全文获取类型
收费全文 | 262篇 |
免费 | 1篇 |
专业分类
公路运输 | 102篇 |
综合类 | 32篇 |
水路运输 | 51篇 |
铁路运输 | 42篇 |
综合运输 | 36篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 1篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 14篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 12篇 |
2008年 | 12篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 5篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
21.
基于Reddy高阶剪切变形板理论,用双重Fourier级数法求得了四边简支的三维四向编织复合材料剪切板自由振动的解析解,并讨论了纤维的体积含量和编织角对剪切板固有频率的影响。 相似文献
22.
李艳 《铁道标准设计通讯》2004,(4):52-53
详细介绍武汉市轨道交通一号线一期工程中 3 0 0m小半径曲线轨道几何尺寸的调试 ,为城市整体道床轨道中小半径曲线的施工提供技术参考 相似文献
23.
采用无缝线路的津滨轻轨高架桥梁下部结构设计研究 总被引:1,自引:1,他引:0
李黎 《铁道标准设计通讯》2003,(8):30-32,35
介绍在津滨轻轨桥梁下部结构设计中 ,由于考虑了桥上无缝线路的纵向力 ,出现了新的问题。通过实例计算 ,分析各种不同荷载组合的计算结果 ,提出考虑无缝线路纵向力后桥下部结构设计的控制工况及应注意的问题 相似文献
24.
Ramon Terrado Connie Lovejoy Ramon Massana Warwick F. Vincent 《Journal of Marine Systems》2008,74(3-4):964
We measured the abundance and biomass of phototrophic and heterotrophic microbes in the upper mixed layer of the water column in ice-covered Franklin Bay, Beaufort Sea, Canada, from December 2003 to May 2004, and evaluated the influence of light and nutrients on these communities by way of a shipboard enrichment experiment. Bacterial cell concentrations showed no consistent trends throughout the sampling period, averaging (± SD) 2.4 (0.9) × 108 cells L− 1; integrated bacterial biomass for the upper mixed layer ranged from 1.33 mg C m− 3 to 3.60 mg C m− 3. Small cells numerically dominated the heterotrophic protist community in both winter and spring, but in terms of biomass, protists with a diameter > 10 µm generally dominated the standing stocks. Heterotrophic protist biomass integrated over the upper mixed layer ranged from 1.23 mg C m− 3 to 6.56 mg C m− 3. Phytoplankton biomass was low and variable, but persisted during the winter period. The standing stock of pigment-containing protists ranged from a minimum value of 0.38 mg C m− 3 in winter to a maximal value of 6.09 mg C m− 3 in spring and the most abundant taxa were Micromonas-like cells. These picoprasinophytes began to increase under the ice in February and their population size was positively correlated with surface irradiance. Despite the continuing presence of sea ice, phytoplankton biomass rose by more than an order of magnitude in the upper mixed layer by May. The shipboard experiment in April showed that this phototrophic increase in the community was not responsive to pulsed nutrient enrichment, with all treatments showing a strong growth response to improved irradiance conditions. Molecular (DGGE) and microscopic analyses indicated that most components of the eukaryotic community responded positively to the light treatment. These results show the persistence of a phototrophic inoculum throughout winter darkness, and the strong seasonal response by arctic microbial food webs to sub-ice irradiance in early spring. 相似文献
25.
主要介绍机械设备中常用的燃料油、润滑油、润滑脂、液压油和某些特种油的特性、牌号、分类和使用范围,以及实际工作中如何正确选用. 相似文献
26.
27.
28.
29.
As urban areas face increasing demands for new transport infrastructure to promote a sustainable future with an increasing reality of constrained government budgets, the debate on whether we should focus on rail or bus-based investments continues unabated in many jurisdictions. Associated with the debate is an emotional (or ideological) bias by communities in favour of one mode, especially rail, which carries much sway at the political level as if there is no budget constraint. This paper presents a stated choice experiment to investigate this context as two unlabelled options described by 20 potential drivers of community preferences for improved public transport, where each choice scenario is conditioned on an estimated construction cost and a total annual transport infrastructure budget for the relevant geographical jurisdiction. This is followed by a labelling of each alternative to reveal whether the option is bus rapid transit (BRT) or light rail (LRT) and to establish whether this additional information influences preference revision. Data is collected in all eight capital cities of Australia in mid 2014. Mixed logit models with heteroscedastic conditioning in terms of the cost of the project infrastructure and whether the alternative is labelled BRT or LRT, provide new evidence on the nature and extent of community modal bias in a budget-constrained choice setting. The conclusions are twofold. On the one hand, if a fully compensatory choice rule is assumed (as is common in all previous modal comparison studies), LRT is predominantly preferred over BRT despite budgetary constraints, similarities in quality of service attributes and the opportunity to choose a greater network coverage for a given construction cost. However, when we allow for attribute non-attendance (a semi-compensatory choice rule), the modal bias is no longer a significant driver of preferences. 相似文献
30.
A potential solution to reduce greenhouse gas (GHG) emissions in the transport sector is the use of alternative fuel vehicles (AFV). As global GHG emission standards have been in place for passenger cars for several years, infrastructure modelling for new AFV is an established topic. However, as the regulatory focus shifts towards heavy-duty vehicles (HDV), the market diffusion of AFV-HDV will increase as will planning the relevant AFV infrastructure for HDV. Existing modelling approaches need to be adapted, because the energy demand per individual refill increases significantly for HDV and there are regulatory as well as technical limitations for alternative fuel station (AFS) capacities at the same time. While the current research takes capacity restrictions for single stations into account, capacity limits for locations (i.e. nodes) – the places where refuelling stations are built such as highway entries, exits or intersections – are not yet considered. We extend existing models in this respect and introduce an optimal development for AFS considering (station) location capacity restrictions. The proposed method is applied to a case study of a potential fuel cell heavy-duty vehicle AFS network. We find that the location capacity limit has a major impact on the number of stations required, station utilization and station portfolio variety. 相似文献