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81.
82.
A serious interest in high speed train has been increasing all over the world. However, recent experiences in Asian countries
show that high speed rail projects are not financially viable even in areas seemingly favorable to rail operations. Considering
the existing intensive highway and airline network, putting public subsidies to high speed rail projects are barely justifiable
from a purely economic point of view. What is required of any government which contemplates high speed rail construction as
a policy option is to show taxpayers the cost/revenues difference between constructing a high speed rail line and expanding
a capacity of other means, before proceeding. 相似文献
83.
Hana Šev?íková Adrian E. Raftery 《Transportation Research Part A: Policy and Practice》2011,45(6):540-553
Uncertainty is inherent in major infrastructure projects, but public decision-making for such projects ignores it. We investigate the uncertainty about the future effects of tearing down the Alaskan Way Viaduct in downtown Seattle, using an integrated model of housing, jobs, land use and transportation, on outcomes including average commute times. Our methodology combines the urban simulation model UrbanSim with the regional transportation model. We assess uncertainty using Bayesian melding, yielding a full predictive distribution of average commute times on 22 different routes in 2020. Of these routes, 14 do not include the viaduct and eight do. For the 14 base routes that do not include the viaduct, the predictive distributions overlap substantially, and so there is no indication that removing the viaduct would increase commute times for these routes. For each of the eight routes that do include the viaduct, the 95% predictive interval for the difference in average travel times between the two scenarios includes zero, so there is not strong statistical support for the conclusion that removing the viaduct would lead to any increase in travel times. However, the median predicted increase is positive for each of these routes, with an average of 6 min, suggesting that there may be some measurable increase in travel time for drivers that use the viaduct as a core component of their commute. 相似文献
84.
Wave impact underneath horizontal decks 总被引:1,自引:0,他引:1
The problem of water impact on a fixed horizontal platform deck from regular incident waves was studied. Two-dimensional potential flow was assumed, and the resulting boundary-value problem was solved by three alternative numerical methods, a method based on a generalization of the impact theory by Wagner, and two different nonlinear boundary-element methods. The Wagner-based method used a von Karman approach during the water exit phase, i.e., when the wetted surface decreases. Experiments of the impact on an idealized platform deck have been performed to validate the theory. Comparisons show that the Wagner-based method yields good results for the water entry phase, when the wetted deck area increases, but poor results when the wetted area diminishes. The boundary-element methods compare well with experiments for the entire impact process. A Kutta condition is necessary at the aft body–free surface intersection during water exit and when the flow separates from the aft edge. Gravity effects matter for the water exit phase. 相似文献
85.
Denis H.?NomiyamaEmail author Tsugukiyo?Hirayama 《Journal of Marine Science and Technology》2003,8(2):88-98
The importance of ocean waves parameters (propagation direction, mean period, significant wave height, etc.) is related to several aspects of a ships safety, efficiency in operation, routing, design, and maintenance. However, some available methods for obtaining those parameters have data limitations and inconvenient aspects. In severe weather conditions, an ocean-wave-field detector is necessary. This can provide two-dimensional ocean-wave-field information directly. Among other conventional methods, ship-borne wave radar has the ability to function as such a detector, and some researchers have tried to develop practical systems. A numerical approach using plan position indicator (PPI) images from conventional marine radars is proposed to retrieve valuable information from the ocean waves. A three-dimensional Fourier transform is applied to a set of consecutive radar PPI images to perform spectrum analysis. The removal of undesired elements in the spectrum is achieved by applying a hi-pass filter to remove static components, and by comparing the data with the expected dispersion shell to correct for nonocean-wave power. Numerical experiments under controlled conditions using simulated PPI images were performed through numerical simulations based on theoretical ocean-wave equations. The results include a comparison between the original wave parameters used in the simulation and the values retrieved from the spectrum analysis. 相似文献
86.
Authors Index
Author Index Volume 30 2003 相似文献87.
88.
Xinlian?XieEmail author Dong-Ling?Xu Jian-Bo?Yang Jin?Wang Jun?Ren Shijun?Yu 《Journal of Marine Science and Technology》2008,13(1):50-62
A method is presented for selecting a preferred ship from a group of candidates as a reference ship for a new design. The
method is based on a recently developed approach for multiple-criteria decision analysis under uncertainty, the evidential
reasoning approach. Using this method, both quantitative and qualitative attributes of a complicated nature can be considered
in the selection process. The method consists of three phases: identifying suitable candidate ships, evaluating them in terms
of both conventional techno-economical and qualitative attributes, and aggregating all the attributes using the evidential
reasoning approach. This three-phase procedure is illustrated by means of an oil tanker selection example. The results of
this study show that the evidential reasoning approach can support multiple-criteria ship selection processes when both qualitative
and quantitative information with or without uncertainties have to be taken into account. The outcomes generated by the method
include the ranking of the candidate ships and indications of their strengths and weaknesses in the format of performance
distributions over different assessment grades. Such information is vital in helping decision makers to make an informed selection
and be aware of any risk implication associated with the selection. 相似文献
89.
The application of social marginal cost pricing (SMCP) in PPP's in the railway sector faces several challenges. We examine in detail the practical applicability of SMCP in railway PPPs from the perspectives of cost accounting and effectiveness of SMCP towards the allocative efficiency goal, addressing the likely drawbacks in conciliating the welfare objectives of SMCP with the objectives of project financing (cost recovery) and value for money that justify the realization of PPP's. To this end, we combine theoretical analysis with the observation of empirical results of a case study. We split the analysis per type of private service provision, which can be for service operation or infrastructure management. For infrastructure management, we recommend splitting the operator remuneration and the track access charges. For service operation, we argue that the correct decision on source of funding of the service operator should depend on the characteristics of the contract. 相似文献
90.
Emissions of exhaust gases and particulate matter from a dual fuel marine engine using methanol as fuel with marine gasoil as pilot fuel have been examined for ... 相似文献