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1.
Sodium alginate was graft-copolymerized with ethyl acrylate using ceric ammonium nitrate as an initiator. In order to optimize the conditions for grafting, the concentrations of nitric acid, initiator and monomer together with temperature, time and amount of substrate were varied. The kinetic scheme of free radical graft copolymerization has been proposed and the equations relating the values of rate of polymerization, rate of graft copolymerization and rate of homopolymerization are also suggested. The experimental results agree very well with the proposed kinetic scheme.  相似文献   
2.
The present work deals with the photopolymerization of bis-aromatic based urethane acrylate macromonomers in the presence of excess end capping agent as reactive diluent and estimation of their kinetic parameters. Formulations were made by independently homogenizing the macromonomers with photoinitiators of three different classes. Three different compositions of photoinitiators were used to study the effect of concentration of photoinitiator on cure kinetics. These compositions obtained were tested for photo curing performance using photo DSC under polychromatic radiation. The heat flows against time were recorded for all formulations under isothermal condition and the rates of polymerization, peak maximum times as well as the percentage conversions were estimated. It was observed that due to a longer timescale for reaction diffusion, formulations with macromonomer containing propoxylated backbone showed higher conversions than the corresponding ethoxylated analogue. The photopolymerization and kinetic estimations of the formulations including evaluation of kinetic model are discussed.  相似文献   
3.
The grafting of acrylonitrile (AN) onto sodium salt of partially carboxymethylated amylose (Na-PCMA) using ceric ammonium nitrate (CAN) as an initiator has been studied in water/solvent mixtures. The solvents used include methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride. The results have been discussed. The effect of reaction medium on the molecular weight of grafted PAN has also been studied. The chain transfer constants (Cs) for solvents like methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride have been evaluated at 30°C by the help of Mayo's equation.  相似文献   
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It is generally accepted that in order to account for the effect of eddy currents in the solid rotor-iron of a round-rotor synchronous machine, two or more fictitious rotor-circuits are to be used in each axis of the d- and q-axis equivalent circuit representations of the machine model. This paper presents a novel technique to estimate the parameters of these rotor-circuits (hereinafter referred to as rotor body parameters) from measurements collected online at several operating conditions. The effects of generator saturation, rotor position and loading are included in the estimation process. Tests conducted on a round-rotor synchronous generator reveal that certain rotor-body parameters are nonlinear functions of generator operating condition. A novel artificial neural network (ANN) based technique is used to map variables representative of generator operating condition to each parameter being modeled. The developed ANN models are validated with measurements not used in the modeling process  相似文献   
6.
In this article we illustrate the performance of Transmission Control Protocol in an overlay cognitive radio network under dynamic spectrum access. We show that the performance of TCP in overlay CR networks that implement DSA to be quite different from its performance in conventional networks, which do not allow DSA. The key difference is that secondary users in an overlay CR network have to cope with a new type of loss called service interruption loss, due to the existence of primary users. We demonstrate on an NS2 simulation testbed the surprising result: Excessive radio resource usage leads to a decrease in aggregate TCP throughput. This behavior is in contrast to the behavior of TCP in conventional networks, where throughput increases monotonically with the available radio resource.  相似文献   
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The friction stir welded joint of wrought ZM21 alloy was divided into five parts, and their localized creep behavior was studied via the impression method. The tests were carried out in the stress range of 300–450 MPa (σimp/G ≈ 0.02–0.03) and in the temperature range of 448–523 K. Optical and SEM micrographs and EDS taken before and after the impression tests were used to study the microstructure of various zones of the FS welded joint. Power law was found to satisfactorily relate the stress and strain rates. The steady-state impression velocity was found to vary significantly between the advancing and retreating sides of TMAZ and HAZ. For TMAZ, the creep exponent on the AS was 4.8, and on the RS, it was 7.8. The activation energy on the AS was ~?133 kJ/mol, and on the RS, it was ~?101 kJ/mol. Similarly, for HAZ, the creep exponent on the AS was found to be 5.5 and on the RS, it was 4.9. The activation energy on the AS was ~?86 kJ/mol and on the RS, it was ~?232 kJ/mol. The cross-over of steady-state impression velocity of different zones indicates that the weak zone was temperature and stress dependent. Within the stresses and temperatures studied, the weld zone's creep resistance (i.e., lower minimum impression velocity) was found to be better than the base material. As it is with most magnesium alloys, dislocation climb was found to be the operative mechanism in the FS weldments of ZM21 alloy. The rate-controlling mechanism remains to be identified because the wide variation in n and Q values suggests that different creep mechanisms are in operation in different zones.

Graphical abstract
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9.
Anthracycline antibiotics, particularly doxorubicin (DOX) and daunorubicin, have been used extensively in the treatment of human malignancies. However, cardiotoxicity and multidrug resistance are significant problems that limit the clinical efficacy of such agents. Rational design to avoid these side effects includes strategies such as drug targeting and prodrug synthesis. The DOX prodrug N-(beta-D-glucopyranosylbenzyloxycarbonyl)-doxorubicin (prodrug 1) was synthesized for specific activation by beta-galactosidase, which is expected to release in necrotic areas of tumor lesions. Described here is the safety, pharmacokinetics, and biodistribution studies of a beta-galactoside prodrug of DOX. In vivo safety evaluation was done in the Ehrlich Ascites Carcinoma (EAC) tumor model. The dose of DOX was 8 mg/kg and the dose of prodrug was 8 mg/kg and 24 mg/kg of DOX equivalents. Our results on cytotoxicity, which demonstrated compression in the number of EAC cells and their viability, substantiate these data. Prodrug 1 was safe up to a dose of 24 mg/kg of DOX equivalents in EAC mice. The pharmacokinetics and biodistribution of prodrug (300 mg/kg) in normal mice were determined and compared with DOX (20 mg/kg). Administration of DOX in normal mice resulted in a peak plasma concentration of 19.45 microM (t = 30 minutes). Prodrug injection resulted in 3- to 16-fold lower concentrations in the tissues of normal mice. As it is more polar, lower levels were observed in tissues and plasma in contrast to the parent compound DOX. In vivo safety studies have shown that prodrug 1 had a maximum tolerated dose compared with DOX and led to improved pharmacokinetics in normal mice.  相似文献   
10.
Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxyapatite (HA) and tricalcium phosphate (TCP) were deposited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and α-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Inductively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chemically gradient functional bioceramic coating can be produced by laser deposition of multiple sintered targets with variable chemical composition.  相似文献   
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