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1.
Accurate quantitative determinations are often difficult to obtain from fluorescence analysis of complex samples due to sample matrix effects and intermolecular interactions between solutes. Organized media can be used to minimize these unwanted processes without physical separation or extraction of the analytes from the sample matrix by isolating the analyte molecules in a uniform microenvironment within the sample. The advantages of bile salt micellar media over conventional detergent micelles are demonstrated for analysis of coal liquids. The bile salt media is shown to increase the sensitivity and dynamic range of fluorescence measurements relative to simple ethanolic solutions, without promoting gound-state and excited-state interactions that occur in the detergent micellar media. 相似文献
2.
Simple bounds on the extreme eigenvalues of Toeplitz matrices 总被引:1,自引:0,他引:1
Hertz D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(1):175-176
Simple bounds are presented on the extreme eigenvalues of n ×n -dimensional Hermitian Toeplitz matrices. Such a matrix, say T n, is determined by its first row. The proposed bounds have low complexity O (n ); furthermore, examples are presented for which the proposed bounds are tighter than the Slepian-Landau bounds at their best, i.e. when the extreme eigenvalues of the submatrix obtained by deleting the first row and first column of T n are known exactly. The bounds are first presented on the extreme eigenvalues of Hermitian Toeplitz matrices: the corresponding bounds for real symmetric Toeplitz matrices follow as a special case. Then, these bounds are extended to Hermitian Toeplitz interval matrices 相似文献
3.
A model of cortical neurons capable of sustaining a low level of spontaneous activity is investigated. Without learning the activity of the network is chaotic. We report on attempts to learn synfire chains in this type of network by introducing a Hebbian learning mechanism and exciting a small set of neurons at random intervals. We discuss the types of instabilities that can arise and prevent the formation of long synfire chains and also discuss various biologically plausible mechanisms which to some extent cure these instabilities. 相似文献
4.
Claudia Archetti Dominique Feillet Alain Hertz M. Grazia Speranza 《Computers & Operations Research》2010,37(11):1860-1869
A profit and a demand are associated with each edge of a set of profitable edges of a given graph. A travel time is associated with each edge of the graph. A fleet of capacitated vehicles is given to serve the profitable edges. A maximum duration of the route of each vehicle is also given. The profit of an edge can be collected by one vehicle only that also serves the demand of the edge. The objective of this problem, which is called the undirected capacitated arc routing problem with profits (UCARPP), is to find a set of routes that satisfy the constraints on the duration of the route and on the capacity of the vehicle and maximize the total collected profit. We propose a branch-and-price algorithm and several heuristics. We can solve exactly instances with up to 97 profitable edges. The best heuristics find the optimal solution on most of instances where it is available. 相似文献
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Kristian Hertz 《Fire Technology》2012,48(4):807-823
The authorities, the construction association, and a number of companies in Denmark have supported the author writing a guide
for design of building structures for parametric fires. The guide is published by the ministry as a supplement to the building
regulations. However, consultants and contractors have asked for a reference in English in order to make the guide-lines and
the background for them available internationally. The paper therefore presents recommendations from the design guide especially
concerning how to assess parametric design fires based on the opening factor method for large compartments. Findings leading
to the guide-lines are discussed, and it is indicated what a safe design fire model means for structural design and how it
differs from a safe design fire model for evacuation. Furthermore, the paper includes some experiences from the application
of the design guide in practise especially concerning implementation of consequences of the latest development of the building
technology, where low-energy windows and step-noise damping give rise to changes of the design fires. 相似文献
8.
David Hertz 《Multidimensional Systems and Signal Processing》1993,4(1):83-90
The purpose of this paper is to evaluate the extreme eigenvalues of a Hermitian Toeplitz interval matrix and a real Hankel interval matrix. A (n×n)-dimensional Hermitian Toeplitz (HT) matrix is determined by the elements of its first row, sayr. If the elements ofr lie in complex intervals (i.e., rectangles of the complex plane), we call the resulting set of matrices an HT interval (HTI) matrix. An HTI matrix can model real world HT matrices where the elements of the vectorr have finite precision (e.g., because of quantization, or imprecise measurement devices). In this paper we prove that the extreme eigenvalues of a given HTI matrix can be easily obtained from the 22(n–1) vertex HT matrices where the first element ofr is set to zero. Similarly, as a special case we obtain that the extreme eigenvalues of a real symmetric Toeplitz interval (RSTI) matrix can be obtained from 2
n–1 vertex matrices. Based on the above results we provide boxlike bounds for the eigenvalues on non-Hermitian complex and real Toeplitz interval matrices. Finally, we consider a real Hankel interval matrix. We prove that the maximal eigenvalue of a (n×n)-dimensional real Hankel interval matrix can be obtained from a subset of the vertex Hankel matrices containing 22n–3 vertex matrices, whereas the minimal eigenvalue can be obtained from another such subset also containing 22n–3 vertex matrices. 相似文献
9.
Many modern compact soft-x-ray and extreme-ultraviolet (EUV) imaging systems operate with small fields of view and therefore benefit from the use of small high-brightness sources. Such systems include water-window microscopes and EUV lithography tools. We show that the photon losses in such systems can be minimized while uniformity of object-plane illumination is maintained by controlled scanning of the source. The improved collection efficiency is demonstrated both theoretically and experimentally for a scanned laser-plasma source compared with static sources. A prospective aerial image microscope and a liquid-xenon-jet laser-plasma source are offered as examples of modern imaging tools that may benefit from such scanning of the source. 相似文献
10.
Audrey Hertz Yves-Marie Corre Stephane Sarrade Christian Guizard Anne Julbe Jean-Christophe Ruiz Bruno Fournel 《Journal of the European Ceramic Society》2010,30(7):1691-1698
The increasing interest of supercritical (SC) fluids for inorganic materials synthesis recently stimulated the development of innovative synthesis processes and strategies. The supercritical CO2 aided sol–gel process, developed for preparing various ceramic oxide powders with attractive applications in cosmetics, chromatography, catalysis or solid oxide fuel cells, usually suffer from both reproducibility problems and poor knowledge of the key parameters defining the final powder characteristics. In the present work a specific effort has been put on the understanding of reaction mechanisms and process parameters like co-solvent polarity and ageing time of the starting solution, which appeared to play a crucial role for the control of powder characteristics. Two different reaction mechanisms have been proposed to explain the formation of tetragonal yttria-doped zirconia powders by a batch process in either CO2/pentane or CO2/isopropanol mixtures. The first mechanism corresponds to a CO2 anti-solvent precipitation process while the other one is based on a condensation reaction as in the conventional sol–gel process. This improved understanding in particle formation allows better control of powder characteristics and reproducibility. 相似文献