全文获取类型
收费全文 | 424篇 |
免费 | 69篇 |
国内免费 | 70篇 |
专业分类
化学 | 203篇 |
晶体学 | 25篇 |
力学 | 58篇 |
综合类 | 21篇 |
数学 | 12篇 |
物理学 | 244篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 18篇 |
2013年 | 68篇 |
2012年 | 18篇 |
2011年 | 20篇 |
2010年 | 8篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 23篇 |
2005年 | 27篇 |
2004年 | 28篇 |
2003年 | 9篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有563条查询结果,搜索用时 156 毫秒
491.
Swanhild Bernstein Helmut Schaeben 《Mathematical Methods in the Applied Sciences》2005,28(11):1269-1289
We consider a one‐dimensional Radon transform on the group SO (3), which is motivated by texture goniometry. In particular, we will derive several inversion formulae and compare them with the inversion of the one‐dimensional spherical Radon transform on ??3 for even functions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
492.
The influence of the high-energy heavy ion irradiation on the short range order and magnetic texture in amorphous FeNiSiB alloys are studied by Mössbauer spectroscopy. The rf-Mössbauer measurements reveal clear changes of the local structure induced due to high electronic energy deposition and related to the anisotropic growth effect. In the substantial volume fraction of irradiated samples the spins change their orientation from the in-plane to the perpendicular one.
相似文献493.
The surface structure and surface mechanical properties of low‐ and high‐density polyethylene were characterized by atomic force microscopy (AFM) as the polymers were stretched. The surfaces of both materials roughened as they were stretched. The roughening effect is attributed to deformation of nodular structures, related to bulk spherulites, at the surface. The surface‐roughening effect is completely reversible at tensile strains in the elastic regime and partially reversible at tensile strains in the plastic regime until the polymers are irreversibly drawn into fibers. AFM force versus distance interaction curves, used to measure changes in the stiffness of the surface and the surface elastic modulus as a function of elongation, show that the surfaces become softer as the polymers are drawn into fibers at high strains. At low elastic strains, however, the surface elastic modulus of HDPE increases—attributed to elastic energy stored by the amorphous regions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2263–2274, 2001 相似文献
494.
495.
On the optimization of surface textures for lubricated contacts 总被引:1,自引:0,他引:1
Gustavo C. Buscaglia 《Journal of Mathematical Analysis and Applications》2007,335(2):1309-1327
The pressure field that develops inside a lubricated contact obeys an elliptic equation known as Reynolds equation, with coefficients that depend on the shape of the contacting surfaces. The load-carrying capacity of a contact, defined as the integral of the pressure field, is an important performance indicator that should be as high as possible to avoid wear and damage of the surfaces. In this article, the effect of arbitrary uniform periodic textures on the load-carrying capacity of lubricated devices known as thrust bearings is investigated theoretically by means of homogenization techniques and first-order perturbation analysis. It is shown that the untextured shape is a local optimum for the load-carrying capacity of the homogenized pressure field. This is proved for bearings of general shape and considering both incompressible and compressible models for the lubricant. The homogenization technique however implies an error. Suitable bounds for the effect of this error are provided in a simplified case. 相似文献
496.
The formation of banded texture both in a semiflexible thermotropic liquid-crystalline polyester (SBH 112, synthesized from
sebacic acid, 4,4′-dihydroxybiphenyl and 4-hydroxybenzoic acid, from Eniricerche, Milan) and in a blend of SBH with graft
copolymers, consisting of a polyolefin (polyethylene or polypropylene) backbone and SBH grafts (COPPE, COPPP) has been studied
by polarization microscopy and by scanning electron microscopy. The influence of the preparation conditions upon the perfection,
characteristics and thermal stability of the banded texture has been investigated. The results show that the banded texture
formed in SBH sheared films possesses greater perfection, smaller band width and larger angle of deviation, and higher thermal
stability than the banded texture formed in COPPE and COPPP prepared under similar conditions. It has been assumed that the
chain rigidity of the macromolecules of the system is mainly responsible for the formation and perfection of the banded texture.
Received: 17 March 2000 Accepted: 26 July 2000 相似文献
497.
498.
表面织构对刀具切削性能及前刀面摩擦特性的影响 总被引:2,自引:1,他引:1
为了研究刀具表面织构对切削性能的影响,通过控制前刀面上微凹坑的直径、深度和面积占有率等参数制备了两组表面高度算术平均值Sa相同的织构刀具.使用Talysurf CCI Lite非接触式三维光学轮廓仪对织构表面进行测量,采用ISO25178参数对测量表面进行表征;通过SL200KS接触角测量仪测量织构刀具前刀面湿润性的变化;随后在CA6140车床上进行45钢切削试验,研究不同织构对切削力、前刀面摩擦特性、工件表面粗糙度和切屑形变的影响.结果表明:合理的表面织构能够改善刀具的切削性能;切削液在前刀面铺展较快的织构刀具获得了较好的切削性能;凹坑直径、深度和面积占有率的协同作用对改善刀具切削性能至关重要,为了协调这三个织构参数,进一步研究三维表征参数Sku、Ssk、Sv、Vvv、Vvc、Sdv、Sda、Spd与刀具切削性能的关联性,为刀具表面设计提供了基础. 相似文献
499.
高分子材料机械密封磨损特性及表面织构的影响 总被引:4,自引:1,他引:3
为提高金属/高分子材料机械密封的抗磨损性能,采用光刻-电解技术在316不锈钢表面制作微凹坑阵列形式的表面织构,与5种不同弹性模量的高分子材料组成摩擦副进行磨损试验.试验结果表明,对弹性模量最小的UHMWPE材料,表面织构起到了增磨作用,对其他四种弹性模量较高的材料,表面织构起到减磨作用,而且,随着高分子材料弹性模量的增大,表面织构表现出的减磨作用也随之增大.为解释这个现象,利用ANSYS有限元分析软件对摩擦副接触面进行了应力和变形分析,结果表明:织构化表面在接触过程中会产生应力集中和表面形变,材料的弹性模量越小,凹坑引起的变形越明显,可能产生的切削作用越显著. 相似文献
500.
偏振成像探测能反映出传统光学成像所无法反映的物体的信息,为了克服计算偏振参量图像丢失细节信息的不足,在已有偏振图像融合方法的基础上,提出一种基于综合图像特征的融合方法。相较于已有算法突出图像的某一方面特征,该算法提取图像的灰度特征、纹理特征和形状特征,据此确定融合权值,对图像进行融合,能够较好地反映目标的细节信息,融合后的图像相较于普通光强图像,方差、信息熵分别提高了12.6%、17.5%,平均梯度从0.59提高到1.83。针对该方法用到的特征维数较高的问题,提供了一种简化算法,耗时从3054降至1337。 相似文献