全文获取类型
收费全文 | 4904篇 |
免费 | 455篇 |
国内免费 | 208篇 |
专业分类
电工技术 | 26篇 |
综合类 | 274篇 |
化学工业 | 1444篇 |
金属工艺 | 80篇 |
机械仪表 | 76篇 |
建筑科学 | 146篇 |
矿业工程 | 296篇 |
能源动力 | 147篇 |
轻工业 | 1424篇 |
水利工程 | 16篇 |
石油天然气 | 851篇 |
武器工业 | 9篇 |
无线电 | 97篇 |
一般工业技术 | 154篇 |
冶金工业 | 385篇 |
原子能技术 | 15篇 |
自动化技术 | 127篇 |
出版年
2024年 | 30篇 |
2023年 | 69篇 |
2022年 | 176篇 |
2021年 | 234篇 |
2020年 | 193篇 |
2019年 | 179篇 |
2018年 | 163篇 |
2017年 | 181篇 |
2016年 | 204篇 |
2015年 | 194篇 |
2014年 | 262篇 |
2013年 | 364篇 |
2012年 | 392篇 |
2011年 | 388篇 |
2010年 | 279篇 |
2009年 | 253篇 |
2008年 | 200篇 |
2007年 | 313篇 |
2006年 | 279篇 |
2005年 | 193篇 |
2004年 | 148篇 |
2003年 | 140篇 |
2002年 | 128篇 |
2001年 | 103篇 |
2000年 | 130篇 |
1999年 | 88篇 |
1998年 | 66篇 |
1997年 | 63篇 |
1996年 | 35篇 |
1995年 | 25篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有5567条查询结果,搜索用时 15 毫秒
11.
Cracking of petroleum vacuum residue (XVR) and its cocracking with plastics (PP or PS), Calotropis procera (CL) as a binary, ternary, and quaternary mixture of these individual plastics, and CL with XVR was carried out in a Perkin-Elmer thermogravimetric analyzer (TGA) for the purpose of comparing the process of the mixture with those of the individual components. Experiments were conducted at a heating rate of 40 K/min, in the temperature range of 30-900°C. Based on the results obtained, three temperature regimes were selected for studying the nonisothermal kinetics of TGA of individual XVR, plastics, and biomass as well as of the cocracking of these with XVR, i.e., below 400°C, between 400-500°C, and above 500°C. The kinetic studies were performed using the Coats and Redfern kinetic modeling equation. The overall activation energies obtained were 25 kJ/mole for petroleum vacuum residue, 99 kJ/mole for polypropylene, 21 kJ/mole for coal, and 35 kJ/mole for the mixture of all these materials. Thus, it has been found that there exists an overall synergy when three materials were coprocessed together. The overall orders and activation energies change during coprocessing of two or three different macromolecules, including mixed vacuum residue as presently observed. The detailed results that were obtained will be reported. 相似文献
12.
13.
14.
References: 《中国炼油与石油化工》2007,(3):35-42
The proton nuclear magnetic resonance spectroscopy (1H-NMR), the synchronous fluorescence spectrometry (SFS) and the ruthenium ions catalyzed oxidation (RICO) method were used to determine the chemical structure of polyaromatic nucleus in Oman residue fractions. The results of 1H-NMR analyses showed that the average numbers of aromatic rings in the aromatics, resins and asphaltenes units were 3.2, 5.6 and 8.2, respectively. SFS was used to investigate the distribution of aromatic rings in residue fractions, the main distribution range of aromatic rings in aromatics, resins and asphaltenes were 3 4 rings, 3--5 rings and more than 5 rings, respectively. The aromatic network in residue fractions was oxidized to produce numerous carboxylic acids. The types and content of benzenepolycarboxylic acids, such as phthalic acid, benzenetricarboxylic acids, benzenetetracarboxylic acids, benzenepentacarboxylic acid and benzenehexacarboxylic acid disclosed the condensed types of aromatic nuclei in the core. The biphenyl fraction (BIPH), the cata-condensed fraction (CATA), the peri-condensed fraction (PERI) and the condensed index (BCI) were calculated based on the benzenepolycarboxylic acids formed. The results implied that there was less biphenyl type structures in all residue fractions. The aromatics fraction was almost composed of the cata-condensed type system, and the asphaltenes fraction was wholly composed of the peri-condensed type system, while in the resins fraction co-existed the two types, herein the peri-con- densed type was predominant over the cata-condensed type. Based on the analytical results obtained in the study, the components --aromatics, resins and asphaltenes -- were given the likely structural models. 相似文献
15.
A newly developed catalyst type DVR-1 for catalytic cracking of Daqing vacuum resid was put into use in a commercial VRFCC unit,This catalyst features uniquely active matrix and modified ultra-stable zeolite.The commercial application results show that the DVR-1 type catalyst has the advantage of high heavy oil conversion,good metal tolerance nd gooed stability for catalyst regeneration,The FCC tests have shown Favorable product distribution,acceptable product quality and enormaous economic benefits whe processing the feedstock containin 75%-100% Daqing VR. 相似文献
16.
叙述了从铅阳极泥回收金银后的渣料中综合回收有价金属的生产实践。根据渣料性质,将火法和湿法工艺相互结合,使渣料中的锑、铋、金、银、铅、铜得以较彻底的分离和回收。 相似文献
17.
18.
19.
脱硫灰渣的排放方式及利用 总被引:1,自引:0,他引:1
火电厂产生的脱硫灰渣的组成和性能与其排放方式有着密切关系。为使其得到较好的处置与利用 ,本文从排放方式方面进行探讨 ,并略述各种脱硫灰渣的性能与利用前景 相似文献
20.