首页 | 官方网站   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   1629篇
  免费   29篇
  国内免费   2篇
工业技术   1660篇
  2023年   10篇
  2022年   19篇
  2021年   23篇
  2020年   18篇
  2019年   19篇
  2018年   19篇
  2017年   24篇
  2016年   35篇
  2015年   18篇
  2014年   23篇
  2013年   99篇
  2012年   50篇
  2011年   80篇
  2010年   60篇
  2009年   42篇
  2008年   62篇
  2007年   66篇
  2006年   74篇
  2005年   59篇
  2004年   60篇
  2003年   58篇
  2002年   49篇
  2001年   33篇
  2000年   38篇
  1999年   35篇
  1998年   22篇
  1997年   34篇
  1996年   32篇
  1995年   30篇
  1994年   24篇
  1993年   35篇
  1992年   30篇
  1991年   12篇
  1990年   32篇
  1989年   23篇
  1988年   19篇
  1987年   24篇
  1986年   22篇
  1985年   19篇
  1984年   24篇
  1983年   21篇
  1982年   18篇
  1981年   14篇
  1980年   14篇
  1978年   10篇
  1977年   13篇
  1976年   14篇
  1975年   16篇
  1974年   9篇
  1973年   9篇
排序方式: 共有1660条查询结果,搜索用时 15 毫秒
21.
22.
The effect of trap design, trap color, and a mixture of isothiocyanates on the capture of Ceutorhynchus assimilis (Paykull) was studied in a series of field experiments. Unbaited yellow water traps, a yellow sticky box trap, and a yellow sticky card trap, mounted vertically, or at 45° to the vertical with the yellow card facing upwards were effective for capturing seed weevils, but a horizontal yellow sticky card trap caught few. White, green, and black traps were unattractive. During migratory periods, trap catch could be enhanced two to four times with a lure consisting of a mixture of allyl, 3-butenyl, 4-pentenyl, and 2-phenylethyl isothiocyanates, but this bait did not attract in a trap with ineffective design. The sticky card trap, mounted at 45° to the vertical and baited with the isothiocyanate mixture, may be useful for monitoring movement of C. assimilis during migratory periods. However, during the colonization phase, lures of either a mixture of isothiocyanates or of allyl isothiocyanate alone were not attractive.  相似文献   
23.
Mobil Zeolite Catalysts for Monomers   总被引:1,自引:0,他引:1  
It has been about 20 years since Plank, Rosinski, and Hawthorne reported their spectacular results with metal-modified zeolite cracking catalysts for more efficient production of gasoline [1]. This discovery has saved an estimated 200 million barrels of crude oil each year in the United States alone [2]. In 1972, a patent by Argauer and Landolt described the preparation of a member of a generation of new synthetic zeolites, called ZSM- 5. It was unique because of its high silica/alumina ratio and greatly reduced coking rates for reactions with hydrocarbons by comparison with known low silica zeolites [3]. This material was an early member of a series of over 50 synthetic zeolitic substances prepared in Mobil laboratories.  相似文献   
24.
During germination of seeds of the gymnosperm,Pinus pinea, radioactivity from [2-14C]-mevalonate proceeded principally through the anaerobic reactions leading to squalene in the first 24 hr in both the haploid endosperm and the diploid embryo, and only with succeeding time (3–9 days) in both cases was label transferred to sterols in oxygen-requiring steps. The rates of turnover must be real and independent in the two tissues, since no consequential interchange of labelled lipids occurred between the endosperm and the embryo. Similar delayed conversion of squalene to sterols has been observed previously during germination of seeds of the angiosperm,Pisum sativum.  相似文献   
25.
Virtual Reality - This research report describes the development of a virtual reality (VR) laboratory stressor to study the effects of exposure to stressful events. The aim of the research was to...  相似文献   
26.
The process of distributed engineering design calls for a methodology making use of the most recent advances in optimization-based design including multidisciplinary and multiobjective optimization. In distributed design, the participating teams do not have access to the design problems of other teams but may exchange limited information about their own current designs, making negotiation among themselves a key mechanism to reach a desired compromise which, nevertheless, is also a Pareto design to the original problem. A mathematical model of this distributed but decomposable design process is posed and solved using Lagrangian relaxation, while Pareto optimality is equivalently converted to single-objective optimality by means of multicriteria decision making strategies. The proposed coordination algorithm allows negotiation among the teams (subproblems) by sharing only limited information that is restricted to values of optimization quantities. The proposed modeling and solution scheme is applied to a numerical example representing the design of vehicle subsystems and components.  相似文献   
27.
Web-scale discovery systems, such as Serial Solutions’ Summon? Service, are replacing older federated search technologies as the tool for users to access library resources quickly and easily. The impact of Web-scale discovery systems on instruction is not known. This study of instruction librarian perceptions of Summon's impact on instruction and student information literacy skills is based on a survey. The survey reveals librarians’ ambivalence toward Summon. While some librarians agree that Summon has the potential to change the way librarians teach information literacy skills, it has not been fully integrated into the classroom.  相似文献   
28.
Organizations today face shortages of IT personnel. We investigated workplace factors in one state government in hope of identifying factors that influence perceived organizational support (POS) within an IT work environment. A combination of job characteristics (challenging job and perceived workload), job stressors (work exhaustion, role conflict, and role ambiguity), and the organization’s discretionary actions (pay-for-performance and mentoring opportunities) were measured and hierarchical regression was used to determine the relationships. Four control variables were also included (age, gender, organizational tenure, and professional versus administrator status). Role ambiguity, role conflict, work exhaustion, career mentoring, and pay-for-performance together explained 62% of the variance in the IT employees’ POS. Career mentoring and role ambiguity explained most of the variance.  相似文献   
29.

