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   100942篇
  免费   2691篇
  国内免费   1563篇
电工技术   2040篇
综合类   3537篇
化学工业   14165篇
金属工艺   5873篇
机械仪表   4133篇
建筑科学   3677篇
矿业工程   1078篇
能源动力   1659篇
轻工业   4815篇
水利工程   1568篇
石油天然气   1348篇
武器工业   141篇
无线电   11126篇
一般工业技术   18175篇
冶金工业   3350篇
原子能技术   594篇
自动化技术   27917篇
  2024年   82篇
  2023年   351篇
  2022年   564篇
  2021年   838篇
  2020年   625篇
  2019年   502篇
  2018年   14923篇
  2017年   13937篇
  2016年   10415篇
  2015年   1343篇
  2014年   1120篇
  2013年   1198篇
  2012年   4210篇
  2011年   10582篇
  2010年   9305篇
  2009年   6514篇
  2008年   7775篇
  2007年   8729篇
  2006年   1136篇
  2005年   2054篇
  2004年   1723篇
  2003年   1669篇
  2002年   1051篇
  2001年   572篇
  2000年   697篇
  1999年   547篇
  1998年   392篇
  1997年   324篇
  1996年   353篇
  1995年   248篇
  1994年   200篇
  1993年   135篇
  1992年   127篇
  1991年   110篇
  1990年   53篇
  1989年   57篇
  1988年   44篇
  1969年   24篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   45篇
  1963年   28篇
  1960年   30篇
  1959年   38篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Duan  Yongrui  Ge  Yao  Feng  Yixuan 《Electronic Commerce Research》2022,22(2):539-559
Electronic Commerce Research - We consider a platform providing free content for users and earning profit from the sale of advertising. The platform can collect and analyze personal data to...  相似文献   
2.
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   
3.
Mitigating gibbsite particle cracking and breakage during industrial alumina production can increase the quality of smelter grade alumina product by reducing the ultrafine particle content. Therefore, it is essential to investigate the particle cracking during static calcination and the breakage of calcined gibbsite particles under external force. In this work, we investigated the impact of the calcination ramping rate and the crystallite size on gibbsite particle cracking during static calcination. A slow ramping rate and a large pristine crystallite size tend to increase particle cracking. Apart from the study of particle cracking behaviour, we also investigated the breakage of calcined gibbsite particle under external force. Cracks on the particle surface can initiate breakage within the crystallite and along the grain boundary under external force. The breakage within crystallite occurs as the cleavage of the crystallite, while the breakage along the grain boundary leads to the shedding of a whole crystallite. We further explored the factors influencing the strength of calcined gibbsite particles. With increasing calcination temperature, the strength of particle increases when gibbsite converts to boehmite, and then decreases when boehmite converts into amorphous alumina. Particles containing smaller crystallites and calcined with fast ramping rates exhibit higher resistance to breakage.  相似文献   
4.
5.
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution.  相似文献   
6.
介绍机械制造厂燃煤锅炉的烟尘特点,分析滤料失效的原因,提出一套针对该工况的滤料解决方案。介绍针对复杂工况条件所选用的纤维种类以及复合面层原料成分配比的确定,最终选用针刺工艺加工并对该新产品的基本性能进行了测试分析。  相似文献   
7.
8.
9.
10.
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