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121.
Roger B. Trent Alon Kvashny Edward S. Neumann Elizabeth Walukas John Halkias 《先进运输杂志》1986,20(3):275-285
Research literature suggests that aesthetic response toward a transportation system may be colored by non-aesthetic values. Photographic depictions of downtown street scenes with and without automated people mover guideways were shown to various community groups. Measures of external utilities—stakes in the local community and in public transportation—bore no relationship to aesthetic assessments of either guideway scenes or street scenes without a guideway. In contrast, aesthetic background and interests depressed evaluations of both guideway and non-guideway scenes. Aesthetic background evidently influences aesthetic assessments of elevated guideways in urban streets far more than do non-aesthetic utilities. This suggests that planners of new transportation systems need to address aesthetic impacts apart from other impacts and that aesthetic criteria will be applied more stringently by some community groups than by others. 相似文献
122.
123.
This paper presents a model of automobile choice by single vehicle households. This effort is distinguished from previous disaggregate automobile holdings models primarily by the use of the nested logit model rather than the more restrictive multinomial logit model. We present a 2-step estimation technique that provides consistent and asymptotically efficient parameter estimates, yet is tractable for very large choice sets. Using disaggregate data on 237 one-vehicle households we estimate the unknown parameters on an automobile choice model containing 785 individual makes, models and vintages of passenger vehicles. 相似文献
124.
John Fossey 《中国远洋航务》2005,(5):58-60
港口阻塞问题没有立竿见影的解决方案 班轮业的问题在于没有立竿见影的解决方案,因为尽管码头工人可以加班加点,新的设备可以购置,码头管理体制可以调整,但上述举措对于解决港口阻塞问题的作用是有限的. 相似文献
125.
Yuping He John McPhee 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2002,38(5):361-390
Summary The lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm. Several steps are taken to validate this integrated approach and to show its effectiveness. First, a hand-derived solution to a 17 degree of freedom linear rail vehicle model is compared to the simulation results from the A'GEM multibody dynamics software. Second, the calculation of the 'critical speed' (above which a rail vehicle response becomes unstable) using sequential quadratic programming is validated for a specific example. In the process, the existence of sharply-discontinuous 'cliffs' in the plots of critical speed versus suspension stiffnesses are identified. These cliffs, which are due to switching of the least-damped mode in the system, greatly hinder the application of gradient-based optimization methods. Two methods that do not require gradient information, a genetic algorithm and the Nelder-Mead's Simplex algorithm, are used to optimize the critical speed. The two algorithms and their results are compared. In recognition of the cliff phenomenon, the definition of critical speed is generalized to make it a more practical measure of lateral stability. 相似文献
126.
127.
John R. Siddorn J. Icarus Allen Jerry C. Blackford Francis J. Gilbert Jason T. Holt Martin W. Holt Jeff P. Osborne Roger Proctor David K. Mills 《Journal of Marine Systems》2007,65(1-4):417
This paper outlines an approach to complex spatio-temporal marine ecosystem modelling as applied to the North Western European Continental Shelf. The model presented here combines an eddy-permitting (approximately 6 km horizontal resolution) baroclinic model, the Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS), with the European Regional Seas Ecosystem Model (ERSEM). This has been run within an operational framework using operationally available high resolution atmospheric and lateral boundary forcing, allowing hindcast and near-real time nowcast simulations to be performed. The modelled surface temperature and chlorophyll distributions are presented, and interannual variations discussed. Validation of both the physical and ecosystem submodels show the system to be effective, whilst highlighting areas where improvements in the system can be made. Distinct regional differences in predictive skill are shown. The system presented is ready for operational implementation to provide products and services for use both scientifically and in coastal zone and shelf seas management activities. A programme of work to update the system is already in place. 相似文献
128.
John Fossey 《中国远洋航务》2005,(3):24-27
按总体上来划分,全世界集装箱船舶的所有权由以下两个集团分别拥有,即承运人和不经营航线的船东.前者是集装箱船的最终用户,他们组织港口到港口的运输业务,或提供全方位的集装箱多式联运服务.而后者则是纯粹的船东,他们将船租给航运公司,自己并不从事实际的班轮运输服务. 相似文献
129.
T. Frede Thingstad Harry Havskum Ulla Li Zweifel Elisa Berdalet M. Montserrat Sala Francesc Peters Miquel Alcaraz Renate Scharek Maite Perez Stphan Jacquet Gro Anita Fonnes Flaten John R. Dolan Celia Marras Fereidoun Rassoulzadegan ke Hagstrm Daniel Vaulot 《Journal of Marine Systems》2007,64(1-4):15
We compared an idealised mathematical model of the lower part of the pelagic food web to experimental data from a mesocosm experiment in which the supplies of mineral nutrients (nitrogen and phosphorous), bioavailable dissolved organic carbon (BDOC, as glucose), and silicate were manipulated. The central hypothesis of the experiment was that bacterial consumption of BDOC depends on whether the growth rate of heterotrophic bacteria is limited by organic-C or by mineral nutrients. In previous work, this hypothesis was examined qualitatively using a conceptual food web model. Here we explore the extent to which a “simplest possible” mathematical version of this conceptual model can reproduce the observed dynamics. The model combines algal–bacterial competition for mineral nutrients (phosphorous) and accounts for alternative limitation of bacterial and diatom growth rates by organic carbon and by silicate, respectively. Due to a slower succession in the diatom–copepod, compared to the flagellate–ciliate link, silicate availability increases the magnitude and extends the duration of phytoplankton blooms induced by mineral nutrient addition. As a result, Si interferes negatively with bacterial consumption of BDOC consumption by increasing and prolonging algal–bacterial competition for mineral nutrients. In order to reproduce the difference in primary production between Si and non-Si amended treatments, we had to assume a carbon overflow mechanism in diatom C-fixation. This model satisfactorily reproduced central features observed in the mesocosm experiment, including the dynamics of glucose consumption, algal, bacterial, and mesozooplankton biomass. While the parameter set chosen allows the model to reproduce the pattern seen in bacterial production, we were not able to find a single set of parameters that simultaneously reproduces both the level and the pattern observed for bacterial production. Profound changes in bacterial morphology and stoichiometry were reported in glucose-amended mesocosms. Our “simplest possible” model with one bacterial population with fixed stoichiometry cannot reproduce this, and we suggest that a more elaborate representation of the bacterial community is required for more accurate reproduction of bacterial production. 相似文献
130.
Since paper freight-hedging tools were introduced to counter volatile tanker freight rates, the hesitant uptake of tanker Forward Freight Agreements (FFAs) has been attributed to traditional risk seeking propensities amongst tanker owners, naturally reluctant to hedge against risk. To test how far the well-documented generic determinants and incentives for corporate hedging could explain this hesitation in the tanker market, the attitudes of tanker owners and charterers towards freight hedging, risk and perceptions of FFAs, were surveyed. Although FFAs were widely viewed as an important development, some respondents were unaware of their function and a majority had not used them. The link between freight hedging activity and participants' risk aversion was not clear-cut, but with market liquidity critical to raising FFA usage improved technical education is essential to widespread acceptance 相似文献