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   507460篇
  免费   8094篇
  国内免费   1896篇
电工技术   8995篇
综合类   1006篇
化学工业   73706篇
金属工艺   17123篇
机械仪表   14538篇
建筑科学   12915篇
矿业工程   1771篇
能源动力   13855篇
轻工业   47800篇
水利工程   4530篇
石油天然气   5062篇
武器工业   26篇
无线电   63470篇
一般工业技术   92266篇
冶金工业   106313篇
原子能技术   8069篇
自动化技术   46005篇
  2021年   3924篇
  2020年   2842篇
  2019年   3462篇
  2018年   6038篇
  2017年   6264篇
  2016年   7003篇
  2015年   4915篇
  2014年   7694篇
  2013年   22499篇
  2012年   13995篇
  2011年   19175篇
  2010年   14035篇
  2009年   15908篇
  2008年   16612篇
  2007年   16414篇
  2006年   14899篇
  2005年   15883篇
  2004年   14859篇
  2003年   14480篇
  2002年   12388篇
  2001年   13055篇
  2000年   11577篇
  1999年   12689篇
  1998年   35190篇
  1997年   24125篇
  1996年   18028篇
  1995年   13311篇
  1994年   11588篇
  1993年   11520篇
  1992年   7729篇
  1991年   7414篇
  1990年   7148篇
  1989年   6780篇
  1988年   6618篇
  1987年   5462篇
  1986年   5295篇
  1985年   6132篇
  1984年   5444篇
  1983年   5191篇
  1982年   4809篇
  1981年   4853篇
  1980年   4611篇
  1979年   4171篇
  1978年   3893篇
  1977年   5121篇
  1976年   7241篇
  1975年   3269篇
  1974年   3104篇
  1973年   3124篇
  1972年   2546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.
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   
6.
The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.  相似文献   
7.
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   
8.
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays.  相似文献   
9.
Wireless Personal Communications - Despite its various benefits, the Mobile Ad-hoc Network (MANET) has a number of obstacles due to its mobility, unstable topology, energy efficiency, and other...  相似文献   
10.
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   
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