全文获取类型
收费全文 | 1665篇 |
免费 | 100篇 |
国内免费 | 117篇 |
专业分类
化学 | 116篇 |
晶体学 | 1篇 |
力学 | 163篇 |
综合类 | 13篇 |
数学 | 1368篇 |
物理学 | 221篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 20篇 |
2020年 | 33篇 |
2019年 | 55篇 |
2018年 | 37篇 |
2017年 | 29篇 |
2016年 | 23篇 |
2015年 | 26篇 |
2014年 | 77篇 |
2013年 | 146篇 |
2012年 | 64篇 |
2011年 | 103篇 |
2010年 | 121篇 |
2009年 | 139篇 |
2008年 | 137篇 |
2007年 | 139篇 |
2006年 | 116篇 |
2005年 | 73篇 |
2004年 | 81篇 |
2003年 | 65篇 |
2002年 | 48篇 |
2001年 | 29篇 |
2000年 | 39篇 |
1999年 | 45篇 |
1998年 | 46篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1882条查询结果,搜索用时 0 毫秒
141.
The Allen-Cahn equation ? Δu = u ? u 3 in ?2 has family of trivial singly periodic solutions that come from the one dimensional periodic solutions of the problem ?u″ =u ? u 3. In this paper we construct a non-trivial family of singly periodic solutions to the Allen-Cahn equation. Our construction relies on the connection between this equation and the infinite Toda lattice. We show that for each one-soliton solution to the infinite Toda lattice we can find a singly periodic solution to the Allen-Cahn equation, such that its level set is close to the scaled one-soliton. The solutions we construct are analogues of the family of Riemann minimal surfaces in ?3. 相似文献
142.
曼合布拜·热合木 《新疆大学学报(理工版)》2003,(1)
讨论了一类具有扩散率和 III类功能性反应的非自治捕食系统 ,证明了在适当条件下 ,系统是持久的 ,进一步如果系统是周期系统 ,则在一定条件下存在惟一全局稳定的周期解 . 相似文献
143.
In this paper, we obtain new peakon and periodic peakon solutions
to a modified Camassa-Holm equation. We change the modified Camassa-
Holm equation into a planar system. Then the first integral and algebraic
curves of this system are obtained. By using the first integral and algebraic
curves, a new peakon solution is given by hyperbolic function. Moreover, some
new periodic peakons are given by elliptic functions and triangle functions. 相似文献
144.
145.
146.
Serge Tabachnikov 《Geometriae Dedicata》2007,129(1):83-87
We prove a recent theorem by C. Culter every polygonal outer billiard in the affine plane has a periodic trajectory.
相似文献
147.
In this paper, the existence and globally exponential stability of periodic solutions for nonlinear impulsive delay systems are studied. Our results improve and generalize some of the previous results found in the literature. Two examples are discussed to illustrate our results. 相似文献
148.
We describe a solution procedure for a special case of the periodic vehicle routing problem (PVRP). Operation managers at an auto parts manufacturer in the north of Spain described the optimization problem to the authors. The manufacturer must pick up parts (raw material) from geographically dispersed locations. The parts are picked up periodically at scheduled times. The problem consists of assigning a pickup schedule to each of its supplier’s locations and also establishing daily routes in order to minimize total transportation costs. The time horizon under consideration may be as long as 90 days. The resulting PVRP is such that the critical decision is the assignment of locations to schedules, because once this is done, the daily routing of vehicles is relatively straightforward. Through extensive computational experiments, we show that the metaheuristic procedure described in this paper is capable of finding high-quality solutions within a reasonable amount of computer time. Our main contribution is the development of a procedure that is more effective at handling PVRP instances with long planning horizons when compared to those proposed in the literature. 相似文献
149.
Michael Polacek Karl F. Doerner Richard F. Hartl Guenter Kiechle Marc Reimann 《European Journal of Operational Research》2007
The problem considered in this paper deals with determining daily routes for a traveling salesperson who provides customers in Upper Austria with product range information of a large, global food wholesaler. Each customer has to be visited at least once a year, with some customers requiring up to one visit per month. Further, some customers may not be visited each day of the week. Our decision support system uses a commercial GIS software to extract customer data for input into the optimization procedure and to visualize the results obtained by the algorithm. The optimization approach is based on the variable neighborhood search algorithm which assigns customers to days and determines routes for the salesperson for each day with the primary objective to minimize the total travel time of the salesperson. Another objective studied is to minimize the number of days needed by the salesperson to visit all customers in a given month. Further we analyze the effects of changes in the business environment like increases in the amount or flexibility of the salesperson’s working time and variations in the possible days for customer visits. Finally, we enrich the objective function by considering periodicity requirements for customer visits. Specifically, we penalize irregular schedules, where the time between two successive customer visits varies. 相似文献
150.
In this paper a periodic review inventory model with finite horizon and remanufacturing, manufacturing options is studied. It is assumed that demand and cost parameters are constant and a sufficiently large quantity of used products is available at the beginning of the horizon. The model is studied within the class of policies with given remanufacturing and manufacturing set up and the optimal policy is obtained within this class. The policy specifies the period of switching from remanufacturing to manufacturing (switching period), the periods where remanufacturing and manufacturing activities take place and the corresponding lot sizes. An explicit formula for the cost function and some of its properties are established. Based on these, an algorithm which partitions the set of holding cost parameters into subsets, computes the optimal policy and constructs its corresponding stability regions on every such subset is proposed. 相似文献