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201.
J.C. Kuijper X. Raepsaet J.B.M. de Haas W. von Lensa U. Ohlig H.-J. Ruetten H. Brockmann F. Damian F. Dolci W. Bernnat J. Oppe J.L. Kloosterman N. Cerullo G. Lomonaco A. Negrini J. Magill R. Seiler 《Nuclear Engineering and Design》2006,236(5-6):615-2004
The high-temperature gas-cooled reactor (HTGR) appears as a good candidate for the next generation of nuclear power plants. In the “HTR-N” project of the European Union Fifth Framework Program, analyses have been performed on a number of conceptual HTGR designs, derived from reference pebble-bed and hexagonal block-type HTGR types. It is shown that several HTGR concepts are quite promising as systems for the incineration of plutonium and possibly minor actinides.These studies were mainly concerned with the investigation and intercomparison of the plutonium and actinide burning capabilities of a number of HTGR concepts and associated fuel cycles, with emphasis on the use of civil plutonium from spent LWR uranium fuel (first generation Pu) and from spent LWR MOX fuel (second generation Pu). Besides, the “HTR-N” project also included activities concerning the validation of computational tools and the qualification of models. Indeed, it is essential that validated analytical tools are available in the European nuclear community to perform conceptual design studies, industrial calculations (reload calculations and the associated core follow), safety analyses for licensing, etc., for new fuel cycles aiming at plutonium and minor actinide (MA) incineration/transmutation without multi-reprocessing of the discharged fuel.These validation and qualification activities have been centred round the two HTGR systems currently in operation, viz. the HTR-10 and the HTTR. The re-calculation of the HTTR first criticality with a Monte Carlo neutron transport code now yields acceptable correspondence with experimental data. Also calculations by 3D diffusion theory codes yield acceptable results. Special attention, however, has to be given to the modelling of neutron streaming effects. For the HTR-10 the analyses focused on first criticality, temperature coefficients and control rod worth. Also in these studies a good correspondence between calculation and experiment is observed for the 3D diffusion theory codes. 相似文献
202.
203.
The optimization of a new or partially existing urban drainage system may be modeled as a subproblems sequence of layout and optimal design within the discrete search space. The design optimization, incorporating the optimal selection of the pumping stations, intermediate manholes, pipe sections, and installation depths, for a general system fixed layout in plan, is a high level sequential decision problem which may be efficiently solved deterministically through a multilevel dynamic programming model. The optimal general layout may be selected in a deterministic way by means of a simple economical comparison of all plan solutions having optimized designs, for small to medium sized systems (if the specific restrictions of the applications are appropriately exploited) in practicable computer time. For larger dimension networks, where it is clearly impossible to achieve plan optimization with full enumeration (which is a NP complete), stochastic search models can be used. For the subproblem layout, an effective enumeration model is presented; the results of a stochastic model proposed previously, using simulated annealing for an application example, are compared and discussed in detail. 相似文献
204.
Florin Manea Carlos Martín-Vide Victor Mitrana 《Electronic Notes in Theoretical Computer Science》2006,135(3):95
We propose a construction of an accepting hybrid network of evolutionary processors (AHNEP) which behaves as a universal device in the class of all these devices. We first construct a Turing machine which can simulate any AHNEP and then an AHNEP which simulates the Turing machine. We think that this approach can be applied to other bio-inspired computing models which are computationally complete. 相似文献
205.
We define three operations on strings and languages suggested by the process of gene assembly in hypotrichous ciliates. This
process is considered to be a prine example of DNA computing in vivo. This paper is devoted to some computational aspects
of these operations from a formal language point of view. The closure of the classes of regular and context-free languages
under these operations is settled. Then, we consider theld-macronuclear language of a given languageL, which consists of allld-macronuclear strings obtained from the strings ofL by iteratively applying the loop-direct repeat-excision. Finally, we discuss some open problems and further directions of
research.
Rudolf Freund: He received his master and doctor degree in computer science from the Vienna University of Technology, Austria, in 1980
and 1982, respectively. In 1986, he received his master degree in mathematics and physics from the University Vienna, Austria.
In 1988 he joined the Vienna University of Technology in Austria, where he became an Associate Professor in September 1995.
He has given various lectures in theoretical computer science, especially on formal languages and automata. His research interests
include array and graph grammars, regulated rewritung, infinite words, syntactic pattern recognition, neural networks, and
especially models and systems for biological computing. In these fields he is author of more than sixty scientific papers.
Carlos Martín-Vide: He is Professor and Head of the Research Group on Mathematical Linguistics at Rovira i Virgili University, Tarragona, Spain.
