首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   61篇
  国内免费   18篇
  完全免费   7篇
  数学   86篇
  2020年   1篇
  2018年   1篇
  2017年   2篇
  2016年   2篇
  2015年   5篇
  2014年   4篇
  2013年   2篇
  2012年   4篇
  2011年   4篇
  2010年   7篇
  2009年   2篇
  2008年   7篇
  2007年   5篇
  2006年   3篇
  2004年   5篇
  2003年   3篇
  2002年   7篇
  2001年   2篇
  2000年   1篇
  1999年   5篇
  1998年   3篇
  1997年   6篇
  1994年   1篇
  1992年   1篇
  1990年   1篇
  1984年   1篇
  1974年   1篇
排序方式: 共有86条查询结果,搜索用时 31 毫秒
1.
Lusin sets   总被引:1,自引:0,他引:1  
We show that a set of real numbers is a Lusin set if, and only if, it has a covering property similar to the familiar property of Rothberger

  相似文献

2.
Open covers and partition relations   总被引:1,自引:0,他引:1  
An open cover of a topological space is said to be an -cover if there is for each finite subset of the space a member of the cover which contains the finite set, but the space itself is not a member of the cover. We prove theorems which imply that a set of real numbers has Rothberger's property if, and only if, for each positive integer , for each -cover of , and for each function from the two-element subsets of , there is a subset of such that is constant on , and each element of belongs to infinitely many elements of (Theorem 1). A similar characterization is given of Menger's property for sets of real numbers (Theorem 6).

  相似文献

3.
The purpose of this paper is to present some results which suggest that the Singular Cardinals Hypothesis follows from the Proper Forcing Axiom. What will be proved is that a form of simultaneous reflection follows from the Set Mapping Reflection Principle, a consequence of PFA. While the results fall short of showing that MRP implies SCH, it will be shown that MRP implies that if SCH fails first at κ then every stationary subset of reflects. It will also be demonstrated that MRP always fails in a generic extension by Prikry forcing.  相似文献
4.
We consider the question of which of the major classes defined by topological diagonalizations of open or Borel covers is hereditary. Many of the classes in the open case are not hereditary already in ZFC, and none of them are provably hereditary. This is in contrast with the Borel case, where some of the classes are provably hereditary. Two of the examples are counter-examples of sizes and , respectively, to the Menger and Hurewicz Conjectures, and one of them answers a question of Steprans on perfectly meager sets.

  相似文献

5.
In this paper I will construct a non-separable hereditarily Lindelöf space (L space) without any additional axiomatic assumptions. The constructed space is a subspace of where is the unit circle. It is shown to have a number of properties which may be of additional interest. For instance it is shown that the closure in of any uncountable subset of contains a canonical copy of .

I will also show that there is a function such that if are uncountable and , then there are in and respectively with . Previously it was unknown whether such a function existed even if was replaced by . Finally, I will prove that there is no basis for the uncountable regular Hausdorff spaces of cardinality .

The results all stem from the analysis of oscillations of coherent sequences of finite-to-one functions. I expect that the methods presented will have other applications as well.

  相似文献

6.
We will present a collection of guessing principles which have a similar relationship to as cardinal invariants of the continuum have to . The purpose is to provide a means for systematically analyzing and its consequences. It also provides for a unified approach for understanding the status of a number of consequences of and in models such as those of Laver, Miller, and Sacks.

  相似文献

7.
We compute two-term skein modules of framed oriented links in oriented -manifolds. They contain the self-writhe and total linking number invariants of framed oriented links in a universal way. The relations in a natural presentation of the skein module are interpreted as monodromies in the space of immersions of circles into the -manifold.

  相似文献

8.
We show that the Dual Borel Conjecture implies that \boldsymbol\aleph_1 $"> and find some topological characterizations of perfectly meager and universally meager sets.

  相似文献

9.
We show that it is consistent that the product of perfectly meager sets is perfectly meager.

  相似文献

10.
We prove that the Kauffman bracket skein algebra of a cylinder over a surface with boundary, defined over complex numbers, is isomorphic to the observables of an appropriate lattice gauge field theory.

  相似文献

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号