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881.
J. Hwang D. Lee K. Huh H. Na H. Kang 《International Journal of Automotive Technology》2011,12(1):119-124
The longitudinal and lateral vehicle control techniques have been widely used in several active driver assistance systems.
The adaptive cruise control, lane keeping assistant control, vehicle platooning and stop-and-go control are typical examples
of the most important applications. In this study, a novel path planning method is proposed considering the driving environment
such as road shape, ego vehicle and surrounding vehicles’ movement. The relative distance and velocity between the ego vehicle
and surrounding vehicles are identified with respect to the predicted lane shape in front of the ego vehicle. Based on the
identified information, the road shape and surrounding vehicles are mapped into the intensity image and the desired vector
for the ego vehicle’s movement is determined by the maximum intensity density tracing method. The desired vehicle path is
followed by the acceleration/deceleration control and the steering assist control, respectively. In order to evaluate the
performance of the proposed system, simulations are conducted and compared with ACC systems. 相似文献
882.
Nonlinear governing equations used to analyze the handling of a ground vehicle are derived from the Lagrange equations of motion. The derived equations are coded using VBA (Visual Basic for Applications) embedded in Microsoft’s Excel Software and simulated in the time domain using the 4th-order Runge-Kutta method. A total of six degrees of freedom are used in the equations; three of these are the directional translation, lateral translation, and yaw of a platform (unsprung) on the base of an inertial ground coordinate, and the other three are the roll, pitch, and yaw of a body (sprung) by a platform-fixed coordinate. Four driving torques and four wheel angles of all tires are used as input control parameters. A simplified Calspan tire model is adopted for the generalized forces of the equations. This is a combined model that can be used to obtain tractional (or braking) and side forces using the inputs of the directional and side-slip ratios and the vertical force. The VBA code realized in this study is validated by comparisons with trimmed equilibrium results and the test data cited in published papers. The major characteristics of this study are: (1) the coordinate systems of the equations are mixed with the inertial frame and the platform-fixed frame, and, as a result, almost all types of driving conditions with long mileages can be simulated; (2) vertical movement is eliminated due the focus on the handling analysis; (3) the body-yaw degree of freedom is separated from the platform-yaw degree of freedom; and (4) the programming is performed by VBA, which is rarely used in the vehicle dynamics field. 相似文献
883.
以新加坡南洋理工大学“地下技术及岩土工程项目”为依托,总结了南洋理工大学近期在岩土工程技术与地下防护技术领域所开展的研究工作. 相似文献
884.
This paper quantifies likely changes in greenhouse gas emissions which contribute to anthropogenic climate change, resulting
from the expansion of the Panama Canal and the consequent increase in ship-borne commercial transportation from east Asia
to the US east coast. Ocean transportation offers higher fuel economy and lower pollutant emissions compared with land transport.
Additionally, truck and train transportation of cargo along the US land bridge threatens to overwhelm existing highway and
rail systems and limit economic growth. The alternate transportation route for easterly transit of the Panama Canal will reduce
overland traffic congestion and enhance economic development by maintaining freight flow efficiency. 相似文献
885.
The case for including agglomeration benefits within transport appraisal rests on an assumed causality between access to economic
mass and productivity. Such causality is justified by the theory of agglomeration, but is difficult to establish empirically
because estimates may be subject to sources of bias from endogeneity and confounding. The paper shows that conventional panel
methods used to address these problems are unreliable due to the highly persistent nature of accessibility measures. Adopting
an alternative approach, by applying semiparametric techniques to restricted sub-samples of the data, we find considerable
nonlinearity in the relationship between accessibility and productivity with no positive effect to be discerned over broad
ranges of the data. A key conclusion is that we are unable to distinguish the role of accessibility from other potential explanations
for productivity increases. For transport appraisal, this implies that the use of conventional point elasticity estimates
could be highly misleading. 相似文献
886.
While the literature has established macroeconomic determinants of shipping freight (charter) rates, there has been no systematic
investigation of the microeconomic determinants of shipping freight rates. Therefore, the purpose of this paper is to investigate
microeconomic determinants of freight rates in the dry bulk shipping market, using a large sample of individual dry bulk charter
contracts from January 2003 to July 2009. Differences in freight rates across major dry bulk shipping routes, the geographical
distribution of shipping activities around the world, and the duration of the laycan period of shipping contracts are also
investigated. Estimated results suggest that the laycan period and dry bulk freight rates are interrelated and determined
simultaneously. Furthermore, vessel deadweight, age and voyage routes are important determinants of dry bulk shipping freight
rates, while determinants of the laycan period of chartered vessels include vessel age, freight rate level, and freight rate
volatility. 相似文献
887.
