全文获取类型
收费全文 | 3884篇 |
免费 | 215篇 |
国内免费 | 117篇 |
专业分类
电工技术 | 25篇 |
综合类 | 192篇 |
化学工业 | 845篇 |
金属工艺 | 375篇 |
机械仪表 | 47篇 |
建筑科学 | 23篇 |
矿业工程 | 73篇 |
能源动力 | 132篇 |
轻工业 | 488篇 |
水利工程 | 3篇 |
石油天然气 | 481篇 |
武器工业 | 10篇 |
无线电 | 26篇 |
一般工业技术 | 120篇 |
冶金工业 | 1298篇 |
原子能技术 | 10篇 |
自动化技术 | 68篇 |
出版年
2024年 | 13篇 |
2023年 | 22篇 |
2022年 | 74篇 |
2021年 | 81篇 |
2020年 | 73篇 |
2019年 | 65篇 |
2018年 | 58篇 |
2017年 | 70篇 |
2016年 | 95篇 |
2015年 | 102篇 |
2014年 | 208篇 |
2013年 | 207篇 |
2012年 | 301篇 |
2011年 | 330篇 |
2010年 | 214篇 |
2009年 | 203篇 |
2008年 | 148篇 |
2007年 | 230篇 |
2006年 | 227篇 |
2005年 | 206篇 |
2004年 | 195篇 |
2003年 | 191篇 |
2002年 | 168篇 |
2001年 | 157篇 |
2000年 | 128篇 |
1999年 | 105篇 |
1998年 | 79篇 |
1997年 | 58篇 |
1996年 | 46篇 |
1995年 | 43篇 |
1994年 | 31篇 |
1993年 | 24篇 |
1992年 | 30篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有4216条查询结果,搜索用时 15 毫秒
1.
2.
3.
A novel AlSiMgAl2O4Al2O3 composite brick was prepared and evaluated in the low vessel of an RH (the initials of Ruhrstahl and Hereaeus) secondary refining furnace; it was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that after use, the AlSiMgAl2O4Al2O3 composite has a functional gradient with an erosion zone–reinforced zone–original zone phase distribution, in which the phases in the erosion zone (0–1.8?cm) are a Mg-hercynite spinel solid solution, α-Al2O3, and minor amount of Al3Fe5O12. Furthermore, the phases in the reinforced zone (1.8–5.0?cm) are γ-AlON, 21RSiAlON, SiC, Mg0.388Al2.408O4, and α-Al2O3; i.e., the Al and Si in the composite are completely converted into non-oxide reinforced phases. Finally, the phases in the original zone (>5.0?cm) show no change. The reaction mechanism is as follows. During operation, a Mg-hercynite spinel solid solution is formed in the erosion zone due to a reaction between MgAl2O4 and FeO from a refinery operation. Therefore, the slag erosion of the material is improved. The Al and Si metals undergo active oxidation, and 21RSiAlON flakes are subsequently formed from the products of the metastable Al2O(g), SiO(g), and N2(g) in the ambient. The γ-AlON is formed by a carbothermal reduction nitridation of the α-Al2O3 and residual active carbon from the resin binder. The 21RSiAlON and γ-AlON reinforce the composite brick and improve its high temperature performance accordingly. Its service life is 110% that of the magnesia-chrome bricks used in the same period. The reaction model was also established. 相似文献
4.
5.
6.
Li Junling Zheng Tinglu Han Zhaping 《中国炼油与石油化工》2006,(3):57-60
The method for refining the straight-run diesel fuel was studied in laboratory scale in order to make the acid number of diesel fraction comply with the standard while removing the naphthenic acids contained in diesel without causing environmental pollution. After comparing the effect of refining using three solvents, the isopropyl alcohol-HOA was specified as the best solvent. Meanwhile, the relationship between the acid number of diesel fraction and the amount of solvent used and the relationship between the concentration of solvent and temperature and the stability of diesel in terms of its acid number were also investigated. Experimental results had shown that when the mass fraction of the HOA-IPA solvent was 20% at a dosage of 17 mL of the solvent and a temperature of 30℃, the acid number of the refined diesel fraction was 0.015 mg KOH/g with a good stability of acidity in the diesel fraction, 相似文献
7.
我国炼油石化产业应对石油短缺时代的科技对策思考 总被引:2,自引:0,他引:2
分析了我国石油消费的增长趋势和石油的增产潜力,指出持续增长的需求和相对稳定的产量使我国对国际石油的依存度越来越高。综合了国际能源机构、能源经济学家和石油地质学家对世界石油供应前景的预测结果,认为世界石油短缺的时代并不遥远。提出了我国炼油石化产业应对世界石油供应短缺时代的科技对策:(I)抓紧开发和完善充分利用石油资源生产运输燃料和石化原料技术;(2)开发用煤炭、石油焦、沥青制氢和炼油过程耦合的廉价氢源技术和用氢优化技术;(3)开发炼油石化过程节能降耗技术;(4)开发天然气及煤制油、甲醇制乙烯、丙烯技术;(5)开发利用生物质生产车用替代燃料、生物材料和生物化学品技术。 相似文献
8.
详细介绍了中国石油抚顺石化分公司石油一厂新区以沈阳、大庆混合原油的减二、减三线馏分油为原料,采用甲苯、甲乙酮脱蜡、糠醛精制、白土补充精制工艺生产HVI润滑油基础油的生产经验。并结合理论分析,提出了完善此类工艺的一系列建议。生产HVI200基础油,要求蒸馏减二线润滑油馏分粘度不大于4.75 mm2/s,脱蜡油粘度不大于56 mm2/s。为保证HVI200基础油粘度指数合格,要降低减二线馏分中多环环烷烃含量。 相似文献
9.
10.
Alexandre Szklo Giovani Machado Roberto Schaeffer Jacqueline Mariano Janaí na Sala Marina Tavares 《Catalysis Today》2005,106(1-4):123-128
This paper assesses the impacts of a GTL plant on the expansion of Brazil's oil refining segment. The GTL plant (50,000 bpd) was sized to start up operations in 2015, producing diesel and naphtha through the indirect route (FT-synthesis). This plant will consume the non-associated natural gas production from the recent discoveries at the Santos Basin (around 419 Bm3), and the associated gas production from the Campos Basin. Both basins are located in the Southeast of Brazil, the most populated, rich and industrialized region of the country. Two different criteria for refinery expansion were simulated in order to meet oil product demand scenarios. Findings show that depending on the refinery expansion criteria considered GTL will play a fundamental hole to meet the oil product demand forecast to Brazil in the next 10 years. 相似文献