全文获取类型
收费全文 | 126篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 48篇 |
金属工艺 | 5篇 |
机械仪表 | 6篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 9篇 |
水利工程 | 3篇 |
无线电 | 5篇 |
一般工业技术 | 33篇 |
冶金工业 | 1篇 |
原子能技术 | 1篇 |
自动化技术 | 5篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 19篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2003年 | 1篇 |
2001年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 0 毫秒
141.
Hung-Yu Tien Mahesh Tanniru Chang-Yu Wu Fereshteh Ebrahimi 《International Journal of Hydrogen Energy》2009
The hydrogen capacity of magnesium is usually below its theoretical value of 7.6 wt.% hydrogen. Based on the model that hydrogen capacity is reached when the hydride colonies/grains nucleated on the surface of Mg powders impinge on each other, we designed two hydrogenation methods in order to shed light on the effect of hydride nucleation rate on the hydrogen capacity of a commercial pure magnesium powder. We have demonstrated that increasing the nucleation rate significantly reduces the hydrogen capacity. It is elucidated that at a high nucleation rate, the complete coverage of the powder surface is reached at a smaller volume fraction of magnesium hydride. The results of the analysis of the hydrogenation curves using the Johnson–Mehl–Avrami (JMA) equation revealed three stages of hydrogenation. The modification of the nucleation rate was found to affect stages 1 and 2, where the nucleation and growth of the hydride take place, most significantly. 相似文献
142.
Fabrication and electrochemical characterization of adsorbed 1,2-naphthoquinone-4-sulfonic acid sodium (Nq)-modified gold
electrode is described in a wide pH range (3.00–9.00) in 0.1 M phosphate buffer solution using cyclic voltammetry (CV), differential
pulse voltammetry (DPV), and double-step potential chronoamperometry methods. The resulting Nq thin film-modified gold electrode
(Nq/Au) was tested successfully to recognize cysteamine in an aqueous solution. It is found that cysteamine participates in
Michael addition reaction with adsorbed Nq on gold electrode to form the corresponding thioquinone derivative. The reoxidation
of the adduct at a potential of about 650 mV less positive than cysteamine at the surface of the bare Au electrode leads to
an increase in the oxidative current, which is proportional to the concentration of cysteamine. The calibration plot for cysteamine
was found to be linear in the ranges of 6.0 × 10−5–4.5 × 10−3 M and 8.0 × 10−6–5.5 × 10−4 by CV and DPV, respectively. 相似文献
143.
The tensile deformation and fracture behavior of electrodeposited nanocrystalline Ni–15% Fe alloy samples after annealing
for 90 min at 250, 400 and 500 °C temperatures were investigated. The structure of the samples was studied using TEM and XRD
techniques and the fracture surfaces were investigated employing SEM. The results of this study indicated that annealing at
250 °C modified grain size distribution slightly but resulted in a significant increase in the initial strain hardening rate.
While the average grain size in the 400 °C sample was increased to 59 nm, its yield strength was comparable to the as-deposited
alloy with a 9 nm grain size. The plastic tensile elongation of all annealed samples was lowered significantly to less than
1% from approximately 6% in the as-deposited state. These results are discussed in terms of the inhomogeneity of plastic deformation
and the evolution of internal stresses in nanocrystalline materials. 相似文献
144.
Eghbali Rojin Soltanizade Ali Rashchi Fereshteh Vahidi Ehsan 《Clean Technologies and Environmental Policy》2023,25(6):2039-2054
Clean Technologies and Environmental Policy - Increasing demand for manganese and rapid depletion of high-grade manganese ores grow attention to other resources. However, environmental impacts and... 相似文献
145.
In this research, zinc sulfide nanoparticles (NPs) with various morphologies such as spherical, flower-like, microspheres decorated with nanoparticles and nanorods were synthesized by two distinct, simple and efficient methods. These approaches include reflux and hydrothermal methods. Zinc nitrate hexahydrate ().6H2O were used as Zn source and thioacetamide (TAA) was used as S source. The effects of TAA to zinc ion mole ratio were investigated on the morphology, particle size, optical and photocatalytic properties of ZnS nanocrystals. In hydrothermal synthesis with increasing Zn2+:TAA mole ratio from 1:1 to 1:2 dendrite-like nanocrystals changed to semi-spherical nanoparticles with average particle size 50–60?nm, with different effect as photocatalysts. But any change at morphology were didn’t observed with changing Zn2+:TAA mole ratio from 1:1 to 1:30 in the reflux method. In the reflux method with increasing in Zn2+:TAA mole ratio, dispersed semi-sphere nanoparticles were observed. The synthesized nanocrystals were characterized by infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. XRD analysis and FESEM images show that the size of synthesized ZnS NPs is in the range of 15–25?nm. UV–vis spectra showed that by increasing the amount of sulfur source and increasing the reaction time, shifted towards lower wavelengths, and the band gap was in the range of ~ 3.9–4.8?eV for all of the samples. Also, photoluminescence (PL) analysis showed by increasing particle size and degree of agglomeration, emission intensity () decreased. The photocatalytic activity of the as-prepared samples has been compared for the photocatalyst degradation of reactive blue 21. The sample with low Pl intensity has higher photocatalyst efficiency. 相似文献
146.
