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   1887篇
  免费   39篇
  国内免费   7篇
电工技术   59篇
综合类   1篇
化学工业   368篇
金属工艺   37篇
机械仪表   29篇
建筑科学   80篇
矿业工程   5篇
能源动力   60篇
轻工业   98篇
水利工程   16篇
石油天然气   6篇
无线电   140篇
一般工业技术   260篇
冶金工业   479篇
原子能技术   24篇
自动化技术   271篇
  2023年   14篇
  2022年   16篇
  2021年   24篇
  2020年   22篇
  2019年   23篇
  2018年   30篇
  2017年   25篇
  2016年   26篇
  2015年   21篇
  2014年   34篇
  2013年   115篇
  2012年   58篇
  2011年   88篇
  2010年   56篇
  2009年   65篇
  2008年   71篇
  2007年   76篇
  2006年   68篇
  2005年   49篇
  2004年   50篇
  2003年   35篇
  2002年   43篇
  2001年   24篇
  2000年   29篇
  1999年   36篇
  1998年   99篇
  1997年   60篇
  1996年   48篇
  1995年   42篇
  1994年   31篇
  1993年   38篇
  1992年   20篇
  1991年   19篇
  1990年   28篇
  1989年   29篇
  1988年   26篇
  1987年   24篇
  1986年   20篇
  1985年   15篇
  1984年   31篇
  1983年   26篇
  1982年   31篇
  1981年   24篇
  1980年   25篇
  1979年   16篇
  1978年   25篇
  1977年   16篇
  1976年   18篇
  1975年   16篇
  1973年   18篇
排序方式: 共有1933条查询结果,搜索用时 15 毫秒
51.
This paper reviews the behavioural research, particularly on language and comprehension, which can be related to the design of forms. Such research gives rise to a number of simple rules which can be implemented by forms' designers. These rules concern the structure, content and organisation of sentences and questions. The paper illustrates how these rules can be applied to forms currently in use. Research findings which point to exceptions to the general rules are discussed in an appendix. The paper recognises that we do not yet have enough information to design perfect forms, but that there is enough for many forms to be improved and potential pitfalls avoided.  相似文献   
52.
A high speed target detection and tracking algorithm for a CNN‐UM chip is presented in this paper. The target confidence value is computed based on the fusion of target existence probabilities of features using products of weighted sums. The target decision is done with such a confidence value and target initiation is done through the temporal accumulation of the confidence. The probability of the target existence for each feature is created in the region of influence depending on the reliability and the strength of the feature. By virtue of the analogic parallel processing structure of the CNN‐UM (Roska T, Chua LO. The CNN universal machine: an analogic array computer. IEEE Trans. Circuits Systems II 1993; CAS‐40 : 163–173), real time tracking can be achieved with presently available technologies with the speed of several kilo‐frames per second. Due to the utilization of multiple features of target, robust target detection is possible via the proposed algorithm. On‐chip experiments of the proposed target‐tracking algorithm have been done and properties of the proposed approach are disclosed through the various experiments. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
53.
This study employs expectancy theory to evaluate some key factors that motivate students to participate in the teaching evaluation process. The results show that engineering students generally consider the improvement of teaching to be the most important outcome of teaching evaluations, followed by the improvement of course content and format. Making the results of evaluations available for students' decisions on course and instructor selection ranked third, while the least important use was influencing a professor's tenure, promotion, and salary raise. Students' motivation to participate in teaching evaluations is also impacted significantly by their expectation that they will be able to provide meaningful feedback.  相似文献   
54.
55.
Capillary zone electrophoresis (CZE) has been applied to separation and characterisation of enzymatic (tryptic) hydrolysates of water-soluble proteins from Bacillus thuringiensis (Bt)-transgenic (Aristis-Bt) and two native non-transgenic (Aristis and Coventry) maize varieties. Water-soluble proteins were extracted from the flour of these maize species and digested by bovine pancreatic trypsin immobilised on agarose gel in 100 mM ammonium hydrocarbonate buffer, pH 7.9. The yielded tryptic digests of proteins were analysed by CZE in four acidic background electrolytes (BGEs) (100 mM H3PO4, 50 mM Tris, pH 2.25; 500 mM acetic acid, pH 2.54; 200 mM formic acid, 200 mM acetic acid, pH 2.05; and 200 mM iminodiacetic acid, pH 2.26) using a lab-made CZE apparatus equipped with bare fused silica capillary and UV-absorption detector operating at 206 nm. Among the tested BGEs, the best resolution of the tryptic peptides of extracted proteins of the above three maize species was obtained in isoelectric BGE, 200 mM iminodiacetic acid, pH 2.26. Selected resolved tryptic peptides of proteins were characterised by effective electrophoretic mobilities and corrected (migration times normalised) peak areas. Some significant relative qualitative and quantitative differences in CZE-UV profiling of tryptic protein digests were found, which can be potentially used to differentiate transgenic Aristis Bt and non-transgenic Aristis varieties or two native non-transgenic varieties, Aristis and Coventry.  相似文献   
56.
