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31.
Si diffusion into GaN was studied as a function of encapsulant type (SiO2 or SiNx) and diffusion temperature. Using a SiO2 encapsulant, the Si diffusion exhibited an activation energy of 0.57 eV with a prefactor of 2.07×10−4 cm2 sec−1 in the temperature range 800–1,000°C. An enhancement-mode MgO/GaN-on-Si metal-oxide semiconductor field-effect transistor (MOSFET) was fabricated utilizing Si-diffused regions under the source and drain to provide an accumulated channel. The gate leakage through the undoped GaN was low enough for us to achieve good saturation behavior in the drain-current-voltage characteristics. The devices showed improved transconductance and drain current relative to previous devices with Si-implanted source/drain regions.  相似文献   
32.
Proton irradiation of Sc2O3/GaN and Sc2O3/MgO/GaN metal-oxide semiconductor diodes was performed at two energies, 10 MeV and 40 MeV, and total fluences of 5 × 109 cm−2, corresponding to 10 years in low-earth orbit. The proton damage causes a decrease in forward breakdown voltage and a flat-band voltage shift in the capacitance-voltage characteristics, indicating a change in fixed oxide charge and damage to the dielectric. The interface state densities after irradiation increased from 5.9 × 1011 cm−2 to 1.03 × 1012 cm−2 in Sc2O3/GaN diodes and from 2.33 × 1011 to 5.3 × 1011 cm−2 in Sc2O3/MgO/GaN diodes. Postannealing at 400°C in forming gas recovered most of the original characteristics but did increase the interfacial roughness.  相似文献   
33.
In this study we examined the cytotoxic effect of ZnO nanoparticles on various human cancer and normal cells. We found that the ZnO nanoparticles exerted a cytotoxic effect on the human glioma cell lines A172, U87, LNZ308, LN18, and LN229, whereas no cytotoxic effect was observed on normal human astrocytes. Similarly, the ZnO nanoparticles induced cell death in breast and prostate cancer cell lines while no major effect was observed in the respective normal breast and prostate cell lines. Using the fluorescent dye 2,7-dichlorofluorescein diacetate, we found that treatment of the glioma cells with ZnO nanoparticles induced a large increase in the generation of reactive oxygen species (ROS) and treatment of the cells with N-acetyl cysteine decreased the cytotoxic effect of the ZnO nanoparticles. In contrast, a smaller effect on ROS generation was observed in the normal astrocytes. These results suggest that ZnO nanoparticles may be employed as a selective cytotoxic agent for the eradication of cancer cells.  相似文献   
34.
    
In this work, a fast method was proposed for estimating the virgin olive oils (VOOs) carotenoids and chlorophylls concentration using color measurement. The pigment content by conventional spectrophotometry method and CIELAB color (L*, a*, and b*) at different degree of sample thickness (from 5 to 50 mm) of one hundred VOOs were measured. Oil carotenoids and chlorophylls content were correlated with the color parameters for the different oil thickness studied to design the prediction models of the new method. The best regression coefficients (R2) were obtained for multiple linear regression model using the three independent variables (L*, a*, and b*) together measured at 5 mm of oil thickness. The R2 were 0.9679, 0.9515, and 0.9644 for predicting carotenoids, chlorophylls, and total pigments, respectively. External validation of these prediction models was satisfactory (relative error < 0.1). Therefore, this new solvent-free colorimetric method is a useful method for determination of carotenoids and chlorophylls content in VOOs. Practical applications: The simple colorimetric method developed in this study offers a fast and accurate alternative to current methods published in the literature to estimate the pigment content in VOOs. It is a rapid (less than 1 min) and cheap method, with the advantage of ease of operation, no sample pretreatment and solvent-free, thus environmentally friendly. This methodology can potentially be used by trained “nonprofessional analytical skilled” people in small laboratories or olive oil mills with limited technical facilities. Therefore, the technique is highly plausible as an alternative to determine the pigment content in VOOs. Finally, future works with this methodology could be carried out to online control of VOOs pigments content in the oil extraction process.  相似文献   
35.
We report on a comparison of different gate oxides for AlGaN/GaN high-electron-mobility transistor (HEMT) pH sensors. The HEMTs show a linear increase in drain-source current as the pH of the electrolyte solutions introduced to the gate region is decreased. Three different gate oxides were examined, namely the native oxide on the AlGaN surface, a UV-ozone-induced oxide and an Sc2O3 gate deposited by molecular beam epitaxy. The Sc2O3 produced superior results in terms of resolution in measuring small changes in pH. The devices with Sc2O3 in the gate region exhibited a linear change in current between pH 3 and 10 of 37 μA/pH with a resolution of <0.1 pH over the entire pH range. In contrast, the native oxide devices showed a larger change in current, ∼70 μA/pH, but with a degraded resolution of ∼0.4 pH. Results for the UV-ozone oxide were intermediate in resolution, 0.2 pH. These HEMTs have promise for detecting pH changes in biological samples and can be readily integrated into a standard package for wireless data transmission.  相似文献   
36.
37.
Although 70% of part cost is determined during the early design stage, designers rarely accurately estimate the costs of their designs. Based on extensive literature review, in-depth industrial survey and close collaboration with multiple manufacturers, forty factors were identified as governing part cost and ranked according to cost impact. Based on parameter ranking and availability at the early stages of design, a cost estimator for designers is proposed. As the design progresses and more parameters become available, a more accurate cost model is derived and proposed to manufacturers. Results are analyzed and compared to actual manufacturing costing demonstrating good fit.  相似文献   
38.
Polyethylene (PE) and polypropylene (PP) were oxygen plasma treated and aged in carefully reproducible conditions. The effect of aging on the surface chemistry, wettability and adhesion were studied using a combination of techniques: contact angle measurements, XPS, SSIMS, adhesion tests (shear and pull).

PE was found to be relatively insensitive to aging both in terms of wettability and adhesion, due to crosslinking during plasma treatment, which is likely to reduce macromolecular mobility within the surface layer.

In the case of PP, dramatic decreases of wettability occur with time, due to macromolecular motions leading to minimization of oxygen-containing functions at the surface. This behavior was shown to affect the adhesion performance of treated PP.  相似文献   
39.
Polyethylene (PE) and polypropylene (PP) were oxygen plasma treated and aged in carefully reproducible conditions. The effect of aging on the surface chemistry, wettability and adhesion were studied using a combination of techniques: contact angle measurements, XPS, SSIMS, adhesion tests (shear and pull).

PE was found to be relatively insensitive to aging both in terms of wettability and adhesion, due to crosslinking during plasma treatment, which is likely to reduce macromolecular mobility within the surface layer.

In the case of PP, dramatic decreases of wettability occur with time, due to macromolecular motions leading to minimization of oxygen-containing functions at the surface. This behavior was shown to affect the adhesion performance of treated PP.  相似文献   
40.
A single fiber action potential (SFAP) can be modelled as the convolution of a biolectrical source and a filter impulse response. In the Dimitrov-Dimitrova (D-D) convolutional model, the first temporal derivative of the intracellular action potential (IAP) is used as the source, and Tspl is a time parameter related to the duration of the IAP waveform. This paper is centred on the relation between Tspl and the main spike duration (MSD), defined as the time interval between the first and third phases of the SFAP. We show that Tspl essentially determines the MSD parameter. As experimental data, we used fibrillation potentials (FPs) of two different muscles to study the D-D model. We found that Tspl should have a certain statistical variability in order to explain the variability in the MSD of our FPs. In addition, we present a method to estimate the Tspl values corresponding to a given SFAP from its measured MSD.  相似文献   
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