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301.
Maciej T. Krzyzanowski 《Maritime Policy and Management》1993,20(4):301-307
At the end of the eighties, fundamental changes took place in Polish shipping. Implementation of the market economy system was at first demonstrated in the introduction of the principles of self-dependence, self-government and self-financing of the shipping companies. Privatization performed a key role in the program of transformation of the centrally planned system into market oriented financially independent shipping organizations. The previous principle of the necessary participation of the home fleet in transporting domestic sea-borne trade has been mostly replaced by cross-trade. Many shipping services have left its basic ports in the country for a West European basis, securing alimentation of home and transit cargoes by feeder-service systems. Joint stock companies in shipping with substantial shares of foreign capital are welcomed, and the previously obligatory system of administrative methods of the state monopoly has been abolished. The principles of shipping policy represented in the past by Poland and also by UNCTAD in the 1960s have lost their impact and must be change and adapted to the new demands of the shipping markets. 相似文献
302.
M. Shino H. Yoshitake M. Hiramatsu T. Sunda M. Kamata 《International Journal of Automotive Technology》2014,15(5):749-755
The objective of this study is to propose the indices which detect the deviated state of drivers while driving by considering drivers’ judgment process and using road environment and naturalistic driving behavior database. To realize this objective, drivers’ speed choice behavior around curve situations was focused and the speed choice process was formulated. Moreover, a deviated state detection method considering the formulated speed choice process around curve situations was proposed and the validity of the method was examined. 相似文献
303.
Hazard perception tests may not be transferable between different countries, due to differences in traffic culture and infrastructure. Therefore, different instruments might be necessary for assessing hazard perception in various countries. The aim of the current study was to develop the Lithuanian hazard perception test based on static traffic images and test its psychometric properties. Thirty-four experienced drivers participated in a pilot study, and 125 drivers with diverse driving experience took part in the main study. The final test contained 27 static traffic scenes and the participants were asked to respond if they saw a hazard or not. Results demonstrated that the test has satisfactory internal consistency and test-retest reliability. It differentiated between inexperienced and experienced drivers, and between those experienced drivers who had less than three or more than three crashes in their driving history. The test has sufficient psychometric properties for research; still further development is needed in order to apply it for individual testing and decisions about licence provision. 相似文献
304.
In-situ measurement of loading stresses with X-ray diffraction for yield locus determination 总被引:1,自引:0,他引:1
A. Güner B. Zillmann T. Lampke A. E. Tekkaya 《International Journal of Automotive Technology》2014,15(2):303-316
The application of the X-ray diffraction method is introduced to solve the problem of inhomogeneous deformation fields in the specimens used for sheet metal characterization. In this method, strains are measured on one side of a specimen with optical measurement systems. On the other side, loading stresses on a specimen are captured with an X-ray diffractometer mounted on a universal testing machine. By this way, the whole stress-strain history of a material point is tracked during testing. The method was first applied to uniaxial tension tests, whereby the applicability of the theory of stress factors and effective X-ray elastic constants were tested. The relaxation behavior of a sheet material which shows itself as stress drops during in-situ experimentation was characterized and compensated by a visco-plastic material model for different stress states. The proposed method was applied to characterize aluminum alloy AA5182 under plane strain tension and shear conditions and the results were compared with the conventionally obtained yield locus. Numerical analyses of a workpiece with the Vegter and Yld2000-2D material models show that the enriched yield locus definition with accurate plane strain tension and shear stresses captures the experimentally obtained surface strains more precisely. 相似文献
305.
O. T. Lim 《International Journal of Automotive Technology》2014,15(4):535-541
The HCCI (Homogeneous Charge Compression Ignition) engine is an internal combustion engine under development, which is capable of providing both high diesel-like efficiency and very low NOx and particulate emissions. However, several technical issues must be resolved before the HCCI engine is ready for widespread application. One issue is that its operating range is limited by an excessive pressure rise rate which is caused by the excessive heat release from its selfaccelerated combustion reaction and the resulting engine knock in high-load conditions. The purpose of this study was to evaluate the potential of thermal and fuel stratification for reducing the pressure rise rate in HCCI engines. The NOx and CO concentrations in the exhaust gas were also evaluated to confirm combustion completeness and NOx emissions. The computational work was conducted using a multi-zone code with detailed chemical kinetics, including the effects of thermal and fuel stratification on the onset of ignition and the rate of combustion. The engine was fueled with dimethyl ether (DME) which has a unique two-stage heat release, and methane which has a one-stage heat release. 相似文献
306.
The intake or exhaust noise of an internal combustion engine is usually predicted by the linear, time-invariant source model in frequency domain with reasonable precision. However, the actual finite amplitude pulsation involves the nonlinear, time-varying characteristics that are prominent in time-domain. To overcome the discrepancy between two source models, an approximate nonlinear and time-varying frequency domain source model can be employed by appending the nonlinear or time-varying terms to the linear, time-invariant source model. Proper selection of the nonlinear describing terms varying with time is important for the realistic and precise prediction of the radiated sound. For the selection of such terms, flow and motional characteristics in the valve and orifice of a simplified fluid machine comprised of very large reservoir, valve, and duct is considered. Effects of each describing term and the combined terms are investigated by comparing the sound spectrum predicted from nonlinear source model to that from linear source model. In the comparison, the sound spectrum calculated by the method of characteristics is used as a reference. It is found that the source model using only the velocityrelated terms yields the best result among all the models using various combinations of the terms with different characteristics. The best model yields a difference from the linear source model within ±5 dB in overall sound level. Change of acoustic loads results in a difference of 20–27 dB in linear source model from the reference data; however, maximum 10–22 dB deviations are observed in using the various nonlinear source models. It is concluded that more than 4 describing terms should be employed in the nonlinear model to obtain a realistic result of the radiated sound from the intake or exhaust system. 相似文献
307.
