全文获取类型
收费全文 | 159篇 |
免费 | 26篇 |
国内免费 | 36篇 |
专业分类
化学 | 16篇 |
晶体学 | 2篇 |
力学 | 109篇 |
综合类 | 1篇 |
数学 | 39篇 |
物理学 | 54篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 10篇 |
2012年 | 6篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 13篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 15篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 2篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有221条查询结果,搜索用时 31 毫秒
151.
This paper presents an analysis, based on a particle image velocimetry method, of soil flow field beneath a grouser wheel traveling over loose soil. Although the grouser wheel is expected to have better traction and mobility over fine, loose soil, its interaction mechanisms with the soil remain to be elucidated. Thus, a particle image velocimetry-based soil flow analysis is conducted to directly observe soil behavior around the grouser wheel. In the experimental analysis, key parameters of the soil flow field, such as general shape, thickness, streamlines of the flow field, soil velocity on the streamlines, and soil failure angle are examined quantitatively. From the results, the soil flow shape periodically changes with wheel rotation, and this change appears, depending on wheel slip varying over time. Furthermore, the experimental result of the soil failure angle differs drastically from its typical theory. These results will contribute to modeling the mechanical interaction between the grouser wheel and soil. 相似文献
152.
Xuefei Li Zongwei Yao Yonghai Yang 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(3):248-263
A seven-degrees-of-freedom (DOF) dynamic model was established based on the Lagrange equation to analyse the lateral stability and instability mechanism of an articulated wheel loader. A scale wheel loader was designed and manufactured to validate the dynamic model in two conditions, namely turning on slopes and passing over obstacles. Experimental data and simulated data fitted well on the whole, so the developed dynamic model was proved to be useful and could serve as an important tool to analyse the stability of wheel loaders. At last, the lateral stability of one ZL50 wheel loader was analysed by using this dynamic model. The results showed that there is a phenomenon of sudden stability losing during the wheel loader cornering due to the relative rotation between the subframe and the rear axle. The subframe can enhance the stability when the wheel loader is passing over obstacles but reduces the stability when it is turning. 相似文献
153.
为实现车轮不圆度激光测量仪与计算机串口之间的数据通信,设计了一套基于Java数据采集分析系统,实现了车轮不圆度测量数据与计算机串口之间的动态采集、显示、分析处理、存储等功能,同时具有友好的人机交互界面,具备实时性、可靠性、安全性特点;测试结果表明基于Java数据采集分析系统为现场车轮不圆度数据采集与分析提供了技术支持。 相似文献
154.
激光离散处理车轮钢-钢轨钢摩擦副的摩擦学性能研究 总被引:1,自引:0,他引:1
将激光离散处理前后的车轮试样分别与钢轨试样匹配,利用滚动接触摩擦磨损试验机测试各摩擦副的摩擦系数和磨损率,研究激光离散处理对轮轨摩擦副滚动接触摩擦磨损性能的影响.结果表明:车轮试样经过激光离散处理后,其抗磨损性能大幅增加,对应的轮轨试样摩擦副的摩擦系数小幅增加,其对摩钢轨试样的磨损加剧.未处理车轮试样主要发生剥层磨损并伴随轻微的疲劳磨损;处理后的车轮试样主要发生疲劳磨损并伴随轻微的剥层磨损.这是由于激光离散处理提高了车轮试样表层材料的抗塑性变形能力,从而抑制了材料的剥层磨损.各钢轨试样均发生剥层磨损,但是车轮试样经激光离散处理后,对应钢轨试样的剥层磨损加剧. 相似文献
155.
Pierre Aboulker 《Journal of Graph Theory》2014,75(4):311-322
A 4‐wheel is a graph formed by a cycle C and a vertex not in C that has at least four neighbors in C. We prove that a graph G that does not contain a 4‐wheel as a subgraph is 4‐colorable and we describe some structural properties of such a graph. 相似文献
156.
157.
1960年, Dirac证明了对一个阶为$n\geq 4$的图$G$,如果$G$的边数大于$2n-3$,那么$G$一定包含一个$K_4$的细分. 作者证明了对一个阶为$n\geq 4$的图$G$和$k\geq 2$,如果$G$的边数至少为$kn-\frac{(k-1)(k+2)}{2}$, 那么$G$一定包含一个$W_{k+1}$的细分,从而推广了Dirac的结果.另外,作者利用范更华提出的边切换的方法,给出了Dirac结果的另一种证明. 相似文献
158.
An equivalent soil mechanics formulation for rigid wheels in deformable terrain, with application to planetary exploration rovers 总被引:1,自引:0,他引:1
A simplified, closed-form version of the basic mechanics of a driven rigid wheel on low-cohesion deformable terrain is presented. This approach allows the formulation of an on-line terrain parameter estimation algorithm, which has important applications for planetary exploration rovers. Analytical comparisons of the original and simplified equations are presented, and are shown to closely agree. Experimental results from a single-wheel testbed operating in dry sand shows that the simplified equations can be used for mobility prediction with good accuracy. Methods for incorporating the simplified equations into an on-line terrain parameter algorithm are discussed. 相似文献
159.
160.
Koichiro Fukami Masami Ueno Koichi Hashiguchi Takashi Okayasu 《Journal of Terramechanics》2006,43(3):287-301
Soil–wheel interaction especially soil deformation caused by the wheel motion was investigated experimentally using a sophisticated soil bin test apparatus and an on-line measurement system for soil displacement. Based on these test results, characteristics of soil deformation were summarized focusing on the behavior and distribution of displacement increment vectors. Mathematical models were examined in order to describe the displacements of soil particles. Properties of the displacement loci are described. The magnitude of the displacement increment vector, its horizontal and vertical components are discussed, and characteristics of these distributions with respect to the relative horizontal distance from the vertical centerline of the wheel to the target point are clarified. Shapes of these distribution curves were closely similar to those of the derivatives of a Gaussian function. A distribution curve of the horizontal displacement increment had two peaks and that of the vertical one had three peaks. Based on the results, mathematical models for those displacement increments were proposed by employing a Gaussian function through multiplication of a linear function and a quadratic function. Predicted distributions and displacement loci of the models agreed with high accuracy to the measured values. The mathematical models were extended taking into consideration the wheel slip. The predicted distributions according to test conditions agreed very well to the measured results. 相似文献