全文获取类型
收费全文 | 6701篇 |
免费 | 494篇 |
专业分类
公路运输 | 3799篇 |
综合类 | 2455篇 |
水路运输 | 391篇 |
铁路运输 | 317篇 |
综合运输 | 233篇 |
出版年
2024年 | 56篇 |
2023年 | 105篇 |
2022年 | 136篇 |
2021年 | 238篇 |
2020年 | 249篇 |
2019年 | 150篇 |
2018年 | 104篇 |
2017年 | 60篇 |
2016年 | 79篇 |
2015年 | 179篇 |
2014年 | 486篇 |
2013年 | 404篇 |
2012年 | 560篇 |
2011年 | 698篇 |
2010年 | 583篇 |
2009年 | 507篇 |
2008年 | 588篇 |
2007年 | 679篇 |
2006年 | 485篇 |
2005年 | 272篇 |
2004年 | 172篇 |
2003年 | 140篇 |
2002年 | 107篇 |
2001年 | 59篇 |
2000年 | 31篇 |
1999年 | 17篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1984年 | 1篇 |
排序方式: 共有7195条查询结果,搜索用时 0 毫秒
1.
旧水泥混凝土路面加铺沥青混凝土面层,当没有路线设计资料时,需对旧有路线进行拟合,重新进行勘测设计,以获得与旧有路线一致的路线设计资料,为旧水泥混凝土路面加铺沥青混凝土面层提供设计依据。结合工程实践,介绍了拟合旧有路线时勘测设计的内容和方法。 相似文献
2.
3.
Despite improvements in road safety over the past several decades, accident rates remain high for young drivers. One accident countermeasure that is expected to improve the safety record of this group is graduated licensing. The philosophy behind this licensing system is that novice drivers, of whom the majority are young, should be restricted to relatively safe driving environments during the initial learning period. Graduated licensing was implemented in the Province of Ontario, Canada in 1994. The objective of this study is to estimate the potential benefits and costs for young drivers associated with two components of the Ontario graduated licensing package: the late-night driving curfew and the high-speed roadway restrictions. Based on accident and travel data for the year 1988, accident-involvement rates per kilometre driven were calculated for different driver groups for various combinations of time of day and roadway speed limit. These rates were then applied to the expected mobility profiles of young drivers affected by graduated licensing. The results of the study support the late-night curfew and suggest that this component of the licensing package should reduce total accident involvements for the affected group by up to 10 percent and fatal accident involvements by up to 24 percent, while reducing their total driving by only four percent. By contrast, the empirical evidence suggest that the high-speed roadway restrictions are likely to increase accident involvements, and thus it is strongly recommended that this component of Ontario's graduated licensing package be changed. 相似文献
4.
5.
从影响沥青路面平整度的各个方面查原因、找对策,总结对道路施工平整度的控制,特别是沥青路面施工平整度控制的经验,为公路设计和施工提供一定的参考. 相似文献
6.
This paper reviews two road-user surveys on the use of mobile phones on the road in Finland where the mobile phone ownership rate is highest in the world (70% in August 2000). From 1998 to 1999 the proportion of drivers that chose to use a mobile phone while driving rose from 56% to 68%, while the proportion of phone using drivers who experienced dangerous situations due to phone use rose from 44% to 50%. The proportion of drivers who used their phones in some way to benefit safety on the road remained at about 55%. The youngest, novice drivers had the highest level of phone usage of all age categories. Over 48% of the interviewees believed that the government should ban the use of hand-held mobile phones while driving, and another 27% believed that all types of mobile phone use should be banned while driving. Those drivers who used their phones the most each day were more likely to want some form of restrictions, than those who had lower usage. This is a strong message to the elected lawmakers and raises the problem of exactly how regulatory bodies would go about controlling the future growth of new driver support and non-driving related communication devices in road vehicles. It was concluded that legislating for hands-free use only would be a reasonable course of action. Mandating that the current generation of equipment should be optimized for hands-free use should result in future generations of in-vehicle equipment also being optimized for hands-free use as a minimum criterion. 相似文献
7.
8.
在分析杭州市交通供需现状的基础上,提出了规划多中心结构和混合功能区,以减少不必要的出行以及合理配置交通源,并对改善中心区交通提出切实可行的对策。 相似文献
9.
对混凝土搅拌运输车的主、副车架进行了定性和定量的受力分析,从中推导出主、副车架的简化强度计算方法和强度校核公式。并以SX5254GJBDM364混凝土搅拌运输车为例进行了实例分析和计算。 相似文献
10.
船舶主机冷却水系统的建模与节能型控制研究 总被引:2,自引:0,他引:2
在对船舶主机高温淡水冷却水系统的各主要器件建立各自的数学模型的基础上,对其整个系统建立了数学模型.然后以主机高温淡水冷却水系统作为研究对象,提出了在此系统中采用神经元自适应控制方式替代传统的PID(比例积分微分)控制方式进行水温调节,以达到改善控制并节约能源的目的.最后以仿真结果说明了神经元自适应控制方式具有良好的适应性与抗干扰性,它比PID控制方式更适用于主机冷却水温度调节系统. 相似文献