全文获取类型
收费全文 | 374篇 |
免费 | 30篇 |
国内免费 | 5篇 |
专业分类
化学 | 6篇 |
力学 | 29篇 |
数学 | 315篇 |
物理学 | 59篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 18篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 16篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 30篇 |
2013年 | 22篇 |
2012年 | 18篇 |
2011年 | 35篇 |
2010年 | 38篇 |
2009年 | 30篇 |
2008年 | 32篇 |
2007年 | 18篇 |
2006年 | 19篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
排序方式: 共有409条查询结果,搜索用时 187 毫秒
181.
We consider a latency problem with a profit pi for each client. When serving a client, a revenue of pi−t is collected. The goal is to find routes for the servers such that total collected revenue is maximized. We study the complexity of different variants of this problem on the line. 相似文献
182.
We study the existence, uniqueness and asymptotic behavior, as well as the stability of a special kind of traveling wave solutions for competitive PDE systems involving intrinsic growth, competition, crowding effects and diffusion. The traveling waves are exclusive in the sense that as the variable goes to positive or negative infinity, different species are close to extinction or carrying capacity. We perform an appropriate affine transformation of the traveling wave equations into monotone form and construct appropriate upper and lower solutions. By this means, we reduce the existence proof to application of well-known theory about monotone traveling wave systems (cf. [A. Leung, Systems of Nonlinear Partial Differential Equations: Applications to Biology and Engineering, MIA, Kluwer, Boston, 1989; J. Wu, X. Zou, Traveling wave fronts of reaction-diffusion systems with delay, J. Dynam. Differential Equations 13 (2001) 651-687] and [I. Volpert, V. Volpert, V. Volpert, Traveling Wave Solutions of Parabolic Systems, Transl. Math. Monogr., vol. 140, Amer. Math. Soc., Providence, RI, 1994]). Then, by using spectral analysis of the linearization over the profile, we prove the orbital stability of the traveling wave in some Banach spaces with exponentially weighted norm. Furthermore, we show that the introduction of some weight is necessary in the sense that, in general, traveling wave solutions with initial perturbations in the (unweighted) space C0 are unstable (cf. [I. Volpert, V. Volpert, V. Volpert, Traveling Wave Solutions of Parabolic Systems, Transl. Math. Monogr., vol. 140, Amer. Math. Soc., Providence, RI, 1994] and [D. Henry, Geometric Theory of Semilinear Parabolic Equations, Lecture Notes in Math., vol. 840, Springer-Verlag, New York, 1981]). 相似文献
183.
Jairo Ernesto Castillo Hernández Alvaro H. Salas José Gonzalo Escobar Lugo Grupo CIBAVIR 《Applied mathematics and computation》2010,217(4):1646-1651
In this paper we show new exact solutions for a type of generalized sine-Gordon equation which is obtained by constructing a Lagrange function for a dynamical coupled system of oscillators. We convert it into a nonlinear system by perturbing the potential energy from a point of view of an approach proposed by Fermi [1]. 相似文献
184.
该文利用扰动方法研究具非线性扩散项及一般形式反应项系统行波解的存在性. 得到该类系统存在行波解的充分条件, 使得相关参考文献的结果成为本文主要定理的推论.作为应用给出了一类具体的反应扩散系统行波解的存在性条件. 相似文献
185.
《Applicable analysis》2012,91(1):133-157
ABSTRACTWe study the traveling waves of reaction-diffusion equations for a diffusive SEIR model with a general nonlinear incidence. The existence of traveling waves is determined by the basic reproduction number of the corresponding ordinary differential equations and the minimal wave speed. Its proof is showed by introducing an auxiliary system, applying Schauder fixed point theorem and then a limiting argument. The non-existence proof is obtained by two-sided Laplace transform when the speed is less than the critical velocity. Finally, we present some examples to support our theoretical results. 相似文献
186.
A.A. ImaniD.D. Ganji Houman B. Rokni H. LatifizadehEsmail Hesameddini M. Hadi Rafiee 《Applied Mathematical Modelling》2012,36(4):1550-1557
Reconstruction of Variational Iteration Method (RVIM) is used for computing the coupled Whitham-Broer-Kaup shallow water. Then RVIM solution is verified against exact one and is compared with powerful approximate solutions, the Homotopy Perturbation Method (HPM) and Homotopy Analysis Method (HAM). The existent error of the methods is computed and convergence of the RVIM solution has been presented. Results obtained expose effectiveness and capability of this method to solve the nonlinear systems in mechanics, analytically. 相似文献
187.
Creating lasso-solutions for the traveling salesman problem with pickup and delivery by Tabu search 总被引:2,自引:0,他引:2
We consider the Traveling Salesman Problem with Pickup and Delivery (TSPPD) where the same costumers might require both deloverie
of goods and pickup of other goods. All the goods should be transported from/to the same depot. A vehicle on a TSPPD-tour
could often get some practical problems when arranging the load. Even if the vehicle has enough space for all the pickups,
one has to consider that they are stored in a way that doesn't block the delivery for the next customer. In real life problems
this occurs for instance for breweries when they deliver bottles of beer or mineral water and collects empty bottles from
the same customers on the same tour. In these situations we could relax the constraints of only checking Hamiltonian tours,
and also try solutions that can visit customers in a way giving rise to a ‘alsso’ model. A solution which first only delivers
bottles until the vehicle is partly unloaded, then do both delivery and pickup at the remaining customers and at last picks
up the empty bottle from the first visited customers, could in these situations be better than a pure Hamiltonian tour, at
least in a practical setting. To find such solutions, we will use the metaheuristic Tabu Search on some well known TSPPD-problems,
and compare them to other kinds of solutions on the same problems. 相似文献
188.
Xinfu Chen 《Journal of Differential Equations》2005,212(1):62-84
We consider entire solutions of ut=uxx-f(u), i.e. solutions that exist for all (x,t)∈R2, where f(0)=f(1)=0<f′(0). In particular, we are interested in the entire solutions which behave as two opposite wave fronts of positive speed(s) approaching each other from both sides of the x-axis and then annihilating in a finite time. In the case f′(1)>0, we show that such entire solution exists and is unique up to space-time translations. In the case f′(1)<0, we derive two families of such entire solutions. In the first family, one cannot be any space-time translation of the other. Yet all entire solutions in the second family only differ by a space-time translation. 相似文献
189.
Christophe Chalons 《Journal of Mathematical Analysis and Applications》2008,348(2):872-893
The aim of this paper is to show how solutions to the one-dimensional compressible Euler equations can be approximated by solutions to an enlarged hyperbolic system with a strong relaxation term. The enlarged hyperbolic system is linearly degenerate and is therefore suitable to build an efficient approximate Riemann solver. From a theoretical point of view, the convergence of solutions to the enlarged system towards solutions to the Euler equations is proved for local in time smooth solutions. We also show that arbitrarily large shock waves for the Euler equations admit smooth shock profiles for the enlarged relaxation system. In the end, we illustrate these results of convergence by proposing a numerical procedure to solve the enlarged hyperbolic system. We test it on various cases. 相似文献
190.
We present two simple results for generalizations of the traveling salesman problem (TSP): for the universal TSP, we show that one can compute a tour that is universally optimal whenever the input is a tree metric. A (randomized) O(logn)-approximation algorithm for the a priori TSP follows as a corollary. 相似文献