全文获取类型
收费全文 | 1664篇 |
免费 | 18篇 |
专业分类
公路运输 | 687篇 |
综合类 | 47篇 |
水路运输 | 443篇 |
铁路运输 | 33篇 |
综合运输 | 472篇 |
出版年
2023年 | 4篇 |
2022年 | 27篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 72篇 |
2017年 | 80篇 |
2016年 | 160篇 |
2015年 | 7篇 |
2014年 | 51篇 |
2013年 | 167篇 |
2012年 | 97篇 |
2011年 | 184篇 |
2010年 | 163篇 |
2009年 | 64篇 |
2008年 | 119篇 |
2007年 | 64篇 |
2006年 | 26篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 23篇 |
2002年 | 20篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 20篇 |
1997年 | 19篇 |
1996年 | 24篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有1682条查询结果,搜索用时 31 毫秒
991.
J. Rodriguez P. T. Freeman J. Wagner W. Bridges P. Pidgeon K. Alexander 《International Journal of Automotive Technology》2016,17(1):71-81
The automotive steering system is the primary channel through which road and vehicle behavior feedback is transmitted to the driver. While the driver provides directional platform control through the steering wheel, perceptions of the vehicle’s handling responsiveness are simultaneously transmitted back to the driver allowing for correction of any instabilities the vehicle may encounter. Based on these factors, drivers often pay special attention to the steering system when deciding what vehicle to purchase. Therefore, a significant amount of effort and time is invested in attempting to determine the optimal design of steering system components and configurations. In this study, the determination of an optimal steering configuration was attempted based on responses obtained from questionnaires that subjects answered. The questions were designed to evaluate the degree of satisfaction regarding the “control”, “ease of operation”, and “fun” participants experienced after each driving run. During the study, human subjects drove a driving simulator for 15 combinations of 3 different roadway environments and 5 different steering configurations, filling out a questionnaire after each scenario. The subjects were also classified as a type of driver (“utility”, “enthusiast”, and/or “performance”). The study attempted to determine if the mean values of questionnaire responses for “control”, “ease”, and “fun” type of questions changed as the scenario and/or driver type changed. Analysis of Variance (ANOVA) was used to determine if the mean values of the three types of questions were statistically different. The overall results suggest that the average responses for vehicle “control”, “ease”, and the “fun” type of questions were dependent on the type of roadway environment; however, only the responses for “fun” type of questions were influenced by the given steering configurations. Indeed, the steering system can impact the driver’s perceptions of the vehicle’s operational experience. 相似文献
992.
J. Son M. Park K. Won Y. Kim S. Son A. McGordon P. Jennings S. Birrell 《International Journal of Automotive Technology》2016,17(1):175-181
It is known that differences in driving styles have a significant impact on fuel efficiency and driving styles are affected by various factors such as driver characteristics, street environment, traffic situation, vehicle performance, and weather conditions. However, existing knowledge about the relationship between driving style and fuel consumption is limited. Thus, the aim of this study was to analyze the relationship beteen driving style and fuel consumption. The analysis presented in this paper used data from three on-road experiments were conducted independently in two different countries, i.e. South Korea and the United Kingdom. In this study, 91 participants, consisting 44 UK drivers and 47 Korean drivers, were asked to drive approximately 28 km of UK road and 21 km of Korean road, respectively. Driving data, including real-time fuel consumption, vehicle speed, and acceleration pedal usage were collected. The results suggested that driving styles including average vehicle speed and average throttle position were highly correlated with the real-world fuel consumption, and the cultural factors, e.g. road environment, traffic design, and driver’s characteristics affected the driving styles and, consequently, fuel efficiency. 相似文献
993.