Micromorphology analysis and bond strength of two adhesives to Er,Cr:YSGG laser‐prepared vs. Bur‐prepared fluorosed enamel
下载免费PDF全文
![点击此处可从《Microscopy research and technique》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fereshteh Shafiei Zahra JOWKAR Reza Fekrazad Abolfazl Khalafi‐nezhad 《Microscopy research and technique》2014,77(10):779-784
Preservation of enamel during composite veneer restorations of fluorosed teeth could be achieved by conservative preparation with Erbium lasers. This study evaluated the effect of fluorosed enamel preparation with Er,Cr:YSGG vs. conventional diamond bur on the micromorphology and bond strength of a self‐etch and an etch‐and‐rinse adhesives. Er,Cr:YSGG laser or diamond bur preparation was performed on the flattened midbuccal surfaces of 70 extracted human premolars with moderate fluorosis (according to Thylstrup and Fejerskov index, TFI = 4–6). Adper Single Bond (SB) with acid etching for 20 or 40 s and Clearfil SE Bond (SEB) alone or with additional etching was applied in four laser groups. The same adhesive procedures were used in three bur groups except for 40 s of etching along with SB. After restoration, microshear bond strength was measured (MPa). Data were analyzed using ANOVA and Tamhane tests (α = 0.05). Six additional specimens were differently prepared and conditioned for scanning electron microscopy evaluation. The highest and lowest bond strengths were obtained for bur‐prepared/SB (39.5) and laser‐prepared/SEB (16.9), respectively, with a significant difference (P = 0.001). The different adhesive procedures used associated to two adhesives exhibited insignificantly lower bonding in laser‐prepared groups compared to bur‐prepared ones (P > 0.05), with the exception of additional etching/SEB, which bonded significantly higher to bur‐prepared (36.4) than to laser‐prepared enamel (18.7, P = 0.04). Morphological analyses revealed a delicate etch pattern with exposed enamel prisms on laser‐prepared fluorosed enamel after acid etching and less microretentive pattern after self‐etching primer. The etch‐and‐rinse adhesive was preferred in the laser‐prepared fluorosed enamel in terms of bonding performance. Microsc. Res. Tech. 77:779–784, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
147.
Esmaeel Darezereshki Mostafa Alizadeh Fereshteh Bakhtiari Mahin Schaffie Mohammad Ranjbar 《Applied Clay Science》2011,54(1):107-111
In this research work, ZnO nanoparticles were prepared by direct thermal decomposition method with Zn4(SO4)(OH)6·0.5 H2O as a precursor. The precursor was calcinated in air for 1 h at 825 °C. Samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), infrared spectrum (IR), and scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD, EDS, and IR results indicated that the ZnO nanoparticles were pure. The average crystallite and particle size of the ZnO nanoparticles were estimated to be 87 nm and 92 nm by XRD and TEM, respectively. The SEM and TEM images showed that the ZnO nanoparticles were of spherical shape. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure ZnO nanoparticles from low concentration ZnSO4 solutions. 相似文献
148.
Nickel catalysts prepared on high‐surface‐area mesoporous MgSiO3 were synthesized and applied in methanation of CO2. N2 adsorption analysis confirmed the presence of the mesoporous structure on the synthesized samples and revealed that the increase in nickel content resulted in a shift of the pore size distributions to smaller pore sizes. Temperature‐programmed reduction analysis illustrated an improvement in reducibility of the catalysts by a higher nickel content. Catalytic results indicated enhanced CO2 conversion with the increase in nickel percentage up to 15 wt %. The catalysts with higher percentage of nickel provided lower CO2 conversion and CH4 selectivity. The %15Ni/MgSiO3 catalyst exhibited high catalytic stability under optimized conditions. 相似文献
149.
Farajollah Mohanazadeh Alireza Sedrpoushan Mohammad Ali Zolfigol Fereshteh Golmohammad Saba Hemmati 《Journal of Sulfur Chemistry》2014,35(1):7-13
Silica bromide (SB) as heterogeneous reagent and promoter is prepared from reaction of silica gel with PBr3 as a non-hydroscopic, filterable, cheap, and stable yellowish powder that can be stored for months. The results show that the SB is suitable and efficient reagent for deoxygenation of sulfoxides to the corresponding sulfides under mild conditions at room temperature. The easy availability of this reagent makes this simple procedure attractive and a practical alternative to the existing methods. 相似文献