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1.
The goal of this paper is to describe essential criteria for image analysis of planar laser-induced fluorescence (PLIF) signals. A new image file conversion method is introduced and some typical illustrative examples showing the potential applications of the method in PLIF experiments are presented. Analysis of row, column, and total pixel counts, and the dark noise related to an image are discussed. Image segmentation, averaging and background correction can be easily done by the reported method. In our analysis it is straightforward to inspect the pixel counts and check for saturation of the camera sensors. It is also feasible to obtain a particular row or column for interpretation and it offers an easy way to check the validity of the captured images. Furthermore, the method offers a sensitive technique to check pulse-to-pulse variation of the excitation laser by using frame-to-frame fluorescence image data comparison, which is more illustrative than power checking by other means. The overall results show that the developed conversion method reported here can be effectively used to obtain more in-depth and quantitative information out of the raw data for the PLIF experiments.  相似文献
2.
A new method to detect leakage in a water-filled plastic pipe is proposed. In this method, a leakage signal-signature in time domain is first captured by monitoring the Short Time Fourier Transforms (STFT) of AE (Acoustic Emission) signals over a relatively long time-interval. The captured signal is then used to find a mother wavelet (tuned wavelet) for the best signal localization in time and frequency domains. The technique for AE signal detection using tuned wavelet is then described. Practical application of the method proposed herein is then presented using a water-filled plastic pipe as a case study. Signals generated from this experimental setup are collected to identify leakage signal-signatures from other interfering signals (background, pipe natural frequency, splash and environmental noise). The results of the experiment prove that using tuned wavelet, AE events can be detected and identified precisely in time. In addition, sources of signals due to leakage and their respective energy levels can also be recognized.  相似文献
3.
This paper presents, for the first time, exact closed-form frequency equations and transverse displacement for thick circular plates with free, soft simply supported, hard simply supported and clamped boundary conditions based on Reddy's third-order shear deformation theory. Hamiltonian and minimum potential energy principles are used to extract the equations of dynamic equilibrium and natural boundary conditions of the plate. The new formulation is verified by comparing the results with their counterparts reported in open literature. Natural frequencies of circular plates with different boundary conditions are tabulated in dimensionless form for various values of thickness-radius ratios. The results presented on the basis of exact, closed-form frequency equations are expected to serve as reliable benchmarks.  相似文献
4.
Image quality measurement besides distortion type classifying   总被引:3,自引:0,他引:3  
To identify the distortion type and quantify the quality of images, a new method is presented based on a comparison among the structural properties as well as consideration of the luminance characteristics of the two compared images. To fulfill this aim, the mathematical concept of the singular value decomposition (SVD) theorem has been applied. The difference vector of the reflection coefficients of the disturbed and the original image on the right singular vector matrix of the original image are considered. Many tests were conducted to evaluate the performance, using a widespread subjective study involving 779 images from the Live Image Quality Assessment Database, Release 2005. The results showed a greatly improved performance along with the ability to distinguish distortion type of images.  相似文献
5.
Mass measurement using an intensity-modulated optical fiber sensor   总被引:2,自引:0,他引:2  
Design and operation of an opto-mechanical sensor for mass measurements is reported. This device uses a pair of optical fibers and a reflecting coated lens. The light intensity modulation is based on the relative motion of the lens due to a given mass with respect to the optical fibers. The modulated intensity because of the weighing mass has been measured by using a digital voltmeter. A full-range sensitivity of about 11.5 mV/g for a dynamic range of 80 g is obtained. A mass resolution of better than 0.25 g has been measured with this device. The measured output response is checked against the expected theoretical one and a general agreement observed. A comparison with similar experimental results shows some advantages of this method and potential use of such a sensor for medium mass measurements.  相似文献
6.
