全文获取类型
收费全文 | 2370篇 |
免费 | 186篇 |
专业分类
公路运输 | 723篇 |
综合类 | 810篇 |
水路运输 | 493篇 |
铁路运输 | 340篇 |
综合运输 | 190篇 |
出版年
2024年 | 16篇 |
2023年 | 24篇 |
2022年 | 53篇 |
2021年 | 81篇 |
2020年 | 87篇 |
2019年 | 71篇 |
2018年 | 57篇 |
2017年 | 67篇 |
2016年 | 62篇 |
2015年 | 107篇 |
2014年 | 198篇 |
2013年 | 166篇 |
2012年 | 208篇 |
2011年 | 225篇 |
2010年 | 151篇 |
2009年 | 152篇 |
2008年 | 145篇 |
2007年 | 206篇 |
2006年 | 171篇 |
2005年 | 91篇 |
2004年 | 47篇 |
2003年 | 39篇 |
2002年 | 20篇 |
2001年 | 22篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
排序方式: 共有2556条查询结果,搜索用时 15 毫秒
91.
基于铝合金模板在唐山港曹妃甸港区联想控股通用件杂货泊位二期工程中的应用,对其应用特点、施工工艺及应用效果进行分析。认为铝合金模板是一种低耗、环保、经济实用的绿色模板,在国内港口工程中具有广阔的推广前景。 相似文献
92.
This paper extends the work on Pareto-improving hybrid rationing and pricing policy for general road networks by considering heterogeneous users with different values of time. Mathematical programming models are proposed to find a multiclass Pareto-improving pure road space rationing scheme (MPI-PR) and multiclass hybrid rationing and pricing schemes (MHPI and MHPI-S). A numerical example with a multimodal network is provided for comparing both the efficiency and equity of the three proposed policies. We discover that MHPI-S can achieve the largest reduction in total system delay, MHPI can induce the least spatial inequity and MHPI-S is a progressive policy which is appealing to policy makers. Furthermore, numerical results reveal that different classes of users react differently to the same hybrid policies and multiclass Pareto-improving hybrid schemes yield less delay reduction when compared to their single-class counterparts. 相似文献
93.
94.
Donghyung Yook 《运输规划与技术》2015,38(8):935-953
In this paper, the crowding effect in a transit vehicle is modeled in a time-expanded network that considers the daily variation in passenger flows. The study models the daily variation of in-vehicle crowding in a real large-scale transit system. A transit assignment for this real network is modeled and implemented by constructing a crowding cost function that follows the valuation of crowding and by using the reliable shortest path finding method. The direct application of the crowding model to a real network for the Utah Transit Authority indicates that crowd modeling with multi-user classes could influence public transportation system planning and affect the revenues of transit agencies. Moreover, the addition of the disutility factor, crowding, does not always appear to cause an increase in disutility for transit users. 相似文献
95.
This paper uses observations from before and during the Stockkholm congestion charging trial in order to validate and improve a transportation model for Stockholm. The model overestimates the impact of the charges on traffic volumes while at the same time it substantially underestimates the impact on travel times. These forecast errors lead to considerable underestimation of economic benefits which are dominated by travel time savings. The source of error lies in the static assignment that is used in the model. Making the volume-delay functions (VDFs) steeper only marginally improves the quality of forecast but strongly impacts the result of benefit calculations. We therefore conclude that the dynamic assignment is crucial for an informed decision on introducing measures aimed at relieving congestion. However, in the absence of such a calibrated dynamic model for a city, we recommend that at least a sensitivity analysis with respect to the slope of VDFs is performed. 相似文献
96.
文章以赣江大桥和宁海新桥特大桥为研究对象,利用有限元模型对其主桥施工最大悬臂状态下P-Δ效应进行了计算,分析了考虑P-Δ效应时的桥梁位移与应力变化情况,为今后类似工程的设计计算和施工监控提供参考。 相似文献
97.
98.
99.
100.
X形桩是一种反拱曲面异型桩,相比于同等截面积的矩形桩和圆形桩,X形桩具有更大的截面周长和惯性矩,受力性能更好。结合京唐港32#泊位遮帘式板桩码头结构,以X形桩代替传统的矩形桩,研究其对结构静力的影响。结果表明:相同桩间中心距时,以X形桩替代后可减小前墙弯矩;在同等桩间净距1.75 m下,两类模型的前墙最大弯矩基本相同。相同荷载作用下,前墙位移主要受桩间中心距影响,X形桩形状影响效应很小;锚碇墙水平位移受桩间中心距和遮帘桩形状的影响均很小。桩间中心距、净距与桩间土体土拱效应直接相关,对前墙弯矩、土压力、遮帘桩弯矩等有显著影响。桩间中心距为4.05 m或桩间净距为1.75 m时,结构内力改善效果较优,可采用该间距的X形桩替代矩形桩,节约工程造价。 相似文献