This paper introduces a vehicle transaction timing model which is conditional on household residential and job relocation
timings. Further, the household residential location and members’ job relocation timing decisions are jointly estimated. Some
researchers have modeled the household vehicle ownership decision jointly with other household decisions like vehicle type
choice or VMT; however, these models were basically static and changes in household taste over time has been ignored in nearly
all of these models. The proposed model is a dynamic joint model in which the effects of land-use, economy and disaggregate
travel activity attributes on the major household decisions; residential location and members’ job relocation timing decisions
for wife and husband of the household, are estimated. Each of these models is estimated using both the Weibull and log-logistic
baseline hazard functions to assess the usefulness of a non-monotonic rather than monotonic baseline hazard function. The
last three waves of the Puget Sound Panel Survey data and land-use, transportation, and built environment variables from the
Seattle Metropolitan Area are used in this study as these waves include useful explanatory variables like household tenure
that were not included in the previous waves. 相似文献
888.
Abdul Rawoof Pinjari Ram M. Pendyala Chandra R. Bhat Paul A. Waddell 《Transportation》2011,38(6):933-958
The integrated modeling of land use and transportation choices involves analyzing a continuum of choices that characterize
people’s lifestyles across temporal scales. This includes long-term choices such as residential and work location choices
that affect land-use, medium-term choices such as vehicle ownership, and short-term choices such as travel mode choice that
affect travel demand. Prior research in this area has been limited by the complexities associated with the development of
integrated model systems that combine the long-, medium- and short-term choices into a unified analytical framework. This
paper presents an integrated simultaneous multi-dimensional choice model of residential location, auto ownership, bicycle
ownership, and commute tour mode choices using a mixed multidimensional choice modeling methodology. Model estimation results
using the San Francisco Bay Area highlight a series of interdependencies among the multi-dimensional choice processes. The
interdependencies include: (1) self-selection effects due to observed and unobserved factors, where households locate based
on lifestyle and mobility preferences, (2) endogeneity effects, where any one choice dimension is not exogenous to another,
but is endogenous to the system as a whole, (3) correlated error structures, where common unobserved factors significantly
and simultaneously impact multiple choice dimensions, and (4) unobserved heterogeneity, where decision-makers show significant
variation in sensitivity to explanatory variables due to unobserved factors. From a policy standpoint, to be able to forecast
the “true” causal influence of activity-travel environment changes on residential location, auto/bicycle ownership, and commute
mode choices, it is necessary to capture the above-identified interdependencies by jointly modeling the multiple choice dimensions
in an integrated framework. 相似文献
889.
This study introduces an extended version of a standard multilevel cross-classified logit model which takes co-variations
into account, i.e., variations jointly caused by two or more unobserved factors. Whilst focusing on mode choice behavior,
this study deals with four different types of variation: spatial variations, inter-individual variations, intra-individual
variations and co-variations between inter-individual and spatial variations. Such co-variations represent individual-specific
spatial effects, reflecting different responses to the same space among individuals, which may for example be due to differences
in their spatial perceptions. In our empirical analysis, we use data from Mobidrive (a continuous six-week travel survey) to clarify the existence of co-variation effects by comparing two models with and without
co-variation terms. The results of this analysis indicate that co-variations certainly exist, especially for utility differences
in bicycle and public transport use in comparison with car use. We then sequentially introduce four further sets of explanatory
variables, examine the sources of behavioral variations and determine what types of influential factors are dominant in mode
choice behavior. 相似文献
890.
Children are an often overlooked and understudied population group, whose travel needs are responsible for a significant number
of trips made by a household. In addition, children’s travel and activity participation during the post-school period have
direct implication for adults’ activity-travel patterns. A better understanding of children’s after school activity-travel
patterns and the linkages between parents and children’s activity-travel needs is necessary for accurate prediction and forecasting
of activity-based travel demand modeling systems. In this paper, data from the 2002 Child Development Supplement of the Panel
Study of Income Dynamics is used to undertake a comprehensive assessment of the post-school out-of-home activity-location
engagement patterns of children aged 5–17 years. Specifically, this research effort utilizes a multinomial logit model to
analyze children’s post-school location patterns, and employs a multiple discrete–continuous extreme value model to study
the propensity of children to participate in, and allocate time to, multiple activity episode purpose-location types during
the after-school period. The results show that a wide variety of demographic, attitudinal, environmental, and others’ activity-travel
pattern characteristics impact children’s after school activity engagement patterns. 相似文献