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   13935篇
  免费   71篇
  国内免费   3篇
电工技术   184篇
综合类   5篇
化学工业   1168篇
金属工艺   354篇
机械仪表   146篇
建筑科学   233篇
矿业工程   27篇
能源动力   129篇
轻工业   357篇
水利工程   66篇
石油天然气   15篇
无线电   557篇
一般工业技术   674篇
冶金工业   1628篇
原子能技术   130篇
自动化技术   8336篇
  2019年   30篇
  2018年   38篇
  2016年   38篇
  2015年   32篇
  2014年   281篇
  2013年   455篇
  2012年   883篇
  2011年   2423篇
  2010年   1190篇
  2009年   1046篇
  2008年   802篇
  2007年   725篇
  2006年   570篇
  2005年   720篇
  2004年   639篇
  2003年   697篇
  2002年   404篇
  2001年   75篇
  2000年   79篇
  1999年   72篇
  1998年   95篇
  1997年   89篇
  1996年   82篇
  1995年   93篇
  1994年   66篇
  1993年   105篇
  1992年   93篇
  1991年   50篇
  1990年   97篇
  1989年   83篇
  1988年   84篇
  1987年   91篇
  1986年   77篇
  1985年   112篇
  1984年   115篇
  1983年   101篇
  1982年   99篇
  1981年   88篇
  1980年   59篇
  1979年   106篇
  1978年   74篇
  1977年   101篇
  1976年   81篇
  1975年   103篇
  1974年   66篇
  1973年   81篇
  1972年   48篇
  1971年   38篇
  1970年   35篇
  1969年   33篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
Poly(ethylene oxide) (PEO) oligomers are employed extensively in pharmaceutical and biomedical arenas mainly due to their excellent physical and biological properties, including solubility in water and organic solvents, lack of toxicity, and absence of immunogenicity. PEO can be chemically modified and reacted with, or adsorbed onto, other molecules and surfaces. Sophisticated applications for PEO have increased the demand for PEO oligomers with tailored functionalities, and heterobifunctional PEOs are often needed. This review discusses the synthesis and applications of heterobifunctional PEO oligomers possessing amine, carboxylate, thiol, and maleimide functional groups.  相似文献   
53.
This meta-analysis examines the influence of electronic communication media on group idea generation tasks. Data from the following three areas of the brainstorming literature are synthesized to assess differences across performance variables and group member satisfaction: (1) electronic brainstorming (EBS) groups versus traditional face-to-face (FTF) interacting groups, (2) EBS groups versus nominal groups, and (3) EBS versus electronic nominal (e-nominal) groups. The results of this integration show that EBS groups are more productive and more satisfied with the interaction process than FTF groups. Additionally, large EBS groups outperformed nominal groups, whereas small nominal groups outperformed EBS groups. These findings have important implications for electronic collaboration and teamwork in both academic and organizational settings, especially given the recent proliferation of virtual teamwork.  相似文献   
54.
55.
Pareto multi-criteria decision making   总被引:1,自引:0,他引:1  
The paper concerns design governed by multiple objective criteria, which are conflicting in the sense of competing for common resources to achieve variously different performance objectives (financial, functional, environmental, esthetical, etc.). A multi-criteria decision making (MCDM) strategy is proposed that employs a tradeoff-analysis technique to identify compromise designs for which the competing criteria are mutually satisfied in a Pareto-optimal sense. The MCDM strategy is initially developed for the case of design governed by n = 2 objective criteria. It is then extended to design governed by n > 2 objective criteria, by introducing the concept of primary and aggregate criteria. It is proved that, from among the theoretically infinite number of feasible designs forming the Pareto front for a design problem governed by n independent objective criteria, there exists a unique Pareto-compromise design that represents a mutually agreeable tradeoff between all n criteria. This remarkable result is illustrated for a flexural plate design governed by n = 2 criteria, a bridge maintenance-intervention protocol design governed by n = 3 criteria, and a media centre envelop design governed by n = 11 criteria.  相似文献   
56.
Resource allocation involves deciding how to divide a resource of limited availability among multiple demands in a way that optimizes current objectives. In this brief paper we focus on one type of distributed resource allocation problem where via an imperfect communication network multiple processors can share the load presented by multiple task types. We introduce asynchronous “cooperative” resource allocation strategies, and show that they lead to a bounded cumulative demand.  相似文献   
57.
Differential equations with discontinuous right-hand side and solutions intended in Carathéodory sense are considered. For these equations, sufficient conditions which guarantee both Lyapunov stability and asymptotic stability in terms of nonsmooth Lyapunov functions are given. An invariance principle is also proven.  相似文献   
58.
A ‘proportional’ order-up-to policy reacting to ARMA demand is analyzed using stochastic optimal control theory. This policy is compared with a full-state-feedback order-up-to policy. Necessary conditions for an optimum of a weighted sum of the inventory and the ordering variances for both policies are formulated. Based on this a relatively simple expression for the ‘full-state’ policy is derived. The comparison between the two policies demonstrates that the ‘intuitively’ designed proportional policy does not fulfill the objective of controlling both the inventory and ordering variance for all parameter values of the demand model as well as the full-state-feedback policy. The full-state-feedback policy outperforms the proportional policy in several aspects.  相似文献   
59.
Negative consequences are an important component of the substance use change process, yet no standardized measure exists to assess consequences of use. This study evaluated the psychometric properties of the Inventory of Drug Use Consequences, a self-report measure assessing drinking and drug use consequences. Participants (N=252) were assessed at entry into outpatient substance abuse treatment. Items loaded strongly on 1 factor, and internal consistency of the total scale was high. Fifteen items with the highest correlations with the total scale were chosen to represent the construct. The shortened measure exhibited good internal consistency, convergent and discriminant validity, and detected change over time and may be the measure of substance use consequences that is lacking in the field. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
60.
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