全文获取类型
收费全文 | 948篇 |
免费 | 35篇 |
国内免费 | 4篇 |
专业分类
化学 | 693篇 |
晶体学 | 9篇 |
力学 | 11篇 |
数学 | 162篇 |
物理学 | 112篇 |
出版年
2023年 | 10篇 |
2022年 | 28篇 |
2021年 | 27篇 |
2020年 | 32篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 16篇 |
2016年 | 30篇 |
2015年 | 31篇 |
2014年 | 27篇 |
2013年 | 48篇 |
2012年 | 73篇 |
2011年 | 63篇 |
2010年 | 36篇 |
2009年 | 33篇 |
2008年 | 46篇 |
2007年 | 48篇 |
2006年 | 50篇 |
2005年 | 55篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 30篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1978年 | 7篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1933年 | 2篇 |
1931年 | 2篇 |
1925年 | 2篇 |
1923年 | 2篇 |
1918年 | 3篇 |
1917年 | 2篇 |
1915年 | 2篇 |
排序方式: 共有987条查询结果,搜索用时 31 毫秒
921.
922.
Alice Mae Guckin 《School science and mathematics》1982,82(2):109-110
923.
924.
Frank Celler Charles R. Leedham-Green Scott H. Murray Alice C. Niemeyer E.A. O'brien 《代数通讯》2013,41(13):4931-4948
We present a "Practical" algorithm to construct random elements of a finite group. We analyse its theoretical behaviour and prove that asymptotically it produces uniformly distributed tuples of elements. We discuss tests to assess its effectiveness and use these to decide when its results are acceptable for some matrix groups. 相似文献
925.
Mustapha Chellali Teresa W. Haynes Stephen T. Hedetniemi Alice McRae 《Discrete Applied Mathematics》2013
A subset S⊆V in a graph G=(V,E) is a [j,k]-set if, for every vertex v∈V?S, j≤|N(v)∩S|≤k for non-negative integers j and k, that is, every vertex v∈V?S is adjacent to at least j but not more than k vertices in S. In this paper, we focus on small j and k, and relate the concept of [j,k]-sets to a host of other concepts in domination theory, including perfect domination, efficient domination, nearly perfect sets, 2-packings, and k-dependent sets. We also determine bounds on the cardinality of minimum [1, 2]-sets, and investigate extremal graphs achieving these bounds. This study has implications for restrained domination as well. Using a result for [1, 3]-sets, we show that, for any grid graph G, the restrained domination number is equal to the domination number of G. 相似文献
926.
927.
An ultramicroporous metal-organic framework based on 9,10-anthracenedicarboxylate (PCN-13) has been synthesized and structurally characterized. The desolvated PCN-13 demonstrates selective adsorption of oxygen and hydrogen over nitrogen and carbon monoxide. 相似文献
928.
Given a metric d on a finite set X, a realization of d is a weighted graph
with
such that for all
the length of any shortest path in G between x and y equals d(x,y). In this paper we consider two special kinds of realizations,
optimal realizations and hereditarily optimal realizations, and their relationship with the so-called tight span. In particular,
we present an infinite family of metrics {dk}k≥1, and—using a new characterization for when the so-called underlying graph of a metric is an optimal realization that we also
present—we prove that dk has (as a function of k) exponentially many optimal realizations with distinct degree sequences. We then show that this family
of metrics provides counter-examples to a conjecture made by Dress in 1984 concerning the relationship between optimal realizations
and the tight span, and a negative reply to a question posed by Althofer in 1988 on the relationship between optimal and hereditarily
optimal realizations. 相似文献
929.
Foster SR Pearce A Blake AJ Welham MJ Dowden J 《Chemical communications (Cambridge, England)》2007,(24):2512-2514
A novel octavalent, resorcin[4]arene derived, cross-linker designed to overcome some of the limitations of commercially available reagents is significantly more efficient for covalent stabilisation of protein-protein interactions. 相似文献
930.
Guigo N Mija A Vincent L Sbirrazzuoli N 《Physical chemistry chemical physics : PCCP》2007,9(39):5359-5366
The complete curing of furfuryl alcohol (FA), was studied by chemorheological analysis and model-free kinetics under isothermal and non-isothermal modes. Polymerization of FA under acidic catalysis involves complex reactions, with several steps (such as condensations and Diels-Alder cycloadditions). To account for the polymerization complexity, kinetic analysis of DSC data was performed with a model-free isoconversional method. The obtained E(alpha)-dependencies were closely-correlated with the variation of complex viscosity during curing. Linear condensations are predominant during the early curing stage and are followed by two distinct stages of branching cycloadditions. Gelation and vitrification, identified by rheometric measurements, were associated with a decrease of the overall reaction rate that becomes controlled by diffusion of small oligomers. Before vitrification, the rate of crosslinking is limited by the mobility of longer polymer chains and diffusion encounters a large energy barrier due to the cooperative nature of the motions, leading to higher E(alpha) values. 相似文献