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   1577530篇
  免费   26504篇
  国内免费   7072篇
电工技术   34739篇
综合类   6467篇
化学工业   274490篇
金属工艺   65732篇
机械仪表   45012篇
建筑科学   47357篇
矿业工程   11573篇
能源动力   50501篇
轻工业   118634篇
水利工程   16215篇
石油天然气   37915篇
武器工业   135篇
无线电   199043篇
一般工业技术   295160篇
冶金工业   201264篇
原子能技术   34301篇
自动化技术   172568篇
  2021年   15703篇
  2020年   12004篇
  2019年   14763篇
  2018年   17528篇
  2017年   16967篇
  2016年   22289篇
  2015年   17632篇
  2014年   28901篇
  2013年   88267篇
  2012年   37213篇
  2011年   50951篇
  2010年   44251篇
  2009年   52307篇
  2008年   47048篇
  2007年   44638篇
  2006年   45793篇
  2005年   41075篇
  2004年   42877篇
  2003年   42694篇
  2002年   41485篇
  2001年   38686篇
  2000年   36787篇
  1999年   36743篇
  1998年   57114篇
  1997年   46284篇
  1996年   40044篇
  1995年   33454篇
  1994年   30993篇
  1993年   30848篇
  1992年   26725篇
  1991年   24055篇
  1990年   24276篇
  1989年   23360篇
  1988年   21914篇
  1987年   20100篇
  1986年   19510篇
  1985年   22821篇
  1984年   22660篇
  1983年   20574篇
  1982年   19491篇
  1981年   19656篇
  1980年   18267篇
  1979年   18700篇
  1978年   17983篇
  1977年   18352篇
  1976年   20511篇
  1975年   16196篇
  1974年   15650篇
  1973年   15742篇
  1972年   13178篇
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
131.
132.
133.
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   
134.
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   
135.
136.
137.
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   
138.
139.
140.
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   
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