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751.
A new data assimilation method for ocean waves is presented, based on an efficient low-rank approximation to the Kalman filter. Both the extended Kalman filter and a truncated second-order filter are implemented. In order to explicitly estimate past wind corrections based on current wave measurements, the filter is extended to a fixed-lag Kalman smoother for the wind fields. The filter is tested in a number of synthetic experiments with simple geometries. Propagation experiments with errors in the boundary condition showed that the KF was able to accurately propagate forecast errors, resulting in spatially varying error correlations, which would be impossible to model with time-independent assimilation methods like OI. An explicit comparison with an OI assimilation scheme showed that the KF also is superior in estimating the sea state at some distance from the observations. In experiments with errors in the driving wind, the modeled error estimates were also in agreement with the actual forecast errors. The bias in the state estimate, which is introduced through the nonlinear dependence of the waves on the driving wind field, was largely removed by the second-order filter, even without actually assimilating data. Assimilation of wave observations resulted in an improved wave analysis and in correction of past wind fields. The accuracy of this wind correction depends strongly on the actual place and time of wave generation, which is correctly modeled by the error estimate supplied by the Kalman filter. In summary, the KF approach is shown to be a reliable assimilation scheme in these simple experiments, and has the advantage over other assimilation methods that it supplies explicit dynamical error estimates. 相似文献
752.
C. G. Shapley 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1975,4(1):1-7
This paper examines the rolling motions of vehicles with pneumatic tires. From a simplified analysis two sources of instability are identified-one related to center of gravity position and the other to tire and suspension characteristics. When a specimen vehicle is considered, it is shown that current semi-trailer design can display instability from either source. 相似文献
753.
S.-J. Lee M.-S. Jang Y.-G. Kim G.-T. Park 《International Journal of Automotive Technology》2011,12(3):425-432
Occupant classification in a passenger seat is one of the critical components for any advanced airbag system. Many automotive
electronic suppliers and engineers predict that the camera will be the next generation sensor for active and passive safety
systems because it has several advantages compared to other sensors. The present paper describes a stereovision-based occupant
classification system (OCS) and intelligent algorithm with embedded system by which triggering of the airbag deployment can
be controlled. The system consists of a pair of stereo cameras and dual Digital Signal Processor (DSP): the first DSP is for
the stereo matching processing, and the second is for occupant classification. The results show that the reaches 97%, and
the processing time is 960 ms. Such performance indicates that the feasibility of the system as an embedded OCS is high. 相似文献
754.
Ana M. Nobre Suzanne B. Bricker João G. Ferreira Xiaojun Yan Martin De Wit João P. Nunes 《Coastal management》2013,41(5):536-555
This article presents an approach that couples coastal ecosystem modeling with integrated environmental assessment methodologies to support coastal management. The focus is to support the development of an ecosystem approach to aquaculture management including interactions with watershed substance loading. A Chinese bay, with intense aquaculture and multiple catchment uses, and where significant modeling efforts were undertaken is used as a case study. The ecosystem model developed for this bay is used to run scenarios that test the local management strategy for nutrient reduction. The corresponding ecological and economic impacts of the managers’ scenarios are analyzed by means of the Differential Drivers-Pressure-State-Impact-Response (ΔDPSIR) analysis. Emphasis is given to the analysis of the eutrophication process in the bay including present eutrophic condition and the expected changes due to the simulated scenarios. For this purpose, the Assessment of Estuarine Trophic Status (ASSETS) screening model is a valuable tool to interpret and classify the data and model outputs regarding eutrophication condition and to evaluate the manageable level of the nutrient loading entering in the bay. 相似文献
755.
756.
