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1.
Vibration-resistant phase-shifting interferometry 总被引:1,自引:0,他引:1
Deck L 《Applied optics》1996,35(34):6655-6662
A method to reduce the sensitivity of phase-shifting interferometry to external vibrations is described. The returning interferogram is amplitude split to form two series of interferograms, taken simultaneously and with complementary properties, one with high temporal and low spatial resolution and the other with low temporal and high spatial resolution. The high-temporal-resolution data set is used to calculate the true phase increment between interferograms in the high-spatial-resolution data set, and a generalized phase-extraction algorithm then includes these phase increments when the topographical phases in the high-spatial-resolution data set are calculated. The measured topography thereby benefits from the best qualities of both data sets, providing increased vibration immunity without sacrificing high spatial resolution. 相似文献
2.
The last generation of infrared imaging aircraft seekers and trackers uses pattern recognition algorithms to find and keep
a lock on an aircraft in the presence of decoy flares. These algorithms identify targets, based on the features of the various
objects in the missile’s field of view. Because modern both aircrafts and missiles fly faster than sound, speed of operation
of the target identifier is critical. In this article, we propose a target recognition system that respects this time constraint.
It is based on an artificial neural network implemented in hardware, as a set of parallel processors on a commercially available
silicon chip called a ZISC, for zero instruction set computer. This chip would be integrated in the infrared missile seeker
and tracker. We describe the characteristics of the images that the image processing module of this seeker and tracker extracts
from the infrared video frames and show how to construct from these translation and rotation invariant features that can be
used as input to the neural network. We determine the individual discriminating power of these features by constructing their
histograms, which allows us to eliminate some as not being useful for our purpose. Finally, by testing our system on real
data, we show that it has a 90% success rate in aircraft-flare identification, and a processing time that during this time,
the aircrafts and missiles will have traveled only a few millimeters. Most of the images on which the neural network makes
its mistakes are seen to be hard to recognize even by a human expert. 相似文献
3.
This letter describes a technique to evaluate the radiometric quality of distributed target responses extracted from Synthetic Aperture Radar (SAR) data. The approach is original in that it aims to estimate the Equivalent Number of Looks of clustered pixels, a parameter which summarizes the first order statistics of speckle. This empirical method can be applied to processed, interpolated, and even speckle-filtered, SAR images. Using ERS-1 Precision Image SAR data, it is shown, first, how to discriminate between uniform and non-uniform targets, and, then, to estimate the radiometric resolution of pixels gathered according to several clustering schemes. 相似文献
4.
A numerical investigation of the overexpanded reactive gas flow in the ATAC nozzle of rectangular section, equipped with an H2 injection, is carried out. This study is aiming at reproducing the reacting phenomena occurring when air engulfed in the separated region at the tip of the extension meets the H2 rich overexpanded flow. Both steady Reynolds Averaged Navier Stokes (RANS) and unsteady Delayed Detached Eddy Simulation (DDES) approaches are used to model turbulence and compared to each other. The effect of the chemical nature of the mixture (either frozen or reacting) on the flow dynamics is discussed. The computations are compared to wall pressure measurements and flowfield visualizations by instantaneous Planar Laser Induced Fluorescence of OH (PLIF-OH) and OH spontaneous emission. A self-sustained flow oscillation at a frequency of around 1 kHz is found numerically, in good agreement with the unsteady wall pressure measurements. An analysis of the space–time characteristics of the propagating disturbances contributes to a better understanding of this phenomenon. 相似文献
5.
6.
F. MOQUET M. RAMOS GUEDES-LAFARGUE R. VEDIE M. MAMOUN J.M. OLIVIER 《Journal of food science》1997,62(5):1054-1079
Cap color was characterized on a wide range of Agaricus bisporus strains. L, a and b tristimulus coordinates were tested by linear model analysis to determine color information related to each parameter. One model was retained: log(L/(100-L)) =α* H +β. Visual cap color variation was continuous and well described by log(L/(100-L)) or H parameters. In the wild, the range of color varied from white to dark brown which would enable mushroom breeding for cap color adapted to the market. 相似文献
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8.
Conversion coatings on metals enhance paint or lacquer adhesion and promote corrosion resistance. Traditionally, these conversion coatings were based on chromium chemistry. In recent years, formulations based on fluotitanic or fluozirconic acid and polymer have demonstrated performance on a par with chromium-based treatments. The choice of fluoacid and polymer in the treatment has a strong impact on coating performance. The impact of pretreatment composition was demonstrated for aluminum extrusion processes. Electrochemical investigation, including linear polarization and electrochemical impedance spectroscopy, was used to differentiate corrosion resistance among the various treatments. Scanning electron microscopy, grazing angle infrared spectroscopy, and X-ray photoelectron spectroscopy were used to elucidate chemical composition of the treated aluminum surfaces. 相似文献
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