全文获取类型
收费全文 | 290篇 |
免费 | 2篇 |
国内免费 | 5篇 |
专业分类
化学 | 77篇 |
晶体学 | 1篇 |
力学 | 18篇 |
综合类 | 1篇 |
数学 | 3篇 |
物理学 | 197篇 |
出版年
2022年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 13篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 15篇 |
2001年 | 22篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 7篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 15 毫秒
61.
Two Dimensions Residual Stresses Analysis Through Incremental Groove Machining Combined with Electronic Speckle Pattern Interferometry 总被引:1,自引:1,他引:0
In this study a new residual stress determination method in two directions simultaneously is presented. This method is based
on stresses relaxation in a groove that is machined incrementally. The residual stresses relaxation occurs simultaneously
from both the depth and the length of the groove. Thus, measuring the surface strain field generated by the relaxation enables
to determine the stress gradient both along the depth and the length of the groove. To measure the surface strain in a direction
perpendicular to the groove, a digital speckle pattern interferometer is used. This method is suitable when the residual stress
field in the structure varies in the depth as well as along the surface of the part, like for example in a welded structure.
The method is tested here on an aluminium plate in which a central band has been shot peened. 相似文献
62.
If a laser beam illuminates a continual deformation object surface, it will lead to a temporal speckle pattern on the observation plane. Recording this time-dependent speckle pattern the deformation of the surface of an object can be obtained. Two methods, scanning phase method (SPM) and time sequence phase method (TSPM), have been introduced for measuring the displacement caused by the deformation in temporal speckle pattern interferometry (TSPI). Their principle is that by capturing a series of speckle interference patterns related to the object deformations, the fluctuations in the intensity of the interference patterns can be obtained. Through scanning these fluctuations and estimating both the average intensity and modulation of the temporal speckle interference patterns, the phase maps for whole-field displacements are calculated. In this way one is capable of quantitatively measuring continual displacements simply using a conventional electronic speckle pattern interferometry (ESPI) system without phase shifting or a carrier. The elaboration on the new methods is given in this paper and experiments are performed to demonstrate their performance with a conventional ESPI system. 相似文献
63.
Quality of chemical measurement is a central issue nowadays with social, political and economic implications. This paper aims
to describe how interlaboratory comparisons (ILCs) can contribute towards better quality of chemical measurements. The importance
of ILCs as well as the different types and the requirements for proper organization of ILCs are explained. The international
structure and organization of metrology is given, highlighting the activities related to chemical measurements. Particularly
the use of ILCs in the service of metrology in chemistry is highlighted. A very important discussion concerning ILCs is how
they can (or cannot) establish traceability. The view of the authors is that traceability cannot, as such, be established
through ILCs. On the other hand, participation in ILCs can clearly support the claims for quality measurements, as ILCs are
experimental and objective demonstrations of measurement capability. 相似文献
64.
S. Echeverría-Villagómez Y. Mitani-Nakanishi H. Nava-Jaimes 《Accreditation and quality assurance》2001,6(2):80-84
The Centro Nacional de Metrología (CENAM) has developed the MESURA Interinstitutional Network in collaboration with other research and development institutes
in Mexico. This network has the aim of providing integral metrological services to industry throughout the country, with uniform
standards of quality and consistency. The fulfillment of this aim has been possible because of a number of factors that have
made the MESURA Program an attractor for the integration of metrological services. Among these factors are: an unswerving
focus on the customer needs, an integral and logical problem solving approach to consultancy, adequate modular classification
of the consultants functions, clear-cut definition of the functions of each member of interdisciplinary groups, and a uniform
code of communication among the members of the network. The next stage of the strategy is to strengthen the link between metrology
and its industrial applications forming a new type of consultant with the technical experts from R&D Centers. These will be
consultants with general knowledge and experience in metrology, specialized in certain type of industrial processes and products.