Trend of laser research developments in global level   总被引:2,自引:0,他引:2  
An up-to-date progress of the international laser research and development is given in this article. The number of scientific publications and filed patents are considered as a figure of merit and based on these numbers the growth pace and important aspects are investigated. We have used the Science Finder Scholar search engine, which indexes more than 4000 journals, in different languages, and represents most significant published materials in laser science and engineering. The growth of the laser and related fields are described in terms of resulting scientific publications for the period of 1990–2003. The share of top nations in scientific publications, and in particular laser publications in terms of their gross domestic product (GDP) is presented. It is noted that the four countries including the USA, Japan, Germany and China have a laser publication contribution of 58.9% while the rest of the world including 189 countries contribute 41.1%. However, for the case of patent, which is a more important factor, these four countries hold a share of 90.1% while the remaining nations have a small share of 9.9%. The USA heads all the nations in the number of scientific publications, citations, and laser publications, however, in terms of accepted laser patents Japan shows a big lead. Scientific scopes of the laser systems are presented and some requirements to be met in each field are described. The key points in this field of research, which might be helpful in the future development of the laser technology are discussed.  相似文献
7.
Adhesive and cohesive properties of the plasma-sprayed hydroxyapatite (HA) coatings, deposited on Ti-6Al-4V substrates by varying the plasma power level and spray distance (SD), were evaluated by an indentation method. The crystallinity and the porosity decreased with increasing both of these two parameters. The microhardness value, Young's modulus (E) and coating fracture toughness (KC) were found to increase with a combinational increase in spray power and SD. The Knoop and Vickers indentation methods were used to estimate E and KC, respectively. The critical point at which no crack appears at the interface was determined by the interface indentation test. This was used to define the apparent interfacial toughness (KCa) which is representative of the crack initiation resistance of the interface. It was found that KCa reaches to a maximum at a medium increase in both spray power and SD, while other mechanical properties of the coatings reaches to the highest value with further increase in these two plasma parameters. The tensile adhesion strength of the coatings, measure by the standard adhesion test, ISO 13779-4, was shown to alter in the same manner with KCa results. It was deduced that a combinational increase in spray power and SD which leads to a higher mechanical properties in the coatings, does not necessarily tends to a better mechanical properties at the interface.  相似文献
8.
9.
Among various speech enhancement methods, dual-microphone methods are of a great importance for their low cost implementation and for exploiting spatial-filtering benefits of the microphone arrays. Coherence based methods are well-known as efficient two-microphone noise reduction techniques. These techniques do not work well, when received noise signals are correlated. These can be improved when the cross power spectral density (CPSD) of noise is available. In this paper, we propose an iterative approach for estimation of the noise CPSD to be employed in coherence based methods. We compare the proposed iterative noise CPSD estimation with a noise CPSD estimation technique based on voice activity detector (VAD), both of which are employed in a two-microphone speech enhancement, separately. Evaluation results show that the two-microphone speech enhancement scheme utilizing the proposed noise CPSD estimation technique performs superior than the enhancement system using the VAD-based noise CPSD estimation.  相似文献
10.
Nanosecond pulsed laser ablation of silicon in liquids   总被引:2,自引:0,他引:2  
Laser fluence and laser shot number are important parameters for pulse laser based micromachining of silicon in liquids. This paper presents laser-induced ablation of silicon in liquids of the dimethyl sulfoxide (DMSO) and the water at different applied laser fluence levels and laser shot numbers. The experimental results are conducted using 15 ns pulsed laser irradiation at 532 nm. The silicon surface morphology of the irradiated spots has an appearance as one can see in porous formation. The surface morphology exhibits a large number of cavities which indicates as bubble nucleation sites. The observed surface morphology shows that the explosive melt expulsion could be a dominant process for the laser ablation of silicon in liquids using nanosecond pulsed laser irradiation at 532 nm. Silicon surface’s ablated diameter growth was measured at different applied laser fluences and shot numbers in both liquid interfaces. A theoretical analysis suggested investigating silicon surface etching in liquid by intense multiple nanosecond laser pulses. It has been assumed that the nanosecond pulsed laser-induced silicon surface modification is due to the process of explosive melt expulsion under the action of the confined plasma-induced pressure or shock wave trapped between the silicon target and the overlying liquid. This analysis allows us to determine the effective lateral interaction zone of ablated solid target related to nanosecond pulsed laser illumination. The theoretical analysis is found in excellent agreement with the experimental measurements of silicon ablated diameter growth in the DMSO and the water interfaces. Multiple-shot laser ablation threshold of silicon is determined. Pulsed energy accumulation model is used to obtain the single-shot ablation threshold of silicon. The smaller ablation threshold value is found in the DMSO, and the incubation effect is also found to be absent.  相似文献
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