全文获取类型
收费全文 | 119篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
化学 | 13篇 |
晶体学 | 1篇 |
力学 | 8篇 |
综合类 | 1篇 |
数学 | 26篇 |
物理学 | 79篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 13篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 15 毫秒
81.
Optical tomography based on infrared laser light absorption is a promising approach for making spatially- and temporally-resolved fuel concentration measurements within combustion devices, but limited optical access often restricts both the number of laser beams and their arrangement. This paper demonstrates how Tikhonov regularization based on a Laplacian smoothing matrix can solve the resulting limited data tomography problem, and provides superior reconstructions for Gaussian phantoms compared to modified Landweber reconstruction. 相似文献
82.
为了同时获取样品的表面和深度信息,研究光学相干层析的成像原理,建立了基于光学相干层析技术的内窥系统,实现了旋转扫描成像,系统的工作波长为1 310 nm,工作带宽为80 nm.理论推导及计算机仿真得到了系统信噪比与干涉仪的分光比、反射率之间的关系并分析了理论分辨率和探测深度.提出外径为5 mm的内窥镜扫描探头,聚焦距离为12 mm,数值孔径NA为0.47,折射率分布常量A=0.218 7.利用微型电机驱动直角棱镜实现扫描,旋转速度为25 rpm,旋转一周得到640个采样点.采用多层盖玻片和洋葱表皮作为样品进行实验分析,得到了盖玻片和洋葱的图像,横向分辨率和纵向分辨率分别为10 μm和15 μm.结果表明,设计的光学相干层析内窥系统能够用于旋转扫描成像,获取更多的组织信息. 相似文献
83.
Atul Srivastava Katsuo Tsukamoto E. Yokoyama K. Murayama M. Fukuyama 《Journal of Crystal Growth》2010,312(15):2254-2262
The present work is concerned with the three-dimensional reconstruction of concentration field around a crystal growing from its aqueous solution using Fourier analysis based phase shift interferometric tomography. Projection data of convective field around a growing NaClO3 crystal have been recorded using a Mach–Zehnder interferometer. A new numerical method based on the concept of real time phase shift interferometry has been employed for the analysis of the interferograms. By interpreting the interferograms as projection data, the 3-D distribution of salt concentration has been determined using principles of tomography. Study shows that the Fourier analysis-based phase shift method is a novel approach for crystal growth studies as it requires only one interferometric image for the determination of full phase information as opposed to the conventional real time phase shift interferometry wherein at least three or more phase-shifted interferograms are needed. Results have been presented in the form of interferograms, path-integrated concentration contours and three-dimensional concentration profiles over select horizontal planes above the growing crystal. Based on the reconstruction results, distribution of salt concentration in the crystal vicinity is determined and an appropriate mechanism of buoyancy-induced fluid movement in the growth chamber is discussed. 相似文献
84.
85.
首先讨论利用网络理论进行电阻抗层析成像的基本原理,并给出了节点导纳知阵所应服从的两个基本约束.为了加速和改进算法,提出了多分辨率的算法.按照这一算法,首先将被测物体离散化为较大的单元,先在粗分辨率下进行求解,利用所得的结果作为估计的初值,再进行下一级较细分辨求解.计算机模拟结果表明,利用多分辨率技术可以加快收敛,减小误差. 相似文献
86.
Spatial and temporal resolution in cryo-electron microscopy—A scope for nano-chemistry 总被引:1,自引:0,他引:1
Cryo-electron microscopy has evolved in an established approach to study the structure of bio-colloids. Recent developments in instrumentation and automation, often demanded by life sciences, made cryo-EM a general tool in colloid chemistry. Recently improved instrumentation for vitrification has resulted in reliable and reproducible preparation of specimen in water and other solvents. A dynamic approach, following processes in time is gaining importance and a time resolution up to 1 ms is expected to become general available. With improved instrumentation and automation 3D reconstructions by cryo-EM tomography are becoming routinely accessible. Tomography as such or in conjunction with time resolved microscopy is expected to give new insights in (macro)molecular assembly/disassembly mechanisms and thus become an essential tool in nano-chemistry. 相似文献
87.
A. G. Ramm 《Proceedings of the American Mathematical Society》1996,124(2):567-577
Let , , be the backprojection operator. The range of this operator as an operator on non-smooth functions is described and formulas for are derived. It is proved that the operator is not injective on but is injective on the subspace of which consists of even functions . Singularities of the function are studied. Here is a piecewise-smooth compactly supported function. Conditions for to have compact support are given. Some applications are considered.
88.
A method for the measurement of the spatial distribution of birefringence, caused by intense femtosecond laser pulses in condensed plasma, is presented for the case of a Gaussian laser beam. For that only two light intensities are to be measured on the probe beam in a polariscope. 相似文献
89.
古琴的材质特性及制作工艺影响着古琴的品质,同时古琴形制与琴腔布局关系到古琴工艺的完善与传承, 因此在不破坏古琴结构的前提下获取内部琴腔特征与参数十分重要。利用CT无损检测技术对古琴整体进行扫描,得到了琴腔构造断层图,从而研究了古琴面板木纹纹理、面板底板的连接方式和内部缺陷,并运用Mimics软件中的面绘制法实现了古琴琴腔构造的三维重建,使CT断层扫描图像由二维转换为三维立体,更加完整全面地展现古琴琴腔构造形态,最后获得古琴具体琴腔尺寸。实验研究表明,仲尼式与落霞式古琴琴腔构造差异显著,其中仲尼式琴腔表面起伏变化较大,落霞式琴腔表面趋于平缓;仲尼式琴腔体积小于落霞式,琴项位对比明显。通过利用CT无损检测技术实现了对古琴内部信息的准确获取,这对于探究古琴的制作工艺及质量检测起到重要的技术支撑作用,同时也为其他传统珍贵器具内部结构的无损研究提供参考依据。 相似文献
90.