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981.
J. A. Bunce 《运输规划与技术》2013,36(4):269-283
A transport system has been proposed using buses operating over ordinary roads and over special reserved tracks (busways) on which they might be automatically guided. Using cost and performance data resulting from an earlier technical study (not reported here), a hypothetical network of routes and services in the West Midlands conurbation is studied. Estimates of patronage diverted from public and private transport enable the profitability of the system and its costs and benefits to be assessed. It is concluded that the system could be attractive both in commercial and in cost/benefit terms, providing acceptable means could be found for handling the buses around and through the inner central areas of cities. The net environmental changes, which would result from additional fixed plant permitting more efficient use of mobile plant, have not been quantified. 相似文献
982.
David A. Hensher 《运输评论》2020,40(5):551-556
983.
Rokicki Bartlomiej Haddad Eduardo A. Horridge Jonathan M. Stępniak Marcin 《Transportation》2021,48(2):747-772
Transportation - Since its EU accession, Poland has invested strongly in the development of fast road transport network. As a result, the total length of modern, high-speed roads has increased from... 相似文献
984.
985.
L. P. Perera J. P. Carvalho C. Guedes Soares 《Journal of Marine Science and Technology》2011,16(1):84-99
This paper focuses on a fuzzy logic based intelligent decision making system that aims to improve the safety of marine vessels
by avoiding collision situations. It can be implemented in a decision support system of an oceangoing vessel or included in
the process of autonomous ocean navigation. Although Autonomous Guidance and Navigation (AGN) is meant to be an important
part of future ocean navigation due to the associated cost reduction and improved maritime safety, intelligent decision making
capabilities should be an integrated part of the future AGN system in order to improve autonomous ocean navigational facilities.
In this study, the collision avoidance of the Target vessel with respect to the vessel domain of the Own vessel has been analyzed
and input, and output fuzzy membership functions have been derived. The if–then rule based decision making process and the
integrated novel fuzzy inference system are formulated and implemented on the MATLAB software platform. Simulation results
are presented regarding several critical collision conditions where the Target vessel fails to take appropriate actions, as
the “Give way” vessel to avoid collision situations. In these situations, the Own vessel is able to take critical actions
to avoid collisions, even when being the “Stand on” vessel. Furthermore, all decision rules are formulated in accordance with
the International Maritime Organization Convention on the International Regulations for Preventing Collisions at Sea (COLREGs),
1972, to avoid conflicts that might occur during ocean navigation. 相似文献
986.
The dynamic response of planing vessels in regular head seas is investigated numerically. Nonlinear time domain simulations
were performed using a 2D + t theory (two-dimensional plus time dependent theory). A prismatic hull form was assumed. We employed a two-dimensional (2D)
boundary element method to solve the initial boundary value problems in 2D cross planes, in which nonlinear free-surface conditions
and exact body boundary conditions were satisfied. At each time step, the total force and moment on the hull could be obtained
by using the sectional forces calculated in those 2D planes. Heave and pitch motions were then acquired by solving the equations
for those motions. The calculated heave and pitch responses were compared with the experiments by Fridsma (A systematic study
of the rough-water performance of planing boats. Davidson Laboratory Report R-1275, 1969) for two different Froude numbers. Three-dimensional (3D) corrections at the transom stern were applied to show the influence
of the 3D effect at the stern on the numerical results. Ship motions were affected by the 3D corrections, especially near
the resonance frequency, while the phase angles were slightly affected and the acceleration peaks at the bow near the resonance
frequency were sensitive to the 3D corrections. Other error sources in the theoretical results are also mentioned. 相似文献
987.
