全文获取类型
收费全文 | 6927篇 |
免费 | 395篇 |
国内免费 | 97篇 |
学科分类
工业技术 | 7419篇 |
出版年
2024年 | 28篇 |
2023年 | 91篇 |
2022年 | 110篇 |
2021年 | 186篇 |
2020年 | 166篇 |
2019年 | 158篇 |
2018年 | 112篇 |
2017年 | 177篇 |
2016年 | 182篇 |
2015年 | 173篇 |
2014年 | 284篇 |
2013年 | 311篇 |
2012年 | 427篇 |
2011年 | 479篇 |
2010年 | 341篇 |
2009年 | 388篇 |
2008年 | 345篇 |
2007年 | 471篇 |
2006年 | 486篇 |
2005年 | 386篇 |
2004年 | 363篇 |
2003年 | 307篇 |
2002年 | 276篇 |
2001年 | 228篇 |
2000年 | 161篇 |
1999年 | 160篇 |
1998年 | 112篇 |
1997年 | 99篇 |
1996年 | 60篇 |
1995年 | 61篇 |
1994年 | 50篇 |
1993年 | 34篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1968年 | 2篇 |
1964年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有7419条查询结果,搜索用时 156 毫秒
91.
以两性离子单体二甲氨基丙基丙烯酰胺-1-羧酸(ZM)、木薯淀粉(CSt)和聚乙烯醇(PVA)为主要原料,采用"一锅法",通过冷冻交联制备ZM接枝共聚CSt-PVA互穿网络复合凝胶(ZPG2)。使用FTIR、TGA、POM、SEM-EDS对ZPG2进行了表征,评价了ZPG2对Cu~(2+)的静态吸附效果。结果表明:300℃以下,ZPG2的热稳定性良好;ZM的存在可产生反聚电解质效应和化学配位效应,显著提高凝胶吸附能力;在吸附温度25℃、ZPG20.1 g、Cu~(2+)质量浓度2×10~3 mg/L、溶液体积100 mL时,饱和吸附量为199 mg/g;吸附过程符合Langmuir等温吸附模型和准二级动力学模型。 相似文献
92.
Lipase-catalyzed alcoholysis of soy phospholipids was investigated to simultaneously make lysophospholipids and fatty acid
esters of individual alcohols. Alcoholysis was carried out by stirring a mixture of soy phospholipids and individual alcohols
in equimolar proportions with 10% (by weight of reactants) Mucor miehei lipase at 55°C for 24 h. The products were isolated by column chromatography after removal of the lipase. Lysophospholipids
(in 69–78% molar yield) were obtained from soy phospholipids, and the yield of esters of various alcohols also conformed nearly
with theoretical yields. 相似文献
93.
94.
Poly(vinyl alcohol)-borate (PVA-borate) aqueous solutions properties with PVA concentrations ranging from 2 to 60 g/L and borax concentrations of 0.0 and 0.2 M were investigated at room temperature using static and dynamic light scattering (SLS and DLS), and dynamic viscoelasticity measurements. Light scattering and viscoelasticity data revealed that all the PVA-borate aqueous systems, except those with [PVA]≥40 g/L and [borax]=0.2 M, behaved as solutions. For PVA-borate aqueous systems with [PVA]≥40 g/L and [borax]=0.2 M, light scattering data revealed that these systems behaved like gels, but viscoelasticity data showed that these systems were in flow states. The experimental data suggest that PVA-borate aqueous systems with [PVA]≥40 g/L and [borax]=0.2 M are thermoreversible gels with finite equilibrium life time of thermoreversible borate-PVA di-diol crosslinks. The thermoreversible crosslinks can be observed by the non-perturbing light scattering technique but not by the pertubing rheometric method. These results indicate the advantage of light scattering relative to rheometers for studying the physical or reversible crosslink gels. 相似文献
95.
甲磺酸伊马替尼的合成 总被引:3,自引:0,他引:3
以4-甲基-3-硝基苯胺为起始原料,经过缩合、还原、环合等反应制得抗肿瘤药物甲磺酸伊马替尼。并分别讨论了采用无水碳酸钾代替二异丙基乙胺、水合肼和普通催化剂代替铂炭催化剂以及采用异戊醇作为溶剂的优点。最终反应总收率超过50%,用高效液相色谱分析产品纯度在99.5%以上。 相似文献
96.
介绍国内外脂肪醇聚氧乙烯醚(AE)和脂肪醇聚氧乙烯醚硫酸盐(AES)的生产现状及供需情况.2003年全球AE的总产能为391.7万t/a,总产量为155.8万t,总消费量为148.3万t;AES的总产能为377.5万t/a,产量约为300万t,消费量约为90万t.2004年我国AE的产能已超过50万t/a,但产量只有15万t,消费量为30.5万t;AES的总产能为37.95万t/a,产量为14万t,市场需求约10万t.最后补充介绍乙氧基化的技术进展. 相似文献
97.
