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   479781篇
  免费   7686篇
  国内免费   1529篇
电工技术   8278篇
综合类   679篇
化学工业   75191篇
金属工艺   17103篇
机械仪表   14210篇
建筑科学   12277篇
矿业工程   1974篇
能源动力   12346篇
轻工业   51007篇
水利工程   4461篇
石油天然气   6947篇
武器工业   43篇
无线电   55467篇
一般工业技术   87529篇
冶金工业   90531篇
原子能技术   8806篇
自动化技术   42147篇
  2021年   4309篇
  2020年   3121篇
  2019年   3961篇
  2018年   6236篇
  2017年   6269篇
  2016年   6806篇
  2015年   4589篇
  2014年   7747篇
  2013年   21933篇
  2012年   12867篇
  2011年   17870篇
  2010年   13906篇
  2009年   15482篇
  2008年   16031篇
  2007年   16080篇
  2006年   14551篇
  2005年   13154篇
  2004年   12724篇
  2003年   12409篇
  2002年   12004篇
  2001年   12058篇
  2000年   11195篇
  1999年   11584篇
  1998年   28132篇
  1997年   19677篇
  1996年   14937篇
  1995年   11391篇
  1994年   10032篇
  1993年   9889篇
  1992年   7273篇
  1991年   6847篇
  1990年   6822篇
  1989年   6502篇
  1988年   6304篇
  1987年   5256篇
  1986年   5230篇
  1985年   6231篇
  1984年   5719篇
  1983年   5181篇
  1982年   4867篇
  1981年   5008篇
  1980年   4714篇
  1979年   4468篇
  1978年   4360篇
  1977年   4934篇
  1976年   6366篇
  1975年   3771篇
  1974年   3532篇
  1973年   3742篇
  1972年   2937篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Materials Science -  相似文献   
2.
3.
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   
4.
5.
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed.  相似文献   
6.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
7.
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some.  相似文献   
8.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
9.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
10.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the...  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