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1.
敖磊  谭久彬  崔继文  康文静 《中国激光》2006,33(12):609-1614
为满足高精度计量和方位瞄准跟踪系统的发展对激光CCD自准直仪测量精度的要求,提出一种基于正交傅里叶-梅林矩的激光CCD自准直仪圆目标中心抗噪声精确定位方法。首先利用正交傅里叶-梅林矩(OFMM)的幅值旋转不变性和更低径向矩阶数在充分提取图像边缘细节信息的同时抑制图像噪声的影响,通过对图像边缘旋转后垂直方向上不同阶次的正交傅里叶-梅林矩之间关系的分析将圆目标轮廓定位至亚像素级,然后采用最小二乘拟合方法实现圆目标中心的精确定位。结果表明,该方法稳定性好,定位精度高且抗干扰能力强,改进后的激光CCD自准直仪的测量分辨力提高了10倍,测量精度由2″提高到±0.18″,可有效满足在小角度测量和瞄准等领域的高精度测量需要。  相似文献   
2.
旋转体表面轮廓测量的激光多普勒信号研究   总被引:7,自引:4,他引:3  
在利用激光多普勒效应对旋转体表面轮廓损伤进行测量时,其散射光的多普勒信号强度及质量是影响测量精度的极其重要的参数。研究了激光多普勒参考光技术、旋转体表面散射光位相无规则变化的平均效应和最小二乘法曲线拟合技术,设计出高信噪比的参考光路,并对物体表面细微结构所引起的信号丢失进行了重构,实现了旋转体表面轮廓损伤的测量,其相对误差约0.3%。  相似文献   
3.
NiAlFe thin films were prepared onto sapphire single crystals by physical vapour deposition (PVD) and these were analysed by X-ray photoelectron spectroscopy (XPS) in combination with argon ion etching to determine the composition depth profile and interfacial characteristics of the samples. Non-linear least square fitting (NLLSF) analysis of the data was required due to the conflict of several peaks of interest. XPS depth profiles show that, for non-annealed NiAlFe–Al2O3, the interface is sharp and oxygen diffusion occurs at different annealing temperatures. Ni remains chemically unaffected by the presence of oxygen while the formation of aluminium oxide compounds occur. Two iron species are present in the film thickness where the low binding energy component is attributed to Fe–Fe or Fe–Al interactions and the higher one to the NiAlFe compound. The reduction-dissolution of the sapphire substrate leads to depletion of oxygen in the sapphire surface layer and the formation of alumina at the NiAlFe–Al2O3 interface. Within the film, aluminium and nickel are present as an intermetallic compound. Annealing of the samples induces surface oxidation and the subsequent formation of an Al2O3 layer. This type of interphase morphology should lead to optimal fibre/matrix (F–M) adhesion, and therefore optimal load transfer between the matrix and reinforcement.  相似文献   
4.
Based on the classic absolute orientation technique, a new method for least-squares fitting of multiple point sets in m-dimensional space is proposed, analyzed and extended to a weighted form in this paper. This method generates a fixed point set from k corresponding original m-dimensional point sets and minimizes the mean squared error between the fixed point set and these k point sets under the similarity transformation. Experiments and interesting applications are presented to show its efficiency and accuracy.  相似文献   
5.
Fitting Gaussian peaks to experimental data is important in many disciplines, including nuclear spectroscopy. Nonlinear least squares fitting methods have been in use for a long time, but these are iterative, computationally intensive, and require user intervention. Machine learning approaches automate and speed up the fitting procedure. However, for a single pure Gaussian, there exists a simple and automatic analytical approach based on linearisation followed by a weighted linear Least Squares (LS) fit. This paper compares this algorithmic method with an abductive machine learning approach based on AIM 1 (Abductory Induction Mechanism). Both techniques are briefly described and their performance compared for analysing simulated and actual spectral peaks. Evaluated on 500 peaks with statistical uncertainties corresponding to a peak count of 100, average absolute errors for the peak height, position and width are 4.9%, 2.9% and 4.2% for AIM, versus 3.3%, 0.5% and 7.7% for the LS. AIM is better for the width, while LS is more accurate for the position. LS errors are more biased, under-estimating the peak position and over-estimating the peak width. Tentative CPU time comparison indicates a five-fold speed advantage for AIM, which also has a constant execution time, while LS time depends upon the peak width.  相似文献   
6.
A simple method for the analysis of stainless steel samples is presented which is based on radioisotope excited energy dispersive X-ray fluorescence (EDXRF) spectrometry and does not require any type-standards. Both absorption and enhancement effects have been taken into account in the fundamental parameter method for quantitative analysis and an iterative approach is followed for calculation of concentrations in steel samples. Non-linear least square fitting (NL-LSF) procedures have been used to determine accurately the fluorescent peak intensities. The method has been tested by analysing several CRM standard reference samples and 304 and 316 steel samples assuming as unknown. The EDXRF results have also been compared with the results of analysis of same samples by vacuum emission spark spectrometry (VES). Obtained values for concentration in steel samples match quite well with their certified values.  相似文献   
7.
细分曲面在逆向工程中的应用   总被引:1,自引:0,他引:1  
本文就细分曲面在逆向工程中的应用作了探讨。相比传统重建方法的不足,本文总结了细分重建的优势并基于Loop模式概述了细分重建的大致流程,包括网格简化与优化、重采样、最小二乘拟合。并简要介绍了Loop细分模式的细分规则和细分极限位置。  相似文献   
8.
一种快速识别变压器励磁涌流和内部故障的新方法   总被引:12,自引:3,他引:9  
基于励磁涌流波形畸变严重,会呈现出尖顶波的凹弧特征,而故障电流则基本保持基频正弦波(凸弧)特征的思想,该文提出了一种利用波形特征快速区分变压器励磁涌流和内部故障的新方法。该方法利用初始5ms内差电流的数据(5ms数据窗),将其拓展为长10ms的数据窗,然后通过最小二乘算法拟合差电流波形得到其近似表达式,再根据拟合曲线在各点处的曲率和凸凹特性来区分变压器励磁涌流和内部故障。动模实验表明:该方法能够快速地切除变压器内部故障,动作时间约为5ms,所需时间较短,识别灵敏度高,且实现方便,不受电流互感器饱和及非周期分量的影响。  相似文献   
9.
通过对上海市内环线高架若干路段的大量实测,获取了描述高架路交通宏观特征的交通流参数分布曲线. 采用非线性最小二乘拟合方法,对交通流性质进行分析,得到2种不同形式的速度-密度关系式,并据此得出畅行速度与阻塞密度这2个重要的交通流临界参数. 分析结果表明:指数形式的速度-密度关系适用于描述相对稀疏的交通流;双曲形式适用于描述较拥挤的交通流.  相似文献   
10.
相移器平移误差与倾斜误差不敏感相移新算法   总被引:1,自引:1,他引:0  
刘伟 《光学精密工程》2000,8(2):185-188
相移器的相移误差包括平移误差与倾斜误差,使同一幅干涉图诸像素点的相移量并不相等,但仍然在同一平面上.据此,本文提出了消除相移器位移误差与倾斜误差的最小二乘迭代算法.通过对相移平面的最小二乘拟合,即可以消除相移器平移误差与倾斜误差对位相分布求解结果的影响.并通过数值模拟,验证了这种算法在消除相移器位移误差与倾斜影响上的有效性.  相似文献   
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