J. T. Yang H. Y. Choi J. H. Lee S. U. Lee 《International Journal of Automotive Technology》2014,15(4):667-672
An empirical analysis was performed in order to examine whether the height of the lumbar support installed on the driver’s seat in a vehicle makes a difference to the initial discomfort when sitting, and among the design variables of the seat lumbar support, which one is the main variable that affects the initial discomfort most when sitting. The subjects who participated in this study were 50th percentile male in their 30s and 40s from Korea and America, had driving experience, and had not experienced any back pain in the last 12 months. In order to figure out the level of discomfort felt by a driver depending on the movement or the shapes of the lumbar support, subjective sensibility evaluation was conducted and sitting body pressure was measured, and the change of lumbar spine angle was observed using X-ray image. Based on the results, design variables that affect the initial discomfort when sitting on a car seat and the correlation among these design variables were verified through statistical significance testing. The empirical analysis suggested that, among design variables of car seat lumbar support, the degree of prominence is the main variable that affects the initial discomfort when sitting for both Koreans and Americans, while the height and support width have very little to do with it. 相似文献
308.
Minimizing vehicle post impact path lateral deviation using optimized braking and steering sequences
D. Yang B. Jacobson M. Jonasson T. J. Gordon 《International Journal of Automotive Technology》2014,15(1):7-17
This paper investigates the optimal control of a vehicle, after a light impact during a traffic accident. To reduce the risk of secondary events, the control target is set: to minimize the maximum lateral deviation from the initial path. In previous analysis path control was achieved by the active control of individual wheel braking. The present paper examines potential benefits from the additional control of front steering angles. Numerical optimization is used to determine optimal control sequences for both actuator configurations. It is found that steering provides significant control benefits, though not for all post-impact kinematics. For all cases considered, the optimal control operates at the boundary of the control domain of available forces and moments. This domain is expanded when steering is available, and there exists an expanded range of conditions for which coupled control of yaw moments and lateral forces is the most effective control strategy. The sensitivity of vehicle response to the individual actuator controls is studied; it reveals this sensitivity is related to the actuator bandwidth and the lack of any dynamic cost in the longitudinal direction. This motivates a further analysis which includes longitudinal and lateral dynamics in the cost function. This is broadly related to real-world crash risks. Further, different versions of such cost functions are compared as a basis for implementation in a closed-loop controller. 相似文献
309.
Pruning and ranking the Pareto optimal set,application for the dynamic multi‐objective network design problem 下载免费PDF全文
Solving the multi‐objective network design problem (MONDP) resorts to a Pareto optimal set. This set can provide additional information like trade‐offs between objectives for the decision making process, which is not available if the compensation principle would be chosen in advance. However, the Pareto optimal set of solutions can become large, especially if the objectives are mainly opposed. As a consequence, the Pareto optimal set may become difficult to analyze and to comprehend. In this case, pruning and ranking becomes attractive to reduce the Pareto optimal set and to rank the solutions to assist the decision maker. Because the method used, may influence the eventual decisions taken, it is important to choose a method that corresponds best with the underlying decision process and is in accordance with the qualities of the data used. We provided a review of some methods to prune and rank the Pareto optimal set to illustrate the advantages and disadvantages of these methods. The methods are applied using the outcome of solving the dynamic MONDP in which minimizing externalities of traffic are the objectives, and dynamic traffic management measures are the decision variables. For this, we solved the dynamic MONDP for a realistic network of the city Almelo in the Netherlands using the non‐dominated sorting genetic algorithm II. For ranking, we propose to use a fuzzy outranking method that can take uncertainties regarding the data quality and the perception of decision makers into account; and for pruning, a method that explicitly reckons with significant trade‐offs has been identified as the more suitable method to assist the decision making process. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
310.
Y. H. Venus Lun Kee-hung Lai Christina W. Y. Wong T. C. E. Cheng 《Maritime Policy and Management》2014,41(2):134-148
Global economic development is facilitated by the commercial shipping industry. Shipping operations contribute to the growth of international trade activities, which heavily count on ships to carry cargoes from places of production to places of consumption. Despite its importance, there have been growing concerns about the environmental impacts caused by shipping activities in international trade. To balance environmental protection and productivity, many shipping firms have begun to adopt green shipping practices (GSPs) to improve their operations in a more environmentally friendly manner. GSP consists of six dimensions, namely, company policy and procedure (CPP), shipping documentation (SD), shipping equipment (SE), shipper cooperation (SC), shipping materials (SM), and shipping design and compliance (SDC). GSP is becoming an important aspect of shipping operations. It is timely for the shipping industry to evaluate firm capability in carrying out greening operations, that is, firms’ “greening” capability. Firm capability comprises two key elements: one is embedded in firms’ business routines or activities, and the other concerns firms’ ability in transforming inputs into outputs. GSPs can be considered as inputs while firm performance measures as outputs. This study uses an input/output approach to examine the greening capability (GC) of shipping firms. The results indicate that shipping firms are relatively weak in the practices of SC and SE, while the capability scores of SM, CPP, SDC, and SD are all close to 1, with an average score of 0.927, 0.920, 0.924, and 0.978, respectively. Academic and managerial significance of the findings are highlighted. 相似文献