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521.
An improved technique for casting highly oriented films of block copolymers from solutions subjected to flow is presented. Polymer solutions were rolled between two counter-rotating adjacent cylinders while at the same time the solvent was allowed to evaporate. As the solvent evaporated, the block copolymers microphase separated into globally oriented structures. Using this method known as ‘roll-casting’ we present in this paper a study of the morphology of polystyrene-polybutadiene-polystyrene (PS/PB/PS) triblock copolymer cast with and without additional high molecular weight homopolymers. The pure copolymer films consisted of polystyrene cylinders assembled on a hexagonal lattice in a polybutadiene matrix in a near single-crystal structure. Blends of copolymer with high molecular weight polystyrene and/or polybutadiene, phase separated into ellipsoidal regions of homopolymer embedded in an oriented block copolymer matrix. Annealing the films resulted in conversion of the homopolymer regions to spheres accompanied by some misalignment of the copolymer microdomains. The morphology of these films as revealed by TEM is discussed. A brief discussion of the flow field that develops in the experimental system is also presented and its similarity to the flow field of our previous work is shown. © 1994 John Wiley & Sons, Inc. 相似文献
522.
A novel image fusion algorithm based on wavelet-based contourlet transform (WBCT) and principal component analysis (PCA) is proposed. The PCA method is adopted for the low-frequency components. Using the proposed algorithm to choose the greater of the active measures, the region consistency test is performed for the high-frequency components. Experiments show that the proposed method works better in preserving the edge and texture information than wavelet transform method and Laplacian pyramid (LP) method do in image fusion. Four indicators for the fusion image are given to compare the proposed method with other methods. 相似文献
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524.
纹理是图像分析和识别中经常使用的关键特征, 而小波变换则是图像纹理表示和分类中的常用工具. 然而, 基于小波变换的纹理分类方法常常忽略了小波低频子带信息, 并且无法提取图像纹理的块状奇异信息. 本文提出小波子带系数的局部能量直方图建模方法、轮廓波特征的Poisson 混合模型建模方法和基于轮廓波子带系数聚类的特征提取方法, 并将其应用于图像纹理分类上. 基于局部能量直方图的纹理分类方法解决了小波低频子带的建模难题, 基于Poisson 混合模型的纹理分类方法则首次将Poisson 混合模型用于轮廓子带特征的建模, 而基于轮廓波域聚类的纹理分类方法是一种快速的分类方法. 实验结果显示, 本文所提出的三类方法都超过了当前典型的纹理分类方法. 相似文献
525.
针对传统人脸检测中的过分类问题,提出一种结合LBP算子与类覆盖捕获图的人脸检测算法.该算法首先用ε-LBP算子提取人脸图像纹理特征,并把对应不同ε值提取的LBP特征数据加权融合起来,形成人脸图像特征向量,然后采用类覆盖捕获图构造分类器,最终对人脸图像实现有效检测.与传统方法相比,基于随机图理论的类覆盖捕获图能够克服过分类缺陷,比其他近邻图分类器更具优势,性能也比较稳定.实验结果表明,该算法可以有效检测人脸图像,尤其对存在模糊和光照异常的人脸图像具有较高的精确度和鲁棒性. 相似文献
526.
Comparative study for the removal of methylene blue via adsorption and photocatalytic degradation 总被引:1,自引:0,他引:1
Physically and chemically activated carbons were prepared from date pits and olive stones. Titania and WO(x)-TiO(2)/MCM-41 were prepared as photoactive catalysts. Surface characterizations were investigated from ash content, pH, base neutralization capacities and FT-IR techniques. The textural characteristics, namely specific surface area (S(BET)) and pore texture, were determined from low temperature adsorption of N(2) at 77 K. The decolorization of aqueous solution of methylene blue was performed by means of two alternative methods. Steam-activated carbons own higher surface area compared with ZnCl(2)-activated carbons, and the micropore surface area represents the major contribution of the total area. Steam-activated carbons were the most efficient decolorizing adsorbents owing to its higher surface area, total pore volume and the basic nature of the surface. The calculated values of DeltaG(0), DeltaH(0) and DeltaS(0) indicate the spontaneous behavior of adsorption. The photocatalytic degradation is more convenient method in decolorizing of methylene blue compared with the adsorption process onto activated carbons. 相似文献
527.
528.
This paper presents a new framework to predict the qualitative and quantitative variation in local plastic anisotropy due to crystallographic texture in body-centered cubic polycrystals. A multiscale model was developed to examine the contribution of mesoscopic and local microscopic behaviour to the macroscopic constitutive response of bcc metals during deformation. The model integrated a dislocation-based hardening scheme and a Taylor-based crystal plasticity formulation into the subroutine of an explicit dynamic FEM code (LS-DYNA). Numerical analyses using this model were able to predict not only correct grain rotation during deformation, but variations in plastic anisotropy due to initial crystallographic orientation. Optimal results were obtained when {1 1 0}〈1 1 1〉, {1 1 2}〈1 1 1〉, and {1 2 3}〈1 1 1〉 slip systems were considered to be potentially active. The predicted material heterogeneity can be utilised for research involving any texture-dependent work hardening behaviour, such as surface roughening. 相似文献
529.
530.
Halima Bubaker-IsheilJérôme Serri Jean-François Fontaine 《Optics and Lasers in Engineering》2011,49(7):793-803
Image correlation methods are widely used in experimental mechanics to obtain displacement field measurements. Currently, these methods are applied using digital images of the initial and deformed surfaces sprayed with black or white paint. Speckle patterns are then captured and the correlation is performed with a high degree of accuracy to an order of 0.01 pixels. In 3D, however, stereo-correlation leads to a lower degree of accuracy. Correlation techniques are based on the search for a sub-image (or pattern) displacement field. The work presented in this paper introduces a new correlation-based approach for 3D displacement field measurement that uses an additional 3D laser scanner and a CMM (Coordinate Measurement Machine). Unlike most existing methods that require the presence of markers on the observed object (such as black speckle, grids or random patterns), this approach relies solely on micro-geometrical surface textures such as waviness, roughness and aperiodic random defects. The latter are assumed to remain sufficiently small thus providing an adequate estimate of the particle displacement. The proposed approach can be used in a wide range of applications such as sheet metal forming with large strains. The method proceeds by first obtaining cloud points using the 3D laser scanner mounted on a CMM. These points are used to create 2D maps that are then correlated. In this respect, various criteria have been investigated for creating maps consisting of patterns, which facilitate the correlation procedure. Once the maps are created, the correlation between both configurations (initial and moved) is carried out using traditional methods developed for field measurements. Measurement validation was conducted using experiments in 2D and 3D with good results for rigid displacements in 2D, 3D and 2D rotations. 相似文献