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11.
García Páez JM Herrero EJ Carrera San Martín A García Sestafe JV Téllez G Millán I Salvador J Cordón A Castillo-Olivares JL 《Journal of materials science. Materials in medicine》2000,11(7):459-464
Poor mechanical properties of biological tissue are known to cause wear, leading to the failure of cardiac bioprostheses made of calf pericardium. Different chemical agents such as sodium dodecyl sulfate (SDS) are presently being tested as possible inhibitors of the calcification process. The objective of this report was to determine the mechanical behavior of calf pericardium treated with SDS for 24 h and the influence of the suture on the mechanical properties of the tissue. Forty-eight samples were tested: 24 subjected to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk suture thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and non-sutured sample was cut into two strips to yield paired samples. All were subjected to tensile stress to breaking point. The mean stress at breaking point in the non-sutured series treated with glutaraldehyde alone was 16.42 and 13.85 MPa depending on the region of the pericardium, while in the sutured samples subjected to glutaraldehyde the mean stress was 7.50 and 7.63 MPa, respectively, differences which were statistically significant (p = 0.03 and p = 0.003, respectively) when the means for non-sutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardium treated with SDS, deformations of 10% were produced with stresses of under 0.4 MPa, an outcome that is intolerable from the constructive point of view. We established a regression model that enabled us to determine the mechanical behavior of a sutured sample by testing a contiguous piece of tissue, with a high correlation coefficient (r > 0.99). We consider this finding to be of interest in the selection of pericardium for use in the construction of leaflets for cardiac bioprostheses. 相似文献
12.
R. Lyonnet A. Khodan A. Barthe´le´my J.-P. Contour O. Durand J.L. Maurice D. Michel J. Teresa de 《Journal of Electroceramics》2000,4(2-3):369-377
We have studied the pulsed laser deposition (PLD) of Zr1-xCexO2 and Ce1-xLaxO2-x/2 initially to grow buffer layers for perovskite films deposited on Si, LaAlO3, SrTiO3 and MgO and then to produce tunneling barriers for cuprate or manganite heterostructures. On (1 0 0) Si, the deposition of Zr1-xCexO2 (x = 0.12) produces a smooth epitaxial layer (R
RMS = 0.25/1m2), which allows the further deposition of high quality YBa2Cu3O7 (Tc 88 K) and La0.7Sr0.3MnO3 films. On the other hand, the use of Ce1-xLaxO2-x/2 (0 x 0.4) makes it possible to match the YBa2Cu3O7 and La0.7Sr0.3MnO3 layers to various substrates. The buffer layers are epitaxially grown with a 45° rotation of the in-plane axes with respect to those of the substrate, and the smoothness is high (R
RMS = 0.25/1m2). In the case of an ultra-thin barrier (2.5 nm) of Ce1-xLaxO2-x/2 sandwiched in a La0.7Sr0.3MnO3, the out-of-plane mismatch of 2 induces distortions at the interface steps, which propagate into the topmost La0.7Sr0.3MnO3 layer. This is in contrast to the case of SrTiO3 barriers where an ideal crystal continuity in the growth direction is observed. 相似文献
13.
Simultaneous mass transfer of solute and solvents in a mixing cell with vibrating stirrers was investigated. The system used was methyl isobutyl ketone-acetic acid-water. The mass transfer rates in steady state were measured and proper compositions of entering streams were selected in order to eliminate the effect of interfacial turbulence. In evaluating the results, convective transport as well as driving force interactions of simultaneously diffusing components were taken into account. For higher concentrations of solute the individual elements of the matrix of diffusive transfer coefficients could be assessed. 相似文献
14.
Polythiophene films were electrochemically deposited on glassy carbon substrates under potentiostatic control and used as cathode active material together with a Zn anode in a rechargeable battery with propylene carbonate, Zn(ClO4)2, LiClO4 electrolyte. Charge–discharge characteristics were studied. The average discharge voltage of the polythiophene/Zn cell was 1.25V. In the low current density region (i.e. 10–50μAcm?2) the cycling coulombic efficiency was above 95%, but in the fast charge–discharge region, where current densities were 0.1–0.5mAcm?2, the coulombic efficiency decreased to 55% with increasing discharge rate. Additionally, it was found that the cyclic coulombic efficiency was a function of the charging depth. 相似文献
15.
V. E. Danil´chenko 《Journal of Engineering Physics and Thermophysics》2008,81(3):633-637
We have investigated the influence of multiple γ-α-γ transformations proceeding by the shear mechanism on the structural-phase
state of austenite in iron-nickel alloys N28T2Yu2 and N32. It has been shown that it is possible to form, by cyclic γ-α-γ
transformations, a fine-grained structure of austenite due to the fragmentation of the initial structure that develops under
the conditions of progressing disorientation of the crystal lattice of the γ-phase. In the process of thermocycling, the reversed
austenite was continuously strengthened under the condition of the development of disorientation of its lattice.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 602–606, May–June, 2008. 相似文献
16.
Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation. 相似文献
17.
Electrocatalytic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carbon substrates 总被引:3,自引:0,他引:3
To achieve methanol fuel cell electrodes allowing a high catalyst use, thin layers of various carbon powders and recast Nafion® were electrochemically plated with platinum. The resulting Pt deposits were characterized by hydrogen and carbon monoxide electrosorption, as well as by transmission electron microscopy. Methanol oxidation was then carried out using cyclic voltammetry. The influence of the amount of carbon surface oxides and the effect of Pt specific surface area on the Pt catalytic activity were thus investigated. 相似文献
18.
K.F. Khaled K. Babi´-Samardžija N. Hackerman 《Journal of Applied Electrochemistry》2004,34(7):697-704
The objective of this work is to provide additional insight on the influence of substituents on heterocyclic piperidine as
acid corrosion inhibitors for iron. This series include piperidine and six derivatives. The inhibiting properties of piperidine
and these derivatives were investigated in 1 M HCl by potentiodynamic polarization (dc) and electrochemical impedance spectroscopy
measurements, and inhibition was found to increases as 26dp < 35dp < 2mp < 3mp < pip < 4bp < 4mp. Polarization curves suggest
that they can all be considered as mixed-type inhibitors. An attempt to correlate electronic properties of the compounds with
their experimental efficiencies using molecular orbital calculation methods did not show any clear-cut relationship. 相似文献
19.
20.
Management of complexity, changes and disturbances is one of the key issues of production today. Distributed, agent-based structures represent viable alternatives to hierarchical systems provided with reactive/proactive capabilities. In the paper, approaches to distributed manufacturing architectures are surveyed, and their fundamental features are highlighted, together with the main questions to be answered while designing new structures. Moreover, an object-oriented simulation framework for development and evaluation of multi-agent manufacturing architectures is introduced. 相似文献