全文获取类型
收费全文 | 156篇 |
免费 | 16篇 |
国内免费 | 36篇 |
专业分类
化学 | 19篇 |
力学 | 6篇 |
综合类 | 6篇 |
数学 | 138篇 |
物理学 | 39篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1993年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 15 毫秒
1.
In this paper we show that the Boltzmann weights of the three-dimensional Baxter-Bazhanov model give representations of the braid group if some suitable spectral limits are taken. In the trigonometric case we classify all possible spectral limits which produce braid group representations. Furthermore, we prove that for some of them we get cyclotomic invariants of links and for others we obtain tangle invariants generalizing the cyclotomic ones. 相似文献
2.
3.
Masamichi Takase 《Topology》2004,43(6):1425-1447
Haefliger has shown that a smooth embedding of the (4k−1)-sphere in the 6k-sphere can be knotted in the smooth sense. In this paper, we give a formula with which we can detect the isotopy class of such a Haefliger knot. The formula is expressed in terms of the geometric characteristics of an extension, analogous to a Seifert surface, of the given embedding. In particular, the Hopf invariant associated to the extension plays a crucial role. This leads us to a new characterisation of Haefliger knots. 相似文献
4.
E. J. Janse van Rensburg E. Orlandini D. W. Sumners M. C. Tesi S. G. Whittington 《Journal of statistical physics》1996,85(1-2):103-130
We consider a discrete ribbon model for double-stranded polymers where the ribbon is constrained to lie in a three-dimensional lattice. The ribbon can be open or closed, and closed ribbons can be orientable or nonorientable. We prove some results about the asymptotic behavior of the numbers of ribbons withn plaquettes, and a theorem about the frequency of occurrence of certain patterns in these ribbons. We use this to derive results about the frequency of knots in closed ribbons, the linking of the boundary curves of orientable closed ribbons, and the twist and writhe of ribbons. We show that the centerline and boundary of a closed ribbon are both almost surely knotted in the infinite-n limit. For an orientable ribbon, the expectation of the absolute value of the linking number of the two boundary curves increases at least as fast as n, and similar results hold for the twist and writhe. 相似文献
5.
C30卡宾三叶结分子结构与稳定性的理论研究 总被引:1,自引:0,他引:1
三叶结分子是最简单的非平凡纽结分子, C30卡宾三叶结分子是由一条闭合的(C≡C—)15 sp杂化碳链组成的, 是具有D3对称性的拓扑手性分子. 本文用密度泛函方法[DFT/RB3LYP/6-31G(D)]对分子结构和光谱性质进行了研究, 在优化构型的基础上通过自然键轨道(NBO)方法和轨道能级研究了它的共轭性、成键情况和稳定性, 并与平面型C30卡宾环分子进行了比较. 计算结果表明三叶结分子的三叶弧上形成了非平面的C≡C共轭和扭曲的内螺旋结构, 交叉处具有弱成键作用, 且分子轨道也发生了扭曲; 三叶结分子比卡宾环的共轭性和赝Jahn-Teller效应都明显小, 而总能量高. 因此, 分子打结是一个能量升高的过程. 相似文献
6.
7.
Two Cp*−RhIII based trefoil knots were obtained in high yield under ambient conditions via the coordination-driven self-assembly of semi-rigid thioether dipyridyl ligand 1,4-bis[(pyridin-4-ylthio)methyl]benzene ( L1 ), ligand chloranilic acid (H2− CA ) and 6,11-dihydroxytetracene-5,12-dione (H2- TtDo ) with Cp*RhIII metal corner units, respectively. Furthermore, using the bulkier 4,4′-{[(2,5-dimethyl-1,4-phenylene)bis(methylene)]bis(sulfanediyl)}dipyridine ( L2 ) in the place of ligand L1 in the construction process resulted in the formation of a teranuclear metallacycle and a template-free Borromean ring in high yields thanks to significantly altered intermolecular forces between the constituent ligands induced by the sterically-hindering methyl groups of L2 , as demonstrated via a detailed X-ray crystallographic analysis and NMR spectroscopy. 相似文献
8.
9.
Vincent Blanloeil Osamu Saeki 《Transactions of the American Mathematical Society》2002,354(10):3955-3971
Consider a closed connected oriented 3-manifold embedded in the -sphere, which is called a -knot in this paper. For two such knots, we say that their Seifert forms are spin concordant, if they are algebraically concordant with respect to a diffeomorphism between the 3-manifolds which preserves their spin structures. Then we show that two simple fibered 3-knots are geometrically concordant if and only if they have spin concordant Seifert forms, provided that they have torsion free first homology groups. Some related results are also obtained.
10.
The Volume of Hyperbolic Alternating Link Complements 总被引:1,自引:0,他引:1
If a hyperbolic link has a prime alternating diagram D, thenwe show that the link complement's volume can be estimated directlyfrom D. We define a very elementary invariant of the diagramD, its twist number t(D), and show that the volume lies betweenv3(t(D) 2)/2 and v3(10t(D) 10), where v3 isthe volume of a regular hyperbolic ideal 3-simplex. As a consequence,the set of all hyperbolic alternating and augmented alternatinglink complements is a closed subset of the space of all completefinite-volume hyperbolic 3-manifolds, in the geometric topology.2000 Mathematics Subject Classification 57M25, 57N10. 相似文献