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   181篇
  免费   0篇
  国内免费   6篇
化学   17篇
力学   18篇
综合类   2篇
数学   140篇
物理学   10篇
  2024年   1篇
  2022年   2篇
  2020年   2篇
  2019年   1篇
  2018年   1篇
  2017年   3篇
  2016年   1篇
  2015年   2篇
  2014年   10篇
  2013年   9篇
  2012年   12篇
  2011年   10篇
  2010年   23篇
  2009年   22篇
  2008年   24篇
  2007年   13篇
  2006年   7篇
  2005年   7篇
  2004年   3篇
  2003年   6篇
  2002年   2篇
  2001年   5篇
  2000年   6篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1994年   2篇
  1992年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
排序方式: 共有187条查询结果,搜索用时 203 毫秒
181.
用电动势和化学分析方法研究了富钛还原熔渣-CaO-SiO_2-Al_2O_3-MgO-TiO_x-FeO_y体系的氧化动力学,得出了氧在熔渣中的扩散速率常数分别为 0. 66×10~(-5) m· s~(-1)和 1. 98×10~(-5) m·s~(-1),研究表明:固体电解质构成的氧浓差电池法得出的结果不仅可靠,且方法快速、简便.  相似文献   
182.
三峡工程移民迁建区灾害地质体改造与利用研究   总被引:2,自引:0,他引:2  
三峡工程移民迁建区地质环境复杂 ,建设用地严重不足。如何在治理的基础上对滑坡等灾害地质体开发利用是一项风险极大 ,但具非常现实意义的课题。本文论述了预应力锚拉桩在库区大型滑坡防治中的应用成果 ,这种方法不仅能有效地控制滑坡体的稳定性 ,同时 ,也能根据移民工程要求提供适宜的建设用地 ;介绍了注浆方法对库区分布较广的以崩塌、滑坡、岩溶成因为主的崩滑堆积体的改造问题 ,它不仅可以大大降低移民迁建区地基与边坡处理的工程造价 ,也为库区灾害地质体的改造提供了范例 ;弃渣是库区极为突出的环境地质问题 ,不仅危害长江 ,也对移民迁建区构成严重威胁 ,本文介绍了巫山新城等利用加筋土技术处理弃渣 ,并大大增加建设用地的实例 ,由于该挡墙高达 5 6 m,超出了一般意义下的加筋土挡墙范畴 (通常不超过 2 0 m) ,因此出现了前缘筋带断裂和面板脱落问题 ,本文介绍了应用锚管注浆技术进行面板修复的设计 ,为复杂地质条件地区高加筋挡土墙的安全修建提供了经验.  相似文献   
183.
184.
Knowledge discovery aims at extracting new knowledge from potentially large databases; this may be in the form of interesting statements about the data. Two interrelated classes of problem arise that are treated here: to put the subjective notion of ‘interesting’ into concrete terms and to deal with large numbers of statements that are related to one another (one rendering the other redundant or at least less interesting). Four increasingly subjective facets of ‘interestingness’ are identified: the subject field under consideration, the conspicuousness of a finding, its novelty, and its deviation from prior knowledge. A procedure is proposed, and tried out on two quite different data sets, that allows for specifying interestingness by various means and that ranks the results in a way that takes interestingness (relevance, evidence) as well as mutual relatedness (similarity, affinity) into account—manifestations of the second and third facets of interestingness in the given data environment.  相似文献   
185.
In Memoriam     
I sketch the rich life and multifaceted work of Philip Morrison (1915–2005), from his early life in Pittsburgh, Pennsylvania, and higher education at the Carnegie Institute of Technology and the University of California at Berkeley, to his contributions to the Manhattan Project, his research at Cornell University and the Massachusetts Institute of Technology after the war, his subsequent political activity on behalf of nuclear disarmament, his role in the search for extraterrestrial intelligence, and his enormous influence as an educator, public speaker, and writer. A.P. French is Professor of Physics, Emeritus, at the Massachusetts Institute of Technology.  相似文献   
186.
In this paper, an overview is presented of the existing metaheuristic solution procedures to solve the multi-mode resource-constrained-project scheduling problem, in which multiple execution modes are available for each of the activities of the project. A fair comparison is made between the different metaheuristic algorithms on the existing benchmark datasets and on a newly generated dataset. Computational results are provided and recommendations for future research are formulated.  相似文献   
187.
This paper introduces a multi-project problem environment which involves multiple projects with assigned due dates; activities that have alternative resource usage modes; a resource dedication policy that does not allow sharing of resources among projects throughout the planning horizon; and a total budget. Three issues arise when investigating this multi-project environment. First, the total budget should be distributed among different resource types to determine the general resource capacities, which correspond to the total amount for each renewable resource to be dedicated to the projects. With the general resource capacities at hand, the next issue is to determine the amounts of resources to be dedicated to the individual projects. The dedication of resources reduces the scheduling of the projects’ activities to a multi-mode resource constrained project scheduling problem (MRCPSP) for each individual project. Finally, the last issue is the efficient solution of the resulting MRCPSPs. In this paper, this multi-project environment is modeled in an integrated fashion and designated as the resource portfolio problem. A two-phase and a monolithic genetic algorithm are proposed as two solution approaches, each of which employs a new improvement move designated as the combinatorial auction for resource portfolio and the combinatorial auction for resource dedication. A computational study using test problems demonstrated the effectiveness of the solution approach proposed.  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