全文获取类型
收费全文 | 393篇 |
免费 | 33篇 |
国内免费 | 15篇 |
专业分类
化学 | 10篇 |
力学 | 4篇 |
综合类 | 9篇 |
数学 | 394篇 |
物理学 | 24篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 21篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 23篇 |
2013年 | 32篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 19篇 |
2009年 | 30篇 |
2008年 | 34篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 17篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1983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441条查询结果,搜索用时 62 毫秒
31.
The resource allocation in SC-FDMA is constrained by the condition that multiple subchannels should be allocated to a single user only if they are adjacent. Therefore, the scheduling scheme of a D2D-cellular system that uses SC-FDMA must also conform to the so-called adjacency constraint. This paper proposes a heuristic algorithm with low computational complexity that applies proportional fair (PF) scheduling in the D2D-cellular system. The proposed algorithm consists of two main phases: (i) subchannel allocation and (ii) adjustment of data rates, which are executed for both CUEs and DUEs. In the subchannel allocation phase for CUEs (or D2D pairs), the users’ data rates are maximized via optimal power allocation to frequency-contiguous subchannels. In the second phase, a PF scheduling problem is solved to decide the modulation and coding scheme (MCS) of both CUEs and D2D pairs. Both phases of the proposed algorithm benefit from the Water-Filling (WF) technique. The simulation results suggest that the proposed scheme performs similar to optimal PF scheduling from the perspective of users’ data rate and their logarithmic sum. An additional benefit of the proposed scheme is its low computational overhead. 相似文献
32.
长三角地区在全国房地产"库存"的背景下,实现了房地产市场的不断向好.对长三角地区有关面板数据进行实证研究,实证结果表明房地产开发投资、医院床位数、工业生产总值与人均房地产成交面积呈正相关.城镇人口数,中、长期贷款利率与人均房地产成交面积呈负相关,高收入城市比低收入城市人均房地产成交面积低14.%,教育支出和城镇居民总的可支配收入对人均房地产成交面积影响不显著. 相似文献
33.
34.
The aggregate claim amount in a particular time period is a quantity of fundamental importance for proper management of an insurance company and also for pricing of insurance coverages. In this paper, we show that the proportional hazard rates (PHR) model, which includes some well-known distributions such as exponential, Weibull and Pareto distributions, can be used as the aggregate claim amount distribution. We also present some conditions for the use of exponentiated Weibull distribution as the claim amount distribution. The results established here complete and extend the well-known result of Khaledi and Ahmadi (2008). 相似文献
35.
In this paper, we consider the optimal proportional reinsurance strategy in a risk model with multiple dependent classes of insurance business, which extends the work of Liang and Yuen (2014) to the case with the reinsurance premium calculated under the expected value principle and to the model with two or more classes of dependent risks. Under the criterion of maximizing the expected exponential utility, closed-form expressions for the optimal strategies and value function are derived not only for the compound Poisson risk model but also for the diffusion approximation risk model. In particular, we find that the optimal reinsurance strategies under the expected value premium principle are very different from those under the variance premium principle in the diffusion risk model. The former depends not only on the safety loading, time and interest rate, but also on the claim size distributions and the counting processes, while the latter depends only on the safety loading, time and interest rate. Finally, numerical examples are presented to show the impact of model parameters on the optimal strategies. 相似文献
36.
Lianming WangXiaoyan Lin 《Statistics & probability letters》2011,81(7):876-883
Analyzing interval-censored data is difficult due to its complex data structure containing left-, interval-, and right-censored observations. An easy-to-implement Bayesian approach is proposed under the proportional odds (PO) model for analyzing such data. The nondecreasing baseline log odds function is modeled with a linear combination of monotone splines. Two efficient Gibbs samplers are developed based on two different data augmentations using the relationship between the PO model and the logistic distribution. In the first data augmentation, the logistic distribution is achieved by the scaled normal mixture with the scale parameter related to the Kolmogorov-Smirnove distribution. In the second data augmentation, the logistic distribution is approximated by a Student’s t distribution up to a scale constant. The proposed methods are evaluated by simulation studies and illustrated with an application of an HIV data set. 相似文献
37.
This paper concerns optimal investment problem with proportional transaction costs and finite time horizon based on exponential
utility function. Using a partial differential equation approach, we reveal that the problem is equivalent to a parabolic
double obstacle problem involving two free boundaries that correspond to the optimal buying and selling policies. Numerical
examples are obtained by the binomial method. 相似文献
38.
This paper investigates proportional and excess-loss reinsurance contracts in a continuous-time principal–agent framework, in which the insurer is the agent and the reinsurer is the principal. Insurance claims follow the classic Cramér–Lundberg process. The insurer believes that the claim intensity is uncertain and he chooses robust risk retention levels to maximize the penalty-dependent multiple-priors utility. The reinsurer designs reinsurance contracts subject to the insurer’s incentive compatibility constraints. The analytical expressions of the two robust reinsurance contracts are derived. Our results show that the robust reinsurance demand and price are greater than their respective standard values without model ambiguity, and increase as the insurer’s ambiguity aversion increases. Moreover, the reinsurer specifies a decreasing reinsurance price to induce increasing demand over time. Specifically, the price of excess-loss reinsurance is higher, relative to that of proportional reinsurance. Further, only if the insurer’s risk aversion is high or the reinsurer’s risk aversion is low, the insurer prefers the excess-loss reinsurance contract. 相似文献
39.
40.
Mathematical reasoning and problem solving are recognised as essential 21st century skills. However, international assessments of mathematical literacy suggest these are areas of difficulty for many students. Evidenced-based learning trajectories that identify the key ideas and strategies needed to teach mathematics for understanding and support these important capacities over time are needed to support teachers and curriculum developers so that they do not have to rely solely on mathematics content knowledge. Given this goal and recent evidence to suggest a relationship between the development of multiplicative thinking and mathematical reasoning, this paper explores the processes involved in developing a single, integrated scale for multiplicative thinking and mathematical reasoning using data from a four-year design-based project to establish learning and assessment frameworks for algebraic, geometrical and statistical reasoning in the middle years of schooling. 相似文献