全文获取类型
收费全文 | 9420篇 |
免费 | 978篇 |
国内免费 | 400篇 |
专业分类
电工技术 | 75篇 |
技术理论 | 1篇 |
综合类 | 656篇 |
化学工业 | 5383篇 |
金属工艺 | 372篇 |
机械仪表 | 62篇 |
建筑科学 | 376篇 |
矿业工程 | 443篇 |
能源动力 | 104篇 |
轻工业 | 945篇 |
水利工程 | 88篇 |
石油天然气 | 618篇 |
武器工业 | 118篇 |
无线电 | 74篇 |
一般工业技术 | 634篇 |
冶金工业 | 763篇 |
原子能技术 | 59篇 |
自动化技术 | 27篇 |
出版年
2024年 | 50篇 |
2023年 | 103篇 |
2022年 | 247篇 |
2021年 | 278篇 |
2020年 | 267篇 |
2019年 | 250篇 |
2018年 | 243篇 |
2017年 | 308篇 |
2016年 | 366篇 |
2015年 | 370篇 |
2014年 | 545篇 |
2013年 | 595篇 |
2012年 | 700篇 |
2011年 | 696篇 |
2010年 | 508篇 |
2009年 | 539篇 |
2008年 | 437篇 |
2007年 | 566篇 |
2006年 | 542篇 |
2005年 | 505篇 |
2004年 | 435篇 |
2003年 | 391篇 |
2002年 | 340篇 |
2001年 | 280篇 |
2000年 | 257篇 |
1999年 | 221篇 |
1998年 | 166篇 |
1997年 | 109篇 |
1996年 | 92篇 |
1995年 | 69篇 |
1994年 | 73篇 |
1993年 | 51篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 28篇 |
1986年 | 15篇 |
1985年 | 4篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1962年 | 1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.
A series of long-chain quaternary ammonium halogen esters (UKK-chemicals), quaternary dimethyl tallow epoxypropyl ammonium
halogens (EPK1), quaternary ditallow methyl epoxypropyl ammonium halogens (EPK2), and EPK2 oligomers (EPK2P) were synthesized.
At acidic, neutral, or slightly basic conditions, EPK1-, EPK2-, EPK2P-, and UKK-chemicals operate as cationic chemicals. They
can be used, for example, as stock sizings, surface sizings, or fixatives. Stock sizing, surface sizing, and fixative experiments
indicate that EPK1-, EPK2-, EPK2P-, and UKK-chemicals function at least as well as or better than the corresponding synthetic
chemicals used in papermaking. 相似文献
13.
Shuichi Osanai Yoshiro Abe 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(1):43-45
Optically active and racemic quaternary ammonium cationics containing a chiral alkyl group, such as N,N-dimethyl-N-(1-phenylethyl)alkylammonium bromides were prepared and showed excellent antimicrobial properties against Gram positive and negative bacteria, with some exceptions, and against fungi. The influence of optical isomerism on their antimicrobial properties showed that the antimicrobial properties between racemic and optically active cationics were obscure. The order of activity of substituted alkyl groups was tetradecyl > dodecyl ° hexadecyl. 相似文献
14.
钼酸铵生产中杂质的分离方法 总被引:1,自引:0,他引:1
简要地介绍了钼酸铵生产中有害杂质的各种分离方达及应用情况,并就各种方法的利弊作了对比说明。 相似文献
15.
经试验发现应用一种化学肥料硫酸铵可以显著提高乌拉嘎金矿石的浮选回收率。闭路试验尾矿工艺矿物学鉴定证明,以硫酸铵作为调整剂的浮选过程中,微细粒单体金和金与石英边生体被有效回收。 相似文献
16.
17.
18.
The impinging streams technology (abbreviated as IS) has good micromixing in the precipitation processes. The experiments were loaded with two reactants, BaCl2 and Na2SO4, to prepare BaSO4 in the impinging streams reactor, comparing with those in the direct precipitation (DP) reactor. XRD and TEM were used to analyze the crystal type, the morphology and size of particles through the photographs. The results indicate the size of the particles from IS is about 30 nm and of narrower distribution and finer dispersibility than that from DP. 相似文献
19.
Jantana Tangaromsuk Abhijeet P. Borole Maleeya Kruatrachue Prayad Pokethitiyook 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1375-1380
BACKGROUND: A single‐stage reactor, in which the growth of bacterial culture, induction of desulfurizing enzymes, and desulfurization reaction are carried out in a single step, was adopted to investigate desulfurization of dibenzothiophene (DBT) at high cell densities. Rhodococcus erythropolis, IGTS8 was used as the biocatalyst. Optimal conditions for bacterial growth and DBT desulfurization were investigated. RESULTS: Optimization of fermentation conditions was necessary to obtain high cell densities including controlling accumulation of acetate. Under optimal operating conditions, the maximum optical density at 600 nm (OD600) was measured to be 26.6 at 118 h of cultivation. When biodesulfurization of DBT in model oil with a high cell density culture of IGTS8 was investigated, accumulation of sulfate was found to limit the extent of desulfurization. A sulfate removal step was added to obtain a single‐stage integrated biodesulfurization process. Sulfate removal was achieved via an aqueous bleed stream and use of a separation unit to recycle the organic phase. CONCLUSION: A proof of principle of a complete system capable of biocatalyst growth, induction, desulfurization and by‐product separation was demonstrated. This system enables simplification of the biodesulfurization process and has potential to lower the operating cost of the bioprocess. Copyright © 2008 Society of Chemical Industry 相似文献
20.
Andrea Engl Benno Kunz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):257-261
Studies took place to investigate the effects of different nutrient conditions on the biosorption ability and selectivity of heavy metals by Saccharomyces cerevisiae. After having grown in media supplemented with additional glucose, ammonium, phosphate or cysteine, the yeast was exposed to an equimolar solution of lead, cadmium, zinc and copper. Lead removal from a mixed solution was significantly higher than that of copper, followed by zinc and cadmium. Generally, yeasts from cysteine-rich media showed greatest sorption capacity whereas phosphate addition influenced zinc selectivity. In addition, glucose, fructose and sucrose as carbon sources were examined. Cultures grown in glucose had a better uptake than those cultivated with fructose at an incubation time of 30 min. 相似文献