全文获取类型
收费全文 | 407篇 |
免费 | 19篇 |
国内免费 | 18篇 |
专业分类
化学 | 3篇 |
综合类 | 3篇 |
数学 | 251篇 |
物理学 | 11篇 |
综合类 | 176篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 18篇 |
2013年 | 30篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 27篇 |
2009年 | 34篇 |
2008年 | 35篇 |
2007年 | 28篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 12篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
141.
The stochastic transportation problem with single sourcing 总被引:1,自引:0,他引:1
We propose a branch-and-price algorithm for solving a class of stochastic transportation problems with single-sourcing constraints. Our approach allows for general demand distributions, nonlinear cost structures, and capacity expansion opportunities. The pricing problem is a knapsack problem with variable item sizes and concave costs that is interesting in its own right. We perform an extensive set of computational experiments illustrating the efficacy of our approach. In addition, we study the cost of the single-sourcing constraints. 相似文献
142.
143.
An existence-uniqueness theorem is proved about a minimum cost order for a class of inventory models whose holding costs grow according to a stock level power law. The outcomes of Mingari Scarpello and Ritelli (2008) [1] are then extended to different environments: i.e., when the holding costs change during time generalizing a model available in Weiss (1982) [11], or with invariable holding costs but adopting a backordering strategy. Application cases are provided assuming several functional behaviors of demand versus the stock level. 相似文献
144.
Abstract Portfolio theory covers different approaches to the construction of a portfolio offering maximum expected returns for a given level of risk tolerance where the goal is to find the optimal investment rule. Each investor has a certain utility for money which is reflected by the choice of a utility function. In this article, a risk averse power utility function is studied in discrete time for a large class of underlying probability distribution of the returns of the asset prices. Each investor chooses, at the beginning of an investment period, the feasible portfolio allocation which maximizes the expected value of the utility function for terminal wealth. Effects of both large and small proportional transaction costs on the choice of an optimal portfolio are taken into account. The transaction regions are approximated by using asymptotic methods when the proportional transaction costs are small and by using expansions about critical points for large transaction costs. 相似文献
145.
Lorenzo Torricelli 《Applied Mathematical Finance》2013,20(3):213-246
ABSTRACTA target volatility strategy (TVS) is a risky asset-riskless bond dynamic portfolio allocation which makes use of the risky asset historical volatility as an allocation rule with the aim of maintaining the instantaneous volatility of the investment constant at a target level. In a market with stochastic volatility, we consider a diffusion model for the value of a target volatility fund (TVF) which employs a system of stochastic delayed differential equations (SDDEs) involving the asset realized variance. First we prove that under some technical assumptions, contingent claim valuation on a TVF is approximately of Black-Scholes type, which is consistent with and supports the standing market practice. In second place, we develop a computational framework using recent results on Markovian approximations of SDDEs systems, which we then implement in the Heston variance model using an ad hoc Euler scheme. Our framework allows for efficient numerical valuation of derivatives on TVFs, whose typical purpose is the assessment of the guarantee costs of such funds for insurers. 相似文献
146.
Abstract In this paper, a numerical model is developed for analyzing the role of species life history and age structure for the optimal management of a commercial resident species that is exposed to an invasive species. It is shown that reproduction and mortality characteristics of both species ands age structure of the invader at the time of invasion are important for the costs of invasions when the invader and resident species compete for scarce resources. Commercially harvested species with low juvenile survival and high reproduction are found to be economically more robust against invasions. Species with these life‐history traits are also the most damaging as invaders. Properties of the harvesting cost function and the discount rate are shown to be of importance for the development of the invader population over time. Hence, it is possible to identify specific combinations of life‐history characteristics and economic conditions under which invasions cause particularly large economic damage. 相似文献
147.
In this paper we analyze the procurement problem of a company that needs to purchase a number of products from a set of suppliers to satisfy demand. The suppliers offer total quantity discounts and the company aims at selecting a set of suppliers so to satisfy product demand at minimum purchasing cost. The problem, known as Total Quantity Discount Problem (TQDP), is strongly NP-hard. We study different families of valid inequalities and provide a branch-and-cut approach to solve the capacitated variant of the problem (Capacitated TQDP) where the quantity available for a product from a supplier is limited. A hybrid algorithm, called HELP (Heuristic Enhancement from LP), is used to provide an initial feasible solution to the exact approach. HELP exploits information provided by the continuous relaxation problem to construct neighborhoods optimally searched through the solution of mixed integer subproblems. A streamlined version of the proposed exact method can optimally solve in a reasonable amount of time instances with up to 100 suppliers and 500 products, and largely outperforms an existing approach available in the literature and CPLEX 12.2 that frequently runs out of memory before completing the search. 相似文献
148.
生产成本信息不对称下差异Bertrand结构中的许可 总被引:1,自引:0,他引:1
建立了差异Bertrand结构市场中,成本降低型厂商创新者在关于生产厂商的生产成本信息不对称条件下,与生产厂商之间的技术许可博奕模型,并分析了从厂商创新者角度出发的最佳许可策略.研究表明,最佳许可方式依赖于创新规模和市场差异程度,具体地说,当创新规模较大或者产品差异程度较大时,固定费用许可最优,反之,固定费用和提成相组合的方式最优. 相似文献
149.
整合能够有效地减少资源的重复建设与盲目浪费,促进资源的可持续发展。基于交易成本、激励相容与信息共享分析了资源整合的原因、前提及对策,研究显示:企业进行资源整合的主要动机在于降低因资产专用性与交易不确定性过高所致的交易成本的增加;企业只有在其通过整合所获得的收益大于其他途径所获得的收益时,即满足激励相容时才会参与到资源整合过程中来;信息共享是企业实现资源整合的有效途径,并需要辅之以相关的政策措施,如构筑信息网络、发展中介机构、完善制度保障等。 相似文献
150.
刘凤根 《吉首大学学报(自然科学版)》2009,30(3):120-125
实证研究表明,投资者往往呈现出对本土市场股票的偏好,这一欠分散化投资行为的产生既有其制度方面成因也存在行为方面的因素.传统金融理论认为:资本管制、风险规避、信息不对称和交易成本是投资者本土偏差行为可能的引致因素,而行为金融理论则认为熟悉、临近性、相对乐观以及语言和文化使得投资者偏好于本土股票投资. 相似文献