin Zhongmin Avachat Ashish Kanies Bryant Woolstenhulme Nicolas Lee Hyoung K. Graham Joseph 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):445-446
Journal of Radioanalytical and Nuclear Chemistry - In the original article, Equation 4 was incorrectly published. The correct equation is provided in this correction 相似文献
113.
Thomas R. Sharp Kyle R. LeemanD.Eugene Bryant George J. Horan 《Tetrahedron letters》2003,44(8):1559-1561
Photostability challenge of ziprasidone in solution shows that the benzisothiazole moiety undergoes isomerization to the corresponding benzthiazole. A model compound, 3-piperazinyl-1,2-benzisothiazole, also undergoes this photoisomerization. Identification of the products has been confirmed by synthesis of the proposed molecules. 相似文献
114.
115.
J Bryant 《The Journal of the Operational Research Society》2007,58(5):602-613
Drama theory is little more than a decade old and has already proved a versatile tool for analysing collaborations and conflicts. However, its widespread use has, it is argued here, been inhibited by a number of factors, some trivial, others more substantial. Following a resume of its emergence and a sketch of the ways that it has thus far been used, this paper sets out to examine and dispel the mist of prejudice, ambiguity and misinterpretation that has accumulated. Some specific application pathways are described, demonstrating how the strengths of the drama theory framework can be most effectively be exploited in practice. The paper includes some pointers for future development and exploitation. 相似文献
116.
A transformation which allows us to obtain an orthogonal double cover of a graph G from any permutation of the edge set of G is described. This transformation is used together with existence results for self-orthogonal latin squares, to give a simple proof of a conjecture of Chung and West. 相似文献
117.
118.
119.
120.
We present drainage simulations that allow trapping of wetting phase in a simple but nontrivial granular medium, a dense random packing of equal spheres. The basis for the simulations is a network model derived directly from the known locations and dimensions of pore space features. This provides a means of evaluating the morphology of trapped wetting phase. The possible morphologies depend on the assumed connectivity of the wetting phase. At one extreme, we assume that the entire wetting phase except for pendular rings is connected. At the opposite extreme, we illustrate a low level of connectivity by assuming that pendular rings are trapped as soon as the pores surrounding them are drained; any wetting phase not yet drained from pore throats connecting these pores is also assumed to be trapped. Finally we consider a set of criteria involving larger neighborhoods within the network, which allows trapping in individual pores. Irreducible wetting phase saturations obtained in the latter case agree with experimental data. The numbers of pendular rings and liquid bridges are also consistent with observations. Because the agreement does not involve adjustable parameters, we conclude that a relatively simple, local evaluation of trapping criteria can yield physically representative wetting phase configurations. 相似文献