Abhra Roy Chowdhury Wang Xue Manasa Ranjan Behera S. K. Panda 《Journal of Marine Science and Technology》2016,21(1):102-114
This paper investigates the hydrodynamic characteristics of the rectilinear motion of a robotic fish underwater vehicle. This 2-joint, 3-link multibody vehicle model is biologically inspired by a body caudal fin carangiform fish propulsion mechanism. Navier–Stokes equations are used to compute the unsteady flow fields generated due to the interaction between the vehicle and the surrounding incompressible and Newtonian fluid (water) environment. The NACA 0014 airfoil aerodynamic profile has been designed to boost the swimming efficiency by reducing drag as the vehicle undergoes an undulatory/oscillatory motion. Using the Lighthill slender body model, a traveling wave mathematical function is defined to undulate the robotic fish posterior (caudal) region while the motion tracking is carried out by dynamic meshing technique. The results obtained show that though the net lift force approaches to zero, the net thrust or negative drag coefficient maintains a finite value dependent on kinematic parameters like tail beat frequency (TBF) and amplitude span (AS) at a given propulsive wavelength and the forward velocity of the vehicle. The results reveal the effects of TBF and AS on the coefficient of drag friction and the thrust force. Drag coefficients obtained from the simulations are compared and validated with the experimental results. The hydrodynamic results are found to be similar to the kinematic study results and suggest that TBF and AS play the most effective roles in the bioinspired propulsion technique. Relation of these parameters with propelling thrust force and forward velocity is also in conjunction over a given range of TBF and AS values. 相似文献
994.
This study examines the hydrodynamic performance of multiple-row vertical slotted breakwaters. We developed a mathematical model based on an eigenfunction expansion method and a least squares technique for Stokes second-order waves. The numerical results obtained for limiting cases of double-row and triple-row walls are in good agreement with results of previous studies and experimental results. Comparisons with experimental measurements of the reflection, transmission, and dissipation coefficients (C R , C T , and C E ) for double-row walls show that the proposed mathematical model adequately reproduces most of the important features. We found that for double-row walls, the C R increases with increasing wave number, kd, and with a decreasing permeable wall part, dm. The C T follows the opposite trend. The C E slowly increases with an increasing kd for lower kd values, reaches a maximum, and then decreases again. In addition, an increasing porosity of dm would significantly decrease the C R , while increasing the C T . At lower values of kd, a decreasing porosity increases the C E , but for high values of kd, a decreasing porosity reduces the C E . The numerical results indicate that, for triple-row walls, the effect of the arrangement of the chamber widths on hydrodynamic characteristics is not significant, except when kd<0.5. Double-row slotted breakwaters may exhibit a good wave-absorbing performance at kd>0.5, where by the horizontal wave force may be smaller than that of a single wall. On the other hand, the difference between double-row and triple-row vertical slotted breakwaters is marginal. 相似文献
995.
Since cargo capacity increases faster than fuel consumption, the significantly larger capacity fleets which will accompany expansion of the Panama Canal will introduce additional fuel economies and cost savings. Enabling larger, more fuel-efficient vessels to carry cargo the entire distance from Asia to US east-coast ports allows vessel operators to realize significant and meaningful savings compared with the alternatives of using smaller Panamax vessels for the whole distance, or sending the cargo over the US land bridge by train or truck. Fuel savings are quantified along with the monetary savings based on various assumptions for the price of fuel. These savings are dramatic and will increase directly with the price of crude petroleum. Finally, microeconomic theory is deployed to determine how cost savings will be distributed between shipping customers and vessel operators. 相似文献
996.
Successful co-deposition of fine particulate matter within an Electroless Nickel-Phosphorous (ENi-P) matrix is dependent on various factors like bath composition, particle compatibility with metallic matrix, bath reactivity (pH), particle size and their distribution. ENi-P deposits incorporating Al2O3/Alumina in a disperse phase have varied effects on properties and attributes like surface roughness (Ra), microhardness, wear resistance, corrosion resistance and surface morphology of the deposits obtained. This paper experimentally investigates the effect of alumina (1.55 g/L) on Ra, microhardness, surface morphology, deposition rate, wettability, wear resistance and corrosion resistance of ENi-P-Al2O3 composite deposits on mild steel substrates at bath pH 5, 7 and 9. Study reveals that optimum deposit parameters and deposition rates are achieved with bath pH. However, not much study has been undertaken concerning composite deposits obtained from higher bath pH or basic bath. This is attributable to the fact that at higher bath pH or alkaline baths, the bath gets unstable and eventually degrades or decomposes, thereby resulting in sub optimal or poor deposition. Hence, experimental investigations carried out by preparing suitable baths, operating under optimum conditions, and enabling successful composite deposition in acidic and alkaline baths have revealed that there is a significant improvement in the above mentioned properties of the as-deposited composite deposits, as the pH is increased from pH 5 to pH 9. This aspect can therefore be advantageously utilized for preparing various marine components like fasteners, nuts, bolts, washers, pipes, cables, components having relative motion etc. 相似文献
997.
