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   19493篇
  免费   922篇
  国内免费   144篇
电工技术   333篇
综合类   33篇
化学工业   4335篇
金属工艺   594篇
机械仪表   639篇
建筑科学   378篇
矿业工程   47篇
能源动力   1387篇
轻工业   1210篇
水利工程   154篇
石油天然气   85篇
武器工业   1篇
无线电   2431篇
一般工业技术   4419篇
冶金工业   1455篇
原子能技术   176篇
自动化技术   2882篇
  2024年   103篇
  2023年   426篇
  2022年   1009篇
  2021年   1181篇
  2020年   931篇
  2019年   964篇
  2018年   1243篇
  2017年   984篇
  2016年   945篇
  2015年   617篇
  2014年   862篇
  2013年   1556篇
  2012年   920篇
  2011年   1116篇
  2010年   879篇
  2009年   831篇
  2008年   740篇
  2007年   585篇
  2006年   487篇
  2005年   376篇
  2004年   279篇
  2003年   250篇
  2002年   199篇
  2001年   181篇
  2000年   176篇
  1999年   170篇
  1998年   296篇
  1997年   241篇
  1996年   226篇
  1995年   172篇
  1994年   160篇
  1993年   158篇
  1992年   110篇
  1991年   137篇
  1990年   99篇
  1989年   96篇
  1988年   80篇
  1987年   89篇
  1986年   75篇
  1985年   87篇
  1984年   73篇
  1983年   71篇
  1982年   60篇
  1981年   70篇
  1980年   48篇
  1979年   31篇
  1978年   27篇
  1977年   26篇
  1976年   35篇
  1971年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Many occupations require workers to stand for long periods of time without proper interventions, which causes discomfort in the back and lower limbs. Therefore, this study aims to assess the effectiveness in alleviating body muscle discomfort during prolonged standing through the use of a calf massager. This study was conducted among male workers at a manufacturer with production line workers and the list was obtained from the HR Department and simple random sampling was done by number categorization. A total of 100 respondents (50 respondents for both the control and the experimental groups) participated in this study. The experiment took place in a room with a similar setup for the production line. Each respondent was requested to perform the simulated task for 2 hr. For the experimental group, the calf massager was turned on every 15 min. At every 15‐min interval after turning on the calf massager, respondents from both groups were required to evaluate their discomfort level on a Borg's scale CR‐10 questionnaire. The results showed that the level of body discomfort among respondents in the experimental group reduced (20–30%) compared with that of the control group. Multivariate analysis results revealed that the discomfort rating for the lower back, knees, thighs, calves, and feet was significantly lower (p < .05) among the experimental group compared with the control group. For lower body parts, the lower back region was statistically significant (p < .05) at the 90th, 105th, and 120th min; the thigh region was statistically significant (p < .05) at the 120th min; the knee region was statistically significant (p < .05) at the 105th and 120th min; the calf region was statistically significant (p < .05) at all minute intervals except the 15th and 45th min, while the feet region, was statistically significant at the 105th and 120th min. Therefore, this study indicates that calf massage treatment is capable of reducing body muscle discomfort during prolonged standing and highlights the significance of calf massage.  相似文献   
6.
7.
8.
Wireless Personal Communications - Data security is currently become a serious concern in wireless communication system for both the users and providers. Without a secure medium, the data...  相似文献   
9.
A flower‐shaped ultra‐wideband fractal antenna is presented. It comprises a fourth iterative flower‐shaped radiator, asymmetrical stub‐loaded feeding line, and coplanar quarter elliptical ground planes. A wide operating band of 12.12 GHz (4.58‐16.7 GHz) for S 11 ≤ ? 10 dB is achieved along with an overall antenna footprint of 15.7 × 11.4 mm2. In addition, other desirable characteristics, that is, omnidirectional radiation patterns, peak gain upto 5 dB, and fidelity factor more than 75% are achieved. A good agreement exists between the simulation and measured results. The obtained results illustrate that this antenna has wide operating range and compact dimensions than available structures.  相似文献   
10.
The Journal of Supercomputing - In the last decade, cloud computing has brought enormous changes to people’s lives. Cloud computing gives a client-driven computational model. In this case,...  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