全文获取类型
收费全文 | 324篇 |
免费 | 13篇 |
专业分类
公路运输 | 72篇 |
综合类 | 82篇 |
水路运输 | 125篇 |
铁路运输 | 37篇 |
综合运输 | 21篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 28篇 |
2013年 | 23篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 19篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有337条查询结果,搜索用时 62 毫秒
101.
Samiul Hasan Satish V. Ukkusuri 《Transportation Research Part B: Methodological》2011,45(10):1590-1605
Individual evacuation decisions are often characterized by the influence of one’s social network. In this paper a threshold model of social contagion, originally proposed in the network science literature, is presented to characterize this social influence in the evacuation decision making process. Initiated by a single agent, the condition of a cascade when a portion of the population decides to evacuate has been derived from the model. Simulation models are also developed to investigate the effects of community mixing patterns and the initial seed on cascade propagation and the effect of previous time-steps considered by the agents and the strength of ties on average cascade size. Insights related to social influence include the significant role of mixing patterns among communities in the network and the role of the initial seed on cascade propagation. Specifically, faster propagation of warning is observed in community networks with greater inter-community connections. 相似文献
102.
以公路两旁护林带为对象,根据实际测试的大量数据,分析超短波经过公路两侧护林带时的电波传播特性。并以树林中通用模型为基础,利用最小二乘法求解模型中的参数,建立树林中电波传播模型,得出树林中超短波电波传播损耗随树林厚度变化的曲线。 相似文献
103.
Line heating process is a very complex phenomenon as a variety of factors affects the amount of residual deformations. Numerical
thermal and mechanical analysis of line heating for prediction of residual deformation is time consuming. In the present work
dimensional analysis has been presented to obtain a new relationship between input parameters and resulting residual deformations
during line heating process. The temperature distribution and residual deformations for 6 mm, 8 mm, 10 mm and 12 mm thick
steel plates were numerically estimated and compared with experimental and published results. Extensive data generated through
a validated FE model were used to find co-relationship between the input parameters and the resulting residual deformation
by multiple regression analysis. The results obtained from the deformation equations developed in this work compared well
with those of the FE analysis with a drop in the computation time in the order of 100 (computational time required for FE
analysis is around 7 200 second to 9 000 seconds and where the time required for getting the residual deformation by developed
equations is only 60 to 90 seconds). 相似文献
104.
105.
106.
107.
108.
针对目前Ф840D货车车轮辐板孔裂纹故障增多及其可能带来的隐患,本文首先采用有限元方法数值模拟了不同运用条件下车轮的机械应力和制动热应力,其次根据线弹性断裂力学理论研究了辐板孔边裂纹的应力强度因子,最后结合Forman疲劳裂纹扩展方程及裂纹扩展门槛值,得到不同运用工况下辐板孔裂纹扩展的基本特性及规律,从而分析出了导致裂纹扩展的载荷条件.分析结果表明:辐板孔裂纹是典型的疲劳裂纹,是由萌生于辐板孔内侧的微细裂纹逐渐扩展而来的,它是由热负荷和机械载荷的综合效应造成的.单纯的机械载荷不会直接导致孔边裂纹的萌生和扩展;坡道制动与机械载荷的叠加才是导致辐板孔裂纹萌生与扩展的最主要的载荷工况.这对预防车轮疲劳失效、优化车轮设计,保障行车安全,具有重要意义. 相似文献
109.
火焰原子吸收分光光度法间接测定水中硫酸盐 总被引:3,自引:0,他引:3
为克服水中硫酸盐分析时操作繁琐,费时,显色不稳定等不足,采用首先将样品中硫酸盐转换成铬,再用火焰原子吸收法测定铬的方法,对水中硫酸盐的分析进行了研究,在选定的试验条件下,线性关系良好,相关系数r=0.9991,变异系数<3.26%,加标回收率在97.0%-106.6%之间,满足实际样品分析要求。 相似文献
110.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(6):565-581
Elastic waves may constitute a nuisance for people living close to high-speed lines. In order to decrease the spread of vibrations, it is common to reinforce the ground with lime cement columns. This article presents the results of simulations of three different ways to install the columns. The calculations have been done with an integrated rigid body—finite element model. Equations from various physical domains are merged into one big system. The results indicate that the straight configuration works best to protect the track. When attention is focused on preventing vibrations from the soil, the leaning column method is more effective. The chosen technique would depend on the aims of the countermeasure. 相似文献