The strategy will be initiated in the year 2000 and with it the MESURA Network is expected to make a strong contribution to
fostering the optimum use of metrology in industry and to act as a channel for the integration of other technologies in which
the participating Centers have expertise. 相似文献
65.
A speckle photographic technique is used for visualizing the planar distribution of the refractive deflection angles of light
transmitted through a compressible turbulent flow. Double exposure speckle photography is applied for the statistical analysis
of such flows. Quantitative visualization of the planar distribution of the refractive deflection angles of the light transmitted
through the compressible turbulent flow is performed. Turbulent structures are visible in the patterns of the deflection angles
isolines. The 2-D correlation functions of these deflection angles are constructed and analyzed. A mathematical procedure
for solving Erbeck-Merzkirch integral transformation is described and the 3-D density correlation functions are evaluated
using 2-D correlation functions of deflection angles of the light passed through the turbulence.
Received 14 November 1999 / Accepted 3 June 2000 相似文献
66.
一种改进的SAR图像边缘检测方法 总被引:6,自引:0,他引:6
针对Ration边缘提取算法对弱边缘检测效果差,边缘定位精度低的缺点,提出了一种改进算法用于检测微弱边缘,并给出具有FCAR特性的阀值选取办法,实际应用中,将两种方法结合为一种综合处理方法,对真实SAR图像的处理结果表明,该综合处理方法具有较高检测正确率及较好的边缘定位精度。 相似文献
67.
Improving estimation in speckled imagery 总被引:2,自引:0,他引:2
Klaus L. P. Vasconcellos Alejandro C. Frery Luciano B. Silva 《Computational Statistics》2005,20(3):503-519
We propose an analytical bias correction for the maximum likelihood estimators of theG
1
0
distribution. This distribution is a very powerful tool for speckled imagery analysis, since it is capable of describing a
wide range of target roughness. We compare the performance of the corrected estimators with the corresponding original version
using Monte Carlo simulation. This second-order bias correction leads to estimators which are better from both the bias and
mean square error criteria. 相似文献
68.
Leonid I. Muravsky Olexander P. Maksymenko Olexander M. Sakharuk 《Optics Communications》2004,240(4-6):275-291
The optical speckle–displacement correlation technique (OSDCT) is proposed for study of in-plane speckle displacements. The joint transform correlator architecture is used to evaluate the displacements of speckle subimages of strained surfaces. The procedure of the correlation response producing as a result of cross-correlation of strainless and strained surfaces in a conventional joint transform correlator (JTC) is considered. The convenient techniques for a joint power spectrum transformation are selected. The systematic and random errors of a mean speckle pattern displacement of a rigid body motion calculated by using the OSDCT and the digital speckle–displacement measurement technique are compared. The robustness of some JTC versions (a conventional JTC, a JTC with median thresholding, a JTC with subset median thresholding, and a fringe adjusted filter JTC) to input noise of speckle patterns and output noise of a correlation response is studied. 相似文献
69.
Roughness measurement of metallic surfaces based on the laser speckle contrast method 总被引:2,自引:0,他引:2
A method of measuring surface roughness of flat lapped, ground and polished metallic surfaces, by the far-field speckle contrast method is presented in this paper. The laser speckle contrast technique depends on the existence of an approximately linear relationship between the speckle contrast and the roughness of the illuminated surface. Initially it was shown that the linear relationship existed up to 0.1 μm Ra (centre-line average) roughness using Helium–Neon light, after which a saturation effect was observed. The effect of varying the incident angle of illumination was investigated with a view to extending the measurement range. The use of high incident angles of illumination has been found to increase the surface roughness range up to 0.4 μm measurement Ra. 相似文献
70.
本文针对散斑照相术中存在的三维位移分离问题进行了详细讨论.利用散斑杨氏条纹图的基本特性和物体变形的连续性提出了正确分离三维位移的方法.使得散斑照相术在三维变形测量方面得到了进一步完善.最后给出了 CMO620型车床主轴的三维热变形结果. 相似文献