全文获取类型
收费全文 | 2211篇 |
免费 | 125篇 |
国内免费 | 124篇 |
专业分类
电工技术 | 36篇 |
综合类 | 114篇 |
化学工业 | 829篇 |
金属工艺 | 614篇 |
机械仪表 | 37篇 |
建筑科学 | 8篇 |
矿业工程 | 43篇 |
能源动力 | 93篇 |
轻工业 | 4篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
武器工业 | 7篇 |
无线电 | 104篇 |
一般工业技术 | 422篇 |
冶金工业 | 116篇 |
原子能技术 | 18篇 |
自动化技术 | 8篇 |
出版年
2024年 | 6篇 |
2023年 | 38篇 |
2022年 | 44篇 |
2021年 | 57篇 |
2020年 | 68篇 |
2019年 | 64篇 |
2018年 | 60篇 |
2017年 | 92篇 |
2016年 | 78篇 |
2015年 | 53篇 |
2014年 | 72篇 |
2013年 | 130篇 |
2012年 | 120篇 |
2011年 | 164篇 |
2010年 | 133篇 |
2009年 | 146篇 |
2008年 | 123篇 |
2007年 | 160篇 |
2006年 | 170篇 |
2005年 | 133篇 |
2004年 | 137篇 |
2003年 | 84篇 |
2002年 | 64篇 |
2001年 | 49篇 |
2000年 | 40篇 |
1999年 | 39篇 |
1998年 | 35篇 |
1997年 | 28篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有2460条查询结果,搜索用时 31 毫秒
81.
A. Egetenmeyer I. Radev D. Durneata M. Baumgärtner V. Peinecke H. Natter R. Hempelmann 《International Journal of Hydrogen Energy》2017,42(19):13649-13660
Nanostructured Pt and Pt3Co cathodes for proton exchange membrane fuel cells (PEMFCs) have been prepared by pulse electrodeposition. For high utilization the catalyst nanoparticles are directly deposited on the microporous layer (MPL) of a commercial available gas diffusion layer (GDL). In order to increase the hydrophilic nature of the substrate surface and thus improve drastically the electrodeposition process and the fuel cell performance, prior to electrodeposition, the carbon substrate is submitted to O2/Ar plasma activation. Cathodes with different amounts and distributions of Aquivion ionomer within the cathode catalyst layer (CCL) thickness (“homogeneous”, “gradient” and “anti-gradient”), different catalysts (Pt and Pt3Co) at varied plasma duration and catalyst loading have been prepared. The cathodes are analysed via attenuated total reflection (ATR-IR), goniometer, SEM, 0.5 M H2SO4 half-cell and 25 cm2 H2/Air single PEMFC. The highest single fuel cell performance is obtained for 2 min plasma activated Pt3Co cathode. 相似文献
82.
Hiroaki NAKANO 《中国有色金属学会会刊》2009,19(4):835-841
Because the lightness, the gloss and the press-formability of electrogalvanized steel sheets change depending on the morphology of deposited Zn, control of this factor is essential to improving these properties. The effects of plating factors on the morphology of deposited Zn were systematically discussed both from the crystallographic viewpoint of epitaxy between Zn and steel and from the electrochemical viewpoint of the overpotential for Zn deposition. Plating factors include crystal orientation of steel substrate, current density, flow rate, temperature, addition of inorganic compounds to the solution and pre-adsorption of organic compounds. These plating factors affect the overpotential for Zn deposition and epitaxy between Zn and steel. The crystal orientation index of the Zn basal plane and the platelet crystal size of Zn are decreased with increasing the overpotential for Zn deposition. They are also decreased with decreasing the epitaxy between Zn and steel, even when the overpotential is kept constant. When the overpotential for Zn deposition is increased, the surface roughness of deposited Zn increases because of an increase in the inclination of the Zn basal plane to the steel substrate. When the epitaxy between Zn and steel is decreased without changing the overpotential, the surface roughness is reduced due to the decrease in platelet crystal size of Zn, although the inclination of the Zn basal plane is somewhat increased. The lightness of deposited Zn is enhanced with decreasing the surface roughness of Zn. 相似文献
83.
K.K. Kasem 《Journal of Applied Electrochemistry》2001,31(10):1125-1129
Novel solid films of a mixed polynuclear hexacyano iron(III) and decavanadates have been electrochemically prepared. The colour of these solid thin films ranged from yellow to blue depending on the thickness. The cyclic voltammograms (CVs) of these solid films indicate the involvement of both vanadium and iron redox centres in performing the electrochemical activities. Evidence of the catalytic activities of these films towards the reduction of some small oxoanions has been reported. 相似文献
84.
Current distribution measurements in through-hole electrodeposition were made on sectioned copper electrodes in a cylindrical flow channel. Two copper plating solutions with the same copper sulfate concentration but with different sulfuric acid concentrations were used. Experiments were conducted potentiostatically and under steady-state conditions. Results were compared with those from the theoretical model. 相似文献
85.