For over 30 years, aviation has conducted training courses to enhance team performance and improve safety involving simulation with observation and directed feedback. Participants’ performance is observed by trained and experienced observers who then provide feedback using behaviour-based evidence noted during the simulator exercise. More recently, in healthcare, operating theatre personnel have adopted simulator-based training (SBT), observation and feedback for learning and practice to reduce the potential for human errors and improve safety. Maritime and nuclear power also incorporate high-fidelity simulators and feedback in team training interventions including technical and non-technical skills. The design and development of drilling rig simulators means that drill crews can now practise and test out their decision-making and receive feedback from observers, with the aim of improving team non-technical skills and consequently reducing the potential for errors. This paper presents five principles gleaned from research and the experiences of both aviation and healthcare to be applied to the development of simulator-based exercising for drilling teams. The principles include: (a) developing learning objectives and expected performance standards; (b) training the team as a whole; (c) using a structured observation tool; (d) providing feedback during a structured debrief; (e) repeat the SBT regularly to enhance expertise and retain performance standards. It is anticipated that these principles can be generalised for simulator-based exercising to benefit team social and cognitive competences in other high-hazard or process industries.

  相似文献   
30.
OBJECTIVE: The study was done to determine whether thermal comfort (TC), thermal sensation (TS), and subjective factors gauging environmental stress were negatively affected with different cooling methods in men exercising in chemical protective clothing. BACKGROUND: Previous studies have reported that intermittent regional cooling improved the efficacy of cooling as compared with constant cooling (CC), but no studies have addressed whether there is any improvement in thermal comfort. METHODS: Eight male volunteers exercised at moderate work intensity (425 W) in three microclimate cooling tests. The circulating fluid in the cooling garment was provided during exercise to the head (6% body surface area [BSA]), torso (22% BSA), and thighs (44% BSA) and manipulated under three methods: (a) CC, (b) pulsed cooling (PC), and (c) PC activated by mean skin temperature (T(sk)) control (PC(skin)). TC and TS ratings were recorded every 20 min during the 80-min test. RESULTS: TC and TS ratings were not different for PC(skin) and CC; thus the participants perceived PC(skin) as being similar to CC. TS was significantly warmer with PC than with PC(skin) and CC (p < .001). In PC(skin), T(sk) was significantly higher than in PC and CC (p < .001), and PC(skin) was rated as being not as warm as PC according to TS. CONCLUSION: This indicates that the PC(skin) method was perceived as being as cool as CC and cooler than PC. APPLICATION: These findings indicate that the PC(skin) cooling method is an acceptable alternative to CC and PC based on human perceptions.  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-23

京公网安备 11010802026262号