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1.
An efficient method for computing the fields of large scatterers is presented. The current is expanded in terms of modes defined as complex exponential functions. The modes are represented efficiently by means of spline functions. Analytical expressions have been obtained to compute efficiently the fields due to the current modes. 相似文献
2.
Hugo E. Delgado Ph.D. Ramanath I. Ramakrishnan M.S. Timothy E. Howson D.E.S. 《JOM Journal of the Minerals, Metals and Materials Society》1994,46(9):21-23
Computer-aided engineering tools are routinely used to simulate forging and heat-treatment operations and to perform thermal and stress analyses. This review gives a few examples of the current uses of process modeling tools and outlines some developing capabilities and near-term applications. 相似文献
3.
J. M. P. Q. Delgado 《加拿大化工杂志》2006,84(6):651-655
In this article, a simple and inexpensive experimental technique easy to build in laboratory, for the measurement of tortuosity of a packed bed of inert particles, is described. Experimental values of the tortuosity were obtained with four different packed beds of sand. The experimental results obtained are in good agreement with the theoretical values of tortuosity in a porous media; and the data reported showed the tortuosity to increase with decrease in the void fraction of the packed bed as expected. 相似文献
4.
J.M.P.Q. Delgado 《Journal of Phase Equilibria and Diffusion》2007,28(5):427-432
Molecular (or tracer) diffusion coefficient data were obtained for 2-naphthol, benzoic acid, salicylic acid, camphor, and
cinnamic acid in water at temperatures that differ significantly from ambient value. Experimental values were determined for
the dissolution of 2-naphthol in water at 283 to 368 K, of benzoic acid in water at 283 to 338 K, of salicylic acid in water
at 283 to 343 K, of camphor in water at 283 to 318 K, and of cinnamic acid in water at 283 to 318 K. Empirical correlations
are presented for the prediction of molecular diffusion coefficient over the entire range of temperatures studied, and they
are shown to predict the obtained data with very good accuracy. 相似文献
5.
Functionalized latexes coated by antibodies are used in diagnostic tests for the detection of antigens in biological fluids. A simple kinetic model is presented which is related to the optical monitoring of the formation of specific complexes between antigen and antibody amplified by latex beads. The antibodies are chemically coupled onto chloromethylstyrene (CMST) particles. The kinetic model is able to describe the immunoprecipitin curves of immunolatex beads. The number of fitting parameters is relatively reduced (only three), and the meaning of these parameters can be interpreted in terms of the chemical equilibrium constant, the percentage of active IgG on the latex beads, and optical response. The model explains very well the optical response of immunolatex prepared by covalent coupling of antibodies on polymer carriers. 相似文献
6.
Summary Three copolymers of ethylene and 1-decene, covering a wide range of compositions, have been synthesized with a MgCl2-supported Ziegler-Natta catalyst. The analysis by DSC and X-ray shows a great degree of heterogeneity in these copolymers and appreciable levels of crystallinity, corresponding to the orthorhombic lattice of polyethylene, are present even for very high 1-decene contents. 相似文献
7.
A.R. Mosier J.A. Delgado V.L. Cochran D.W. Valentine W.J. Parton 《Nutrient Cycling in Agroecosystems》1997,49(1-3):71-83
Increasing concentrations of methane (CH4) in the atmosphere are projected to account for about 25% of the net radiative forcing. Biospheric emissions of CH4 to the atmosphere total approximately 400 Tg C y-1. An estimated 300 Tg of CH4-C y-1 is oxidized in the atmosphere by hydroxyl radicals while about 40 Tg y-1 remains in the atmosphere. Approximately 40 Tg y-1 of the atmospheric burden is oxidized in aerobic soils. Research efforts during the past several years have focused on quantifying
CH4 sources while relatively less effort has been directed toward quantifying and understanding the soil sink for atmospheric
CH4.
Recent research has demonstrated that land use change, including agricultural use of native forest and grassland systems has
decreased the soil sink for atmospheric methane. Some agricultural systems consume atmospheric CH4 at rates less than 10% of those found in comparable undisturbed soils.
While it has been necessary to change land use practices over the past centuries to meet the required production of food and
fiber, we need to recognize and account for impacts of land use change on the biogeochemical nutrient cycles in the biosphere.
Changes that have ensued in these cycles have and will impact the atmospheric concentrations of CH4 and N2O. Since CH4 and N2O production and consumption are accomplished by a variety of soil microorganisms, the influence of changing agricultural,
forest, and, demographic patterns has been large. Existing management and technological practices may already exist to limit
the effect of land use change and agriculture on trace gas fluxes. It is therefore important to understand how management
and land use affect trace gas fluxes and to observe the effect of new technology on them.
This paper describes the role of aerobic soils in the global CH4 budget and the impact of agriculture on this soil CH4 sink. Examples from field studies made across subarctic, temperate and tropical climate gradients in grasslands are used
to demonstrate the influence of nutrient cycle perturbations on the soil consumption of atmospheric CH4 and in increased N2O emissions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
M.D. Foster I. Rivin M.M.J. Treacy O. Delgado Friedrichs 《Microporous and mesoporous materials》2006,90(1-3):32-38
We have applied Delaunay triangulation to models of the known zeolite frameworks. We show that this well-established technique from computational geometry provides for each framework; (i) the location and shape of the open pores and channels, (ii) the diameter of the largest possible included sphere, and indirectly (iii) the diameter of the largest-free-sphere that can diffuse through the framework by at least one lattice translation. Since Delaunay triangulation naturally locates the empty spaces within a set of points, it provides a powerful computer-automated tool for determining the physical characteristics of pores and channels of zeolite frameworks. Such tools will further enhance the usefulness of large databases of hypothetical framework materials.
Here, we tabulate results for the 165 zeolite frameworks that are presently listed in the Atlas of Zeolite Frameworks. Of the known zeolites, refined as pure silicates, the largest included sphere occurs in the TSC framework, with a diameter of 16.39 Å. The largest-free-sphere has a diameter of 11.33 Å, for diffusion along the [0 0 1] direction in the VFI framework. 相似文献
9.
In the present study, different types of 75% Cr3C2-25% NiCr coatings were applied on a steel substrate by means of high velocity oxygen fuel spraying (HVOF), and studied using ac and dc electrochemical measurements in an aerated and unstirred 0.5 M H2SO4 solution. Structural characterization was determined before and after electrochemical tests. Differences between all sprayed systems are related to the gun transverse speed and number of deposited layers, which strongly affected the electrochemical characteristics of the coated steels. The coating obtained with a higher torch speed showed better resistance against corrosion. The electrochemical impedance results were analyzed using an equivalent circuit where porosity of the coatings and substrate oxidation were considered. 相似文献
10.
Nirvana Delgado Otalvaro Pembe Gül Bilir Karla Herrera Delgado Stephan Pitter Jörg Sauer 《化学,工程师,技术》2021,93(5):754-761
Artificial neural networks (ANNs) are designed and implemented to model the direct synthesis of dimethyl ether (DME) from syngas over a commercial catalyst system. The predictive power of the ANNs is assessed by comparison with the predictions of a lumped model parameterized to fit the same data used for ANN training. The ANN training converges much faster than the parameter estimation of the lumped model, and the predictions show a higher degree of accuracy under all conditions. Furthermore, the simulations show that the ANN predictions are also accurate even at some conditions beyond the validity range. 相似文献