His specialities are formal language theory and mathematical linguistics. His last volume edited is Where Mathematics, Computer
Science, Linguistics and Biology Meet (Kluwer, 2001, with V. Mitrana). He published 150 papers in conference proceedings and
journals such as: Acta Informatica, BioSystems. Computational Linguistics, Computers and Artificial Intelligence, Information
Processing Letters, Information Sciences, International Journal of Computer Mathematics, New Generation Computing, Publicationes
Mathematicae Debrecen, and Theoretical Computer Science. He is the editor-in-chief of the journal Grammars (Kluwer), and the
chairman of the 1st International PhD School in Formal Languages and Applications (2001–2003).
Victor Mitrana, Ph.D.: He is Professor of Computer Science at the Faculty of Mathematics, University of Bucharest. He received his MSc and PhD
from the University of Bucharest in 1986 and 1993, respectively. In 1999 he was awarded with the “Gheorghe Lazar” Prize for
Mathematics of the Romanian Academy. His research interests include: formal language theory and applications, combinatorics
on words, computational models inspired from biology, mathematical linguistics. In these areas, he published three books,
more than 100 papers, and edited two books. He is an associate editor of “The Korean Journal of Computational and Applied
Mathematics” and an editor of “Journal of Universal Computer Science”. 相似文献
206.
Victor T. Witusiewicz Ferdinand Sommer 《Metallurgical and Materials Transactions B》2000,31(2):277-284
The partial (Δ
and the integral (ΔH) enthalpies of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys have been determined by high-temperature isoperibolic calorimetry
at 1565 ± 5 K. The heat capacity (C
p) of liquid Ni26Zr74 has been measured by adiabatic calorimetry (C
p=53.5±2.2 J mol−1 K−1 at 1261±15 K). The integral enthalpy of mixing changes with composition from a small positive (Cu-Ni, ΔH (x
Ni=0.50, T=1473 to 1750 K)=2.9 kJ mol−1) to a moderate negative (Cu-Zr; ΔH(x
Zr=0.46, T=1485 K)=−16.2 kJ mol−1) and a high negative value (Ni-Zr; ΔH(x
Zr=0.37, T=1565 K)=−45.8 kJ mol−1). Regression analysis of new data, together with the literature data for liquid Ni-Zr alloys, results in the following relationships
in kJ mol−1 (standard states: Cu (1), Ni (1), and Zr (1)):for Ni-Zr (1281≤T≤2270 K),
for Cu-Ni-Zr (T=1565±5 K),
相似文献
207.
The validity of the -expansion in the turbulence problem is discussed using the example of diffusion of a passive scalar in a random velocity field. A generalization of Wilson's rule for calculating a diagram of arbitrary order is introduced. The resulting perturbation series, while having zero radius of convergence, is summed exactly yielding amplitudes which differ from those obtained to lowest order in the -expansion by only a few percent. The properties of the expansion are analyzed in detail and it is shown that various subsets of diagrams, while differing by an infinite number of terms, give close results in the vicinity of the fixed point. This indicates nontrivial compensation of high-order interactions in turbulence. The irrelevance of high-order couplings is demonstrated for arbitrary values of . The quality the approximation is tested by comparison with numerical experiments on diffusion of a passive scalar in a band-limited random velocity field in the limit of infinite Peclet number. 相似文献
208.
209.
210.
Positron annihilation lifetime (PAL) spectra were measured for two different kinds of polymers: polypropylene (PP) and polytetrafluoroethylene (PTFE), during sorption of vapors of the following molecules: n-hexane, cyclohexane, benzene, methyl methacrylate, acrylic acid, and water. The behavior of ortho-positronium (o-Ps) annihilation parameters: lifetime, τ3, and intensity, I3, can be explained by considering different sorption mechanisms in rubbery and glassy polymers. The mean size of the intermolecular-space holes and the relative free-volume fraction of PP and PTFE were estimated before and during the sorption process from the o-Ps parameters obtained. Sorption of n-hexane, cyclohexane, and benzene in both polymers affect the o-Ps component in a systematic way, for PP τ3 and I3 tend to decrease, while in PTFE, τ3 stay almost constant and I3 diminishes. These effects are interpreted in relation to the different states of the polymers studied: rubbery for PP and glassy for PTFE. In case of methyl methacrylate molecules, the behavior of o-Ps parameters was more complicated. For acrylic acid and water, their associated polarity provokes a diminution in I3, which is explained from the viewpoint of the spur model of positronium formation. Large changes in the mean size and the fraction of free volume, as well as their constant behavior in some cases, were interpreted to be due to positive or negative interactions, respectively, between vapor molecules and PP and PTFE, which could be correlated with the solvent-interaction parameters calculated. © 1995 John Wiley & Sons, Inc. 相似文献