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811.
R. Dosthosseini A. Z. Kouzani F. Sheikholeslam 《International Journal of Automotive Technology》2011,12(6):943-950
Hybrid electric vehicles are powered by an electric system and an internal combustion engine. The components of a hybrid electric
vehicle need to be coordinated in an optimal manner to deliver the desired performance. This paper presents an approach based
on direct method for optimal power management in hybrid electric vehicles with inequality constraints. The approach consists
of reducing the optimal control problem to a set of algebraic equations by approximating the state variable which is the energy
of electric storage, and the control variable which is the power of fuel consumption. This approximation uses orthogonal functions
with unknown coefficients. In addition, the inequality constraints are converted to equal constraints. The advantage of the
developed method is that its computational complexity is less than that of dynamic and non-linear programming approaches.
Also, to use dynamic or non-linear programming, the problem should be discretized resulting in the loss of optimization accuracy.
The propsed method, on the other hand, does not require the discretization of the problem producing more accurate results.
An example is solved to demonstrate the accuracy of the proposed approach. The results of Haar wavelets, and Chebyshev and
Legendre polynomials are presented and discussed. 相似文献
812.
L. Bouillaut O. François P. Aknin R. Donat S. Bondeux S. Dubois 《Recherche - Transports - Sécurité》2011,27(4):241-257
This article deals with a generic approach called VirMaLab (virtual maintenance laboratory) for reliabilitybased maintenance modeling for complex systems (with multi-components and multi-states). Based on the probabilistic graphical models formalism (also known as Bayesian networks), this stochastic approach takes into account both the degradation process of the considered system (an original semi-Markovian model is proposed) and maintenance strategies (from diagnosis factors to all kinds of maintenance actions). For complete decision support tools, cost parameters should also be considered (maintenance actions, unavailability of the system, running, etc.). In this article, two applications of this approach to rail maintenance are introduced. The first one focuses on the optimization of the compromise refurbishment/repairing of central part of the RER A line. The second one focuses on the comparison and evaluation of various maintenance strategies in the modernization of the command control systems of Paris metro lines. 相似文献
813.
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
814.
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
815.
This paper introduces a new procedure to forecast the future O/D demand. It is a hybrid of logit and Fratar model. The hybrid model has the long run, policy sensitive, characteristic of a logit model, calibrated at sector‐level with little/no zero O/D cells. This feature, joint with a Fratar‐type operation at zonal level within a sector, gives a better performance to this model than either of the two types of the models alone. The performance of the hybrid model is contrasted with a neural network model, and shows encouraging results in a real case. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
816.
The maximum approximate composite marginal likelihood (MACML) estimation of multinomial probit-based unordered response choice models 总被引:1,自引:0,他引:1
Chandra R. Bhat 《Transportation Research Part B: Methodological》2011,45(7):923-939
The likelihood functions of multinomial probit (MNP)-based choice models entail the evaluation of analytically-intractable integrals. As a result, such models are usually estimated using maximum simulated likelihood (MSL) techniques. Unfortunately, for many practical situations, the computational cost to ensure good asymptotic MSL estimator properties can be prohibitive and practically infeasible as the number of dimensions of integration rises. In this paper, we introduce a maximum approximate composite marginal likelihood (MACML) estimation approach for MNP models that can be applied using simple optimization software for likelihood estimation. It also represents a conceptually and pedagogically simpler procedure relative to simulation techniques, and has the advantage of substantial computational time efficiency relative to the MSL approach. The paper provides a “blueprint” for the MACML estimation for a wide variety of MNP models. 相似文献
817.
818.
819.
820.
Nonlinear finite element (FE) collapse pressure predictions are compared to experimental results for submarine pressure hull test specimens with and without artificial corrosion and tested to collapse under external hydrostatic pressure. The accuracy of FE models, and their sensitivity to modeling and solution procedures, are investigated by comparing FE simulations of the experiments using two different model generators and three solvers. The standard FE methodology includes the use of quadrilateral shell elements, nonlinear mapping of measured geometric imperfections, and quasi-static incremental analyses including nonlinear material and geometry. The FE models are found to be accurate to approximately 11%, with 95% confidence, regardless of the model generator and solver that is used. Collapse pressure predictions for identical FE models obtained using each of the three solvers agree within 2.8%, indicating that the choice of FE solver does not significantly affect the predicted collapse pressure. The FE predictions are found to be more accurate for corroded than for undamaged models, and neglecting the shell eccentricity that arises due to one-sided shell thinning is found to significantly decrease the resulting accuracy of the FE model. 相似文献