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   26852篇
  免费   921篇
  国内免费   28篇
电工技术   341篇
综合类   50篇
化学工业   4653篇
金属工艺   455篇
机械仪表   514篇
建筑科学   1442篇
矿业工程   63篇
能源动力   716篇
轻工业   2722篇
水利工程   339篇
石油天然气   70篇
武器工业   1篇
无线电   2329篇
一般工业技术   3724篇
冶金工业   5912篇
原子能技术   201篇
自动化技术   4269篇
  2023年   138篇
  2022年   261篇
  2021年   585篇
  2020年   311篇
  2019年   383篇
  2018年   519篇
  2017年   463篇
  2016年   552篇
  2015年   466篇
  2014年   702篇
  2013年   1247篇
  2012年   1133篇
  2011年   1488篇
  2010年   1030篇
  2009年   1122篇
  2008年   1115篇
  2007年   1054篇
  2006年   893篇
  2005年   824篇
  2004年   755篇
  2003年   702篇
  2002年   604篇
  2001年   477篇
  2000年   452篇
  1999年   542篇
  1998年   2061篇
  1997年   1305篇
  1996年   884篇
  1995年   552篇
  1994年   540篇
  1993年   535篇
  1992年   258篇
  1991年   258篇
  1990年   249篇
  1989年   254篇
  1988年   238篇
  1987年   170篇
  1986年   173篇
  1985年   232篇
  1984年   201篇
  1983年   142篇
  1982年   141篇
  1981年   146篇
  1980年   122篇
  1979年   124篇
  1978年   113篇
  1977年   168篇
  1976年   187篇
  1975年   116篇
  1974年   99篇
排序方式: 共有10000条查询结果,搜索用时 949 毫秒
11.
12.
Production planning and control (PPC) systems that employ aspects from both make-to-order (MTO) and make-to-stock (MTS) production control are known as hybrid MTS/MTO systems. While both MTO and MTS separately have been studied extensively, their combined use has received less attention. However, the literature on this topic is growing and this paper shows that the review performed in this paper is an important addition to the field. We categorise relevant literature according to a novel taxonomy and show that hybrid MTS/MTO production control can be used in different contexts. In addition, an overview of the modelling techniques and methods used in these papers is provided. Based on the reviewed literature, relevant research questions and directions for future research are identified. Finally, it is shown that hybrid MTS/MTO production control is prevalent in practice by discussing research with industrial applications. The paper contains an overview of research on hybrid MTS/MTO production control to be used as reference for researchers active in the field, and provides managerial insights and directions for future research on this topic.  相似文献   
13.
14.
15.
16.
Digital distractions can interfere with goal attainment and lead to undesirable habits that are hard to get red rid of. Various digital self-control interventions promise support to alleviate the negative impact of digital distractions. These interventions use different approaches, such as the blocking of apps and websites, goal setting, or visualizations of device usage statistics. While many apps and browser extensions make use of these features, little is known about their effectiveness. This systematic review synthesizes the current research to provide insights into the effectiveness of the different kinds of interventions. From a search of the ‘ACM’, ‘Springer Link’, ‘Web of Science’, ’IEEE Xplore’ and ‘Pubmed’ databases, we identified 28 digital self-control interventions. We categorized these interventions according to their features and their outcomes. The interventions showed varying degrees of effectiveness, and especially interventions that relied purely on increasing the participants' awareness were barely effective. For those interventions that sanctioned the use of distractions, the current literature indicates that the sanctions have to be sufficiently difficult to overcome, as they will otherwise be quickly dismissed. The overall confidence in the results is low, with small sample sizes, short study duration, and unclear study contexts. From these insights, we highlight research gaps and close with suggestions for future research.  相似文献   
17.
Studies on color preferences are dependent on the topic and the relationships with personal characteristics, particularly personality, but these are seldom studied in one population. Therefore a questionnaire was collected from 1095 Dutch people asking for color preferences about different topics and relating them to personal characteristics. Color preferences regarding different topics show different patterns and significant differences were found between gender, age, education and personality such as being technical, being emotional or being a team player. Also, different colors were mentioned when asked for colors that stimulate to be quiet, energetic, and able to focus or creative. Probably, due to unconsciousness of contexts, many people had no color preference, a result that in the literature seldom is mentioned. Blue was the overall favorite color; however, most males chose for blue (25%) while most females had no color preference (18%). Black was the overall favorite color for clothing, mainly chosen by females (40%), while males primarily chose blue (27%). For building interiors subjects preferred white. For moods, subjects preferred white for being quiet or being able to focus, red for being energetic and had no color preference for being creative. It is concluded that color preferences are dependent upon the topic, and personal characteristics. The findings are important for architects, interior designers, fashion designers and product designers to have a basic idea of preferred colors for different objects by different types of people. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 62–71, 2015  相似文献   
18.
Andel  T.R. Yasinsac  A. 《Computer》2006,39(7):48-54
Simulation is useful for evaluating protocol performance and operation. However, the lack of rigor with which it's applied threatens the credibility of the published research within the manet research community. Mobile ad hoc networks (manets) allow rapid deployment because they don't depend on a fixed infrastructure. Manet nodes can participate as the source, the destination, or an intermediate router. This flexibility is attractive for military applications, disaster-response situations, and academic environments where fixed net working infrastructures might not be available.  相似文献   
19.
The influence of network density on the strain hardening behaviour of amorphous polymers is studied. The network density of polystyrene is altered by blending with poly(2,6-dimethyl-1,4-phenylene-oxide) and by cross-linking during polymerisation. The network density is derived from the rubber-plateau modulus determined by dynamic mechanical thermal analysis. Subsequently uniaxial compression tests are performed to obtain the intrinsic deformation behaviour and, in particular, the strain hardening modulus. At room temperature, the strain hardening modulus proves to be proportional to the network density, irrespective of the nature of the network, i.e. physical entanglements or chemical cross-links. With increasing temperature, the strain hardening modulus is observed to decrease. This decrease appears to be related to the influence of thermal mobility of the chains, determined by the distance to the glass-transition temperature (TTg).  相似文献   
20.
We present a 3-12 GHz compact mixer-based reflectometer (CMR) and horn antenna system, and demonstrate its use in detecting backscatter signals with a free space calibration procedure. We evaluate the frequency-domain performance of the CMR-antenna system for measuring the complex reflection coefficient of a dielectric slab and compare it with that of a commercial vector network analyzer (VNA)-antenna setup. Time-domain responses are also investigated, and show the effectiveness of this calibration method. This low-cost, compact system eliminates the need for traditional mechanical standards and a VNA, is effective in reducing reflection artifacts, and allows for flexibility in the placement of reference planes; thus it is well suited for array-based imaging applications  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