全文获取类型
收费全文 | 3608篇 |
免费 | 301篇 |
国内免费 | 214篇 |
专业分类
电工技术 | 209篇 |
综合类 | 191篇 |
化学工业 | 608篇 |
金属工艺 | 204篇 |
机械仪表 | 219篇 |
建筑科学 | 273篇 |
矿业工程 | 100篇 |
能源动力 | 94篇 |
轻工业 | 254篇 |
水利工程 | 59篇 |
石油天然气 | 268篇 |
武器工业 | 23篇 |
无线电 | 416篇 |
一般工业技术 | 467篇 |
冶金工业 | 171篇 |
原子能技术 | 29篇 |
自动化技术 | 538篇 |
出版年
2024年 | 18篇 |
2023年 | 61篇 |
2022年 | 126篇 |
2021年 | 166篇 |
2020年 | 132篇 |
2019年 | 108篇 |
2018年 | 123篇 |
2017年 | 89篇 |
2016年 | 119篇 |
2015年 | 149篇 |
2014年 | 195篇 |
2013年 | 224篇 |
2012年 | 215篇 |
2011年 | 234篇 |
2010年 | 208篇 |
2009年 | 198篇 |
2008年 | 166篇 |
2007年 | 178篇 |
2006年 | 190篇 |
2005年 | 217篇 |
2004年 | 130篇 |
2003年 | 111篇 |
2002年 | 99篇 |
2001年 | 84篇 |
2000年 | 103篇 |
1999年 | 79篇 |
1998年 | 76篇 |
1997年 | 61篇 |
1996年 | 51篇 |
1995年 | 42篇 |
1994年 | 41篇 |
1993年 | 24篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有4123条查询结果,搜索用时 15 毫秒
1.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
2.
3.
5.
6.
A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze trace elements,especially lead,in vehicle exhaust of Shanghai city.The result shows that the chemical composition and its corresponding x-ray relative intensity are different among different vehicle exhausts.There are many kinds of metal elements in particles of vehicle exhaust.most are harmful to people,such as Ti,Cr,Mn,Pb,etc.We found that the lead concentration was 6820μg/g and the bromine concentration was 5300μg/g in the exhaust from Santana using leaded gasoline(SULG).which is higher than any other kinds of vehicle exhausts.We have also detected the minimum lead in the particles of unleaded gasoline and its content varies from one to another.Its mean concentration was 450μg/g and the highest reached 6210μg/g.The unleaded gasoline‘s Pb existed in the whole particle while the leaded gasoline‘s enriched in the surface of the particle and was more harmful to the human beings. 相似文献
7.
8.
9.
10.