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   327038篇
  免费   25245篇
  国内免费   12953篇
电工技术   17700篇
技术理论   35篇
综合类   20705篇
化学工业   56233篇
金属工艺   18763篇
机械仪表   20702篇
建筑科学   26135篇
矿业工程   10449篇
能源动力   8933篇
轻工业   21001篇
水利工程   5633篇
石油天然气   21934篇
武器工业   2596篇
无线电   35482篇
一般工业技术   38061篇
冶金工业   16729篇
原子能技术   3325篇
自动化技术   40820篇
  2024年   1380篇
  2023年   5195篇
  2022年   8960篇
  2021年   12826篇
  2020年   9584篇
  2019年   8068篇
  2018年   9156篇
  2017年   10316篇
  2016年   9063篇
  2015年   12633篇
  2014年   15710篇
  2013年   18779篇
  2012年   20422篇
  2011年   22365篇
  2010年   19404篇
  2009年   18504篇
  2008年   18090篇
  2007年   17474篇
  2006年   18282篇
  2005年   16088篇
  2004年   10418篇
  2003年   8940篇
  2002年   8333篇
  2001年   7323篇
  2000年   7879篇
  1999年   9288篇
  1998年   7481篇
  1997年   6342篇
  1996年   5907篇
  1995年   4907篇
  1994年   4049篇
  1993年   2852篇
  1992年   2331篇
  1991年   1744篇
  1990年   1274篇
  1989年   1024篇
  1988年   833篇
  1987年   561篇
  1986年   441篇
  1985年   286篇
  1984年   204篇
  1983年   133篇
  1982年   140篇
  1981年   101篇
  1980年   86篇
  1979年   31篇
  1978年   4篇
  1976年   7篇
  1975年   4篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media.  相似文献   
82.
“Smart firefighting” construction as a part of the “smart city” has been a concern of the public security and fire agencies at all levels. In this study, the status, problems, and reflections of “smart firefighting” construction in China are discussed. A recent survey indicates that China has launched its smart firefighting construction and initially created a new perspective on its regional smart firefighting work based on three main aspects: intelligent disaster perception by Internet of Things (IoT) construction, intelligent disaster prevention by big data construction, and intelligent disaster disposal by emergency rescue platform construction. However, the current smart firefighting construction in China still has some prominent problems such as the data interconnectivity and normalized management of various platforms, the extensibility of smart firefighting platforms, and the intelligent level of smart firefighting researches, which need to be solved urgently. Therefore, we argue that smart firefighting construction in China should establish data interconnectivity, industrial normalized management, 2D/3D geographic information interaction and extension, high-integration fire protection theory, and many other aspects in the near future and truly realize firefighting visualization and efficient data applications for 4D time space. This study could provide valuable reference for smart firefighting and smart city construction.  相似文献   
83.
84.
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst.  相似文献   
85.
86.
87.
88.
89.
90.
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