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   1379篇
  免费   161篇
  国内免费   65篇
化学   216篇
晶体学   1篇
力学   34篇
综合类   159篇
数学   748篇
物理学   447篇
  2024年   3篇
  2023年   21篇
  2022年   27篇
  2021年   34篇
  2020年   35篇
  2019年   47篇
  2018年   32篇
  2017年   30篇
  2016年   39篇
  2015年   31篇
  2014年   56篇
  2013年   60篇
  2012年   37篇
  2011年   58篇
  2010年   59篇
  2009年   96篇
  2008年   75篇
  2007年   91篇
  2006年   87篇
  2005年   79篇
  2004年   63篇
  2003年   66篇
  2002年   64篇
  2001年   45篇
  2000年   38篇
  1999年   39篇
  1998年   33篇
  1997年   28篇
  1996年   31篇
  1995年   52篇
  1994年   24篇
  1993年   26篇
  1992年   17篇
  1991年   9篇
  1990年   13篇
  1989年   13篇
  1988年   8篇
  1987年   8篇
  1986年   5篇
  1985年   6篇
  1984年   3篇
  1983年   5篇
  1982年   2篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1977年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有1605条查询结果,搜索用时 15 毫秒
161.
We define a direct translation from finite rooted trees to finite natural functions which shows that the Worm Principle introduced by Lev Beklemishev is equivalent to a very slight variant of the well‐known Kirby‐Paris' Hydra Game. We further show that the elements in a reduction sequence of the Worm Principle determine a bad sequence in the well‐quasi‐ordering of finite sequences of natural numbers with respect to Friedman's gapembeddability. A characterization of gap‐embeddability in terms of provability logic due to Lev Beklemishev is also presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
162.
本文在作者以前研究的基础上,进一步研究最佳通用逻辑门ULG.2的应用,提出了用ULG.2组成的一些脉冲电路。  相似文献   
163.
By means of several examples of structural operational semantics for a variety of languages, we justify the importance and interest of using the notions of strategies and simulations in the semantic framework provided by rewriting logic and implemented in the Maude metalanguage. On the one hand, we describe a basic strategy language for Maude and show its application to CCS, the ambient calculus, and the parallel functional language Eden. On the other hand, we show how the concept of stuttering simulation can be used inside Maude to show that a stack machine correctly implements the operational semantics of a simple functional language.  相似文献   
164.
This paper articulates the structure of a two species of weakly aggregative necessity in a common idiom, neighbourhood semantics, using the notion of a k-filter of propositions. A k-filter on a non-empty set I is a collection of subsets of I which (i) contains I, (ii) is closed under supersets on I, and (iii) contains ∪{XiXj : 0 ≤ i < jk} whenever it contains the subsets X0,…, Xk. The mathematical content of the proof that weakly aggregative modal logic is complete relative to k-ary frame theory, the standard semantic idiom for weakly aggregative modal logic (see [1]) is presented in language-independent terms as a representation theorem for k-filters: every non-trivial k-filter is included in the union of ≤ k non-trivial filters. The elementary theory of k-filters is developed and then applied in the form of an ultrafilter extension result for k-ary frame theory. Mathematics Subject Classification: 03B45.  相似文献   
165.
A learning process for fuzzy control rules using genetic algorithms   总被引:10,自引:0,他引:10  
The purpose of this paper is to present a genetic learning process for learning fuzzy control rules from examples. It is developed in three stages: the first one is a fuzzy rule genetic generating process based on a rule learning iterative approach, the second one combines two kinds of rules, experts rules if there are and the previously generated fuzzy control rules, removing the redundant fuzzy rules, and the thrid one is a tuning process for adjusting the membership functions of the fuzzy rules. The three components of the learning process are developed formulating suitable genetic algorithms.  相似文献   
166.
Application of fuzzy control to a road tunnel ventilation system   总被引:8,自引:0,他引:8  
This paper deals with the serious problems of ventilation system in a large road tunnel. Higher visibility and lower concentration of carbon monoxide are the key issues concerning the ventilation system. Prior to designing the fuzzy control model, a configuration layout of the ventilation system including sensing, control and traffic prediction as well is conceptually constructed. Based on the layout that offers assignments of sensors and control elements, a fuzzy logic control model is developed. Membership functions of sensor errors and control increments are physically submitted in order to set up the fuzzy logic rules. Timing and spacing filtering in terms of weighting approaches is employed in the fuzzy logic rules. A dynamic equation describing the concentration of air pollution is also given so as to cooperate with the fuzzy logic rules and to play roles in the computer simulation. The result of computer simulation involving five cases indicates that a multi-level scheme is able to solve the engineering problems.  相似文献   
167.
Grzegorczyk's modal logic (Grz) corresponds to the class of upwards well‐founded partially ordered Kripke frames, however all known proofs of this fact utilize some form of the Axiom of Choice; G. Boolos asked in [1], whether it is provable in plain ZF. We answer his question negatively: Grz corresponds (in ZF) to a class of frames, which does not provably coincide with upwards well‐founded posets in ZF alone. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
168.
In this paper we propose a Kripke‐style semantics for second order intuitionistic propositional logic and we provide a semantical proof of the disjunction and the explicit definability property. Moreover, we provide a tableau calculus which is sound and complete with respect to such a semantics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
169.
In this paper, after recounting the basic properties of perfect MV-algebras, we explore the role of such algebras in localization issues. Further, we analyze some logics that are based on Łukasiewicz connectives and are complete with respect to linearly ordered perfect MV-algebras.   相似文献   
170.
Pr值逻辑函数相关免疫的等价判别条件   总被引:2,自引:0,他引:2  
杨锐  曾本胜  李世取 《应用数学》2006,19(1):139-144
本文首先基于环Zpr中的元的padic分解并结合概率论的思想,给出了pr值随机变量的分解性质及pr值随机变量独立性的等价描述,然后在对pr值逻辑函数及其变元都进行padic分解的基础上,直接通过p值逻辑函数的Chrestenson谱给出了padic分解意义下pr值逻辑函数k阶相关免疫的线性组合引理和谱判别定理.  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