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   329745篇
  免费   3990篇
  国内免费   1092篇
工业技术   334827篇
  2022年   3914篇
  2021年   5572篇
  2020年   4285篇
  2019年   5178篇
  2018年   4747篇
  2017年   4319篇
  2016年   4285篇
  2015年   2824篇
  2014年   4598篇
  2013年   12938篇
  2012年   7455篇
  2011年   10818篇
  2010年   8809篇
  2009年   10027篇
  2008年   9681篇
  2007年   9579篇
  2006年   8686篇
  2005年   8286篇
  2004年   8766篇
  2003年   8360篇
  2002年   8502篇
  2001年   7954篇
  2000年   7215篇
  1999年   7090篇
  1998年   15494篇
  1997年   11705篇
  1996年   9108篇
  1995年   6977篇
  1994年   6504篇
  1993年   6256篇
  1992年   4923篇
  1991年   4762篇
  1990年   4544篇
  1989年   4665篇
  1988年   4539篇
  1987年   3831篇
  1986年   3928篇
  1985年   4435篇
  1984年   4167篇
  1983年   3867篇
  1982年   3642篇
  1981年   3725篇
  1980年   3545篇
  1979年   3500篇
  1978年   3646篇
  1977年   4157篇
  1976年   5183篇
  1975年   3341篇
  1974年   3149篇
  1973年   3147篇
排序方式: 共有10000条查询结果,搜索用时 23 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