全文获取类型
收费全文 | 640篇 |
免费 | 12篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 7篇 |
综合类 | 38篇 |
化学工业 | 279篇 |
金属工艺 | 7篇 |
机械仪表 | 12篇 |
建筑科学 | 19篇 |
矿业工程 | 8篇 |
能源动力 | 27篇 |
轻工业 | 131篇 |
石油天然气 | 25篇 |
无线电 | 4篇 |
一般工业技术 | 20篇 |
冶金工业 | 12篇 |
原子能技术 | 3篇 |
自动化技术 | 66篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 55篇 |
2012年 | 30篇 |
2011年 | 36篇 |
2010年 | 20篇 |
2009年 | 37篇 |
2008年 | 33篇 |
2007年 | 35篇 |
2006年 | 30篇 |
2005年 | 41篇 |
2004年 | 37篇 |
2003年 | 46篇 |
2002年 | 21篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 23篇 |
1998年 | 24篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有658条查询结果,搜索用时 312 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(99):41920-41931
A polymer electrolyte membrane is considered as the heart of fuel cells. Here we report the preparation of proton exchange membranes (PEMs) of poly (vinylidene fluoride) (PVDF) blend poly (methyl methacrylate)-co-poly (sodium-4-styrene sulfonate) (PMMA-co-PSSNa) by solvent evaporation method. Three different types of PEMs have been prepared by using different ratios of PVDF and PMMA-co-PSSNa copolymer. We have investigated the effect of concentration of PVDF on water uptake, ion exchange capacity, mechanical, thermal, and oxidative stability, proton conductivity (Km), and methanol permeability (PM) of the blend membranes. These blend PEMs showed good physicochemical and electrochemical properties along with thermal and oxidative stability. The membrane prepared from PVDF (45% w/w) to PMMA-co-PSSNa (55% w/w) exhibited optimum PM at room temperature (8.38 × 10?7 cm2s?1). This low fuel crossover and high relative selectivity can make our prepared blend membranes a potential candidate in polymer electrolyte membrane fuel cells (PEMFCs) or direct methanol fuel cells (DMFCs). 相似文献
2.
Stability of Cold-Pressed Oil from Commercial Indian Niger (Guizotia abyssinica (L.f.) Cass.) Seed as affected by Blending and Interesterification 下载免费PDF全文
A. S. Bhatnagar A. G. Gopala Krishna 《Journal of the American Oil Chemists' Society》2015,92(11-12):1671-1680
Blending and interesterification of cold‐pressed oil from commercially available niger (Guizotia abyssinica (L.f.) Cass.) seeds was performed to improve its stability. The fatty acid composition of cold‐pressed niger seed oil (NSO) revealed that it contained a huge amount of polyunsaturated linoleic acid (69.2 %). NSO being rich in polyunsaturated fatty acids (PUFA) was susceptible to oxidation and hence was blended with saturated fatty acid (SFA) rich coconut oil (CNO) and monounsaturated fatty acid (MUFA) rich olive–pomace oil (OO) to enhance its stability. CNO contained a total of 91.3 % of SFA, while OO had oleic acid, C18:1 (74.3 %) as MUFA. Two blends of NSO with CNO and OO, i.e. NSO + CNO(B) and NSO + OO(B), were prepared in the ratio of 1:1. The blends were further interesterified using the lipase enzyme from Rhizomucor meihei and interesterified oils, i.e. NSO + CNO(I) and NSO + OO(I), were obtained. The oxidative stability of the oils was evaluated by incubating them at 37 °C and 55 % relative humidity (RH) for a period of 45 days. The peroxide values of NSO + CNO(B), NSO + OO(B), NSO + CNO(I) and NSO + OO(I) showed a reduction by 53.3, 42.6, 65.3 and 55.4 %, respectively, while the conjugated diene values showed a reduction by 75.0, 66.9, 76.7 and 75.3 %, respectively, as compared to NSO during the incubation period. This is probably the first report on the stability improvement of niger seed oil through blending and interesterification. 相似文献
3.
采用熔融共混法将丙烯腈-丁二烯-苯乙烯共聚物(ABS)与多壁碳纳米管(MWCNT)复合,并对所得的复合材料进行了力学性能、热性能和电学性能分析。结果表明,添加MWCNT能够提高复合材料的力学性能、电导率和耐热性,力学性能在MWCNT添加量为2%时最佳,电导率随MWCNT添加量的增加而增大,MWCNT添加量为4%时,其电导率能达到4.35×10-6S/m。将添加4%MWCNT的复合材料拉丝,然后以三种打印方向进行熔融沉积(FDM)打印,研究了打印试样的力学性能,用扫描电镜(SEM)观察了其断面形貌。结果表明,水平方向打印的试样力学强度最好,侧向打印的试样次之,垂直方向打印的样品由于仅靠丝材的层间黏结,其力学强度比较差,与纯ABS丝材打印试样相比,复合丝材打印试样的拉伸强度和弯曲强度均有明显提高,冲击强度有所下降。 相似文献
4.
