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   292322篇
  免费   24060篇
  国内免费   17777篇
电工技术   17480篇
技术理论   51篇
综合类   39496篇
化学工业   29753篇
金属工艺   10256篇
机械仪表   14906篇
建筑科学   46145篇
矿业工程   21223篇
能源动力   8907篇
轻工业   15289篇
水利工程   21665篇
石油天然气   15576篇
武器工业   2640篇
无线电   17174篇
一般工业技术   19479篇
冶金工业   16697篇
原子能技术   2702篇
自动化技术   34720篇
  2024年   915篇
  2023年   2780篇
  2022年   5597篇
  2021年   6839篇
  2020年   7228篇
  2019年   5999篇
  2018年   5659篇
  2017年   6866篇
  2016年   8212篇
  2015年   9099篇
  2014年   16595篇
  2013年   14883篇
  2012年   19762篇
  2011年   21052篇
  2010年   16597篇
  2009年   17389篇
  2008年   16100篇
  2007年   20861篇
  2006年   19757篇
  2005年   17527篇
  2004年   14901篇
  2003年   13388篇
  2002年   10975篇
  2001年   9222篇
  2000年   7929篇
  1999年   6463篇
  1998年   4921篇
  1997年   4282篇
  1996年   3931篇
  1995年   3350篇
  1994年   3013篇
  1993年   2193篇
  1992年   1911篇
  1991年   1424篇
  1990年   1215篇
  1989年   1075篇
  1988年   862篇
  1987年   595篇
  1986年   454篇
  1985年   357篇
  1984年   336篇
  1983年   242篇
  1982年   219篇
  1981年   174篇
  1980年   134篇
  1979年   121篇
  1978年   62篇
  1977年   72篇
  1976年   57篇
  1975年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation.  相似文献   
13.
14.
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter.  相似文献   
15.
16.
17.
This study aims to assess the degree of HACCP implementation in small business butcher shops and understand which factors most influence butchers' intention to fully implement it, through the application of the Theory of Planned Behaviour. One hundred and one butchers managing or owning small butcher's responded to the interview regarding their Attitudes, Subjective Norm, Perceived Behavioural Control, Personal Norm, and Knowledge with regard to their Intention to fully implement a HACCP system in their shops. Before the interviews, a certified veterinarian visited all the shops. Visits included an inspection of the establishments using the Official Portuguese Control Plan checklist for meat retailers. Conformance level measured past performance regarding food safety practices. Based on past performance, butchers were divided into “high performers” and “low performers”. “High performers” yielded high values of Attitude and Intention towards the Behaviour. For these, Attitude and Personal Norm emerge as predictors of the Intention to fully implement a HACCP system. For “low performers”, Personal Norm was the strongest predictor of Intention, with results pointing to the need for an intervention from the authorities to promote increased conformance to food safety practices. For both groups, neither Social Norm nor Perceived Behavioural Control acted as significant predictors of Intention.  相似文献   
18.
Enhanced gravity, or centrifugal, separators have revolutionised gold processing over the past decades, significantly increasing the recovery of fine (−100 μm) free gold. One of the main drawbacks of centrifugal gravity concentrators is the large volume of water required (even if it is all recycled). With water becoming an ever increasingly important “commodity”, reducing this is of importance both from an environmental and a monetary point of view. This work investigated operating a laboratory scale Knelson Concentrator with a dry feed and using air as the fluidising medium. The feed used was a synthetic mixture of tungsten and quartz, used to mimic a gold ore. The response surface method and central composite design techniques were used to design the experiments and to model the results, with the experimental variables being the bowl speed (G-Level), air fluidising pressure and the feed rate. The models corresponded well to the experimental results, indicating that for this experimental setup, the optimal conditions were a bowl G-Level of 40 G, a feed rate of 220 g/min and an air fluidising pressure of 8 psi.  相似文献   
19.
The 2011 AASHTO Roadside Design Guide (RDG) contains perhaps the most widely used procedure for choosing an appropriate length of need (LON) for roadside barriers. However, this procedure has several limitations. The procedure uses a highly simplified model of vehicle departure, and the procedure does not allow designers to specify an explicit level of protection. A new procedure for choosing LON that addresses these limitations is presented in this paper. This new procedure is based on recent, real-world road departure trajectories and uses this departure data in a more realistic way. The new procedure also allows LON to be specified for a precisely known level of protection – a level which can be based on number of crashes, injury outcomes or even estimated crash cost – while still remaining straightforward and quick to use like the 2011 RDG procedure.  相似文献   
20.
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