首页 | 官方网站   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   318375篇
  免费   4670篇
  国内免费   1187篇
工业技术   324232篇
  2022年   3910篇
  2021年   5690篇
  2020年   4352篇
  2019年   5430篇
  2018年   4828篇
  2017年   4523篇
  2016年   4454篇
  2015年   2956篇
  2014年   4893篇
  2013年   13210篇
  2012年   7866篇
  2011年   11308篇
  2010年   8936篇
  2009年   9944篇
  2008年   10196篇
  2007年   10200篇
  2006年   9270篇
  2005年   8764篇
  2004年   9447篇
  2003年   9095篇
  2002年   8806篇
  2001年   8369篇
  2000年   7551篇
  1999年   7418篇
  1998年   15382篇
  1997年   11239篇
  1996年   8530篇
  1995年   7028篇
  1994年   6440篇
  1993年   6180篇
  1992年   5114篇
  1991年   4571篇
  1990年   4499篇
  1989年   4311篇
  1988年   4100篇
  1987年   3579篇
  1986年   3589篇
  1985年   4091篇
  1984年   3776篇
  1983年   3495篇
  1982年   3232篇
  1981年   3302篇
  1980年   3061篇
  1979年   2952篇
  1978年   2871篇
  1977年   3350篇
  1976年   3854篇
  1975年   2656篇
  1974年   2596篇
  1973年   2528篇
排序方式: 共有10000条查询结果,搜索用时 687 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the...  相似文献   
2.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
3.
4.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
5.
6.
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,...  相似文献   
7.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  相似文献   
8.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
9.
Objective

Neonatal brain and cardiac imaging would benefit from the increased signal-to-noise ratio levels at 7 T compared to lower field. Optimal performance might be achieved using purpose designed RF coil arrays. In this study, we introduce an 8-channel dipole array and investigate, using simulations, its RF performances for neonatal applications at 7 T.

Methods

The 8-channel dipole array was designed and evaluated for neonatal brain/cardiac configurations in terms of SAR efficiency (ratio between transmit-field and maximum specific-absorption-rate level) using adjusted dielectric properties for neonate. A birdcage coil operating in circularly polarized mode was simulated for comparison. Validation of the simulation model was performed on phantom for the coil array.

Results

The 8-channel dipole array demonstrated up to 46% higher SAR efficiency levels compared to the birdcage coil in neonatal configurations, as the specific-absorption-rate levels were alleviated. An averaged normalized root-mean-square-error of 6.7% was found between measured and simulated transmit field maps on phantom.

Conclusion

The 8-channel dipole array design integrated for neonatal brain and cardiac MR was successfully demonstrated, in simulation with coverage of the baby and increased SAR efficiency levels compared to the birdcage. We conclude that the 8Tx-dipole array promises safe operating procedures for MR imaging of neonatal brain and heart at 7 T.

  相似文献   
10.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  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-23

京公网安备 11010802026262号