全文获取类型
收费全文 | 2409篇 |
免费 | 18篇 |
国内免费 | 29篇 |
专业分类
化学 | 56篇 |
力学 | 40篇 |
综合类 | 23篇 |
数学 | 2171篇 |
物理学 | 166篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 27篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 26篇 |
2016年 | 36篇 |
2015年 | 29篇 |
2014年 | 96篇 |
2013年 | 121篇 |
2012年 | 129篇 |
2011年 | 158篇 |
2010年 | 103篇 |
2009年 | 191篇 |
2008年 | 131篇 |
2007年 | 172篇 |
2006年 | 141篇 |
2005年 | 98篇 |
2004年 | 73篇 |
2003年 | 63篇 |
2002年 | 73篇 |
2001年 | 108篇 |
2000年 | 77篇 |
1999年 | 63篇 |
1998年 | 64篇 |
1997年 | 52篇 |
1996年 | 48篇 |
1995年 | 36篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 49篇 |
1984年 | 48篇 |
1983年 | 19篇 |
1982年 | 38篇 |
1981年 | 32篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 3篇 |
排序方式: 共有2456条查询结果,搜索用时 15 毫秒
141.
The goal programming (GP) model is probably the best known in mathematical programming with multiple objectives. Available in various versions, GP is one of the most powerful multiple objective methods which has been applied in much varied fields. It has also been the target of many criticisms among which are those related to the difficulty of determining precisely the goal values as well as those concerning the decision-maker's near absence in this modelling process. In this paper, we will use the concept of indifference thresholds for modelling the imprecision related to the goal values. Many classical imprecise and fuzzy GP model formulations can be considered as a particular case of the proposed formulation. 相似文献
142.
143.
从映射的图可换角度对扩张原理进行解释。使得扩张原理更加直观,更易于理解,同时从图可换的角度研究张原理的若干性质及广义模糊扩张原理。 相似文献
144.
145.
一阶模糊谓词逻辑公式的解释模型真度理论及其应用 总被引:5,自引:0,他引:5
基于一阶模糊谓词逻辑公式的有限和可数解释真度的理论,引入了一阶模糊谓词逻辑公式的解释模型及解释模型真度的概念,并讨论了它们的一系列性质及其在近似推理中的应用. 相似文献
146.
Przemysaw Grzegorzewski 《Fuzzy Sets and Systems》2008,159(11):1354-1364
Fuzzy number approximation by trapezoidal fuzzy numbers which preserves the expected interval is discussed. Algorithms for calculating the proper approximations are proposed and some properties of the approximation operators are discussed. It is shown that an adequate approximation operator might be chosen through the comparisons of some characteristics of the fuzzy number, like its ambiguity, width, its value and weighted expected value. 相似文献
147.
Van-Nam Huynh Yoshiteru Nakamori Mina Ryoke Tu-Bao Ho 《Fuzzy Optimization and Decision Making》2007,6(3):255-278
This paper discusses the issue of how to use fuzzy targets in the target-based model for decision making under uncertainty.
After introducing a target-based interpretation of the expected value on which it is shown that this model implicitly assumes
a neutral behavior on attitude about the target, we examine the issue of using fuzzy targets considering different attitudes
about the target selection of the decision maker. We also discuss the problem for situations on which the decision maker’s
attitude about target may change according to different states of nature. Especially, it is shown that the target-based approach
can provide an unified way for solving the problem of fuzzy decision making with uncertainty about the state of nature and
imprecision about payoffs. Several numerical examples are given for illustration of the discussed issues. 相似文献
148.
X.S. Qin G.H. Huang G.M. Zeng A. Chakma Y.F. Huang 《European Journal of Operational Research》2007,180(3):182
Planning for water quality management systems is complicated by a variety of uncertainties and nonlinearities, where difficulties in formulating and solving the resulting inexact nonlinear optimization problems exist. With the purpose of tackling such difficulties, this paper presents the development of an interval-fuzzy nonlinear programming (IFNP) model for water quality management under uncertainty. Methods of interval and fuzzy programming were integrated within a general framework to address uncertainties in the left- and right-hand sides of the nonlinear constraints. Uncertainties in water quality, pollutant loading, and the system objective were reflected through the developed IFNP model. The method of piecewise linearization was developed for dealing with the nonlinearity of the objective function. A case study for water quality management planning in the Changsha section of the Xiangjiang River was then conducted for demonstrating applicability of the developed IFNP model. The results demonstrated that the accuracy of solutions through linearized method normally rises positively with the increase of linearization levels. It was also indicated that the proposed linearization method was effective in dealing with IFNP problems; uncertainties can be communicated into optimization process and generate reliable solutions for decision variables and objectives; the decision alternatives can be obtained by adjusting different combinations of the decision variables within their solution intervals. It also suggested that the linearized method should be used under detailed error analysis in tackling IFNP problems. 相似文献
149.
Solving fuzzy queueing decision problems via a parametric mixed integer nonlinear programming method
This paper proposes a mathematical programming method to construct the membership functions of the fuzzy objective value of the cost-based queueing decision problem with the cost coefficients and the arrival rate being fuzzy numbers. On the basis of Zadeh’s extension principle, three pairs of mixed integer nonlinear programs (MINLP) parameterized by the possibility level α are formulated to calculate the lower and upper bounds of the minimal expected total cost per unit time at α, through which the membership function of the minimal expected total cost per unit time of the fuzzy objective value is constructed. To provide a suitable optimal service rate for designing queueing systems, the Yager’s ranking index method is adopted. Two numerical examples are solved successfully to demonstrate the validity of the proposed method. Since the objective value is completely expressed by a membership function rather than by a crisp value, it conserves the fuzziness of the input information, thus more information is provided for designing queueing systems. The successful extension of queueing decision models to fuzzy environments permits queueing decision models to have wider applications in practice. 相似文献
150.
The concept of super value nodes was established to allow dynamic programming to be performed within the theory of influence diagrams and to reduce the computational complexity in solving problems by means of influence diagrams. This paper is focused on how influence diagrams with super value nodes are affected by the presence of imprecise information. We analyze how to reduce the complexity when evaluating an influence diagram in this framework by modelling these kinds of nodes and random magnitudes in terms of fuzzy random variables. Finally, an applied example of the theoretical results is developed. 相似文献