全文获取类型
收费全文 | 229篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 95篇 |
金属工艺 | 6篇 |
机械仪表 | 6篇 |
建筑科学 | 2篇 |
能源动力 | 16篇 |
轻工业 | 12篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 32篇 |
冶金工业 | 18篇 |
原子能技术 | 7篇 |
自动化技术 | 23篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 23篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 16篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1963年 | 1篇 |
1947年 | 2篇 |
1944年 | 1篇 |
1942年 | 1篇 |
排序方式: 共有242条查询结果,搜索用时 31 毫秒
51.
52.
53.
BSS: block-based sharing scheme for secure data storage services in mobile cloud environment 总被引:1,自引:0,他引:1
Abdul Nasir Khan M. L. Mat Kiah Mazhar Ali Sajjad A. Madani Atta ur Rehman Khan Shahaboddin Shamshirband 《The Journal of supercomputing》2014,70(2):946-976
For the last few years, academia and research organizations are continuously investigating and resolving the security and privacy issues of mobile cloud computing environment. The additional consideration in designing security services for mobile cloud computing environment should be the resource-constrained mobile devices. The execution of computationally intensive security services on mobile device consumes battery’s charging quickly. In this regard, the study presents a novel energy-efficient block-based sharing scheme that provides confidentiality and integrity services for mobile users in the cloud environment. The block-based sharing scheme is compared with the existing schemes on the basis of energy consumption, CPU utilization, memory utilization, encryption time, decryption time, and turnaround time. The experimental results show that the block-based sharing scheme consumes less energy, reduces the resources utilization, improves response time, and provides better security services to the mobile users in the presence of fully untrusted cloud server(s) as compared to the existing security schemes. 相似文献
54.
Ayman M. Atta Manar E. Abdel-Rauf Nermine E. Maysour A. M. Abdul-Rahiem Abdel-Azim A. Abdel-Azim 《Journal of Polymer Research》2006,13(1):39-52
Recycled poly (ethylene terephthalate), PET, can be modified to produce nonionic surfactants. Recycling of PET waste was carried
out in presence of different weight ratios of diethanolamine and triethanolamine and manganese acetate as catalyst. The molecular
weights of the prepared oligomers were calculated from hydroxyl number and determined from GPC measurements. The produced
oligomers were reacted with polyethylene glycol, PEG, which have different molecular weights 400, 1000 and 4000. Interfacial
tension and the effectiveness in oil dispersion of the synthesized surfactants were reported. It was found that, the maximum
efficiency of oil spill dispersants was reached to maximum when the surfactant molecules ended with two PEG 1000 moities. 相似文献
55.
Ayman M. Atta Rasha A. M. El-Ghazawy Reem K. Farag Abdel-Azim A. Abdel-Azim 《Journal of Polymer Research》2006,13(4):257-266
Cinnamoyloxy ethyl methacrylate (CEMA) monomer was copolymerized with different monomer feed ratios of alkyl acrylate, such as dodecyl and octadecyl acrylate DDA and ODA, respectively. The monomers were copolymerized with different mole% to produce different compositions for each CEMA/alkylacrylate copolymer with low conversion. 1HNMR was used to determine the copolymer compositions. The monomer reactivity ratios of each CEMA/alkylacrylate copolymer were determined using Fineman-Ross and Kelen-Tudos methods. CEMA was copolymerized with DDA or ODA and crosslinked using azobis isobutyronitrile (AIBN) as the initiator and 1% weight content of either 1,1,1-trimethylolpropane triacrylate (TPT) or 1,1,1-trimethylolpropane trimethacrylate (TPTm) crosslinkers. The swelling parameters, such as the maximum oil absorbency (Q
max), characteristic oil sorbency (Q), characteristic swelling time (T), and swelling rate constant (k), were evaluated for the synthesized sorbers. The network parameters, such as the polymer solvent interaction (χ), effective crosslink density (υ
e), equilibrium modulus of elasticity (G
T), average molecular weight between crosslinks (M
c), and the theoretical crosslink density (υ
t), were determined and correlated with the structure of the synthesized sorbers. 相似文献
56.
