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   213193篇
  免费   2974篇
  国内免费   566篇
电工技术   3630篇
综合类   164篇
化学工业   33357篇
金属工艺   10435篇
机械仪表   7185篇
建筑科学   4397篇
矿业工程   2198篇
能源动力   4724篇
轻工业   14033篇
水利工程   2955篇
石油天然气   7737篇
武器工业   22篇
无线电   22058篇
一般工业技术   47358篇
冶金工业   34527篇
原子能技术   6682篇
自动化技术   15271篇
  2021年   2194篇
  2019年   2110篇
  2018年   3954篇
  2017年   4006篇
  2016年   4309篇
  2015年   2465篇
  2014年   4075篇
  2013年   9294篇
  2012年   6049篇
  2011年   7648篇
  2010年   6215篇
  2009年   6862篇
  2008年   7038篇
  2007年   6885篇
  2006年   5853篇
  2005年   5342篇
  2004年   4814篇
  2003年   4748篇
  2002年   4542篇
  2001年   4625篇
  2000年   4306篇
  1999年   4303篇
  1998年   10264篇
  1997年   7265篇
  1996年   5583篇
  1995年   4177篇
  1994年   3660篇
  1993年   3884篇
  1992年   3019篇
  1991年   3037篇
  1990年   2915篇
  1989年   2885篇
  1988年   2890篇
  1987年   2538篇
  1986年   2611篇
  1985年   2946篇
  1984年   2750篇
  1983年   2600篇
  1982年   2341篇
  1981年   2306篇
  1980年   2388篇
  1979年   2391篇
  1978年   2419篇
  1977年   2506篇
  1976年   2898篇
  1975年   2204篇
  1974年   2091篇
  1973年   2192篇
  1972年   1949篇
  1971年   1765篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
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   
64.
65.
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented.  相似文献   
66.
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures.  相似文献   
67.
68.
69.
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed.  相似文献   
70.
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor...  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