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821.
Solution of the Multiple Wheel and Rail Contact Dynamic Problem 总被引:1,自引:0,他引:1
G. Sauvage J.-P. Pascal 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1990,19(5):257-272
An unconventional method for calculating the forces developing in the wheel and rail contact patches of a railway vehicle has been implemented at the New Technology Laboratory of INRETS. It takes into account the elastic deformations of the materials in the Hertzian elliptical contact areas; the possibility of having simultaneously several contact patches on each wheel, is introduced in the simulation of the dynamic phenomena.
The theory is applied for a high speed bogie running on a perfectly straight track. 相似文献
The theory is applied for a high speed bogie running on a perfectly straight track. 相似文献
822.
823.
G. Guardabassi A. Locatelli M. Papageorgiou 《Transportation Research Part B: Methodological》1984,18(2):111-113
An existence condition for the solution of an optimal control problem for a single traffic intersection is derived in this note. The optimal control problem has been initially formulated and solved in the pioneering work of Gazis (1963, 1964) and coworkers. It is shown that existence conditions are fairly restrictive if control is required to dissolve all intersection queues at the same time. 相似文献
824.
Analysis of sea ice cover, runoff and air temperature observations in Hudson Bay shows marked interannual variability. This variability is thought to play a major role in determining overall productivity of the coastal ecosystem by changes to river plume extent, under-ice light conditions and nutrient levels during spring. Extensive field work off the Great Whale River in southeastern Hudson Bay has shown the importance of freshwater discharge, sea ice cover and meteorological forcing on the production of under-ice microalgae and the success of first feeding in fish larvae.Recent global climate model (GCM) results for a doubling of present atmospheric carbon dioxide indicate increases of both air temperature and precipitation in the Hudson Bay area. Predictions based on GCM results are used to estimate future changes to the sea ice and runoff regime. Sea ice breakup in the offshore is predicted to occur about one month earlier than presently. Estimates of the spring freshet in the Great Whale River indicate it will also advance by approximately one month. Onset of the spring freshet will occur about one month before Hudson Bay ice breakup, similar to present. A predicted reduction of about 35% in maximum sea ice thickness will lead to an increase in the ice-ocean interface irradiance and a decrease in melt water input to the Hudson Bay surface waters. These results are used in a discussion of potential effects of global climate change on northern coastal marine environments. 相似文献
825.
The purpose of this paper is to present the results of a survival analysis for the duration of particular trip-making activities based on sex. Specifically, this study investigates the duration of those activities related to household and family support shopping, personal business, and free time and how these durations vary between men and women. It was found that there were no significant differences in the survival curves (i.e., durations) of free-time or personal business activities; this suggests that men and women spend approximately similar amounts of time on these activities, although it is not known if the activities themselves are similar (for example, banking versus getting gas). Alternatively, sex was found to be a very significant indicator of the duration of household and family support shopping activities. In the model specification, assuming all variables except sex are the same, it was found that women were 1.32 times more likely than men to spend a longer period of time in a household and family support shopping activity. Additionally, it was found that women are 1.33 times more likely than men to have a longer household and family support activity duration if the activity is nested in the journey to work trip. 相似文献
826.
827.
828.
A major research study funded by the UK Overseas Development Administration (ODA) and designed to establish the necessary considerations for viability of mass rapid transit railways in developing cities was recently completed. The analytical core of the study was a pre-appraisal model, which combines an innovative strategic land use/transport model utilizing relationships from developing cities and an economic evaluation model. This model — MRTAP — has now been developed into a user-friendly package which the ODA intend should be made widely available in the developing world. The paper describes the basis of this model. 相似文献
829.
Formulation and specification of activity analysis models require better understanding of time allocation behavior that goes
beyond the more recent within household analyses to understand selfish and altruistic behavior and how this relates to travel
behavior. Using data from 1,471 persons in a recent 2-day time use/activity diary and latent class cluster analysis we identify
11 distinct daily behaviors that span from the intensely self-serving to intensely altruistic. Predicted cluster membership
is then used to study within household interactions. The analysis shows strong correlation exists between social role and
patterns of altruistic behavior. However, a substantial amount of heterogeneity is also found within social roles. In addition,
travel behavior is also very different among altruistic and self-serving time allocation groups. At the household level, a
substantial number of households contain persons with similar behavior. Another group of households contains a mix of self-serving
and altruistic persons that follow specialized household roles within their households. The majority of households, however,
are populated by altruistic persons. Single person households are more likely to be in the self-serving groups but not in
their entirety. Altruism at home is directed most often toward the immediate family members. This is less pronounced when
we examine altruistic acts outside the home.
Konstadinos G. Goulias is a professor of Geography at the University of California Santa Barbara, has been a professor of Civil Engineering at the
Pennsylvania State University from 1991 to 2004, and he is the founder and chair of the TRB task force on moving activity-based
approaches to practice.
Kriste M. Henson is a technical staff member at Los Alamos National Laboratory in the Decision Applications Division and is currently pursing
a Ph.D. in Geography at the University of California—Santa Barbara. 相似文献
830.
In this paper, we present an approach for determining dynamic user equilibria. The method is suitable for disaggregated microscopic and mesoscopic simulation-based models. It is a modification of the convex-simplex method, which disposes with the line search step, and controls the subset of travelers to be re-routed at each step while updating the link travel times after each assignment. To guarantee finite termination, a suitable stopping criterion is adopted. The proposed method is implemented within TRANSIMS, the Transportation Analysis and Simulation System, as a two-stage process that employs a combined use of link performance functions and a microsimulator in order to design a framework suitable for application to real transportation systems. To demonstrate this capability, we apply the developed methodology to a large-scale network, Bignet, which is part of the transportation city network of Portland, Oregon; and a medium-scale network, Blacksburg, Virginia; and provide some comparative analyses. Our results exhibit that an improved distribution of travelers is obtained while consuming less than 17–33% of the effort required by the current version of TRANSIMS. 相似文献