Heba Ahmed Amgad R. Rezk Benjamin J. Carey Yichao Wang Md Mohiuddin Kyle J. Berean Salvy P. Russo Kourosh Kalantar‐zadeh Leslie Y. Yeo 《Advanced materials (Deerfield Beach, Fla.)》2018,30(20)
While the remarkable properties of 2D crystalline materials offer tremendous opportunities for their use in optics, electronics, energy systems, biotechnology, and catalysis, their practical implementation largely depends critically on the ability to exfoliate them from a 3D stratified bulk state. This goal nevertheless remains elusive, particularly in terms of a rapid processing method that facilitates high yield and dimension control. An ultrafast multiscale exfoliation method is reported which exploits the piezoelectricity of stratified materials that are noncentrosymmetric in nature to trigger electrically‐induced mechanical failure across weak grain boundaries associated with their crystal domain planes. In particular, it is demonstrated that microfluidic nebulization using high frequency acoustic waves exposes bulk 3D piezoelectric crystals such as molybdenum disulphide (MoS2) and tungsten disulphide (WS2) to a combination of extraordinarily large mechanical acceleration (≈108 m s?2) and electric field (≈107 V m?1). This results in the layered bulk material being rapidly cleaved into pristine quasi‐2D‐nanosheets that predominantly comprise single layers, thus constituting a rapid and high throughput chip‐scale method that opens new possibilities for scalable production and spray coating deposition. 相似文献
57.
Numerical simulation of flow and heat transfer in two adjacent channels is conducted with one of the channels partially blocked. This system simulates typical channels of a material testing reactor. The blockage is assumed due to the buckling of one of the channel plates inward along its width. The blockage ratio considered in this work is defined as the ratio between the cross-sectional area of the blocked and the unblocked channel. In this work, we consider a blockage ratio of approximately 40%. However, the blockage is different along the width of the channel, ranging from 0% at the end of the channel to 90% in the middle. The channel walls are sandwiching volumetric heat sources that vary spatially as chopped cosine functions. Interesting patterns are highlighted and investigated. The reduction in the flow area of one channel results in the flow redistributing among the two channels according to the changes in their hydraulic conductivities. The results of the numerical simulations show that the maximum wall temperature in the blocked channel is well below the boiling temperature at the operating pressure. 相似文献
58.
The electrodeposition of sub-micro/nano-size Pt–Pd co-catalyst on conducting poly(3-methylthiophene) (PMT) films and the use
of the resulting hybrid material for the oxidation of methanol are reported. Several factors affecting the electrocatalytic
activity for this process were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), namely,
the polymer film thickness, and the catalyst amount/ratio. In addition, the effects of methanol concentration and the operating
temperature were also investigated. Thermal gravimetric analysis (TGA) showed that the thermal stability of the polymer film
increased by the incorporation of the metallic particles. Scanning electron micrographs (SEM) were obtained to identify the
relative size of the metallic particles and their distribution. The size ranged between 3 μm and 500 nm. Energy dispersive
X-rays analysis (EDAX) was performed to identify the composition of the metallic particles. It was found that the particle
composed of Pt and Pd in ratio that is comparable to that present in the feed solution. 相似文献
59.
Ayman M Atta 《Polymer International》2007,56(8):984-995
Poly(ethylene terephthalate) waste was recycled to oligomers in the presence of diethanolamine and manganese acetate as a catalyst. The oligomers produced were reacted with stearic acid and poly(ethylene glycol) with different number average molecular weights of 400, 1000 and 4000 g mol?1 to produce nonionic polymeric surfactants having different hydrophile–hydrophobe balances. The surface tension, critical micelle concentration and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γmax), the area per molecule at interface (Amin) and the effectiveness of surface tension reduction (ΠCMC) were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption process were calculated and are discussed. Copyright © 2007 Society of Chemical Industry 相似文献
60.
Aiman M Atta 《Polymer International》1999,48(7):571-579
A series of maleic diester monomers have been prepared by esterification of maleic anhydride with a series of n-alkanols and poly(ethylene glycol) with different molecular weights. These monomers were polymerized in acetic anhydride solution in the presence of cumene hydroperoxide as initiator. The synthesized polymers have been characterized by IR and 1H NMR spectroscopy, and their surface and thermodynamic properties as non-ionic surfactants is investigated. The surface tension as a function of concentration of the surfactant in aqueous solutions was measured at 298, 308, 318 and 328 K. The surface parameters are calculated. The data reveal that the CMC value of the polymeric surfactant is lower than that of the monomeric surfactant. It is also found that the CMC value decreases with increasing temperature and the number of ethylene oxide units in the surfactant molecule. The thermodynamic parameters of micellization and adsorption are also determined. The structural effectiveness of surface tension is discussed in terms of these parameters. © 1999 Society of Chemical Industry 相似文献