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981.
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
982.
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
983.
Myeong-jo Son Sang Chul Lee Ki-chang Kwon Tae-wan Kim Rajiv Sharma 《Journal of Marine Science and Technology》2011,16(4):367-378
Ships are complex engineering structures that are designed and built on the basis of technical experience. A shipowner will
often be required to estimate the price of a new ship on the basis of the value of comparable ships identified in trade journals.
Similarly, shipbuilders are often interested in estimating approximate costs during the tendering phase in order to determine
whether a ship is likely to be competitive for a particular order. Thus, when designing a ship prior to having obtained a
contract, one of the most important processes is the estimation of approximate costs, including materials, associated labor,
and overhead. During this preliminary design phase, the design is temporary and subject to change based on variations in the
shipowner’s requirements. Hence, quick and flexible responses are key during this period and an integral aspect of the competitive
powers of the shipbuilder. Given this environment, we propose a “configuration estimation method.” Our method is based on
the configuration design method that is widely used in three-dimensional (3D) computer aided design (CAD) systems. We assume
that a product lifecycle management system is furnished and that the cost is then estimated via the configuration of the ship,
using an engineering bill of materials (E-BOM). In referring to the E-BOM, we utilize technical parametric costs derived from
similar ships built previously. Using the proposed method, it is possible to obtain an accurate list of materials from the
quotation, as well as a detailed work assessment for labor costs and overhead rates, so that reliable cost estimates can be
generated quickly and flexibly. To demonstrate the practical applicability and effectiveness of the proposed method, we implement
the prototype of a shipbuilding configuration estimation system by using a Microsoft Structured Query Language database and
an E-BOM from AVEVA Marine version 12.01, which is a representative CAD system for shipbuilding. 相似文献
984.
Hyun Park Nam Hyun An Nicholas Hutchins Kwing-So Choi Ho Hwan Chun Inwon Lee 《Journal of Marine Science and Technology》2011,16(4):390-401
An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first
devised by Hutchins and Choi (Proceedings of ASME FEDSM’02 2002 ASME Fluids Engineering Division Summer Meeting, Montreal)
and Hutchins (An investigation of larger-scale coherent structures in fully developed turbulent boundary layers, Hutchins
N (2003), PhD thesis, University of Nottingham). The reported drag reduction efficiency, which was as much as 30%, was quantified
only in terms of the reduction in the local skin-friction coefficient. The assessment of the drag reducing efficiency did
not take the side effects of the inclusion of the blades into considerations. Those effects are the increase in the wetted
surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements
in towing tank has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical
blades. It was found that for the case of h 4.0 × z 4.0 (h/δ = 1.04), the outer-layer vertical blades array achieved about 9.6% drag reduction without considering the increase in the
wetted surface area. A proper scaling method to give collapsed plot of drag reduction efficiency C
F/C
F0 was attempted, but the correlation remained limited. Of the two scaling methods, the outer scaling is found to be relevant
one. 相似文献
985.
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
986.
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
987.
Moira L. McConnell 《WMU Journal of Maritime Affairs》2011,10(2):127-141
This paper begins by providing a brief overview of the International Labour Organization’s Maritime Labour Convention, 2006 (MLC, 2006), noting that this Convention, often called the “Seafarers’ bill of rights”, seeks to achieve both social and labour rights (“decent work”) for seafarers and fair competition (achieving a level-playing field) for shipowners. It has been described as the “fourth pillar” of the international maritime regulatory regime complementing the major International Maritime Organization conventions. The paper provides a brief update on international efforts to achieve the 30/33 formula needed to bring the Convention into force [at present, the tonnage element, 33% has been achieved already with coverage now at 54% of the world fleet (by gross tonnage), with 18 ratifications]. It then explores challenges faced by flag States in connection with capacity to implement the ship inspection and certification system under the MLC, 2006 and other difficulties with respect to legal implementation by the flag States. The paper also comments on some challenges in connection with port State, coastal State and labour-supplying State responsibilities. The paper points out that the MLC, 2006 is a comprehensive code that covers diverse issues and a wider range of both ships and seafarers than previous conventions. It often requires interdepartmental cooperation to implement its requirements at the national level. The paper concludes that, despite the slower pace of ratification in some regions, largely because of the recent economic and other crises, it appears that many actors in the maritime sector are already actively engaged in MLC, 2006 implementation, often ahead of governments. The question is not “if” but “when” the formula will be achieved to allow the MLC, 2006 to enter into force. 相似文献
988.
B. C. Choi S. K. Choi S. H. Chung J. S. Kim J. H. Choi 《International Journal of Automotive Technology》2011,12(2):183-191
Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot
formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were
investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an
ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C6H6) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of
propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination
of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects.
These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number
density. 相似文献
989.
We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the
carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied
petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting
the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was
because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting
spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element
lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance
optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design,
the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased
by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure
and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating
film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through
the seal was minimal. 相似文献
990.
Quasistatic fractures at high joint angles constitute a chronic quality problem in CV joints. This type of fracture occurs
when a driver unintentionally depresses the brake and accelerator simultaneously under a full-turn retreat condition. In general,
the cage in a ball joint can be broken only at these high joint angles. Here we present a flexible quasistatic simulation
model developed to simulate fracture in a CV joint. The cause and process of the quasistatic fracture were analyzed using
simulations and physical tests. Static fracture simulations and tests at high joint angles showed that, initially, only one
of the six cage posts was damaged. In a simulation of one revolution at constant torque, we found that an imbalance in ball
loads generated an excessive cage load. Moreover, if this high cage load was applied when the cage protruded outward, the
cage post was subjected to severe shear loading. The cage post was damaged in this specific rotational range. Quasistatic
fracture simulations and tests at high joint angles showed that all six cage posts were damaged sequentially. Because entire
cage posts were damaged, the quasistatic fracture torque was approximately half of the static torque. The plastic strain in
each cage post displayed one step-like jump per revolution in the quasistatic simulations. The ball indentation created by
a high ball load was interrupted by the cage-window edges as the ball joint rotated. This hindrance by ball indentation triggered
the final breakage of the cage, although it was not the major cause of cage fractures. 相似文献