全文获取类型
收费全文 | 2658篇 |
免费 | 131篇 |
国内免费 | 121篇 |
专业分类
化学 | 108篇 |
力学 | 15篇 |
综合类 | 14篇 |
数学 | 912篇 |
物理学 | 57篇 |
综合类 | 1804篇 |
出版年
2024年 | 6篇 |
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 51篇 |
2020年 | 57篇 |
2019年 | 48篇 |
2018年 | 35篇 |
2017年 | 50篇 |
2016年 | 71篇 |
2015年 | 68篇 |
2014年 | 145篇 |
2013年 | 176篇 |
2012年 | 176篇 |
2011年 | 202篇 |
2010年 | 191篇 |
2009年 | 205篇 |
2008年 | 192篇 |
2007年 | 200篇 |
2006年 | 172篇 |
2005年 | 158篇 |
2004年 | 127篇 |
2003年 | 111篇 |
2002年 | 87篇 |
2001年 | 57篇 |
2000年 | 37篇 |
1999年 | 27篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 3篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有2910条查询结果,搜索用时 15 毫秒
131.
The liberalization of European natural gas markets forces market participants to base their decisions on market prices. For owners and operators of natural gas storage facilities it is therefore necessary to take market prices into account for their decisions. In this framework this paper provides a new approach for the valuation of natural gas storage facilities. Using stochastic dynamic programming on multinomial recombining trees, the optimal storage strategy and value are determined. For this we (i) estimate the deterministic and random impacts on natural gas prices, (ii) simulate gas prices considering the results of the first step, (iii) construct numerically the recombining tree using the simulation results, (iv) determine the optimal storage strategy and value. Besides the determination of the optimal storage value and operation schedule the value quantiles are calculated. Via the quantiles relevant risk measures like value at risk and conditional value at risk are determined. 相似文献
132.
Olga Boudali Antonis Economou 《European Journal of Operational Research》2012,218(3):708-715
We consider a Markovian queue subject to Poisson generated catastrophes. Whenever a catastrophe occurs, all customers are forced to abandon the system, the server is rendered inoperative and an exponential repair time is set on. We assume that the arriving customers decide whether to join the system or balk, based on a natural reward-cost structure. We study the balking behavior of the customers and derive the corresponding Nash equilibrium and social optimal strategies. 相似文献
133.
利用分数布朗运动研究了一种强路径依赖型期权—回望期权的定价问题.首先列出了有关的定义和引理;其次利用该定义和引理建立了分数布朗运动情况下的价格模型,通过鞅方法,得到了回望期权价格所满足的方程;最后分别给出了看跌回望期权和看涨回望期权的定价公式的显式解. 相似文献
134.
We derive in closed form distribution free lower bounds and optimal subreplicating strategies for spread options in a one-period static arbitrage setting. In the case of a continuum of strikes, we complement the optimal lower bound for spread options obtained in [Rapuch, G., Roncalli, T., 2002. Pricing multiasset options and credit derivatives with copula, Credit Lyonnais, Working Papers] by describing its corresponding subreplicating strategy. This result is explored numerically in a Black-Scholes and in a CEV setting. In the case of discrete strikes, we solve in closed form the optimization problem in which, for each asset S1 and S2, forward prices and the price of one option are used as constraints on the marginal distributions of each asset. We provide a partial solution in the case where the marginal distributions are constrained by two strikes per asset. Numerical results on real NYMEX (New York Mercantile Exchange) crack spread option data show that the one discrete lower bound can be far and also very close to the traded price. In addition, the one strike closed form solution is very close to the two strike. 相似文献
135.
Håkan Hedenmalm 《Journal of Mathematical Analysis and Applications》2006,314(1):345-362
In practical work with American put options, it is important to be able to know when to exercise the option, and when not to do so. In computer simulation based on the standard theory of geometric Brownian motion for simulating stock price movements, this problem is fairly easy to handle for options with a short lifespan, by analyzing binomial trees. It is considerably more challenging to make the decision for American put options with long lifespan. In order to provide a satisfactory analysis, we look at the corresponding free boundary problem, and show that the free boundary—which is the curve that separates the two decisions, to exercise or not to—has an asymptotic expansion, where the coefficient of the main term is expressed as an integral in terms of the free boundary. This raises the perspective that one could use numerical simulation to approximate the integral and thus get an effective way to make correct decisions for long life options. 相似文献
136.
Xiaotie Deng Yonggeng Gu Shunming Zhang 《Journal of Mathematical Analysis and Applications》2006,313(1):353-365
We examine the valuation of American put options by a semi-analytical method, and obtain the prior estimate and the convergence of the approximate solution. Our proofs are based on the embedding theorem in Sobolev space and the theory of functional analysis, in particular, the theory of weak compactness. The results in this paper theoretically confirm empirical observations that these methods are accurate and computationally efficient. 相似文献
137.
N. C. P. Edirisinghe 《Computational Optimization and Applications》2005,32(1-2):29-59
This paper is concerned with an investor trading in multiple securities over many time periods in order to meet an outstanding liability at some future date. The investor is concerned with maximizing the expected profits from portfolio rebalancing under an initial wealth restriction to meet the future liabilities. We formulate the problem as a discrete-time stochastic optimization model and allow asset prices to have continuous probability distributions on compact domains. For the case of Markovian price uncertainty and convex terminal liability, we develop a simplicial approximation, under which bounds on the problem can be computed efficiently. Computations only require evaluating a dynamic programming recursion, which thus, allows its application to problems with a large number of trading periods. The bounds are tight in that they are exact in certain cases. Numerical results are given to demonstrate the computational efficiency of the procedure. 相似文献
138.
本文主要借助期权理论,讨论项目投资分多阶段进行时选择最佳投资的问题.首先通过在单阶段投资下建立项目投资的最佳选择框架,然后展开到项目投资分两个阶段进行的情形上进行讨论分析,得出此情形下的投资选择结论,最后把这一结论扩展到项目投资分多阶段进行的项目上. 相似文献
139.
本文根据风险中性定价原理,用较简单的数学方法推导出了股票欧式复合期权的定价公式。该公式和求解B lack-Scho les微分方程所得结果一致。 相似文献
140.