Diesel hydro-processing (DHP) is an important refinery process which removes the undesired sulfur from the oil feedstock followed by hydro-cracking and fractionation to obtain diesel with desired properties. The DHP plant operates with varying feed-stocks. Also, changing market conditions have significant effects on the diesel product specifications. In the presence of such a dynamic environment, the DHP plant has to run in the most profitable and safe way and satisfy the product requirements. In this study, we propose a hierarchical, cascaded model predictive control structure to be used for real-time optimization of an industrial DHP plant. 相似文献
5.
In this study, combustion from the co-firing of coal and wood biomass, and thermal characteristics such as ignition temperature, burn-out temperature, and activation energy were discussed using a thermogravimetric analyzer (TGA). We investigated the effects of biomass blending with two kinds of pulverized coal (bituminous Shenhua, and sub-bituminous Adaro) under air and oxy-fuel conditions. The coal fraction in the blended samples was set to 1, 0.8, and 0.5. The oxygen fraction in the oxidant was set to 0.21, 0.3, 0.5, and 0.8. The ignition temperature was governed by the fuel composition, particularly in the blended biomass which has a much higher content of volatile matter comparing to coal. However, the burnout temperature, which shows a strong relationship with char combustion, depended on the oxidant ingredients rather than on the fuel components. Thermal characteristics such as ignition, burnout temperature, reaction region, and heat flow were very similar between air and a 0.3 oxygen concentration under oxy-fuel conditions with Shenhua coal. 相似文献
6.
采用扩链剂2,4-甲苯二异氰酸酯(TDI)、2,2′-双(2-恶唑啉)(BOZ)以及新型扩链剂ADR-4370对聚丁二酸丁二醇酯(PBS)进行扩链,对比研究3种扩链剂对PBS性能的影响。采用聚乳酸(PLA)与PBS共混,选择最佳配比以及合适的共混工艺。结果表明,新型扩链剂ADR-4370可以良好的改善PBS的加工性能和机械性能,m(PBS)/m(PLA)最佳配比为70:30,在共混同时进行扩链比扩链后再共混可以更好的提高PBS/PLA的性能。 相似文献
7.
采用扩链剂2,4甲苯二异氰酸酯(TDI)、2,2'-双(2-恶唑啉)(BOZ)以及新型扩链剂ADR-4370对聚丁二酸丁二醇酯(PBS)进行扩链,研究了三种扩链剂对PBS性能的影响。采用聚乳酸(PLA)与PBS共混,选择最佳配比以及合适的共混工艺。结果表明:新型扩链剂ADR-4370可以明显改善PBS的加工性能和力学性能,PBS/PLA最佳配比为70:30,在共混同时进行就地增容扩链改性可以更好地提高PBS/PLA的性能。 相似文献
8.
聚苯硫醚共混改性研究进展 总被引:1,自引:0,他引:1
概述了聚苯硫醚(PPS)与弹性体、通用塑料、工程塑料、特种工程塑料和其他聚合物的共混改性研究,并展望了PPS合金的发展前景。 相似文献
9.
10.
A. J. Groszek 《摩擦学汇刊》2013,56(4):490-496
High-surface-area graphites, that can be prepared by grinding synthetic graphites in vibratory ball mills, can be used in a novel refining technique which can markedly reduce pour points of various petroleum distillates and can be used to prepare oil fractions with high viscosity indices. The treatment also lowers the content of aromatic and sulfur compounds and completely eliminates polycyclic aromatics. Some of the oils obtained by selective adsorption on graphite may well have some of the desirable properties of naphthenic oils and also constitute improved base stocks for multigrade lubricating oils, oils for gas-turbine engines, hydraulic oil and transmission lubricants. Results obtained to date indicate that graphite refining can produce oils similar to those that can be obtained by super-refining treatment i.e., high pressure hydrogenation and deep dewaxing. Otherwise, the process can be used to prepare good quality base oils in one step, thus eliminating furfural extraction, dewaxing and ferrofining or clay contacting. A notable feature of base oils prepared by this new process is then relatively low viscosity at low temperatures (0°F) which makes them good candidates for the preparation of lubricating oils with fuel saving properties. 相似文献