Wey Yang Teoh Frans Denny Rose Amal Donia Friedmann Lutz Mädler Sotiris E. Pratsinis 《Topics in Catalysis》2007,44(4):489-497
A comparative photocatalytic analysis was carried out on TiO2 made in a Flame Spray Pyrolysis (FSP) process and flame-made Degussa P25. Both have similar crystallinity, phase composition,
phase segregation and a non-porous surface. Hence comparison was made based on their difference in specific surface area,
organic adsorption and the amount of OH• generated upon illumination. The photocatalytic activity tests were carried out using
the following series of organic compounds: sucrose, glucose, fructose, maleic acid, glyoxylic acid, oxalic acid, isobutyric
acid, phenol and methanol. FSP-made TiO2 outperformed P25 for saccharides mineralisation, while for phenol and methanol mineralisation P25 was better than FSP-made
TiO2. Similar mineralisation rates were observed for both FSP-made and P25 TiO2 for the mineralisation of carboxylic acids. This shows that the relative performance of the photocatalysts depends on the
type of organic compounds to be degraded. The high surface area and possibly a more efficient interfacial charge transfer
of FSP-made TiO2 provided an efficient pathway for saccharides mineralisation. As for phenol and methanol, the mineralisation rates were higher
when using P25 due to the greater amount of OH• radicals generated by this photocatalyst. The fast mineralisation rates of
carboxylic acids made degradation of these organic compounds to be less affected by the TiO2 photocatalyst properties and conditions tested in this work. 相似文献
98.
Anthony J. O'Lenick Jr. Jeffrey K. Parkinson 《Journal of the American Oil Chemists' Society》1996,73(7):935-937
A study was undertaken to determine the surfactant properties of various sulfated alcohols. Most notably, the Krafft point
and the ability to emulsify decane were studied. A series of sulfated Guerbet alcohol and Guerbet alcohol alkoxylate sulfates
with 16 carbon atoms and an analogous series based upon cetyl alcohol, a linear C16, were studied as hydrophobes. 相似文献
99.
使用糠醇单体在多孔氧化铝管的内表面成功制备了炭分子筛膜。其制备采用了3种方法:(Ⅰ)将酸性催化剂加入到糠醇中使糠醇聚合,然后采用浸渍法涂膜;(Ⅱ)先将催化剂浸渍在支撑体上,然后将支撑体浸入到糠醇溶液中制膜;(Ⅲ)先将催化剂浸渍在支撑体上,然后将支撑体置于糠醇蒸汽中制膜。方法Ⅱ制备的炭膜质量最大。方法Ⅲ制备的炭膜质量次之,方法Ⅰ制备的炭膜质量最小。方法Ⅲ制得的炭膜具有最好的气体选择性,CO2/N2的理想选择性为79.3,O2/N2的理想选择性为10.6,方法Ⅰ、Ⅱ制得的炭膜的气体分离性能相近,CO2/N2的理想选择性为20,O2/N2的理想选择性为6。 相似文献
100.
Gao Sujun Zhang Daijia Sun Yaqin Xiu Zhilong 《Frontiers of Chemical Engineering in China》2007,1(2):202-207
The separation of 1,3-propanediol from the glycerol-based fermentation broth of Klebsiella pneumoniae plays an important role during the microbial production of 1,3-propanediol. In this paper, the separation of 1,3-propanediol
from fermentative broth by a combination of ultrafiltration and alcohol dilution crystallization was investigated. The broth
was first filtered by ultrafiltration, and 99% of cells, 89.4% of proteins and 69% of nucleic acids were removed. The obtained
broth was further condensed by vacuum distillation, and then alcohol was added. The macromolecular impurities, such as nucleic
acids, polysaccharides and proteins, were precipitated, and inorganic and organic salts were crystallized. The optimal volume
ratio of alcohol added to the condensed fermentation broth was determined to be 2:1. As a result, proteins, nucleic acids
and electric conductivity decreased by 97.4%, 89.7% and 95.8%, respectively, compared with the fermentative broth. The influences
of pH and water content in condensed broth on alcohol precipitation and dilution crystallization were also investigated. The
experimental results indicated that alcohol precipitation and dilution crystallization was feasible and effective for the
separation of 1,3-propanediol from actual fermentation broth.
Translated from The Chinese Journal of Process Engineering, 2006, 6(3): 454–457 [译自: 过程工程学报] 相似文献