Hydrogen as a secondary energy carrier promises a large potential as a long term storage for fluctuating renewable energies. In this sense a highly efficient solar hydrogen generation is of great interest especially in southern countries having high solar irradiation. The patented Hydrogen Concentrator (HyCon) concept yields high efficiencies combining multi-junction solar cells with proton exchange (PEM) membrane water electrolysis. In this work, a special PEM electrolysis cell for the HyCon concept was developed and investigated. It is shown that the purpose-made PEM cell shows a high performance using a titanium hybrid fiber sinter function both as a porous transport layer and flow field. The electrolysis cell shows a high performance with 1.83 V at 1 A/cm2 and 24 °C working under natural convection with a commercially available catalyst coated membrane. A theoretical examination predicts a total efficiency for the HyCon module from sunlight to hydrogen of approximately 19.5% according to the higher heating value.  相似文献   
57.
Resonant ultrasound spectroscopy (RUS) is an NDE technique that evaluates a sample based on its predicted resonant behavior, but RUS is limited by lack of spatial resolution and small specimen size. Air-coupled ultrasonic resonance imaging (ACURI) is a new NDE technique that is based on RUS but introduces a spatial resolution by generating an image of the flexural vibration modes. This paper presents experimental results of ACURI applied to hexagonal silicon carbide tiles. Frequency sweep scans demonstrate the ability of air-coupled transducers to detect resonance modes. Several mode shapes are imaged and compared to Finite Element simulations with good agreement. Visual comparison allows for easy detection of material differences such as density variations.  相似文献   
58.
Polycarbonate is known to suffer from dramatic reductions in ductility upon exposure to hot, humid environments, such as during steam sterilization. Two phenomena have been proposed to be the main causes of this embrittlement: hydrolysis and microcavity formation. The present study focuses on a third phenomenon, whose contribution to the embrittlement has until now been considered insignificant: (physical) aging. By studying the influence of steam sterilization on the tensile deformation behavior of polycarbonate, it is shown that aging actually is one of the dominant factors in the embrittlement.  相似文献   
59.
60.
Eco-driving campaigns have traditionally assumed that drivers lack the necessary knowledge and skills and that this is something that needs rectifying. Therefore, many support systems have been designed to closely guide drivers and fine-tune their proficiency. However, research suggests that drivers already possess a substantial amount of the necessary knowledge and skills regarding eco-driving. In previous studies, participants used these effectively when they were explicitly asked to drive fuel-efficiently. In contrast, they used their safe driving skills when they were instructed to drive as they would normally. Hence, it is assumed that many drivers choose not to engage purposefully in eco-driving in their everyday lives. The aim of the current study was to investigate the effect of simple, periodic text messages (nine messages in 2 weeks) on drivers’ eco- and safe driving performance. It was hypothesised that provision of eco-driving primes and advice would encourage the activation of their eco-driving mental models and that comparable safety primes increase driving safety. For this purpose, a driving simulator experiment was conducted. All participants performed a pre-test drive and were then randomly divided into four groups, which received different interventions. For a period of 2 weeks, one group received text messages with eco-driving primes and another group received safety primes. A third group received advice messages on how to eco-drive. The fourth group were instructed by the experimenter to drive fuel-efficiently, immediately before driving, with no text message intervention. A post-test drive measured behavioural changes in scenarios deemed relevant to eco- and safe driving. The results suggest that the eco-driving prime and advice text messages did not have the desired effect. In comparison, asking drivers to drive fuel-efficiently led to eco-driving behaviours. These outcomes demonstrate the difficulty in changing ingrained habits. Future research is needed to strengthen such messages or activate existing knowledge and skills in other ways, so driver behaviour can be changed in cost-efficient ways.  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