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   501005篇
  免费   6422篇
  国内免费   1742篇
电工技术   8500篇
综合类   2628篇
化学工业   70942篇
金属工艺   20840篇
机械仪表   15507篇
建筑科学   12407篇
矿业工程   2605篇
能源动力   12636篇
轻工业   38627篇
水利工程   5362篇
石油天然气   7041篇
武器工业   23篇
无线电   62180篇
一般工业技术   98141篇
冶金工业   84010篇
原子能技术   9533篇
自动化技术   58187篇
  2021年   3484篇
  2020年   2562篇
  2019年   3247篇
  2018年   19129篇
  2017年   18156篇
  2016年   15223篇
  2015年   4350篇
  2014年   6713篇
  2013年   19269篇
  2012年   13357篇
  2011年   23222篇
  2010年   19363篇
  2009年   18475篇
  2008年   20159篇
  2007年   21032篇
  2006年   12129篇
  2005年   11966篇
  2004年   11519篇
  2003年   11699篇
  2002年   10306篇
  2001年   10453篇
  2000年   9948篇
  1999年   10435篇
  1998年   26428篇
  1997年   18519篇
  1996年   14389篇
  1995年   10591篇
  1994年   9558篇
  1993年   9374篇
  1992年   6858篇
  1991年   6620篇
  1990年   6311篇
  1989年   6185篇
  1988年   5994篇
  1987年   5058篇
  1986年   4935篇
  1985年   5552篇
  1984年   5088篇
  1983年   4881篇
  1982年   4450篇
  1981年   4476篇
  1980年   4259篇
  1979年   4169篇
  1978年   3979篇
  1977年   4721篇
  1976年   6452篇
  1975年   3414篇
  1974年   3303篇
  1973年   3258篇
  1972年   2750篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
1.
2.
3.
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   
4.
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   
5.
6.
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   
7.
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   
8.
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   
9.
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   
10.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  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