全文获取类型
收费全文 | 911篇 |
免费 | 18篇 |
专业分类
公路运输 | 261篇 |
综合类 | 70篇 |
水路运输 | 275篇 |
铁路运输 | 46篇 |
综合运输 | 277篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2019年 | 11篇 |
2018年 | 23篇 |
2017年 | 26篇 |
2016年 | 42篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 147篇 |
2012年 | 41篇 |
2011年 | 31篇 |
2010年 | 53篇 |
2009年 | 56篇 |
2008年 | 48篇 |
2007年 | 45篇 |
2006年 | 21篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 36篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 17篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 25篇 |
1994年 | 5篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有929条查询结果,搜索用时 234 毫秒
21.
In this study, we optimize the loading and discharging operations of the Liquefied Natural Gas (LNG) carrier. First, we identify the required precautions for LNG carrier cargo operations. Next, we prioritize these precautions using the analytic hierarchy process (AHP) and experts’ judgments, in order to optimize the operational loading and discharging exercises of the LNG carrier, prevent system failure and human error, and reduce the risk of marine accidents. Thus, the objective of our study is to increase the level of safety during cargo operations. 相似文献
22.
无接缝、平整、行车舒适、噪音低以及振动小、易于养护等优点,使沥青混凝土路面成为我国国内公路面层普遍采用的一种比较好的结构形式。但是如果施工中不能按照施工工艺严格的进行施工质量控制,则很容易导致路面的一系列质量问题,这不仅影响使用功能,还影响影响其社会效益。 相似文献
23.
Maksym Spiryagin Peter Wolfs Colin Cole Sebastian Stichel Mats Berg Plöchl Manfred 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2017,55(8):1241-1264
The main task for heavy haul railway operators is to reduce the cost of exported minerals and enhance the long-term viability of rail transport operations through increasing productivity by running longer and heavier trains. The common opinion is that this is achievable by means of implementation of high adhesion locomotives with advanced AC traction technologies. Modern AC high adhesion locomotives are very complex mechatronic systems and can be designed with two alternative traction topologies of either bogie or individual axle controls. This paper describes a modelling approach for these two types of AC traction systems with the application of an advanced co-simulation methodology, where an electrical system and a traction algorithm are modelled in Matlab/Simulink, and a mechanical system is modelled in a multibody software package. Although the paper concentrates on the analysis of the functioning for these two types of traction control systems, the choice of reference slip values also has an influence on the performance of both systems. All these design variations and issues have been simulated for various adhesion conditions at the wheel–rail interface and their influence on the high traction performance of a locomotive equipped with two three-axle bogies has been discussed. 相似文献
24.
文中采用Fluent模拟与理论计算结合比较的方法,研究了不同因素对蒸汽管道散热损失的影响规律,并分析了理论计算模型的相对误差.发现增加注汽管线距地面高度,对其散热损失影响较弱;空气温度升高,注汽管道表面散热损失降低;风速和表面发射率对注汽管线表面热损失影响较大;数值模拟结果与理论计算数据相对误差较大. 相似文献
25.
The robustness of questionnaire results to various forms of bias are explored in the context of a dual-mode (web and hardcopy)
survey of employers’ anticipations of levels of employee commuting and business travel activity under a range of future ICT
scenarios. The questionnaire incorporated several innovative features which, together with the dual-mode format, allowed an
unusually wide range of analyses. For example: the robustness of respondents’ opinions was tested by examining the effect
of incorporating alternative versions of a briefing text, one being very positive and one very negative, about the role of
ICT; instrument bias was identified via detailed comparison of the results from the two versions of the questionnaire; and
the impact of exogenous factors which are often ignored or taken as constant was assessed via special supplementary questions.
Analysis showed that the robustness of opinions and expectations varied and was influenced by respondent characteristics,
and that results from the two versions of the questionnaire differed significantly. It is concluded that opinions and expectations
are less robust, and questionnaire results are more subject to bias and myopic interpretation, than is generally recognised
and that web-based surveys seem particularly vulnerable to sampling bias. Methods are suggested for measuring robustness,
for reducing bias and for validating and contextualising results. The use of contrasting briefing texts is recommended as
a means of establishing the robustness of opinions and expectations while supplementary questions are recommended for validating
and contextualising SP and SE exercises.
Peter Bonsall Professor of Transport Planning at the Institute for Transport Studies, University of Leeds. His research interests include: use of innovative data sources, microsimulation, multi-criteria appraisal of policy interventions, travellers’ perception of modal attributes, their ability to cope with uncertainty and complexity and their response to new information and charges. Jeremy Shires Senior Research Fellow at the Institute for Transport Studies, University of Leeds. His research interests include behavioural modelling, the impact of “soft factors” on travel, stated preference design and public transport demand modelling. 相似文献
Peter BonsallEmail: |
Peter Bonsall Professor of Transport Planning at the Institute for Transport Studies, University of Leeds. His research interests include: use of innovative data sources, microsimulation, multi-criteria appraisal of policy interventions, travellers’ perception of modal attributes, their ability to cope with uncertainty and complexity and their response to new information and charges. Jeremy Shires Senior Research Fellow at the Institute for Transport Studies, University of Leeds. His research interests include behavioural modelling, the impact of “soft factors” on travel, stated preference design and public transport demand modelling. 相似文献
26.