The aim of this work was to investigate the anti‐corrosive properties of nanocomposite Zn? Ni coatings containing Al2O3 nanoparticles, prepared from alkaline commercial electrolytes (pH 13), (PERFORMA 280.5, COVENTYA S.A.S, France), by electrodeposition on carbon steel (OL37). The corrosion resistance of the coatings prepared with different concentrations of Al2O3 (5, 10, and 15 g/L) was evaluated in 0.2 g/L Na2SO4 solution (pH 5) by open circuit potential (OCP) measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The results of electrochemical measurements were corroborated with those obtained by using X‐ray diffraction analysis. The obtained results show that the introduction of Al2O3 nanoparticles in the plating bath generally brings an increase in corrosion resistance of Zn? Ni layers and put in evidence the existence of an optimal Al2O3 concentration. Under the examined conditions, the optimal concentration determined from polarization measurements was proven to be 5 g/L Al2O3. The highest value of the polarization resistance, Rp, obtained from impedance measurements corresponds also to Zn? Ni with 5 g/L Al2O3, which is in agreement with the results obtained from polarization and XRD measurements. 相似文献
86.
CdSxSe1−x films of different composition (0 < x < 1) were deposited by pulse plating technique at different duty cycles in the range of 10-50%. The films were polycrystalline and exhibited hexagonal structure. The band gap of the films varies from 1.68 to 2.39 eV as the concentration of CdS increases. Energy Dispersive analysis of X-rays (EDAX) measurements indicate that the composition of the films are nearly the same as that of the precursors considered for the deposition. Atomic force microscopy studies indicated that the grain size increased from 20 to 200 nm as the concentration of CdSe increased. Photoelectrochemical (PEC) cell studies indicated that the films of composition CdS0.9Se0.1 exhibited maximum photoactivity. Mott-Schottky studies indicated that the films exhibit n-type behaviour. Spectral response measurements indicated that the photocurrent maxima occurred at the wavelength value corresponding to the band gap of the films. 相似文献
87.
铝在路易斯酸性1-烯丙基-3甲基米唑氯铝酸离子液体中的低温电沉积(英文) 总被引:1,自引:0,他引:1
Lewis acidic 1-allyl-3-methylimidazolium chloroaluminate ionic liquids were used as promising elec-trolytes in the low-temperature electrodeposition of aluminium.Systematic studies on deposition process have been performed by cyclic voltammetry and chronoamperometry.The surface morphology and X-ray diffraction(XRD) patterns of deposits prepared at different experimental conditions were also investigated.It was shown that the nu-cleation density and growth rate of crystallites had a great effect on the structure of aluminium deposited.The crys-tallographic orientation of deposits was mainly influenced by temperature and current density.Smooth,dense and well adherent aluminium coatings were obtained on copper substrates at 10-25 mA?cm?2 and 313.2-353.2 K.More-over,the current efficiency of deposition and purity of aluminium have been significantly improved,demonstrating that the ionic liquids tested have a prospectful potential in electroplating and electrorefining of aluminium. 相似文献
88.
Galvanostatic nucleation of copper onto pretreated ruthenium is investigated using experimental methods and numerical simulations in the presence of two different suppressor molecules; polyethylene glycol (PEG) and ethylene glycol-propylene glycol-ethylene glycol block copolymer (EPE). The model parameters have been largely determined from electrochemical characterization. Results suggest that a fast adsorption rate of the suppressor results in higher nucleus densities. Simulation results provide insight why EPE is more effective than PEG at increasing nucleus density. In addition, the simulations are used to predict the impact of pulse plating paramaters, showing that both the properties of the additive and the waveform need to be considered to optimize nucleus density enhancement. 相似文献
89.
Francisco Alcaide Garbiñe Álvarez José Alberto Blázquez Pere L. Cabot Oscar Miguel 《International Journal of Hydrogen Energy》2010
This paper presents, for the first time, a five-cell polymer electrolyte membrane fuel cell (PEMFC) short stack with electrodeposited hydrogen diffusion anodes. The anodes were manufactured by means of galvanostatic pulse electrodeposition and the cathodes by air-brushing. Nafion® 212 was employed as a solid polymer electrolyte membrane in all cases. The short stack, whose cells had an active geometric area of 14 cm2, was assembled and tested under different operating conditions. A peak power of about 11 W was obtained at 50 °C and atmospheric pressure using hydrogen and air feed, whereas a smaller value of 8.6 W was obtained from a five-cell short PEMFC stack with conventional hydrogen diffusion anodes under the same operating conditions. The better performance of the cells described in this paper has been assigned to the higher utilization of the platinum in the electrodeposited anodes compared to the conventional ones. 相似文献
90.
Enhancement of hydrogen evolution at cobalt-zinc deposited graphite electrode in alkaline solution 总被引:1,自引:0,他引:1
Ali DönerRamazan Solmaz Gülfeza Karda? 《International Journal of Hydrogen Energy》2011,36(13):7391-7397
Thin Co layers were electrochemically deposited on a graphite electrode at different deposition current densities and thicknesses. After determining the best deposition conditions for hydrogen evolution (deposition current density and thickness), co-deposits of Co with Zn were prepared on the graphite electrode. The binary coatings prepared on the graphite electrode (CoZn) were etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). After the leaching process, a low amount of Pt was deposited onto the etched CoZn deposit in order to further improve the catalytic activity of the electrode for the HER. The HER activity is assessed by recording cathodic current-potential curves, electrochemical impedance spectroscopy (EIS) and electrolysis techniques. Chemical composition of layers after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies of coatings were investigated by scanning electron microscopy (SEM). It was found that, the HER activity of coatings depends on the metal ratio of Co and Zn, deposition current density and the thickness of coatings. The alkaline leached CoZn coating has a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media. Moreover, deposition of a low amount of Pt over the CoZn can further enhance its hydrogen evolution activity. 相似文献