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   415篇
  免费   19篇
  国内免费   17篇
化学   136篇
晶体学   1篇
力学   18篇
综合类   4篇
数学   204篇
物理学   88篇
  2025年   1篇
  2024年   5篇
  2023年   21篇
  2022年   18篇
  2021年   19篇
  2020年   23篇
  2019年   21篇
  2018年   15篇
  2017年   12篇
  2016年   8篇
  2015年   12篇
  2014年   24篇
  2013年   22篇
  2012年   13篇
  2011年   24篇
  2010年   21篇
  2009年   22篇
  2008年   17篇
  2007年   28篇
  2006年   12篇
  2005年   12篇
  2004年   12篇
  2003年   6篇
  2002年   10篇
  2001年   10篇
  2000年   7篇
  1999年   10篇
  1998年   8篇
  1997年   4篇
  1996年   3篇
  1995年   8篇
  1994年   1篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1982年   2篇
  1981年   4篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
排序方式: 共有451条查询结果,搜索用时 78 毫秒
101.
一类具有偏差变元的Liénard型方程的周期解   总被引:1,自引:0,他引:1  
利用重合度理论研究了一类具偏差变元的Liénard型方程x″+f1(x)|x′|2n+f2(t,x(t),x(t-0τ(t)))x′+g(t,x(t-1τ(t)))=p(t).获得了该方程存在ω-周期解的若干新结论,改进推广了有关文献中的已有结果.  相似文献   
102.
研究了一类具有分布式偏差变元的中立型向量双曲泛函微分方程解的H-振动性.给出了判别解的H-振动性的一些充分条件.  相似文献   
103.
By means of the continuation theorem of the coincidence degree theory and analysis techniques,sufficient conditions for the existence of periodic solutions to a kind of third-order neutral delay functional differential equation with deviating arguments are obtained.  相似文献   
104.
The main purpose of this paper is to investigate high dimensional limiting behaviors, as m becomes infinite (m → ∞), of matrix statistics on the Stiefel manifold Vk, m, which consists of m × k (mk) matrices X such that XX = Ik. The results extend those of Watson. Let X be a random matrix on Vk, m. We present a matrix decomposition of X as the sum of mutually orthogonal singular value decompositions of the projections P X and P X, where and are each a subspace of Rm of dimension p and their orthogonal compliment, respectively (pk and mk + p). Based on this decomposition of X, the invariant measure on Vk, m is expressed as the product of the measures on the component subspaces. Some distributions related to these decompositions are obtained for some population distributions on Vk, m. We show the limiting normalities, as m → ∞, of some matrix statistics derived from the uniform distribution and the distributions having densities of the general forms f(P X) and f(m1/2P X) on Vk, m. Subsequently, applications of these high dimensional limit theorems are considered in some testing problems.  相似文献   
105.
This paper presents a multiclass, multicriteria (cost versus time) logit-based traffic equilibrium assignment model in road networks served by advanced traveler information systems (ATIS). All users are differentiated by their own value of time (VOT) that follows some probability distribution. Users of each class, having their own VOT, are further divided into two groups, equipped and unequipped with ATIS respectively. The travel disutility received by each user is defined as a linear bi-criteria combination of travel time and monetary travel cost. It is assumed that all users make their route choices in a logit-based stochastic manner, but the equipped users have lower perception variation on the travel disutility than the unequipped due to the ATIS service. The model is formulated as a fixed-point problem and solved by the method of successive averages in conjunction with logit assignment. Numerical results show that the traditional single-class and/or single-criterion models may overestimate or underestimate the benefit from ATIS services.  相似文献   
106.
In this paper, we investigate the existence and uniqueness of new almost periodic type solutions, so-called pseudo almost periodic solutions for the systems of differential equations with piecewise constant argument by means of introducing the notion of pseudo almost periodic vector sequences.  相似文献   
107.
This paper is concerned with a class of boundary value problems for nonlinear mixed impulsive integro-differential equations with deviating arguments. We establish a new comparison principle and use the method of upper and lower solutions together with the monotone iterative technique. Under suitable conditions, we obtain the existence results of extremal solutions for the problems. An example is also given to illustrate our results.  相似文献   
108.
Quick response (QR) to passenger needs is a key objective for advanced public transportation systems (APTS), and it has become increasingly important for contemporary metropolitan bus operations to gain a competitive advantage over private transportation. This paper presents a real-time control methodology for demand-responsive bus operations that respond quickly to passenger needs. The proposed method primarily involves two levels of functionality: (1) short-term forecasting of passenger demands using time-series prediction models, and (2) identification of service strategies coupled with the associated bus service segments using fuzzy clustering technologies in response to variances in passenger demand attributes and traffic conditions. The proposed bus operations method identifies the demand-responsive vehicle service strategies primarily according to the predicted up-to-date attributes of passengers’ demands, rather than deterministic passenger arrival rates, which were generally used in previous literature. In addition, the variation of traffic conditions along bus lines is considered in the proposed method. Results from numerical studies using real data of passengers’ demands, including passenger volume at each bus stop and the passenger origin-destination (O-D) patterns, are presented to demonstrate the effectiveness of the proposed method for real-world applications.  相似文献   
109.
110.
COMPARISON AND OSCILLATION THEOREMS FOR AN ADVANCED TYPE DIFFERENCE EQUATIONCOMPARISONANDOSCILLATIONTHEOREMSFORANADVANCEDTYPE...  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