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   1480087篇
  免费   25243篇
  国内免费   6969篇
电工技术   34087篇
综合类   6392篇
化学工业   268657篇
金属工艺   63867篇
机械仪表   41141篇
建筑科学   45458篇
矿业工程   11289篇
能源动力   50154篇
轻工业   108227篇
水利工程   15017篇
石油天然气   37272篇
武器工业   131篇
无线电   195115篇
一般工业技术   277451篇
冶金工业   156676篇
原子能技术   33785篇
自动化技术   167580篇
  2021年   15495篇
  2020年   11796篇
  2019年   14551篇
  2018年   14462篇
  2017年   13605篇
  2016年   20649篇
  2015年   17231篇
  2014年   28607篇
  2013年   87676篇
  2012年   34234篇
  2011年   45712篇
  2010年   41250篇
  2009年   49818篇
  2008年   43188篇
  2007年   40027篇
  2006年   43852篇
  2005年   38228篇
  2004年   40744篇
  2003年   40703篇
  2002年   39987篇
  2001年   36761篇
  2000年   35211篇
  1999年   34299篇
  1998年   42530篇
  1997年   37685篇
  1996年   34455篇
  1995年   30212篇
  1994年   28437篇
  1993年   28288篇
  1992年   25987篇
  1991年   23151篇
  1990年   23410篇
  1989年   22518篇
  1988年   21029篇
  1987年   19319篇
  1986年   18651篇
  1985年   22012篇
  1984年   22230篇
  1983年   20204篇
  1982年   19246篇
  1981年   19324篇
  1980年   17928篇
  1979年   18476篇
  1978年   17755篇
  1977年   17542篇
  1976年   18766篇
  1975年   16010篇
  1974年   15521篇
  1973年   15582篇
  1972年   13052篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
ABSTRACT

The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style.  相似文献   
123.
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   
124.
125.
126.
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs.  相似文献   
127.
128.
129.
The principles and design of “active” self‐propelling particles that can convert energy, move directionally on their own, and perform a certain function is an emerging multidisciplinary research field, with high potential for future technologies. A simple and effective technique is presented for on‐demand steering of self‐propelling microdiodes that move electroosmotically on water surface, while supplied with energy by an external alternating (AC) field. It is demonstrated how one can control remotely the direction of diode locomotion by electronically modifying the applied AC signal. The swimming diodes change their direction of motion when a wave asymmetry (equivalent to a DC offset) is introduced into the signal. The data analysis shows that the ability to control and reverse the direction of motion is a result of the electrostatic torque between the asymmetrically polarized diodes and the ionic charges redistributed in the vessel. This novel principle of electrical signal‐coded steering of active functional devices, such as diodes and microcircuits, can find applications in motile sensors, MEMs, and microrobotics.  相似文献   
130.
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