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   49篇
  免费   13篇
  国内免费   6篇
化学   5篇
力学   7篇
综合类   1篇
数学   20篇
物理学   35篇
  2022年   2篇
  2018年   1篇
  2016年   3篇
  2015年   1篇
  2014年   6篇
  2013年   2篇
  2012年   1篇
  2011年   10篇
  2010年   13篇
  2009年   3篇
  2007年   1篇
  2006年   4篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   4篇
  2000年   2篇
  1999年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
排序方式: 共有68条查询结果,搜索用时 15 毫秒
31.
超紧集的刻划与层次结构   总被引:1,自引:0,他引:1  
周武能  孟培源 《数学杂志》1996,16(2):204-208
本文给出了LF集的超紧性的网式、滤子式等几种刻划,剖析了超紧集的层次结构,得出了在导出分明拓扑满足T2分离性的前提下子集的超紧性与其任一α-截集的紧性等价等一系列结果。  相似文献   
32.
对中等雷诺数下壁面常温和壁面加热的平板湍流边界层中速度和温度粗粒化的耗散率结构函数标度指数进行了实验测量.用热线风速仪测量了风洞中壁面常温和加热的平板湍流边界层中不同法向位置的流向速度分量和温度的时间序列信号,研究了由于湍流边界层近壁区域相干结构的存在而导致的非各向同性、非均匀性对湍流耗散率结构函数标度指数的影响,研究发现,中等雷诺数下壁面加热的边界条件和剪切湍流的平均速度梯度对速度和温度耗散率结构函数的标度指数没有影响,均匀各向同性湍流的耗散率结构函数标度指数的层次结构模型对壁面加热平板湍流边界层的速度和温度耗散率结构函数的标度指数也是适用的.  相似文献   
33.
With the aid of the zero-curvature equation, a novel integrable hierarchy of nonlinear evolution equations associated with a 3 x 3 matrix spectral problem is proposed. By using the trace identity, the bi-Hamiltonian structures of the hierarchy are established with two skew-symmetric operators. Based on two linear spectral problems, we obtain the infinite many conservation laws of the first member in the hierarchy.  相似文献   
34.
With the help of a Lie algebra, an isospectral Lax pair is introduced for which a new Liouville integrable hierarchy of evolution equations is generated. Its Hamiltonian structure is also worked out by use of the quadratic-form identity.  相似文献   
35.
In the quantum mechanical Hilbert space formalism, the probabilistic interpretation is a later ad-hoc add-on, more or less enforced by the experimental evidence, but not motivated by the mathematical model itself. A model involving a clear probabilistic interpretation from the very beginning is provided by the quantum logics with unique conditional probabilities. It includes the projection lattices in von Neumann algebras and here probability conditionalization becomes identical with the state transition of the Lueders-von Neumann measurement process. This motivates the definition of a hierarchy of five compatibility and comeasurability levels in the abstract setting of the quantum logics with unique conditional probabilities. Their meanings are: the absence of quantum interference or influence, the existence of a joint distribution, simultaneous measurability, and the independence of the final state after two successive measurements from the sequential order of these two measurements. A further level means that two elements of the quantum logic (events) belong to the same Boolean subalgebra. In the general case, the five compatibility and comeasurability levels appear to differ, but they all coincide in the common Hilbert space formalism of quantum mechanics, in von Neumann algebras, and in some other cases.  相似文献   
36.
P2P计算近年来已经日趋普遍。它提供很多吸引人的特性。比如自主性、负载平衡、有效性、容错冗余和匿名。但它同样面临一些严峻的挑战。在本论文中,提出一种有效的簇集主干点层级P2P结构模型(ECGP)。该模型提供了一种半结构化的层次结构(类似混合P2P系统),克服了现存的非结构化P2P系统中存在的扩展性不好和效率不高的问题。  相似文献   
37.
 1937年,诺贝尔奖获得者,英国物理学家狄拉克在《自然》杂志的139卷323页上发表了《大数假说及其后果》的论文,提出了著名的“大数假说”。宇宙中存在着两个数量级相等的神秘大数,一个大数是氢原子中静电力和万有引力之比:e2/Gmpme=2.3×1039,e是电子或质子的电量,G是万有引力常量,me、mp分别是电子和质子的质量。另一个大数是根据大爆炸宇宙模型,以原子单位来量度的宇宙年龄t=7×1039s,这两个貌似毫不相干的大数,分别来自一个小世界和一个大世界,却有着相同的数量级。狄拉克不认为这仅仅是一种巧合,他说:“这样两个大数如此接近,在自然界一定有某种基本的原因,我们目前不知道这个原因.  相似文献   
38.
A novel method based on discrete wavelet transform (DWT) and cross-covariance for revealing the evolution of species at different spatial resolutions is presented. The trypsin proteins of different species are chosen as an example to describe the evolution relationship according to the evolution vectors by using this method. The results indicated that this method is a promising approach to reveal species evolution at different spatial resolutions.  相似文献   
39.
Two kinds of higher-dimensional Lie algebras and their loop algebras are introduced, for which a few expanding integrable models including the coupling integrable couplings of the Broer-Kaup (BK) hierarchy and the dispersive long wave (DLW) hierarchy as well as the TB hierarchy are obtained. From the reductions of the coupling integrable couplings, the corresponding coupled integrable couplings of the BK equation, the DLW equation, and the TB equation are obtained, respectively. Especially, thecoupling integrable coupling of the TB equation reduces to a few integrable couplings of the well-known mKdV equation. The Hamiltonian structures of the coupling integrable couplings of the three kinds of soliton hierarchies are worked out, respectively, by employing the variational identity. Finally, we decompose the BK hierarchy of evolution equations into x-constrained flows and tn-constrained flows whose adjoint representations and the Lax pairs are given.  相似文献   
40.
A super Jaulent-Miodek hierarchy and its super Hamiltonian structures are constructed by means of a kind of Lie super algebras and super trace identity. Moreover, the self-consistent sources of the super Jaulent-Miodek hierarchy is presented based on the theory of self-consistent sources. Further- more, the infinite conservation laws of the super Jaulent-Miodek hierarchy are also obtained. It is worth noting that as even variables are boson variables, odd variables are fermi variables in the spectral problem, the commutator is different from the ordinary one.  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