全文获取类型
收费全文 | 2250篇 |
免费 | 110篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 54篇 |
综合类 | 32篇 |
化学工业 | 366篇 |
金属工艺 | 63篇 |
机械仪表 | 55篇 |
建筑科学 | 202篇 |
矿业工程 | 36篇 |
能源动力 | 48篇 |
轻工业 | 168篇 |
水利工程 | 12篇 |
石油天然气 | 70篇 |
武器工业 | 10篇 |
无线电 | 187篇 |
一般工业技术 | 244篇 |
冶金工业 | 408篇 |
原子能技术 | 35篇 |
自动化技术 | 412篇 |
出版年
2023年 | 12篇 |
2022年 | 34篇 |
2021年 | 43篇 |
2020年 | 30篇 |
2019年 | 27篇 |
2018年 | 31篇 |
2017年 | 39篇 |
2016年 | 41篇 |
2015年 | 63篇 |
2014年 | 60篇 |
2013年 | 132篇 |
2012年 | 87篇 |
2011年 | 131篇 |
2010年 | 104篇 |
2009年 | 114篇 |
2008年 | 94篇 |
2007年 | 98篇 |
2006年 | 128篇 |
2005年 | 117篇 |
2004年 | 104篇 |
2003年 | 75篇 |
2002年 | 77篇 |
2001年 | 57篇 |
2000年 | 48篇 |
1999年 | 52篇 |
1998年 | 55篇 |
1997年 | 50篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 15篇 |
1990年 | 29篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 23篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1973年 | 10篇 |
排序方式: 共有2402条查询结果,搜索用时 171 毫秒
1.
2.
Guangbo Zeng Dongqing Zhang Liuming Yan Baohua Yue Ting Pan Yidong Hu Shufa He Hongbin Zhao Jiujun Zhang 《International Journal of Hydrogen Energy》2021,46(39):20664-20677
Side-chain optimized poly (2,6-dimethyl-1,4-phenylene oxide)-g-poly (styrene sulfonic acid) (PPO-g-PSSA) is designed with balanced water-resistance and sulfonation degree. The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization (ATRP) from brominated poly (2,6-dimethyl-1,4-phenylene oxide) (PPO-xBr) and ethyl styrene-4-sulfonate and followed by hydrolysis. A series of PPO-g-PSSA are prepared possessing different bromination degree (x) of PPO-xBr and polymerization degree (m) of the side-chains and the water-resistances of the fabricated membranes are investigated. The results show that a PPO-g-PSSA at relatively low x (x < 0.2) and high m (m > 4) exhibits good balance between the water-resistance and the sulfonation degree. Namely, it displays suitable proton conductivity with compromised water-resistance. Moreover, a maximum ion exchange capacity (IEC) of 3.24 mmol g?1 is reached without the sacrifice of water-resistance. In addition, PPO-g-0.08PSSA-13 and PPO-g-0.14PSSA-4 are chosen characterized by thermogravimetric analysis, proton conductivities and mechanical properties. At 90% RH, the optimized PPO-g-0.08PPSA-13 possesses a proton conductivity of 37.9 mS cm?1 at 40 °C and 45.5 mS cm?1 at 95 °C, respectively. 相似文献
3.
4.
本部分将讲述PortletConfig对象及其PortletContext对象的概念及应用。 相似文献
5.
6.
Several N-(phosphonomethyl) amides have previously been reported to act as particularly effective flame retardants for cellulose. It has also been demonstrated previously that the efficiency of a flame retardant on cellulose frequently parallels its ability to phosphorylate cellulosic hydroxyls at elevated temperatures. This study of the hydrolysis and alcoholysis reactions of N-(phosphonomethyl) amides establishes their unique reactivity. An explanation for this high reactivity is proposed on the basis of intramolecular assistance of the attack of water or alcohols at phosphorus by the carbonyl oxygen of the amide moiety. 相似文献
7.
8.
Macroscopic analysis of design processes based on a scheme for coding designers' cognitive actions 总被引:1,自引:0,他引:1
We have devised a new scheme for coding designers' cognitive actions from video/audio design protocols. Designers' actions are coded into four cognitive levels; physical, perceptual, functional and conceptual. Relations between actions belonging to different levels, such as dependencies and triggering relations, are also coded. The present scheme has two benefits. First, we found that design actions are definable in a systematic way using the vocabulary of the scheme, and thus a designer's cognitive behaviours in each of local design stages is represented as a structure composed of defined primitive actions. This is expected to lay the foundation for microscopic analyses of how particular types of actions contribute to the formation of key design ideas. Second, this scheme is suitable for macroscopic analyses of how designers cognitively interact with their own sketches. We examined, for a practising architect, the ways in which drawing, inspection of drawings, perception, and functional thoughts correlated with one another in his design process. The findings suggest that design sketches serve not only as external memory or as a provider of visual cues for association of non-visual information, but also as a physical setting in which design thoughts are constructed on the fly. 相似文献
9.
10.