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   396643篇
  免费   6148篇
  国内免费   1514篇
电工技术   7078篇
综合类   285篇
化学工业   59859篇
金属工艺   14643篇
机械仪表   11473篇
建筑科学   10356篇
矿业工程   1369篇
能源动力   11041篇
轻工业   41157篇
水利工程   3578篇
石油天然气   4854篇
武器工业   6篇
无线电   49080篇
一般工业技术   73460篇
冶金工业   74117篇
原子能技术   7047篇
自动化技术   34902篇
  2021年   2845篇
  2019年   2670篇
  2018年   4277篇
  2017年   4284篇
  2016年   4683篇
  2015年   3440篇
  2014年   5815篇
  2013年   18355篇
  2012年   10342篇
  2011年   14632篇
  2010年   11408篇
  2009年   13096篇
  2008年   13491篇
  2007年   13546篇
  2006年   12196篇
  2005年   11222篇
  2004年   10719篇
  2003年   10398篇
  2002年   9844篇
  2001年   10259篇
  2000年   9449篇
  1999年   10044篇
  1998年   24488篇
  1997年   17265篇
  1996年   13115篇
  1995年   10050篇
  1994年   8609篇
  1993年   8480篇
  1992年   6175篇
  1991年   5902篇
  1990年   5611篇
  1989年   5440篇
  1988年   5316篇
  1987年   4473篇
  1986年   4307篇
  1985年   5189篇
  1984年   4704篇
  1983年   4348篇
  1982年   3992篇
  1981年   4106篇
  1980年   3789篇
  1979年   3647篇
  1978年   3445篇
  1977年   4038篇
  1976年   5140篇
  1975年   2977篇
  1974年   2907篇
  1973年   2991篇
  1972年   2381篇
  1971年   2193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.
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   
3.
4.
5.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  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.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
8.
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   
9.
10.
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting.  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