全文获取类型
收费全文 | 78篇 |
免费 | 0篇 |
专业分类
公路运输 | 11篇 |
综合类 | 20篇 |
水路运输 | 14篇 |
铁路运输 | 14篇 |
综合运输 | 19篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 1篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有78条查询结果,搜索用时 31 毫秒
21.
阳安铁路增建第二线山区地质选线 总被引:2,自引:2,他引:0
《铁道标准设计通讯》2015,(7):3-8
近年来随着我国山区铁路的大量修建,山区铁路地质选线的重要性日益凸显。阳安铁路是典型的山区铁路增建第二线项目,该项目进行地质选线对于降低后期勘察设计难度、减少投资、降低后期维护费用等方面起决定性作用。针对既有河谷线地段,增建第二线线路穿越区域性大断裂等工程地质问题,采取何种地质选线的技术原则进行研究。研究结论:(1)本次地质选线过程中,综合采用遥感解译、地质调绘、钻探、试验等勘探方法,查清沿线的工程地质条件;(2)对线位比选起决定性作用的工程地质条件主要是断层、滑坡等不良地质,线路通过断层应以大角度、简单工程通过,其余不良地质应以绕避为主;(3)在充分总结汲取山区铁路综合选线技术经验的基础上,提出地质选线、定线原则;(4)通过对阳平关至响水、西乡至石泉、石泉至池河三段线路方案的比选,得出推荐方案。 相似文献
22.
23.
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
24.
The shelf-slope front (SSF) is a continuous shelf-break front running from the Tail of the Grand Banks to Cape Hatteras, North Carolina, separating colder and less-saline continental shelf waters from warmer and more saline slope waters. Time series containing mean monthly SSF positions were produced along each of 26 longitude lines between 75° and 50°W by workers located at Bedford Institute of Oceanography by digitizing individual frontal charts and computing mean monthly latitudinal positions over a 29-year (1973–2001) period. After removing seasonal variability at each longitude, interannual variability (IAV) of the SSF position at each longitude was computed as the annual mean of all monthly SSF position anomalies for each year over the 29-year period. Despite some missing data, a longitude-time plot reveals alternating bands of offshore (late-1970s, late-1980s, late-1990s) and onshore (early-1980s, early-1990s, early-2000s) annual mean SSF anomaly values, exhibiting a period of approximately 10 years. Annual mean SSF anomaly amplitudes are largest in the east, with maxima of O (± 100 km) located east of 60° W for years when data are available. Empirical orthogonal function (EOF) modes 1–4 (accounting for > 90% of the variance) form a set of basis functions that describe the SSF anomaly data and allow reconstruction of the entire data set since missing data are relatively few (14%). A complex empirical orthogonal function (CEOF) analysis using the “reconstructed” data reveals a wavelength scale of approximately 20° of longitude, a distance nearly equal to the entire study domain, along with steady, westward phase propagation of SSF anomalies over approximately the same distance. Speed calculations for the westward-propagating features yield a value of approximately 1.2 to 2.4 cm s− 1 (1 to 2 km d− 1), with annual mean SSF anomalies thus requiring about 4 years to propagate from the Tail of the Grand Banks in the east to Cape Hatteras, North Carolina, in the west. This propagation speed and the timing of the SSF positional anomalies at the Tail of the Grand Banks for the 29-year study period are in agreement with speeds computed for the propagation of quasi-decadal salinity anomalies through the Labrador Sea and the time of their arrival at the Tail of the Grand Banks. The small westward SSF anomaly propagation speed is an order of magnitude smaller than the associated currents, in agreement with a highly damped flow-through system originating from both Davis Strait and the West Greenland Current as discussed by other workers. Observations from both southern and northern portions of the study domain, within both continental shelf and slope waters, show that interannual changes in the volume of shelf water along with shelf water bulk properties exhibit a strong relationship with IAV of the SSF position over long time periods. 相似文献
25.
26.
27.
28.
RS-CR与RS-Turbo两类级联码的结构与性能分析 总被引:2,自引:0,他引:2
如果采用随机交织器和迭代的最大后验概率译码算法,Turbo码的译码性能接近Shannon限。但是当误比特率(BER)≤10-5时,性能曲线下降缓慢,趋近于水平线,影响了Turbo码的推广与应用。级联RS码能够有效地改善这一现象,但是RS Turbo级联码结构复杂,译码时延大。因此,本文基于交错与级联的思想,提出了一种新型的前向纠错码,即RS CR码(RS 复转码),设计构造了该码的编译码算法。RS码和复数旋转码同时对信息元进行编码,级联后新产生的二维前向纠错码,编码时间短,译码速度快,纠错能力可调,尤其适用于自适应的差错控制系统。 相似文献
29.
本文根据Hasofer-Lind关于结构可靠性指标的定义,提出改进的复形优化方法来计算可靠性指标,可避免复杂非线性极限状态函数的求导问题,亦可处理随机变量相关的问题。其突出的优点是,方法的通用性强,编制程序简单,便于推广应用。计算实例证明了本文方法的有效性。 相似文献
30.
Analysis of disc brake instability due to friction-induced vibration using a distributed parameter model 总被引:1,自引:0,他引:1
Y. -G. Joe B. -G. Cha H. -J. Sim H. -J. Lee J. -E. Oh 《International Journal of Automotive Technology》2008,9(2):161-171
This paper deals with friction-induced vibration of a disc brake system with a constant friction coefficient. A linear, lumped,
and distributed parameter model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are
used to investigate the dynamic stability, and, in order to verify simulations which are based on the theoretical model, an
experimental modal test and dynamometer test are performed. The comparison of experimental and theoretical results shows good
agreement, and the analysis indicates that modal coupling due to friction forces is responsible for disc brake squeal. Also,
squeal type instability is investigated, using a parametric analysis. This indicates which parameters have influence on the
propensity of brake squealing. This is helpful for validating the analysis model and establishing confidence in the experimental
results of the modified system. These results may also be useful during system development or diagnostic analysis. 相似文献