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31.
32.
The surface coverage analysis derived from two formal steady-state kinetic models is compared to values directly obtained
from steady-state isotopic transient analysis (SSITKA) for the selective catalytic reduction (SCR) of NO by CH4 over Co-ZSM-5 catalysts. It is shown that the most abundant reacting intermediates are NO
x
adspecies, though no clear differentiation between the various adspecies identified by DRIFT spectroscopy was achieved. Less
numerous carbon containing adspecies were identified and quantified in the reacting system, essentially as methoxy species.
Nitromethane-like intermediates remained undetectable due to a very rapid transformation into N2 and CO2. On the basis of these converging kinetic analyses related to each elementary step of the SCR process, a microkinetic model
can be derived, which allows describing transient operation, in view of a non steady-state application. 相似文献
33.
N. E. Ermolin 《Combustion, Explosion, and Shock Waves》2007,43(5):549-561
To verify the adequacy of various models of heat release in ammonium dinitramide flame to real processes, chemical processes
in products of thermal decomposition at a pressure of 10 torr and in ammonium dinitramide [ADN; NH4N(NO2)2] flame at a pressure of 0.4 to 60 atm are numerically simulated. The calculations are performed on the basis of a detailed
kinetic mechanism and boundary conditions correlated with experimental data, thermodynamic properties, and chemical composition
of ADN. The kinetic mechanism includes submechanisms that describe high-temperature chemical processes in NH3/N2O/NO/NO2/HNO2/HNO3 and NH3/HN(NO2)2 mixtures, and the global stages of aerosol decomposition. Based on calculated and experimental data, the role of dinitraminic
acid HN(NO2)2, aerosols, and ADN vapor in heat release in the ADN flame zone adjacent to the burning surface is estimated. The calculations
predict that the main source of heat release in the cold flame zone at p ≥ 3 atm is dinitraminic acid incoming through the channel of dissociative evaporation ADNliq → NH3 + HN(NO2)2 from the burning surface. In the high-temperature flame zone, heat release is caused by the reaction that occurs in the NH3/N2O/NO/NO2/HNO2/HNO3 mixture. At moderate pressures, the high-temperature and low-temperature zones are separated by an induction zone. The stage
governing production of the OH radical, which plays an important role in combustion, in the induction zone is the reaction
HNO3 + M → OH + NO2 + M. Because of a high activation energy of the stage, small temperature perturbations in the induction zone at low pressures
lead to a finite change in the stand-off distance between the high-temperature flame zone and the burning surface. Therefore,
small temperature perturbations in the induction zone, which are caused by admixtures in the sample or by heat transfer between
the reacting gas and the ambient medium, may be responsible for disagreement between various experimental data and between
experimental and calculated data on the stand-off distance between the high-temperature flame zone and the burning surface.
In numerical calculations, the position of the high-temperature zone is effectively controlled by varying rate constants of
elementary stages within admissible limits.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 64–76, September–October, 2007. 相似文献
34.
The curing kinetics of bismaleimide modified with diallylbisphenol A were investigated for different ratios of 1,1′‐(methylene di‐4,1‐phenylene) bismaleimide and diallylbisphenol A with differential scanning calorimetry. Multiheating‐rate and isothermal methods were used to study the kinetics of the curing process. The results indicated that the activation energy changed with the extent of conversion. The activation energy obtained by the multiheating‐rate method was higher than that obtained by the isothermal method. Two kinetic models (autocatalytic and nth‐order) were successfully used to model the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2229–2240, 2003 相似文献
35.
对前文 (I)的共聚动力学模型进行了分析与简化 ,并分别通过对各影响因素的单因素实验和多因素相互作用实验对模型进行了进一步的考核 ,确定了模型参数并通过模型对聚合动力学行为作了说明 相似文献
36.
Y. Castrillejo M. R. Bermejo A. M. Martínez C. Abejón S. Sánchez G. S. Picard 《Journal of Applied Electrochemistry》1999,29(1):65-73
The stability of indium chloride and oxide as well as the electrochemical behaviour of indium ions have been studied in the equimolar CaCl2–NaCl melt at 550 C by X-ray diffraction (XRD) and different electrochemical techniques, using molybdenum and tungsten wires as working electrodes. Voltammetric and chronopotentiometric studies showed signals attributed to the presence of three oxidation states of indium, i.e. 0, i and iii. The standard potential of the redox couples, as well as the solubility products of indium oxides have been determined, showing that In(iii) ions are completely reduced to monovalent indium by the indium metal according to the reaction: In () + 2 In 3 In () and that In2O is a strong oxide donor according to the reaction: In2O(s) 2 In() + O2- These results have allowed the construction of E-pO2– equilibrium diagrams summarising the properties of In–O compounds. The electrodeposition of indium was uncomplicated at Mo and W electrodes. Very good adherence of liquid indium to the electrode materials was observed, with the formation of Na–In alloys at highly reducing potentials, and there was no evidence of indium dissolution into the melt. Moreover, the voltammograms corresponding to the electrochemical In(iii)/In(i) exchange were well defined. The two electrochemical steps were found to be quasi-reversible, and the values of the kinetic parameters, ko and , for both reactions, as well as the diffusion coefficients, DIn(III) and DIn(I) were calculated. 相似文献
37.
38.
39.
V. P. Sinditskii 《Combustion, Explosion, and Shock Waves》2007,43(3):297-308
For model systems with known kinetics of elementary reactions (CH3NO2 and HN3), temperature ranges are established in which the rate-controlling reactions are the initial endothermic decomposition of
the starting material or the subsequent secondary reactions. Heat release in reactions of NO2, NO, and N2O with various fuels, such as CH2O, CO, H2, and HCN, is modeled to establish the kinetic parameters and nature of the rate-controlling reactions in gas flames of nitro
compounds. It is shown that the activation energy of the heat-release reaction due to the interaction of NO2 with a hydrocarbon fuel (which is characteristic of the first flame of nitro compounds) is in the range of 29–33 kcal/mole,
depending on the type of fuel. According to the calculations performed, the activation energy of the rate-controlling heat-releasing
process due to the deoxidation of NO and N2O (which is typical of the second flame of nitro compounds) is 43–58 kcal/mole. In the range of high pressures, where the
flames merge, the kinetic parameters of heat release are determined by the reactions of the most reactive nitrogen oxide NO2.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 59–71, May–June, 2007. 相似文献
40.
NH3-NO/NO2 SCR for diesel exhausts after treatment: mechanism and modelling of a catalytic converter
Nova Isabella Ciardelli Cristian Tronconi Enrico Chatterjee Daniel Weibel Michel 《Topics in Catalysis》2007,42(1-4):43-46
We review herein the key mechanistic and kinetic features of the reactions involved in the NH3-NO/NO2 SCR system investigated by dynamic reactive experiments over a V-based commercial powdered catalyst, eventually leading to
the proposal of an original redox scheme which accounts for stoichiometry, selectivity and intrinsic kinetics of the global
SCR process. 相似文献