全文获取类型
收费全文 | 729篇 |
免费 | 101篇 |
国内免费 | 12篇 |
专业分类
化学 | 60篇 |
力学 | 8篇 |
综合类 | 31篇 |
数学 | 693篇 |
物理学 | 50篇 |
出版年
2023年 | 4篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 25篇 |
2019年 | 22篇 |
2018年 | 26篇 |
2017年 | 36篇 |
2016年 | 35篇 |
2015年 | 30篇 |
2014年 | 42篇 |
2013年 | 68篇 |
2012年 | 49篇 |
2011年 | 56篇 |
2010年 | 43篇 |
2009年 | 34篇 |
2008年 | 30篇 |
2007年 | 45篇 |
2006年 | 38篇 |
2005年 | 30篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有842条查询结果,搜索用时 15 毫秒
131.
运用在线问题与竞争分析的方法研究了购买价格递减的在线租赁问题。通过揭示相关费用函数的性质,先后给出了最优离线策略以及在线策略。通过竞争比分析,证明了我们给出的在线策略是该问题唯一最优策略,而且该策略的竞争比随购买价格的优惠率的增加呈严格递减趋势。竞争分析结果表明考虑购买价格递减因素能够改进在线策略的竞争比从而提高决策效率。 相似文献
132.
133.
介绍一种利用全反射原理测定水的折射率的方法。实验中利用He-Ne激光束在水底产生点光源,根据全反射原理对水底的暗影和水深进行测量,求出水的折射率。 相似文献
134.
In this paper, we address the simultaneous determination of price and inventory replenishment when customers return product to the firm. We examine cases when the quantity of returned product is a function of both the quantity sold and the price, in single and multi-period problems, with and without uncertainty in demand. 相似文献
135.
We address asymptotic analysis of option pricing in a regime switching market where the risk free interest rate, growth rate and the volatility of the stocks depend on a finite state Markov chain. We study two variations of the chain namely, when the chain is moving very fast compared to the underlying asset price and when it is moving very slow. Using quadratic hedging and asymptotic expansion, we derive corrections on the locally risk minimizing option price. 相似文献
136.
根据06~07年间全国主要滑雪场的门市价和季卡价,首先运用EVIEWS6计量软件做出散点图、残差分析图以及残差的自相关-偏相关图,然后运用最小二乘估计方法确定回归方程系数,建立回归和序列组合模型,并将滑雪场的门市价代入相应方程计算出季卡付费方式下滑雪场应制定的最优价格,最后做相应的误差分析并总结本文模型的优点与不足. 相似文献
137.
Fima C. Klebaner Zinoviy Landsman 《Methodology and Computing in Applied Probability》2009,11(3):339-357
We derive an option pricing formula on assets with returns distributed according to a log-symmetric distribution. Our approach
is consistent with the no-arbitrage option pricing theory: we propose the natural risk-neutral measure that keeps the distribution
of returns in the same log-symmetric family reflecting thus the specificity of the stock’s returns. Our approach also provides
insights into the Black–Scholes formula and shows that the symmetry is the key property: if distribution of returns X is log-symmetric then 1/X is also log-symmetric from the same family. The proposed options pricing formula can be seen as a generalization of the Black–Scholes
formula valid for lognormal returns. We treat an important case of log returns being a mixture of symmetric distributions
with the particular case of mixtures of normals and show that options on such assets are underpriced by the Black–Scholes
formula. For the log-mixture of normal distributions comparisons with the classical formula are given.
相似文献
138.
Rafał Weron 《Mathematical Methods of Operations Research》2009,69(3):457-473
In this paper we first analyze the stylized facts of electricity prices, in particular, the extreme volatility and price spikes
which lead to heavy-tailed distributions of price changes. Then we calibrate Markov regime-switching (MRS) models with heavy-tailed
components and show that they adequately address the aforementioned characteristics. Contrary to the common belief that electricity
price models ‘should be built on log-prices’, we find evidence that modeling the prices themselves is more beneficial and
methodologically sound, at least in case of MRS models. 相似文献
139.
An EOQ model for perishable products with discounted selling price and stock dependent demand 总被引:2,自引:0,他引:2
A single item economic order quantity model is considered in which the demand is stock dependent. After a certain time the
product starts to deteriorate and due to visualization effect and other aspects of deterioration the demand becomes constant.
In that situation a discount on selling price provides significant increment in demand rate. In this paper we investigate
how much discount on selling price may be given during deterioration to maximize the profit per unit time and whether a pre-deterioration
discount affects the unit profit or not. A mathematical model is developed incorporating both pre- and post deterioration
discounts on unit selling price, where analytical results reveal some important characteristics of discount structure. A numerical
example is presented and sensitivity analysis of the model is carried out. 相似文献
140.
根据经济学中的后悔理论,首次在经典的最优序贯搜索问题中引入了决策者在搜索过程中的后悔和欣喜心理. 模型发现,如果决策者具备完美预期,那么她对后悔和欣喜的敏感度之差将直接决定她的搜索行为与最优搜索的偏差程度和方向,并且对于预期性后悔的敏感度越大则搜索程度越低. 这符合实验文献里“搜索过少”的结论. 进一步分析发现,在停止搜索后能知晓反事件价格的情况下,带有预期性后悔和欣喜的搜索将会趋向于经典的最优搜索策略. 如果对于后悔和欣喜的敏感度会受到搜索过程中经历过的类似心理的影响,模型对价格召回也作出了合理解释. 相似文献