Using structural equations modeling to unravel the influence of land use patterns on travel behavior of workers in Montreal 总被引:1,自引:0,他引:1
João de Abreu e Silva Catherine Morency Konstadinos G. Goulias 《Transportation Research Part A: Policy and Practice》2012,46(8):1252-1264
This paper addresses the relations between travel behavior and land use patterns using a Structural Equations Modeling (SEM) framework. The proposed model structure draws on two earlier models developed for Lisbon and Seattle which show significant effects of land use patterns on travel behavior. The travel behavior variables included here are multifaceted including commuting distance, car ownership, the amount of mobility by mode (car, transit and non-motorized modes), both in terms of total kilometers travelled and number of trips. The model also includes a travel scheduling variable, which is the total time spent between the first and last trips to reflect daily constraints in time allocation and travel.The modeled land use variables measure the levels of urban concentration and density, diversity, both in terms of types of uses and the mix between jobs and inhabitants/residents, the transport supply levels, transit and road infrastructure, and accessibility indicators. The land use patterns are described both at the residence and employment zones of each individual included in the model by using a factor analysis technique as a data reduction and multicollinearity elimination technique. In order to explicitly account for self selection bias the land use variables are explicitly modeled as functions of socioeconomic attributes of individuals and their households.The results obtained show that people with different socioeconomic characteristics tend to work and live in places of substantially different urban environments. But besides these socioeconomic self-selection effects, land use variables significantly affect travel behavior. More precisely the effects of land use are in great part passed thru variables describing long term decisions like commuting distance, and car ownership. These results point to similar conclusions from the models developed for Lisbon and Seattle and thus give weight to the use of land use policies as tools for changing travel behavior. 相似文献
757.
Amaya Alvarez-Ellacuria Alejandro Orfila Maitane Olabarrieta Luís Gómez-pujol Raúl Medina Joaquín Tintoré 《Coastal management》2013,41(6):569-584
A real-time beach hazard level associated with nearshore hydrodynamics is presented in this article. The suitability of the discussed alert system is illustrated via its application to fifteen beaches in the Balearic Islands (Western Mediterranean Sea) providing nearshore safety conditions for beach safety manager. The system provides daily forecasts of nearshore wave conditions using the deep water wave forecasts. The shallow water wave data (wave height, period, and direction) together with the morphology of the site (presence of bars, capes, beach type, etc.) are used to define a hazard level (low, medium, and high) associated with local conditions. The resulting hazard level is transmitted via SMS to lifeguards and local authorities for real-time beach management. The low computational cost of this system after the initial implementation and subsequent calibration results in a very suitable approach for beach management in order to mitigate risks related to local hydrodynamics. 相似文献
758.
Bonnet weight reduction and VRU protection: Design proposals implementing non-conventional materials
G. Belingardi G. Chiandussi E. Gobetto A. Scattina 《International Journal of Automotive Technology》2010,11(6):831-842
The use of non-conventional and innovative materials is increasingly important in automotive design. They allow reductions
in the weights of structures with consequent reductions in fuel consumption and carbon dioxide emissions. At the same time,
they ensure excellent safety levels. Once excellent results in terms of active and passive safety have been obtained, the
attention of car manufacturers, and of the public opinion, is focused on the safety of vulnerable road users (VRU), pedestrians
and cyclists. Some examples concerning the redesign of a bonnet with the double targets of weight reduction and pedestrian
safety are illustrated. Hybrid metal/plastic and more conventional metal sheet solutions are compared. The static performance
(stiffness and denting resistance), as well as the impact against a pedestrian head, are evaluated by means of FEM models
along with actual regulations. 相似文献
759.
Michael G H Bell 《先进运输杂志》2001,35(3):199-214
Buses will remain the backbone of public transport systems for some time to come because of their lower cost and higher flexibility in relation to rail transport. However, buses are perceived as being an inferior mode of public transport and do not offer as much carrying capacity as rail transport. Following the Curitiba model, this paper looks at the potential for transferring some of the key advantages of rail transport to bus operations. This involves transforming bus stops into enclosed stations, with ticket purchase and/or checking in the station and at‐grade access to vehicles. It also involves the extensive use of bus lanes. The potential contribution of transport telematics is looked at, in particular the use of smartcards for payment in a closed fare system. The potential role of the Curitiba model for China is assessed in the context of toll road construction. 相似文献
760.