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141.
刘丽丽 《计算机工程与应用》2011,47(31):185-188
马尔可夫随机场(MRF)在SAR图像分割中有着广泛的应用。由于合成孔径雷达(SAR)图像本身所固有的相干斑噪声的影响,传统方法很难获得准确的分割,因此提出了一种新的基于MRF(Markov Random Field)融合Gaussian-Hermite矩(GHM)的SAR图像无监督分割算法。利用Gaussian-Hermite矩的不同阶矩作为SAR图像特征得到初始分割;将得到的初始分割结果作为MRF随机场的先验模型,通过引入一个基于两成分权重参数的能量函数,利用最大后验概率(MAP)得到最终的分割结果。通过对合成图像及SAR图像分割实验结果的比较,表明了该方法在误分率、抗噪性以及视觉效果上具有更好的效果。 相似文献
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研究了金属疲劳断口图像的分割问题,提出了一种基于马尔可夫随机场(MRF)的金属疲劳断口图像的条带分割方法。由于疲劳断口图像中的纹理记录了整个断裂过程中的受力情况,通过对疲劳断口的条带纹理进行分析可以反演断裂的过程,因此研究疲劳断口图像的分割可以对失效分析有重要的科学价值。文中构造了图像的马尔可夫随机场模型,并且提出了一种基于该模型的图像分割算法。马尔可夫随机场模型是一种描述图像结构的概率模型,能够充分利用图像的空间相关信息,能够实现对低信噪比的金属疲劳断口图像进行条带分割。结果表明算法具有收敛速度快、稳健性好等优点。 相似文献
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基于图像分割的立体匹配算法 总被引:1,自引:0,他引:1
基于马尔可夫随机场(MRF)的立体匹配算法利用MRF模型来对匹配取值进行连续性约束。然而,MRF模型是产生式模型,图像自身特征难以得到准确描述。提出了一种基于图像分割的立体匹配算法SGC。SGC算法预先对图像进行分割,基于图像分割信息建立立体匹配的MRF模型,从而连续性(平滑)约束可以保留视差图中分割的边缘信息;并针对图像的深度连续性约束,定义了一个反映图像自身特征的新能量函数,应用于图割算法,提高了视差计算精度。实验结果表明,与以往算法相比,SGC算法更准确地反映了图像中深度信息,避免了平滑约束所引入的误差,有效提高了视差计算精度。 相似文献
147.
Benjin Wang Hans De Backer Airong Chen Franziska Schmidt 《Structure and Infrastructure Engineering》2017,13(12):1639-1652
This paper presents a multi-scale approach to predict the macro-crack initiation life (MCIL) of welded joints. This fully adaptive multi-scale technique is designed to take into account micro-scale material heterogeneity due to the existence of defects and to consider the uncertainties regarding defect occurrence and characteristics and traffic loading. The procedure of the proposed approach was introduced along with an orthotropic steel deck. Firstly, a homogenisation method was used to link defects in the heat-affected zone with the macro-scale structure. This allows for estimating the effective Paris constant, required for a Paris Law-based fatigue damage analysis. Secondly, a traffic flow, based on weigh-in-motion measurements, was used to simulate the load effects on the examined joint. Afterwards, the extended finite element method was adopted to calculate the stress intensity factors with respect to the weld geometries. Finally, the damage before macro-crack initiation was obtained using the Paris Law. In addition, Monte Carlo simulation was integrated within this multi-scale crack growth procedure to consider the randomness in pore and inclusion occurrence and characteristics. Hence, the MCIL is expressed in the form of a probability distribution. Results show that the proposed approach enables to provide a rational maintenance and inspection intervention time. 相似文献
148.
It is shown that an analogy can be made between the failure of unidirectional carbon fibre reinforced epoxy plates and filament wound carbon fibre composite pressure vessels and that their strengths and failure probabilities can be determined. Fibres in filament wound composite structures are placed on geodesic paths around the mandrel, which becomes the liner; so that when the structure is pressurised the fibres are only subjected to tensile forces, as in a unidirectional composite. Multiscale modelling reveals that composite failure is controlled by fibre breakage and that clustering of fibre breaks determines ultimate reliability of the structure. Time dependent relaxation of the matrix leads to delayed failure of the elastic fibres. A statistical study, using the stochastic properties of the fibres, determines the range of lifetimes which will be obtained in a given class of pressure vessel, leading to an evaluation of failure probabilities as a function of internal pressures. In this way the definition of safety factors, based on an understanding of the physical processes governing damage accumulation, becomes possible. 相似文献
149.
针对基于非负矩阵分解(NMF)的高光谱解混存在的初始化与"局部极小"等问题,提出一种基于马尔可夫随机场(MRF)的空间相关约束NMF线性解混算法(MRF-NMF)。首先,通过基于最小误差的高光谱信号识别(HySime)法估算端元数量,同时利用顶点成分分析(VCA)和全约束最小二乘法(FCLS)初始化端元矩阵与丰度矩阵;其次,利用MRF模型建立描述地物空间分布规律的能量函数,以此描述地物分布的空间相关特征;最后,将基于MRF的空间相关约束函数与NMF标准目标函数以交替迭代的形式参与解混,得出高光谱数据的端元信息与丰度分解结果。理论分析和真实数据实验结果表明,在高光谱数据空间相关程度较低的情况下,相比最小体积约束的NMF (MVC-NMF)、分段平滑和稀疏约束的NMF (PSNMFSC)和交互投影子梯度非负矩阵分解(APS-NMF)三种参考算法,所提算法的端元分解精度仍分别提高了7.82%、12.4%和10.1%,其丰度分解精度仍分别提高了8.34%、12.6%和9.87%。MRF-NMF能够弥补NMF对于空间相关特征描述能力的不足,减小解混结果中地物的空间能量分布误差。 相似文献
150.
In this paper, a two-step scale-up procedure based on asymptotic homogenization theory is proposed for hierarchical structures consisting of multigrains and multidomains in piezoelectric materials. Intragranular domains are modeled as a microstructure during the first-step homogenization. Then, in the second-step homogenization, an aggregate of randomly oriented grains is modeled by applying the first-step homogenized material properties of multidomains to every grain. A dual-domain structure consisting of positive and negative directional domains with a 180° orientation gap is computed for case study analysis. The three-dimensional electron backscatter diffraction-measured microstructure is employed for the multigrain structure. The effect of the domain configuration on the macroscopic homogenized material properties of polycrystalline piezoelectric materials is investigated through the two-step homogenization process. In particular, the material property changes caused by the piezoelectric effect, which cannot be estimated by the mixture law, are discussed for multigrain and multidomain structures. 相似文献