全文获取类型
收费全文 | 64篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 15篇 |
数学 | 34篇 |
物理学 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2013年 | 4篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 4篇 |
1999年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有66条查询结果,搜索用时 15 毫秒
31.
The following results are proved. In Theorem 1, it is stated that there exist both finitely presented and not finitely presented
2-generated nonfree groups which are k-free-like for any k ⩾ 2. In Theorem 2, it is claimed that every nonvirtually cyclic (resp., noncyclic and torsion-free) hyperbolic m-generated group is k-free-like for every k ⩾ m + 1 (resp., k ⩾ m). Finally, Theorem 3 asserts that there exists a 2-generated periodic group G which is k-free-like for every k ⩾ 3.
Supported by NSF (grant Nos. DMS 0455881 and DMS-0700811). (A. Yu. Olshanskii, M. V. Sapir)
Supported by RFBR project No. 08-01-00573. (A. Yu. Olshanskii)
Supported by BSF grant (USA–Israel). (M. V. Sapir)
Translated from Algebra i Logika, Vol. 48, No. 2, pp. 245–257, March–April, 2009. 相似文献
32.
Koshkakaryan G Jiang P Altoe V Cao D Klivansky LM Zhang Y Chung S Katan A Martin F Salmeron M Ma B Aloni S Liu Y 《Chemical communications (Cambridge, England)》2010,46(45):8579-8581
Symmetrically substituted hexakis(alkoxy)triphenylene (HAT) derivatives were assembled into single molecular thick 2D nanosheets, which stacked further to give multilayered nanofibers through a convenient solution process. Detailed information on molecular arrangement was unraveled by various imaging techniques and diffraction studies. 相似文献
33.
We describe interlayer force measurements during prolonged, cyclic telescoping motion of a multiwalled carbon nanotube. The force acting between the core and the outer casing is modulated by the presence of stable defects and generally exhibits ultralow friction, below the measurement limit of 1.4 x 10(-15) N/atom and total dissipation per cycle lower than 0.4 meV/atom. Defects intentionally introduced in the form of dangling bonds lead to temporary mechanical dissipation, but the innate ability of nanotubes to self heal rapidly optimizes the atomic structure and restores smooth motion. 相似文献
34.
35.
We introduce a concept of tree-graded metric space and we use it to show quasi-isometry invariance of certain classes of relatively hyperbolic groups, to obtain a characterization of relatively hyperbolic groups in terms of their asymptotic cones, to find geometric properties of Cayley graphs of relatively hyperbolic groups, and to construct the first example of a finitely generated group with a continuum of non-π1-equivalent asymptotic cones. Note that by a result of Kramer, Shelah, Tent and Thomas, continuum is the maximal possible number of different asymptotic cones of a finitely generated group, provided that the Continuum Hypothesis is true. 相似文献
36.
In this paper, we introduce the concept of the independence graph of a directed 2-complex. We show that the class of diagram groups is closed under graph products over independence graphs of rooted 2-trees. This allows us to show that a diagram group containing all countable diagram groups is a semi-direct product of a partially commutative group and R. Thompson's group F. As a result, we prove that all diagram groups are totally orderable. 相似文献
37.
Abstract. – We construct a finitely presented non-amenable group without free non-cyclic subgroups thus providing a finitely
presented counterexample to von Neumann’s problem. Our group is an extension of a group of finite exponent n ≫ 1 by a cyclic group, so it satisfies the identity [x,y]
n
= 1.
Manuscrit reĉu le 8 février 2001.
RID="*"
ID="*"Both authors were supported in part by the NSF grant DMS 0072307. In addition, the research of the first author was
supported in part by the Russian Fund for Basic Research 99-01-00894 and by the INTAS grant, the research of the second author
was supported in part by the NSF grant DMS 9978802. 相似文献
38.
An algebra is inherently non-finitely (Q-)based if it is not a member of any locally finite (quasi-)variety, whose (quasi-)identities
are finitely based. We prove that no finite semigroup is inherently non-finitely Q-based. This is in marked contrast to the
case of varieties, where there are many inherently non-finitely based finite semigroups which have all been described by the
second author.
Research of both authors supported in part by NSF and the Center for Communication and Information Sciences of the University
of Nebraska at Lincoln. 相似文献
39.
We have imaged boron nitride nanotubes with atomic scale resolution using scanning tunneling microscopy. While some nanotubes show the expected triangular lattice pattern, the majority of the nanotubes show unusual stripe patterns which break the underlying symmetry of the boron nitride lattice. We identify the origin of the symmetry breaking and demonstrate that conventional STM imaging analysis is inadequate for boron nitride nanotubes. 相似文献
40.