全文获取类型
收费全文 | 605篇 |
免费 | 2篇 |
专业分类
化学 | 7篇 |
力学 | 11篇 |
综合类 | 4篇 |
数学 | 567篇 |
物理学 | 18篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 14篇 |
2013年 | 28篇 |
2012年 | 75篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 28篇 |
2008年 | 13篇 |
2007年 | 23篇 |
2006年 | 25篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 15篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 28篇 |
1979年 | 19篇 |
1978年 | 30篇 |
1977年 | 5篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有607条查询结果,搜索用时 31 毫秒
41.
42.
The management of technology in multi-service computer networks, such as university networks, has become a challenge with the explosive growth of entertainment oriented peer-to-peer (P2P) traffic. Traffic shaping is one of the tools used to manage bandwidth to improve system performance by allocating bandwidth between P2P and non-peer-to-peer (NP2P) traffic. We present a model for traffic shaping and bandwidth management that considers the trade-offs from allocating different amounts of bandwidths for different application categories and use data from a university network. The current policy allocates varying bandwidths over the day to P2P and NP2P traffic to reflect the importance of not letting entertainment based traffic choke the network during the day time at the expense of the more important traffic, such as Web traffic. We highlight the difficulties in obtaining data in the form required for analysis, and the need to estimate demand for allocations not covered by current policy. We present a goal programming model for this estimation task. We also model the traffic shaping problem as a Markov decision process and develop an algorithm for determining the optimal bandwidth allocation to maximize the utility of all users. Finally we use a numerical example to illustrate our approach. 相似文献
43.
简要叙述了并行程序设计语言CMFortran的计算模式、并行数据结构及其主要特征.并对Fortran77和Fortran90上的扩展部分作了概要描述. 相似文献
44.
Goal programming is an important technique for solving many decision/management problems. Fuzzy goal programming involves applying the fuzzy set theory to goal programming, thus allowing the model to take into account the vague aspirations of a decision-maker. Using preference-based membership functions, we can define the fuzzy problem through natural language terms or vague phenomena. In fact, decision-making involves the achievement of fuzzy goals, some of them are met and some not because these goals are subject to the function of environment/resource constraints. Thus, binary fuzzy goal programming is employed where the problem cannot be solved by conventional goal programming approaches. This paper proposes a new idea of how to program the binary fuzzy goal programming model. The binary fuzzy goal programming model can then be solved using the integer programming method. Finally, an illustrative example is included to demonstrate the correctness and usefulness of the proposed model. 相似文献
45.
进化规划动态寻优机理分析 总被引:3,自引:0,他引:3
为了从整体上揭示进化规划 ( EP)算法的内在运行机制 ,探寻算法的动态寻优机理 ,本文从种群角度出发 ,建立了一种种群动态寻优微分方程模型 ,并对该模型进行了理论分析 .数值模拟结果说明了所建模型的正确性 ,并得出了一些有意义的结论 相似文献
46.
Sergio Delgado-Quintero Juan-José Salazar-González 《Mathematical Methods of Operations Research》2008,68(3):407-428
The editing-and-imputation problem concerns the question of finding errors in a record which does not satisfy a set of consistency
rules. Once some potential errors have been localizated, it is also necessary to impute new values to the associated fields.
The output dataset should consist of valid records and preserve similar statistical properties as the input dataset. Most
of this work is usually done manually by statistical agencies, thus consuming a great deal of human resources. This paper
presents a mathematical programming model to optimally solve the problem on surveys with categorical values and particular
edits. We also describe a heuristic approach to deal with the more complex surveys. The heuristic procedure follows a combination
of the widely-accepted hot-deck donor scheme and the multivariate regression analysis. It has been implemented in a graphical
user interface running on standard personal computers, and has been tested on real-world surveys. This paper demonstrates
the satisfactory performance of our automatic procedure. 相似文献
47.
48.
49.
This study shows how data envelopment analysis (DEA) can be used to reduce vertical dimensionality of certain data mining databases. The study illustrates basic concepts using a real-world graduate admissions decision task. It is well known that cost sensitive mixed integer programming (MIP) problems are NP-complete. This study shows that heuristic solutions for cost sensitive classification problems can be obtained by solving a simple goal programming problem by that reduces the vertical dimension of the original learning dataset. Using simulated datasets and a misclassification cost performance metric, the performance of proposed goal programming heuristic is compared with the extended DEA-discriminant analysis MIP approach. The holdout sample results of our experiments shows that the proposed heuristic approach outperforms the extended DEA-discriminant analysis MIP approach. 相似文献
50.
Programming is a key process for thermally activated stress or strain recovery of shape memory polymers (SMPs). Typically, programming requires an initial heating above the glass transition temperature (Tg), subsequent cooling below Tg and removal of the applied load, in order to fix a temporary shape. This work adopted a new approach to program thermoset SMPs directly at temperatures well below Tg, which effectively simplified the shape fixing process. 1-D compression programming below Tg and free shape recovery of a thermoset SMP were experimentally investigated. Functional stability of the shape fixity under various environmental attacks was also experimentally evaluated. A mechanism-based thermoviscoelastic-thermoviscoplastic constitutive model incorporating structural and stress relaxation was then developed to predict the nonlinear shape memory behavior of the SMP trained below Tg. Comparison between the prediction and the experiment showed good agreement. The structure dependence of the thermomechanical behavior of the SMP was further discussed through a parametric study per the validated constitutive model. This study validates that programming by cold-compression is a viable alternative for thermally responsive thermoset SMPs. 相似文献