Stated preference (SP) experiments are becoming an increasingly popular survey methodology for investigating travel behaviour.
Nevertheless, some evidence suggests that SP experiments do not mirror decisions in real markets. With an increasing number
of real world decisions made using the internet, an opportunity exists to improve the realism of the SP counterparts of such
choices by aligning the choice environment with such online portals. In this paper, we illustrate the benefits of such an
approach in the context of air travel surveys. Our survey is modelled on the interface and functionality of an online travel
agent (OTA). As with a real OTA, many ticket options are presented. Sort tools allow the options to be reordered, search tools
allow options to be removed from consideration, and a further tool allows attributes to be hidden and shown. Extensive use
of these tools is made by the 462 respondents. A traditional SP component was also completed by the respondents. Our exploratory
analysis as well as random utility model estimation results confirm not only that respondents seem to engage more actively with the interactive survey, but also that the resulting data allows for better performance in model estimation
compared to a more conventional SP experiment. These results have implications for the study of other complex travel choices
where interactive surveys may similarly be preferable to standard approaches. 相似文献
27.
Water bursts during tunnel construction endanger construction, and it is therefore necessary to reserve a waterproof dike with the required thickness to avoid water bursts and to take reinforcement of the dike and treatment of the structure liable to trigger a water burst. Using the water burst at K5+398 of the Mingyueshan tunnel of the Shanghai-Chengdu expressway as an example, and considering the type of tunnel section and the upright mudstone of the dike, the waterproof dike at the work face is simplified as a round thin plate. A formula for the calculation of a minimum safety thickness for the critical waterproof dike is deduced by analyzing the force applied on the water-proof dike, and the minimum safety thickness for the water burst section at K5+398 of the Mingyueshan tunnel is cal-culated. The numerical simulation analysis demonstrates the critical thickness of waterproof dike at K5+398 of the Mingyueshan tunnel is 1.4-1.55 m, and the calculated water inflow and water burst basically agree with the actual condition. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
28.
In order to study the diffusion law of grouting slurry in the water-rich sand layer under flowing water conditions, a grouting test model consisting of a main test system, a grouting system, and a measurement system was developed. And for detecting the diffusion scope of the grouts, a new resistivity method was proposed. It is found that the relationship between grouting pressure and grouting rate during the test is strong. Under hydrodynamic conditions, the grouting slurry diffuses elliptically. Due to gravity and the effect of the upper water flow, the center of gravity of the ellipsoid is below the grouting outlet, and the grouting effectively improves the physical and mechanical properties of water-rich sand bodies. At the same time, the resistivity method has a good application effect on the detection of grouting diffusion range. The range of slurry diffusion obtained by the resistivity method is basically consistent with the boundary of the stone body after excavation, indicating that the resistivity method is reliable for detection of grouting range in dynamic water-rich sand layer. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
29.
The problems of TBM construction data loss, information barriers and absence of data mining have con⁃ strained the advancement of basic technologies in TBM field. Aimed at building a cloud computation platform for TBM operation information, a new concept of 3B, i. e. Born by digit, Born in format and Born to the cloud, was pre⁃ sented, the issues of information acquisition, transmission and storage during TBM operation were solved, and massive heterogeneous information intelligent transmission system and big data warehouse of TBM group were established. A structure model of cloud computation platform was designed by taking Hadoop system as ecosphere, and a cloud computation platform was built to deploy related algorithm, realizing on-line monitoring and data sharing, further⁃ more the data law mining of interaction of rock mass versus TBM machine was conducted based on big data tech⁃ nique, exploring the development direction of the information platform. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
30.
Within the literature concerned with aspects of competitiveness, innovation and strategic management of industrial clusters, the body regarding forecasting of strategic management is still nascent. This work aspires to render a contribution within the domain of strategic management forecasting, through the indicative case of European maritime clusters. For this end, a two-tier model is formulated. A quantitative strengths, weaknesses, opportunities, and threats (SWOT) methodology that derives from the fusion of a quondam situation analysis and crosstabs’ theory is generated. This leads to the utilization of the crosstab’s conditional probabilities as transition probabilities; the latter are called to compile the transition matrix of a Markov chain. Through this methodology, and the successive Markov chain’s transition matrices, strategic forecasts are extracted for a devised European maritime cluster case. This work relinquishes a novel application with respect to strategic management forecasting, that provides a dichotomy of practical interpretations and scenarios for quantitative situation analysis. Thus, it may enable effective real-time decision-making for strategic management and/or policy drafting. The situation analysis forecasting model may find applicability in a plethora of practical and theoretical cases, wherein forecasting may be desirable. It may as well pertain to an intrinsic methodology for situation analysis forecasting of maritime clusters. 相似文献