全文获取类型
收费全文 | 724篇 |
免费 | 35篇 |
专业分类
公路运输 | 124篇 |
综合类 | 308篇 |
水路运输 | 180篇 |
铁路运输 | 78篇 |
综合运输 | 69篇 |
出版年
2024年 | 7篇 |
2023年 | 10篇 |
2022年 | 14篇 |
2021年 | 20篇 |
2020年 | 19篇 |
2019年 | 20篇 |
2018年 | 22篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 38篇 |
2013年 | 43篇 |
2012年 | 39篇 |
2011年 | 58篇 |
2010年 | 46篇 |
2009年 | 52篇 |
2008年 | 29篇 |
2007年 | 62篇 |
2006年 | 60篇 |
2005年 | 36篇 |
2004年 | 29篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有759条查询结果,搜索用时 0 毫秒
211.
212.
This article examines the evacuation behavior of residents in two South Carolina communities, Hilton Head and Myrtle Beach, during the 1996 hurricane season. Two hurricanes that approached South Carolina but hit in North Carolina allowed us to study the impact of repeated “false alarms”; (evacuations ordered based on expectations of a hurricane landfall that proved to be wrong). Differences in evacuation behavior, specific information and concerns prompting evacuation, and the reliability of information sources between hurricane events are examined to determine the impact of false alarms on the credibility of warning systems. Data were derived from a face‐to‐face survey of residents 2 weeks after Hurricane Fran in September 1996. We found that the role of official advisories was more limited than reported in previous research as people sought information on more diverse sets of concerns in their decision making. Reliance on the media and the Weather Channel, in particular, for storm characteristics and advisories was an important factor in evacuation decision making during both hurricane events. The perceived lack of reliability of gubernatorial warnings coupled with dependence on the media suggests that residents find other sources of information more personally relevant. Thus, while residents do not find that officials are “crying wolf,”; they are searching elsewhere for information to assess their own risk—what does it mean to me if there is a wolf? This increased attention toward individual differences in perceived threat may become more pronounced in future evacuations from hurricanes. 相似文献
213.
装备研制项目是一项复杂的系统工程,其实施前景不确定,科学及时地中止没有前景的研制项目对于优化国防资源配置有重要意义。针对目前中止决策方法中的定性方法主观性大,而定量方法损失信息较多的问题,引入了云理论,通过云变换把定性评语转化为评价云,建立了云决策模型。 相似文献
214.
针对炮兵随行作战时的动态火力目标匹配问题,运用马尔可夫决策理论进行了探索。首先检验了马尔可夫决策理论对动态火力目标匹配的可行性,其次在可行性的基础上建立动态决策模型,最后再对模型进行了验证,所得结果符合炮兵射击的客观实际,为炮兵作战指挥员在动态火力目标匹配上提供了一种合理的决策依据和决策方法。 相似文献
215.
216.
基于模糊综合决策及Shannon熵的关键链缓冲确定方法 总被引:4,自引:0,他引:4
为了进一步推广关键链方法在项目管理中的运用,对关键链缓冲的设置问题进行了探讨.通过将模糊综合决策和Shannon熵的结合,综合了“专家”和“一线工人”两方面对项目的评价信息,使得所提的方法更具针对性.采用本方法可以使得关键链缓冲数量设置适当,能够较好地应对项目管理中的不确定性.最后,通过一个算例在MATLAB7.0平台上用正态分布模拟各活动的实际运行情况,说明了此方法的可行性及优越性. 相似文献
217.
This paper examines how the existing fleet in the shipping industry can be adapted to the new emission regulations through the two main techniques that currently exist: (a) the use of low-sulphur marine diesels; and (b) the installation of scrubbers. A method is presented here for drawing up an economic assessment of both these techniques under uncertainty. It enables the best option to be selected at any given time taking into account fuel prices (spot and futures), scrubber installation costs, the time that the vessel operates in an Emission Control Area (ECA) and the remaining useful lifetime of the vessel. The paper also considers the possibility of an unexpected change from a non-ECA navigation area to an ECA. The assessment is carried out in a manner consistent with marine diesel and crude oil spot and futures market quotes. Our results show the net present value of investing in the installation of scrubbers and investing in changing fuel types for different assumptions on how vessels are operated. We also analyse increases in fuel consumption and CO2 emissions as a consequence of using scrubbers and how they affects the financial analysis if such incremental emissions must be paid under a CO2 pricing mechanism. 相似文献
218.
219.
This paper tests a group decision-making model to examine the school travel behavior of students 6–18 years old in the Minneapolis-St. Paul Metropolitan area. The school trip information of 1737 two-parent families with a student is extracted from Travel Behavior Inventory data collected by the Metropolitan Council between the Fall 2010 and Spring 2012. The model has four distinct characteristics including: (1) considering the student explicitly in the model, (2) allowing for bargaining or negotiation within households, (3) quantifying the intra-household interaction among family members, and (4) determining the decision weight function for household members. This framework also covers a household with three members, namely, a father, a mother, and a student, and unlike other studies it is not limited to dual-worker families. To test the hypotheses we build two models, each with and without the group-decision approach. The models are separately built for different age groups, namely students 6–12 and 12–18 years old. This study considers a wide range of variables such as work status of parents, age and gender of students, mode of travel, and distance to school. The findings of this study demonstrate that the elasticities of the two modeling approaches differ not only in the value, but in the sign in some cases. In 63% of the cases the unitary household model underestimates the results. More precisely, the elasticities of the unitary household model are as much as 2 times more than that of the group-decision model in 20% of cases. This is a direct consequence of model misspecification that misleads both long- and short-term policies where the intra-household bargaining and interaction is overlooked in travel behavior models. 相似文献
220.
随着数字化造船技术的发展,在舰船装备研制过程中,对定量风险分析的需求越来越强烈。针对我国舰船装备系统复杂、研制周期长的特点,本文提出了一种基于全寿命周期数据管理(PLM/PDM)系统的风险管理和决策支持系统。并结合概率风险分析方法与定性风险分析方法在船舶系统应用的特点,在风险数据收集、风险模型和风险知识库建立及完善等几个方面进行了深入分析。 相似文献