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   270079篇
  免费   28283篇
  国内免费   16965篇
电工技术   20877篇
技术理论   7篇
综合类   24794篇
化学工业   38691篇
金属工艺   17244篇
机械仪表   18447篇
建筑科学   21265篇
矿业工程   10417篇
能源动力   7298篇
轻工业   26457篇
水利工程   7117篇
石油天然气   12739篇
武器工业   3356篇
无线电   28811篇
一般工业技术   26309篇
冶金工业   11626篇
原子能技术   3848篇
自动化技术   36024篇
  2024年   1464篇
  2023年   4464篇
  2022年   9705篇
  2021年   12740篇
  2020年   9572篇
  2019年   6946篇
  2018年   7540篇
  2017年   9051篇
  2016年   7588篇
  2015年   11804篇
  2014年   14605篇
  2013年   16991篇
  2012年   20104篇
  2011年   21230篇
  2010年   19680篇
  2009年   19025篇
  2008年   19081篇
  2007年   18061篇
  2006年   16614篇
  2005年   13685篇
  2004年   9798篇
  2003年   7213篇
  2002年   6702篇
  2001年   6056篇
  2000年   5561篇
  1999年   3974篇
  1998年   2877篇
  1997年   2418篇
  1996年   2206篇
  1995年   1908篇
  1994年   1530篇
  1993年   1125篇
  1992年   904篇
  1991年   711篇
  1990年   553篇
  1989年   487篇
  1988年   378篇
  1987年   269篇
  1986年   175篇
  1985年   103篇
  1984年   72篇
  1983年   57篇
  1982年   71篇
  1981年   58篇
  1980年   65篇
  1979年   40篇
  1978年   3篇
  1965年   3篇
  1959年   31篇
  1951年   29篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
A long fatty side chain was introduced into the macromolecule of hydroxyethyl cellulose (HEC) via esterification reaction. The hydrophobicity of hydroxyethyl cellulose lauric acid ester (HECLAE) was enhanced in comparison with HEC. The obtained HECLAE was used as macromolecular coupling agent in poly (butylene succinate)/wood flour composites and exhibited a positive influence on improving the mechanical performance of composites. Besides, HECLAE plays a role as a hydrophobic agent in composites. A significant increase in storage modulus (E’) was observed upon the incorporation of treated wood flour. SEM images showed that the dispersion of treated wood flour in PBS matrix was improved.  相似文献   
132.
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory.  相似文献   
133.
With increasing consumption of natural gas (NG), small NG reservoirs, such as coalbed methane and oil field associated gas, have recently drawn significant attention. Owing to their special characteristics (e.g., scattered distribution and small output), small-scale NG liquefiers are highly required. Similarly, the mixed refrigerant cycle (MRC) is suitable for small-scale liquefaction systems due to its moderate complexity and power consumption. In consideration of the above, this paper reviews the development of mobile miniature NG liquefiers in Technical Institute of Physics and Chemistry (TIPC), China. To effectively liquefy the scattered NG and overcome the drawbacks of existing technologies, three main improvements, i.e., low-pressure MRC process driven by oil-lubricated screw compressor, compact cold box with the new designed heat exchangers, and standardized equipment manufacturing and integrated process technology have been made. The development pattern of “rapid cluster application and flexible liquefaction center” has been eventually proposed. The small-scale NG liquefier developed by TIPC has reached a minimum liquefaction power consumption of about 0.35 kW·h/Nm3. It is suitable to exploit small remote gas reserves which can also be used in boil-off gas reliquefaction and distributed peak-shaving of pipe networks.  相似文献   
134.
135.
In this paper, based on adaptive dynamic programming (ADP) with concurrent learning, the problem of optimal guaranteed cost tracking is studied for a class  相似文献   
136.
137.
本文旨在改善某选厂硫精矿浓密机溢流跑浑问题,对生产现场进行勘察和分析,分析浓密机溢流跑浑的原因,并开展原矿配比和沉降试验研究。对采场原矿矿样和硫精矿矿浆进行系统的试验研究,分别采用不同沉降方案进行条件试验,考察絮凝剂种类、絮凝剂用量、pH调整剂用量、不同药剂之间的配比等条件对沉降的影响,确定合适的原矿配比及合理药剂制度,有效地控制金属在溢流中的损失,充分获取现有产品的蕴含价值。  相似文献   
138.
139.
针对电站锅炉回转式空气预热器运行时上下表面不可见的问题,本文提出了一种视频监控与故障分析系统,可直接监测转子表面情况。该系统通过视频监控获取图像,结合改进的Retinex算法对其进行处理,实现了以下2个功能:1)能分析积灰程度以判断转子堵塞 情况;2)与温度场融合实时显示转子表面热点分布以预防二次燃烧。该系统已应用于某600 MW机组,实现了在热态环境下对空气预热器转子积灰程度、热点分布、堵塞程度的估算与可视化,大大提高了空气预热器运行的可靠性。  相似文献   
140.
Simulating the psychological experience of human vision,a road extraction model based on the format tower is proposed to extract the road in the high resolution remote sensing image from the perspective of morphology.Firstly,based on the spectral and texture information,the suspected road targets are extracted by using segmentation technology.Then these targets are classified according to their reliability and extract the road targets for each category.Finally,three types of identified road information are verified and merged,and the continuous smooth road extraction results are obtained.Experiments on real high resolution images show that the results are consistent with the visual perception of the human eye,and the overall classification accuracy is higher,indicating that the algorithm is effective and feasible and has good use value.  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