首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2062篇
  免费   337篇
  国内免费   74篇
化学   73篇
晶体学   1篇
力学   156篇
综合类   112篇
数学   1828篇
物理学   303篇
  2024年   2篇
  2023年   8篇
  2022年   37篇
  2021年   96篇
  2020年   39篇
  2019年   36篇
  2018年   30篇
  2017年   95篇
  2016年   129篇
  2015年   69篇
  2014年   166篇
  2013年   123篇
  2012年   126篇
  2011年   125篇
  2010年   116篇
  2009年   138篇
  2008年   112篇
  2007年   125篇
  2006年   118篇
  2005年   118篇
  2004年   90篇
  2003年   95篇
  2002年   79篇
  2001年   46篇
  2000年   43篇
  1999年   29篇
  1998年   48篇
  1997年   26篇
  1996年   30篇
  1995年   22篇
  1994年   14篇
  1993年   13篇
  1992年   23篇
  1991年   11篇
  1990年   5篇
  1989年   13篇
  1988年   8篇
  1987年   1篇
  1986年   4篇
  1985年   23篇
  1984年   9篇
  1983年   10篇
  1982年   7篇
  1981年   6篇
  1980年   6篇
  1979年   2篇
  1978年   1篇
  1959年   1篇
排序方式: 共有2473条查询结果,搜索用时 177 毫秒
51.
A 3D graphical representation of DNA sequences, which has no circuit or degeneracy, is derived for mathematical denotation of DNA sequence. Based on this graphical representation, we propose a new sequence distance measure. We make use of the corresponding similarity matrix to construct a phylogenic tree by virtue of the fuzzy theory. The examination of phylogenic tree belong to eight species illustrates the utility of our approach. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006  相似文献   
52.
53.
随机模糊集与随机集   总被引:2,自引:2,他引:2  
本文研究了三个方面的工作:一是定义了一种模糊集上的可测结构,从而定义了随机模糊集,这些定义都与论域X上的拓扑结构无关。将通常意义下的集合看成特殊模糊集得到的通常集合上的超可测结构与文(3)中的定义一致;二是给出了随机模糊集、随机集的一些等价条件;三是研究了随机模糊集、随机集的分布与其有限维落影族的关系。  相似文献   
54.
TH型区间值模糊正规子群   总被引:8,自引:1,他引:8  
本文在区间值模糊集空间上,引入了幂等区间范数TH,在此基础上,定义了TH型区间值模糊正规子群,并研究了它的一些性质和结构特征,从而拓广了区间值模糊集的理论。  相似文献   
55.
建立并讨论了一类含有一般模糊弹性约束的广义模糊变量线性规划问题.首先,简单介绍了结构元方法并对结构元加权排序中权函数表征决策者风险态度进行了深入分析.然后选取风险中性的决策者来定义序关系,应用Verdegay模糊线性规划方法将含一般模糊弹性约束的广义模糊变量线性规划转化经典的线性规划问题,简化了原问题的求解.最后通过数值算例进一步说明了该方法的有效性.  相似文献   
56.
A dual hesitant fuzzy set (DHFS) consists of two parts, that is, the membership hesitancy function and the nonmembership hesitancy function, supporting a more exemplary and flexible access to assign values for each element in the domain, and can handle two kinds of hesitancy in this situation. It can be considered as a powerful tool to express uncertain information in the process of group decision making. Therefore, we propose a correlation coefficient between DHFSs as a new extension of existing correlation coefficients for hesitant fuzzy sets and intuitionistic fuzzy sets and apply it to multiple attribute decision making under dual hesitant fuzzy environments. Through the weighted correlation coefficient between each alternative and the ideal alternative, the ranking order of all alternatives can be determined and the best alternative can be easily identified as well. Finally, a practical example of investment alternatives is given to demonstrate the practicality and effectiveness of the developed approach.  相似文献   
57.
The purpose of this paper is to design a new extension of the ELECTRE, known as the elimination and choice translating reality method, for multi-criteria group decision-making problems based on intuitionistic fuzzy sets. This method is widely utilized when a set of alternatives should be identified and evaluated with respect to a set of conflicting criteria by reflecting decision makers’ (DMs’) preferences. However, handling the exact data and numerical measure is difficult to be precisely focused because the DMs’ judgments are often vague in real-life decision problems and applications. A more realistic and practical approach can be to use linguistic variables expressed in intuitionistic fuzzy numbers instead of numerical data to model DMs’ judgments and to describe the inputs in the ELECTRE method. The proposed intuitionsitic fuzzy ELECTRE utilizes the truth-membership function and non-truth-membership function to indicate the degrees of satisfiability and non-satisfiability of each alternative with respect to each criterion and the relative importance of each criterion, respectively. Then, a new discordance intuitionistic index is introduced, which is extended from the concept of the fuzzy distance measure. Outranking relations are defined by pairwise comparisons and a decision graph is depicted to determine which alternative is preferable, incomparable or indifferent in the intuitionistic fuzzy environment. Finally, a comprehensive sensitivity analysis is employed to further study regarding the impact of threshold values on the final evaluation, and a comparative analysis is demonstrated with an application example in flexible manufacturing systems between the proposed ELECTRE method and the existing intuitionistic fuzzy technique for order preference by similarity to ideal solution (IF-TOPSIS) method.  相似文献   
58.
提出国家电网公司在实施设备的检修作业时尽量减少停电时间,以实现电缆线路状态的有效监控的重要意义.分析缩短单点作业时间的末端影响因素.提出三角模糊集、指数模糊集用于权重设置的具体途径,应用OWA算子于因素排序评价数值的加权,并拓展其基本原理和方法,使其对极端评分值有所抑制对中间评分值有所提升.以上海市电力公司检修公司为研究背景,应用直觉模糊集及其IFHA集成方法于缩短单点作业时间的末端影响因素评价指标排序,并得出u_≥u_≥u_1u_4u_6≥u_2u_3的结论.  相似文献   
59.
Incomplete data in soft sets lead to uncertainty and inaccuracy in representing and handling information. This paper introduces notions of complete distance between two objects and relative dominance degree between two parameters. Based on both the notions, an object-parameter method is proposed to predict unknown data in incomplete fuzzy soft sets. The proposal makes full use of known data, including the information from the relationship between known values of all objects on a certain parameter and the information from the relationship between known values of an object on all parameters. The effectiveness of the proposal is verified by many examples under the compared investigation of classical predicted methods.  相似文献   
60.
In this paper, the notion of almost fuzzy compactness is defined in L-fuzzy topological spaces by means of inequality, where L is a completely distributive DeMorgan algebra. Its properties are discusse...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号