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21.
Formation mechanism of bainitic ferrite and carbide 总被引:6,自引:0,他引:6
Hong-Sheng Fang Jia-Jun Wang Yan-Kang Zheng Ph.D. 《Metallurgical and Materials Transactions A》1994,25(9):2001-2007
Superledges on the broad faces of bainitic ferrite plates have been observed with transmission electron microscope (TEM).
The observed superledges, ranging from less than 1 to 24 nm in height, are imaged in three dimension by way of tilt operation
under TEM. Also, an array of smaller superledges are observed to pile up in front of a secondary phase. Pileup of superledges
in front of a barrier is indicative of the mobility of an individual superledge. The precipitation of carbide associated with
bainitic ferrite is also studied. It is observed that a carbide of a wedgelike shape may exist in front of a superledge with
its tip(i.e., thinner end) penetrating the austenite and its root (the other end) originating at α:γ boundary. This condition indicates
that the observed carbides may nucleate at the austenite side of α:γ phase boundary and grow toward austenite matrix.
This article is based on a presentation made at the Pacific Rim Conference on the “Roles of Shear and Diffusion in the Formation
of Plate-Shaped Transformation Products,” held December 18-22, 1992, in Kona, Hawaii, under the auspices of ASM INTERNATIONAL’S
Phase Transformations Committee. 相似文献
22.
LIU Guangzhen MA Zhanfang SHEN Jianquan 《武汉理工大学学报(材料科学英文版)》2006,21(4):16-18
1 IntroductionGold nanoparticles have attracted considerable atten-tionin manyfields duetotheir some special properties al-though goldis very popularfor beingchemicallyinert[1-3].For example ,gold nanoparticles as amplificationtags havebeenthe subject of research directed at gene analysis[4]and antibody or antigen detection[5-7]due to the large di-electric constant ,ease of preparation,andits biocompati-bility[8].Nanoparticles in the range of 1-10 nmin diameterwould display electronic structur… 相似文献
23.
Joseph D. Rigney M.S. Preet M. Singh Ph.D. John J. Lewandowski Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(8):36-41
A variety of materials have been toughened via the addition of a ductile phase. Brittle silicide intermetallics such as Nb5Si3 have been significantly toughened by niobium particles incorporated during in-situ processing techniques. In the work described here, toughness tests conducted on Nb5Si3 were monitored in a scanning electron microscope to view the process of toughening provided by the niobium particles. In particular, the behavior of the ductile phase was monitored and related to the toughness obtained. In an attempt to vary the behavior of the ductile phase, the composite materials were exposed to a variety of gaseous environments and subsequently tested in air. The resulting toughness, resistance-curve behavior, and in-situ results highlight the importance of the behavior of the ductile phase on subsequent properties. 相似文献
24.
Shiun Ling Ph.D. Michael P. Anderson D.Eng.Sc. 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(9):30-36
The prediction and control of metal grain structures during processing have been major objectives of materials science. However, methodologies that are accurate and can be easily generalized to a variety of processing conditions have been difficult to formulate due to the complexity of the grain interactions. A novel Monte Carlo-based approach that explicitly incorporates these interactions has been developed to simulate the microstructural evolution driven by the minimization of grain boundary energy and lattice defect density. The applicability of this procedure has been demonstrated by the good correspondence between simulation results and experimental observations. This article reviews recent advances in the application of this technique to the investigation of a variety of phenomena, including normal and abnormal grain growth as well as static and dynamic recrystallization. 相似文献
25.
Alton T. Tabereaux Ph.D 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(11):20-26
Refractories for aluminum reduction cell cathodes are changing to meet the needs of new, energy-efficient long-life cathode designs. New refractories and modified versions of old refractories have been introduced, and information on their performance is becoming available. This article reviews some of the advantages and disadvantages of new and old cathode refractory materials. 相似文献
26.
D. M. Kroeger Ph.D. A. Goyal Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(10):42-47
Critical current density (Jc) in the presence of a magnetic field is the property that currently limits many applications of the high-critical-temperature oxide superconductors. Poor current transmission at grain boundaries and weak flux pinning are responsible for the low critical current densities observed in bulk materials. Since 1986, substantial progress has been made both in understanding the microstructural factors affecting Jc and in developing practical fabrication methods. Much of the fundamental understanding has been obtained from studies of YBa2Cu3O7?x while the bismuth and thallium-based compounds appear to offer greater potential as the basis for the first practical conductors. 相似文献
27.
Encompassing such versatile analytical techniques as scanning tunneling microscopy and atomic (or scanning) force microscopy, scanning probe microscopes produce high-resolution three-dimensional images. Because of their power as quantitative tools for three-dimensional surface measurement and analysis, the techniques are being used in materials science and engineering for the study of a variety of advanced materials and for investigations into numerous phenomena, including reaction chemistry, crystallinity, kinetics, equilibrium processes, tribology, and conductivity. 相似文献
28.
Three-dimensional, turbulent fluid flow analysis with computational methods has emerged as a viable tool in the design process
of engine components for passenger cars. If applied in the early stages of the component development such analysis can help
reduce the product development time drastically, and may support the design engineer to evaluate several competing design
aspects before product completion. However the grid generation for complex geometries still poses a difficult and time consuming
taks which strongly influences the accuracy of the numerical solution. The present paper studies the numerical solution of
the flow in an inlet-manifold of a five-cylinder engine with two intake-ports for each cylinder. A fast and reliable grid
generation technique is discussed in detail. The finite volume based Navier-Stokes solver with schemes of first and second
order accuracy for the convective terms is used. Numerical results at several mass flow rates and different boundary conditions
at the intake ports are compared with measurements. Finally, the computational results are discussed with respect to their
applicability to support the design process of an inlet-manifold. 相似文献
29.
Mosfata Khattab Ph.D.
F. Choobineh P.E.
Ph.D. 《Computers & Industrial Engineering》1991,21(1-4):291-295Two important characteristics of a project network are the network's topology and the amount of resources available. Most published project scheduling procedures take one or both of these two characteristics into account. Project scheduling procedures that are robust over variations of network characteristics are desirable. The degree of robustness is generally gauged by one or more measures of performance.
The objective of this paper is to compare a set of priority rules that are useful for a single resource project scheduling problem. The set of networks suggested by Patterson (1973) is used along with the set of performance measures proposed by Khattab and Choobineh 1991. The result of this comparison allows one to design a multiattribute heuristic for a single resource project scheduling problem. 相似文献
30.
C. Sarrazin-Baudoux F. Loubat Ph.D. S. Potiron 《Metallurgical and Materials Transactions A》2006,37(4):1201-1209
The influence of gaseous atmosphere on the fatigue crack propagation behavior of a Ti6242 alloy is studied at 550 °C. The
aim of this paper is to obtain reference data in controlled environments at the atmospheric pressure in view of a further
evaluation of the corrosion-fatigue resistance of this alloy in super-critical water medium for a new process for hydrothermal
treatment of organic effluents. Tests were conducted in ambient air, high vacuum, and humidified gaseous atmospheres (80 pct
RH) including pure argon, 80 pct argon + 20 pct oxygen, and 80 pct nitrogen + 20 pct oxygen. The loading specimen was triangular
at a frequency of 0.05 Hz. Some additional tests were performed at frequencies ranging from 0.001 to 35 Hz. The crack propagation
rate is shown to be highly sensitive to the environment, with a predominant detrimental influence of water vapor. A crack
growth model is proposed accounting for the influence of partial pressures of water vapor, oxygen, test, and frequency. 相似文献