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   322篇
  免费   29篇
  国内免费   45篇
化学   9篇
力学   4篇
综合类   8篇
数学   333篇
物理学   42篇
  2024年   1篇
  2023年   3篇
  2022年   1篇
  2021年   8篇
  2020年   9篇
  2019年   10篇
  2018年   14篇
  2017年   16篇
  2016年   8篇
  2015年   1篇
  2014年   20篇
  2013年   38篇
  2012年   13篇
  2011年   20篇
  2010年   19篇
  2009年   15篇
  2008年   17篇
  2007年   15篇
  2006年   11篇
  2005年   13篇
  2004年   19篇
  2003年   10篇
  2002年   17篇
  2001年   13篇
  2000年   12篇
  1999年   13篇
  1998年   13篇
  1997年   11篇
  1996年   8篇
  1995年   11篇
  1994年   5篇
  1993年   1篇
  1991年   1篇
  1989年   1篇
  1985年   3篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有396条查询结果,搜索用时 15 毫秒
1.
Human brain, a dynamic complex system, can be studied with different approaches, including linear and nonlinear ones. One of the nonlinear approaches widely used in electroencephalographic (EEG) analyses is the entropy, the measurement of disorder in a system. The present study investigates brain networks applying approximate entropy (ApEn) measure for assessing the hemispheric EEG differences; reproducibility and stability of ApEn data across separate recording sessions were evaluated. Twenty healthy adult volunteers were submitted to eyes-closed resting EEG recordings, for 80 recordings. Significant differences in the occipital region, with higher values of entropy in the left hemisphere than in the right one, show that the hemispheres become active with different intensities according to the performed function. Besides, the present methodology proved to be reproducible and stable, when carried out on relatively brief EEG epochs but also at a 1-week distance in a group of 36 subjects. Nonlinear approaches represent an interesting probe to study the dynamics of brain networks. ApEn technique might provide more insight into the pathophysiological processes underlying age-related brain disconnection as well as for monitoring the impact of pharmacological and rehabilitation treatments.  相似文献   
2.
本文讨论了每个元都有幂等元作为右单位元的左消半群与幂单半群N的Schuzenberger积M◇N的ρ类,证明了这种半群M与N的Schuzenberger积M◇N的ρ类是右E一半适合半群和弱E-headged半群.  相似文献   
3.
We investigate the basic properties of the different socles that can be considered in not necessarily semiprime associative systems. Among other things, we show that the socle defined as the sum of minimal (or minimal and trivial) inner ideals is always an ideal. When trivial inner ideals are included, this inner socle contains the socles defined in terms of minimal left or right ideals. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
4.
In this paper, among other things, we state and prove the mean ergodic theorem for amenable semigroup algebras.  相似文献   
5.
Let be a semigroup and a topological space. Let be an Abelian topological group. The right differences of a function are defined by for . Let be continuous at the identity of for all in a neighbourhood of . We give conditions on or range under which is continuous for any topological space . We also seek conditions on under which we conclude that is continuous at for arbitrary . This led us to introduce new classes of semigroups containing all complete metric and locally countably compact quasitopological groups. In this paper we study these classes and explore their relation with Namioka spaces.

  相似文献   

6.
A K Giri  L Maharana  R Mohanta 《Pramana》1996,46(1):41-50
An estimation of the mass difference of system with heavy quark symmetry formalism is presented. The effective Hamiltonian describing the transition (whereh=b forB d 0 -system) is considered in a manifest left right symmetric (MLRS) model along with contribution from neutral Higgs boson. We use the spin and flavor symmetry for heavy quarks to obtain the transition matrix element 〈B d 0 |ℋeff(x)| d 0 〉 in terms of Isgur-Wise function. Assuming thatB d 0 and states are at rest, we find that Isgur-Wise function turns out to be unity. However using the experimental values of ΔM K and as input, we find thatM R=835 GeV andM H⩾2·9 TeV.  相似文献   
7.
8.
TH型区间值模糊正规子群   总被引:8,自引:1,他引:8  
本文在区间值模糊集空间上,引入了幂等区间范数TH,在此基础上,定义了TH型区间值模糊正规子群,并研究了它的一些性质和结构特征,从而拓广了区间值模糊集的理论。  相似文献   
9.
右心室分割对肺动脉高压等疾病的心功能分析具有重要的临床意义.然而,右心室心肌薄、易变且不规则,其传统的医学图像分割方法仍然未能取得突破性进展.本文提出基于COLLATE(Consensus Level,Labeler Accuracy and Truth Estimation)的多图谱分割方法,首先以归一化互信息为相似测度对目标图像和图谱集进行B样条配准以获取粗分割结果;然后利用COLLATE对粗分割结果进行融合;最后采用基于形状约束的区域生长算法修正出现错误的数据.10例临床心脏磁共振短轴电影图像被用于算法验证.本文还将使用基于COLLATE的多图谱分割方法得到的结果与深度学习算法及手动分割进行了比较.结果显示与深度学习算法比较,使用本文算法得到的射血分数(Ejection Fraction,EF)与手动分割更加一致和相关,表明该算法的分割结果有望辅助临床心脏功能诊断.  相似文献   
10.
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