全文获取类型
收费全文 | 10901篇 |
免费 | 963篇 |
国内免费 | 478篇 |
专业分类
电工技术 | 216篇 |
技术理论 | 1篇 |
综合类 | 715篇 |
化学工业 | 6465篇 |
金属工艺 | 470篇 |
机械仪表 | 147篇 |
建筑科学 | 250篇 |
矿业工程 | 367篇 |
能源动力 | 207篇 |
轻工业 | 942篇 |
水利工程 | 66篇 |
石油天然气 | 482篇 |
武器工业 | 118篇 |
无线电 | 160篇 |
一般工业技术 | 1031篇 |
冶金工业 | 568篇 |
原子能技术 | 89篇 |
自动化技术 | 48篇 |
出版年
2024年 | 38篇 |
2023年 | 136篇 |
2022年 | 244篇 |
2021年 | 352篇 |
2020年 | 282篇 |
2019年 | 262篇 |
2018年 | 240篇 |
2017年 | 423篇 |
2016年 | 448篇 |
2015年 | 409篇 |
2014年 | 538篇 |
2013年 | 640篇 |
2012年 | 806篇 |
2011年 | 836篇 |
2010年 | 605篇 |
2009年 | 595篇 |
2008年 | 512篇 |
2007年 | 673篇 |
2006年 | 593篇 |
2005年 | 539篇 |
2004年 | 477篇 |
2003年 | 393篇 |
2002年 | 377篇 |
2001年 | 300篇 |
2000年 | 295篇 |
1999年 | 257篇 |
1998年 | 178篇 |
1997年 | 142篇 |
1996年 | 110篇 |
1995年 | 115篇 |
1994年 | 98篇 |
1993年 | 77篇 |
1992年 | 75篇 |
1991年 | 51篇 |
1990年 | 45篇 |
1989年 | 25篇 |
1988年 | 29篇 |
1987年 | 41篇 |
1986年 | 26篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977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
31.
32.
磷酸酯淀粉在纯棉细特高密织物浆纱中的应用 总被引:2,自引:0,他引:2
就磷酸酯淀粉在纯棉细号高密织物中的上浆情况进行了试验,提出了具体浆纱工艺和减少织造断头率,提高织物效率及布面质量对策,实验表明,磷酸酯淀粉完全适应于纯绵细特高密织物的上浆要求。 相似文献
33.
34.
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
35.
Hauke Harms Hans-Peter Volkland Andreas Hiltpolt Alexander J.B Zehnder 《Corrosion Science》2003,45(8):1717-1732
To study the effect of strong iron-ligands on steel corrosion, mild steel electrodes were immersed in solutions containing 20 mM phosphate buffer (pH=7.2) and between 0.01 mM and 1 M of either the iron(II)-chelators 2,2′-bipyridine or FerroZine, or the iron(III)-chelators citrate or acetylacetonate. Resulting surface reactions were investigated by quantifying the electrochemical potential (E), the electrochemical polarization resistance (Rp), the corrosion current (Icorr) and the release of iron into solution. The surface was further analyzed by scanning electron microscopy (SEM/SEM-EDAX) and atomic force microscopy. Concentrations of 0.1 mM of any of the chelators led to slight, temporary changes in E, Icorr and Rp. Concentrations of 10 mM resulted in characteristic changes of E, which were the same for all chelators and in the precipitation of FePO4 in the case of citrate and acetylacetonate, or vivianite [Fe3(PO4)2 · 8H2O] in the case of bipyridine and FerroZine. Concentrations of 1 mM of both iron(III)-chelators led to a temporary drop of E similar to that found with 0.1 mM chelator. With iron(II)-chelators, E dropped to about −500 mV before oscillating for several days. The amplitudes of the oscillations were up to 200 mV with periods of 30 and 20-25 min for bipyridine and FerroZine, respectively. 相似文献
36.
合成了十六烷基辛基二甲基溴化铵和十六烷基癸基二甲基溴化铵两个新型杀生剂。用元素定量分析和红外光谱核磁共振谱等方法进行分析和结构鉴定。评定了两个化合物对硫酸盐还原菌的杀生作用。结果表明,两个化合物有很好的杀生效果。 相似文献
37.
The fractions obtained from bagasse after activation with 17.5% NaOH, alternative alkylation with quarternary ammonium groups and extraction with 80% ethanol, water and 5% NaOH, were analyzed using pyrolysis-field ionization mass spectrometry (Py-FIMS). The proposed degradation products from lignin were mostly symmetric fragments containing two aromatic rings while the compounds formed from polysaccharides were the result of dehydration reactions. From the temperature-resolved Py-FIMS it could be seen that ethanol-lignin starts to degrade at temperatures lower than 180°C before the degradation of the hemicellulose fraction. The lignin markers are eliminated from hemicellulose fractions before the polysaccharide gasification starts. The quarternary ammonium groups are cleaved from the fractions at temperatures lower than 200°C. 相似文献
38.
39.
以椰油酸甲酯、单乙醇胺,P2O5等为原料制备一种新型阴离子表面活性剂-烷醇酰胺磷酸酯盐。初步探讨了工艺条件,测定了其物化性能。 相似文献
40.
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