全文获取类型
收费全文 | 18216篇 |
免费 | 1681篇 |
国内免费 | 850篇 |
专业分类
电工技术 | 1169篇 |
综合类 | 1207篇 |
化学工业 | 2673篇 |
金属工艺 | 1209篇 |
机械仪表 | 1211篇 |
建筑科学 | 1460篇 |
矿业工程 | 634篇 |
能源动力 | 426篇 |
轻工业 | 1488篇 |
水利工程 | 338篇 |
石油天然气 | 1196篇 |
武器工业 | 163篇 |
无线电 | 2055篇 |
一般工业技术 | 2090篇 |
冶金工业 | 889篇 |
原子能技术 | 144篇 |
自动化技术 | 2395篇 |
出版年
2024年 | 121篇 |
2023年 | 355篇 |
2022年 | 570篇 |
2021年 | 798篇 |
2020年 | 613篇 |
2019年 | 502篇 |
2018年 | 535篇 |
2017年 | 637篇 |
2016年 | 507篇 |
2015年 | 735篇 |
2014年 | 943篇 |
2013年 | 1059篇 |
2012年 | 1163篇 |
2011年 | 1195篇 |
2010年 | 1085篇 |
2009年 | 1061篇 |
2008年 | 992篇 |
2007年 | 970篇 |
2006年 | 1074篇 |
2005年 | 990篇 |
2004年 | 626篇 |
2003年 | 553篇 |
2002年 | 533篇 |
2001年 | 422篇 |
2000年 | 414篇 |
1999年 | 414篇 |
1998年 | 354篇 |
1997年 | 313篇 |
1996年 | 280篇 |
1995年 | 231篇 |
1994年 | 183篇 |
1993年 | 113篇 |
1992年 | 90篇 |
1991年 | 69篇 |
1990年 | 62篇 |
1989年 | 57篇 |
1988年 | 43篇 |
1987年 | 22篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology,which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO2 capture.The develop-ment of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process.As the solid by-product from the sulfuric acid production,pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process.The main components in pyrite cinder are Fe2O3,CaSO4,Al2O3 and SiO2 in which Fe2O3 is the active component to provide lattice oxygen.In order to sys-tematic investigate the functions of supports (CaSO4,Al2O3 and SiO2) in pyrite cinder,three oxygen car-riers (Fe2O3-CaSO4,Fe2O3-Al2O3 and Fe2O3-SiO2) were prepared and evaluated in this study.The results showed that Fe2O3-CaSO4 displayed high redox activity and cycling stability in the multiple redox cycles.However,both Fe2O3-Al2O3 and Fe2O3-SiO2 experienced serious deactivation during redox reactions.It indicated that the inert Fe-Si solid solution (Fe2SiO4) was formed in the spent Fe2O3-SiO2 sample,which decreased the oxygen carrying capacity of this sample.The XPS results showed that the oxygen species on the surface of Fe2O3-CaSO4 could be fully recovered after the 20 redox cycles.It can be concluded that CaSO4 is the key to the high redox activity and cycling stability of pyrite cinder. 相似文献
13.
Xiong Xiang Huang Baiyun Lei Changmin Lu Haibo Central South University of Technology Changsha China 《中国有色金属学会会刊》1993,(2)
The microstructure,alloying reaction and sintering behavior of the powder produced by Mechanical Al-loying(MA)for 8 h from 64 wt.-% Ti powder and 36 wt.-% Al powder were studied by scanning electronmicroscopy,optical microscopy,X-ray diffractometry,differential scanning calorimetry(DSC)and dilatometry.The mechanically alloyed powder partictes are Ti-Al composite particles.Thus,titanium aluminides can formeasily in the powder through diffusion during heat treatment.It is shown that the sintering behavior of this pow-der,different from the behaviors of TiAl alloy powder and mixed powder of 64 wt.-% Ti powder and 36 wt.-%Al powder,changes from expansion at temperatures below 1000℃ to shrinkage at temperatures above 1000℃.Homogeneously alloyed TiAl material with a density over 96% of the theoretical density can be produced fromthe mechanically alloyed powder by compaction-sintering. 相似文献
14.
介绍了使用一种专用改性荆加入普通水玻璃中,使CO2水玻璃砂在低温环境下也能速硬,可防止铸型(芯)蠕变的技术。 相似文献
15.
16.
目前,通信条件已发生了革命性的变化,由早期的载波、微波和电缆等通信介质发展成为以光缆为主的通信网络.电力系统以OPGW光缆、ADSS光缆为主,已覆盖了几乎所有的输变电场所.因此,应建立与之适应的通信模式.通过研究现代通信条件、变电站通信的需求,提出了统一化的、简单的变电站通信模式. 相似文献
17.
宋子健 《武汉理工大学学报(材料科学英文版)》2014,29(2):329-333
The applicability of the rapid iodide migration test was systematically studied. Comparative experimental tests of different test conditions, including several external voltages, test durations, concrete ages and mixing proportions, were carried out to make clear the transport behaviors of iodide under parallel electric fields. Numerical simulations were also done using the finite element method to found the correlation between chloride and iodide transport behaviors. The test and numerical results show that the chloride transport behaviors of RIM and RCM tests have a good correlation under the several conditions used in the present paper. Moreover, the influence of external conditions (external voltages, test durations) on the test results is small. Thus, it can be concluded that the RIM method is available to determine the chloride penetration resistance of the chloride-eroded structural concrete. 相似文献
18.
车用空调器压缩机前端板铸件壳型铸造工艺实践 总被引:1,自引:0,他引:1
对前端板铸件壳型铸造中存在的铸造缺陷,采用优化浇注系统,对铁水进行二次孕育处理,调整碳当量控制在3.90%~4.15%,硅含量降低0.15%~0.20%,使产品抗拉强度≥270MPa,硬度(HB)为187~241,满足用户要求。 相似文献
19.
20.