Manivannan Kandasamy Daniele Peri Seng Keat Ooi Pablo Carrica Frederick Stern Emilio F. Campana Philip Osborne Jessica Cote Neil Macdonald Nic de Waal 《Journal of Marine Science and Technology》2011,16(2):143-156
The wakes of high-speed passenger-only ferries that operated through Rich Passage, on the Seattle-Bremerton ferry route, caused
beach erosion and damage to habitat. A task was initiated to design a low-wake high-speed vessel using multi-fidelity CFD
based design optimization by using low-fidelity potential flow solvers for initial global design optimization and by using
URANS solvers for high-fidelity tuning of the optimized design. This simulation based design process involved a close collaboration
between ship designers, and hydrodynamics and CFD specialists, whose collective expertise guided the evolution of the design
based on both hydrodynamic and structural aspects. The initial hull shape optimization using potential flow code was carried
out by blending three different initial concepts provided by the designers. Subsequently, URANS was used to evaluate the potential
flow optimized hull and to further optimize the hull configuration parameters, namely, the centre-of-gravity, demihull spacing,
foil location, foil angle and slenderness ratio at different displacement conditions. The URANS based configuration optimization
also took into account the far field wakes’ energy spectrum with an objective of reducing the energetic, low frequency far
field wakes which are associated with beach flattening on the mixed sand and gravel beaches. Calculation of the far field
wake using URANS would require an unfeasibly large domain size; therefore, a Havelock code with a source distribution matching
the URANS calculated near field wave elevation was used to propagate the wakes into the far field. The end result of the optimization
was a design with significantly reduced far field wake, which is currently being built for experimental testing. 相似文献
988.
DongYoung Lee GyungNam Jo YunHo Kim Hang S. Choi Odd M. Faltinsen 《Journal of Marine Science and Technology》2011,16(3):323-330
In this paper, we investigated the effect of sloshing on the sway motions of two-dimensional rectangular cylinders in regular
waves, bearing in mind possible applications for LNG-FPSO and LNG-FSRU. First, we carried out experiments for two models with
different drafts, or the same draft but different filling ratios, in which the models were firmly connected to each other.
The sway motion was measured with a noncontact video camera. This is an extension of Rognebakke and Faltinsen’s work for a
single model (J Ship Res 47(3):208–221, 2003). It was found that the sway motion became small when the incident wave frequency was close to the lowest natural frequency
of each model. The sway motion greatly increased when the wave frequency was higher than this frequency. The measured data
were compared with numerical results obtained by a single-dominant multi-modal method; relatively good agreement was noted.
However, the numerical results deviated from the experimental results near the lowest natural frequency of the smaller model,
which was believed to be due to overturning waves, as observed during the experiment. Since this is out of the valid range
for the single-dominant multi-modal method, other, more appropriate, methods such as the multi-dominant modal method must
be applied instead. 相似文献
989.
Thomas Spenkuch Stephen R. Turnock Matteo Scarponi R. Ajit Shenoi 《Journal of Marine Science and Technology》2011,16(2):115-128
An approach for enhancing the realism of yacht fleet race simulations based on a lifting line method is developed. The wake
of an upwind sailing yacht is represented as a single heeled horseshoe vortex and image system. At each time step, changes
in vortex strength are convected into the wake as a pair of vortex line elements. These subsequently move in accordance with
the local wind, the self-induced velocity and the velocity induced by the presence of the wakes of other yachts. In addition,
the lifting line model has a model for the viscous wake due to the drag associated with the yacht and its sails superimposed
on it. A synthesis of sail yacht wake representations based on detailed 3D Reynolds-averaged Navier–Stokes computational fluid
dynamics calculations with wind tunnel test results is used to capture the initial strength of the combined main-jib vortex
system and its vertical height. The implementation of the lifting line algorithm within Robo-Race, a real-time yacht race strategy analysis tool, is described. Two upwind race interaction case studies are presented, and
these show that the newly implemented wake model makes an important contribution to enhancing the realism of the sailing simulation. 相似文献
990.
This paper presents an integrated design procedure for determination of structural arrangement and scantlings for the complete structure of small high-speed craft. The purpose of the procedure is to serve as a tool in the preliminary design stage where it enables generation of weight minimized designs with very limited effort. The design procedure is applied in a material concept study for a high-speed patrol craft. The various concepts include single skin and sandwich composites, aluminum and steel. It is demonstrated that the mass of the aluminum hull structure can be reduced from the original 11.7 tonnes to 9.6 tonnes through application of the presented design procedure. The most weight efficient material concept is a carbon-fiber foam-cored sandwich with a structural mass of 4.8 tonnes, which is about 50% less than the refined aluminum version. Through simple hydromechanic analysis, potential for fuel and CO2 emission reductions of 8% for the refined aluminum version and 27% for the carbon-fiber sandwich version in relation to the original craft are indicated. 相似文献