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   384162篇
  免费   4183篇
  国内免费   1269篇
电工技术   6915篇
综合类   2516篇
化学工业   52772篇
金属工艺   18927篇
机械仪表   15510篇
建筑科学   9019篇
矿业工程   2078篇
能源动力   8806篇
轻工业   24767篇
水利工程   4046篇
石油天然气   4892篇
武器工业   15篇
无线电   47771篇
一般工业技术   79129篇
冶金工业   55388篇
原子能技术   6253篇
自动化技术   50810篇
  2021年   2217篇
  2020年   1616篇
  2019年   1963篇
  2018年   22522篇
  2017年   22159篇
  2016年   15712篇
  2015年   3202篇
  2014年   4262篇
  2013年   11736篇
  2012年   10973篇
  2011年   23418篇
  2010年   20399篇
  2009年   18448篇
  2008年   19431篇
  2007年   21900篇
  2006年   7543篇
  2005年   10757篇
  2004年   8882篇
  2003年   8848篇
  2002年   7008篇
  2001年   6654篇
  2000年   6224篇
  1999年   6458篇
  1998年   16534篇
  1997年   11433篇
  1996年   8845篇
  1995年   6626篇
  1994年   5943篇
  1993年   5885篇
  1992年   4159篇
  1991年   4069篇
  1990年   3859篇
  1989年   3653篇
  1988年   3577篇
  1987年   3019篇
  1986年   2943篇
  1985年   3209篇
  1984年   2929篇
  1983年   2827篇
  1982年   2641篇
  1981年   2542篇
  1980年   2462篇
  1979年   2306篇
  1978年   2107篇
  1977年   2606篇
  1976年   3562篇
  1975年   1765篇
  1974年   1730篇
  1973年   1666篇
  1972年   1466篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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   
3.
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   
4.
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   
5.
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   
6.
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   
7.
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   
8.
Mobile Networks and Applications - Project MindCatcher is an art/research project which has the intention to explore the potential of interactive artistic environments for measuring and a better...  相似文献   
9.
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   
10.
Wireless Networks - In Wireless Sensor Networks (WSNs), where power consumption is a huge concern, the improvement of the network’s lifetime is an area of constant study and innovation. 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