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   403篇
  免费   21篇
  国内免费   28篇
化学   18篇
力学   29篇
综合类   5篇
数学   359篇
物理学   41篇
  2023年   1篇
  2022年   3篇
  2021年   11篇
  2020年   12篇
  2019年   11篇
  2018年   7篇
  2017年   13篇
  2016年   11篇
  2015年   7篇
  2014年   24篇
  2013年   41篇
  2012年   22篇
  2011年   31篇
  2010年   14篇
  2009年   24篇
  2008年   31篇
  2007年   23篇
  2006年   17篇
  2005年   14篇
  2004年   11篇
  2003年   10篇
  2002年   18篇
  2001年   12篇
  2000年   12篇
  1999年   10篇
  1998年   11篇
  1997年   6篇
  1996年   2篇
  1995年   3篇
  1994年   9篇
  1993年   2篇
  1992年   5篇
  1991年   3篇
  1990年   3篇
  1989年   1篇
  1988年   3篇
  1987年   2篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
排序方式: 共有452条查询结果,搜索用时 312 毫秒
21.
带有Bernoulli反馈的多级适应性休假的Geo/G/1排队系统分析   总被引:2,自引:0,他引:2  
考虑带有Bernoulli反馈的多级适应性休假的Geo/G/1离散时间排队系统.通过引入服务员忙期和使用一种简洁的分解方法,讨论了队长的瞬时分布,得到了在任意时刻n队长为j的概率关于时刻n的z-变换的递推式,及队长平稳分布的递推式,且证明了稳态队长的随机分解性质.最后,给出了在特殊情形下相应的一些结果和数值计算实例.  相似文献   
22.
Given a sample of binary random vectors with i.i.d. Bernoulli(p) components, that is equal to 1 (resp. 0) with probability p (resp. 1−p), we first establish a formula for the mean of the size of the random Galois lattice built from this sample, and a more complex one for its variance. Then, noticing that closed α-frequent itemsets are in bijection with closed α-winning coalitions, we establish similar formulas for the mean and the variance of the number of closed α-frequent itemsets. This can be interesting for the study of the complexity of some data mining problems such as association rule mining, sequential pattern mining and classification.  相似文献   
23.
广义Stirling数偶的理论及应用   总被引:5,自引:2,他引:3  
The object of this expository paper is to sum up several results concerning generalized Stirling number (GSN) pairs investigated earlier by the author. Also expounded in some detail are two kinds of extended GSN pairs with applications (illustrative examples).  相似文献   
24.
A construction of new sequences of generalized Bernoulli polynomials of first and second kind is proposed. These sequences share with the classical Bernoulli polynomials many algebraic and number theoretical properties. A class of Euler-type polynomials is also presented.  相似文献   
25.
R. Janma  S.P. Singh  V. Dwivedi 《Optik》2011,122(2):173-176
The modal dispersion characteristics of EM waves in a new unconventional plasma loaded doubly clad waveguide having a shape of the lemniscates of Bernoulli-type core cross-section have been studied analytically. The proposed waveguide has three parts namely the core with slighter high index, the inner cladding with plasma and the outer cladding with air. Now using the necessary orthogonal coordinates for the proposed structure and imposing the boundary conditions under the weak guidance condition, the modal characteristics equation has been obtained considering variations in plasma width and plasma frequency, the dispersion curves and cutoff frequencies have been obtained and presented in this paper. It is noted that as the width of plasma layer increases, the cutoff frequency also increases considerably in all considered cases. This shows that using plasma width as a new parameter we can control any particular mode on our wish.  相似文献   
26.
We study the stability of a robot system composed of two Euler–Bernoulli beams with non-collocated controllers. By the detailed spectral analysis, we prove that the asymptotical spectra of the system are distributed in the complex left-half plane and there is a sequence of the generalized eigenfunctions that forms a Riesz basis in the energy space. Since there exist at most finitely many spectral points of the system in the right half-plane, to obtain the exponential stability, we show that one can choose suitable feedback gains such that all eigenvalues of the system are located in the left half-plane. Hence the Riesz basis property ensures that the system is exponentially stable. Finally we give some simulation for spectra of the system.  相似文献   
27.
The paper gives first quantitative estimates on the modulus of continuity of the spectral measure for weak mixing suspension flows over substitution automorphisms, which yield information about the “fractal” structure of these measures. The main results are, first, a Hölder estimate for the spectral measure of almost all suspension flows with a piecewise constant roof function; second, a log-Hölder estimate for self-similar suspension flows; and, third, a Hölder asymptotic expansion of the spectral measure at zero for such flows. Our second result implies log-Hölder estimates for the spectral measures of translation flows along stable foliations of pseudo-Anosov automorphisms. A key technical tool in the proof of the second result is an “arithmetic-Diophantine” proposition, which has other applications. In Appendix A this proposition is used to derive new decay estimates for the Fourier transforms of Bernoulli convolutions.  相似文献   
28.
It is well known that when ββ is a Pisot number, the corresponding Bernoulli convolution νβνβ has Hausdorff dimension less than 11, i.e. that there exists a set AβAβ with νβ(Aβ)=1νβ(Aβ)=1 and dimH(Aβ)<1dimH(Aβ)<1. We show explicitly how to construct for each Pisot number ββ such a set AβAβ.  相似文献   
29.
This paper aims to contribute to the exploration of quadrature formulae by proving that the error of a quadrature formula has the Schur‐convexity property. The emphasis is on the quadrature formulae with the maximum degree of precision. The Schur‐convexity of the error has an interesting implication – the monotonicity of the error. Namely, it turns out that the absolute value of the error is always smaller on a smaller interval (of the two which share the same midpoint).  相似文献   
30.
The main purpose of this paper is to use the generalized Bernoulli numbers, Gauss sums and the mean value theorems of Dirichlet L-functions to study the asymptotic property of one class of number-theoretic functions, and to give four interesting hybrid mean value formulae.  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