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   187419篇
  免费   16227篇
  国内免费   8572篇
电工技术   11474篇
技术理论   13篇
综合类   11601篇
化学工业   29467篇
金属工艺   10969篇
机械仪表   11683篇
建筑科学   13928篇
矿业工程   5336篇
能源动力   5729篇
轻工业   12712篇
水利工程   3323篇
石油天然气   10669篇
武器工业   1404篇
无线电   22898篇
一般工业技术   24490篇
冶金工业   9995篇
原子能技术   2076篇
自动化技术   24451篇
  2024年   392篇
  2023年   3247篇
  2022年   5376篇
  2021年   8134篇
  2020年   6303篇
  2019年   5055篇
  2018年   5819篇
  2017年   6435篇
  2016年   5826篇
  2015年   7682篇
  2014年   9599篇
  2013年   11987篇
  2012年   12721篇
  2011年   13581篇
  2010年   11524篇
  2009年   11116篇
  2008年   10564篇
  2007年   9786篇
  2006年   9912篇
  2005年   8422篇
  2004年   5819篇
  2003年   4847篇
  2002年   4350篇
  2001年   3946篇
  2000年   3816篇
  1999年   4416篇
  1998年   4021篇
  1997年   3323篇
  1996年   3052篇
  1995年   2466篇
  1994年   1981篇
  1993年   1448篇
  1992年   1164篇
  1991年   902篇
  1990年   659篇
  1989年   547篇
  1988年   430篇
  1987年   285篇
  1986年   244篇
  1985年   161篇
  1984年   153篇
  1983年   111篇
  1982年   105篇
  1981年   83篇
  1980年   81篇
  1979年   47篇
  1978年   45篇
  1977年   41篇
  1976年   34篇
  1975年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Zheng  Yang  Guo  Yangyang  Xu  Xiaofei  Zhu  Tingyu 《Catalysis Letters》2022,152(6):1752-1759
Catalysis Letters - To explore the possibility of coreaction of selective catalytic reduction with NH3 (NH3-SCR) and CO oxidation (CO-O), bimetallic doping catalysts of Mn and Cu were synthesized...  相似文献   
74.
以红花菜籽油中亚油酸为原料,偏铁酸钠为催化剂,在单因素试验的基础上,选取反应温度、反应时间、催化剂用量为考察因素,以异构化产物共轭亚油酸(CLA)转化率为响应值,通过响应面分析法对异构化反应进行优化,并建立相应的回归模型,试验结果表明,红花菜籽油中亚油酸异构化为CLA的最佳工艺为:反应温度195℃、反应时间4.7 h、催化剂用量0.6 g,在此条件下得到CLA转化率为92.90%,与预测值93.92%相比,误差为1.02%.然后再通过脲素包合纯化、经2%的H2SO4-CH3OH溶液甲酯化后,用气相色谱-质谱联用仪检测CLA含量为64.27%.  相似文献   
75.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system.  相似文献   
76.
An increasing number of social media and networking platforms have been widely used. People usually post the online comments to share their own opinions on the networking platforms with social media. Business companies are increasingly seeking effective ways to mine what people think and feel regarding their products and services. How to correctly understand the online customers’ reviews becomes an important issue. This study aims to propose a method with the aspect-oriented Petri nets (AOPN) to improve the examination correctness without changing any process and program. We collect those comments from the online reviews with Scrapy tools, perform sentiment analysis using SnowNLP, and examine the analysis results to improve the correctness. In this paper, we apply our method for a case of the online movie comments. The experimental results have shown that AOPN is helpful for the sentiment analysis and verifying its correctness.  相似文献   
77.
The effects of soybean variety and germination time on structural changes, antinutritional factor content, antioxidant activity of germinated soybean, and on the functional properties of soymilk were comprehensively investigated. The results showed that the antioxidant activity increased with increasing germination time. The content of antinutritional factors decreased with increasing germination time. Soybean varieties with the lowest tannin and trypsin inhibitor content were DN690 and HJ1. Lipoxygenase activity and phytic acid content showed no significant differences among soybean varieties. The content of α-helices and β-turns in soybean protein decreased with increasing germination time, while the content of β-sheets was increased. Soybean protein was progressively broken down into smaller molecular peptides during the germination process. The digestion and content of soluble protein in soymilk increased with germination. In summary, we show that germination is an effective, cheap, and green method that improves the functional properties of soybean and soymilk.  相似文献   
78.
Gao  Zehai  Liu  Yang  Li  Nan  Ma  Kangjie 《Water Resources Management》2022,36(8):2685-2702
Water Resources Management - Urban river not only has the important function in urban hydrological environment, but also is an area for entertainment. Water quality assessment is the core technique...  相似文献   
79.
80.
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