Optimal toll design from a network reliability point of view is addressed in this paper. Improving network reliability is proposed as a policy objective of road pricing. A reliability‐based optimal toll design model, where on the upper level network performance including travel time reliability is optimized, while on the lower level a dynamic user‐equilibrium is achieved, is presented. Road authorities aim to optimize network travel time reliability by setting tolls in a network design problem. Travelers are influenced by these tolls and make route and trip decisions by considering travel times and tolls. Network performance reliability is analyzed for a degradable network with elastic and fluctuated travel demand, which integrates reliability and uncertainty, dynamic network equilibrium models, and Monte Carlo methods. The proposed model is applied to a small hypothesized network for which optimal tolls are derived. The network travel time reliability is indeed improved after implementing optimal tolling system. Trips may have a somewhat higher, but more reliable, travel time. 相似文献
998.
Despite the widespread use of synthetic data in discrete choice analysis, little is known about how the methodology used to
generate synthetic datasets influences the properties of parameter estimates and the validity of results based on these estimates.
That is, there are two potential sources of biases when using synthetic discrete choice data: (1) bias due to the method used
to generate the dataset; and, (2) bias due to parameter estimation. The primary objective of this study is to examine bias
due to the underlying data generation method. This study compares three methods for generating synthetic datasets and uses
design of experiments and analysis of variance methods to investigate the ability to recover estimates for “true” logsum parameters
for nested logit models. The method that uses nested logit probabilities to generate the chosen alternative results in unbiased
parameter estimates. The method that is based on Gumbel error component approximations reveals that while the error components
themselves are unbiased, subtle empirical identification problems can arise when these error components are combined with
synthetically generated utility functions. The method that is based on normal error component approximations reveals that
all logsum coefficients are biased upwards; the bias dramatically increases for those nests that have a low choice frequency
and is most pronounced for those nests with high correlations among alternatives. Based on the results of the analysis, several
recommendations for the generation of synthetic datasets for discrete choice analyses are provided. 相似文献
999.
Modeling the interaction between the built environment and travel behavior is of much interest to transportation planning
professionals due to the desire to curb vehicular travel demand through modifications to built environment attributes. However,
such models need to take into account self-selection effects in residential location choice, wherein households choose to
reside in neighborhoods and built environments that are conducive to their lifestyle preferences and attitudes. This phenomenon,
well-recognized in the literature, calls for the specification and estimation of joint models of multi-dimensional land use
and travel choice processes. However, the estimation of such model systems that explicitly account for the presence of unobserved
factors that jointly impact multiple choice dimensions is extremely complex and computationally intensive. This paper presents
a joint GEV-based logit regression model of residential location choice, vehicle count by type choice, and vehicle usage (vehicle
miles of travel) using a copula-based framework that facilitates the estimation of joint equations systems with error dependence
structures within a simple and flexible closed-form analytic framework. The model system is estimated on a sample derived
from the 2000 San Francisco Bay Area Household Travel Survey. Estimation results show that there is significant dependency
among the choice dimensions and that self-selection effects cannot be ignored when modeling land use-travel behavior interactions. 相似文献
1000.
Scrutinizing individuals’ leisure-shopping travel decisions to appraise activity-based models of travel demand 总被引:1,自引:0,他引:1
Diana Kusumastuti Els Hannes Davy Janssens Geert Wets Benedict G. C. Dellaert 《Transportation》2010,37(4):647-661
Activity-based models for modeling individuals’ travel demand have come to a new era in addressing individuals’ and households’
travel behavior on a disaggregate level. Quantitative data are mainly used in this domain to enable a realistic representation
of individual choices and a true assessment of the impact of different Travel Demand Management measures. However, qualitative
approaches in data collection are believed to be able to capture aspects of individuals’ travel behavior that cannot be obtained
using quantitative studies, such as detailed decision making process information. Therefore, qualitative methods may deepen
the insight into human’s travel behavior from an agent-based perspective. This paper reports on the application of a qualitative
semi-structured interview method, namely the Causal Network Elicitation Technique (CNET), for eliciting individuals’ thoughts
regarding fun-shopping related travel decisions, i.e. timing, shopping location and transport mode choices. The CNET protocol
encourages participants to think aloud about their considerations when making decisions. These different elicited aspects
are linked with causal relationships and thus, individuals’ mental representations of the task at hand are recorded. This
protocol is tested in the city centre of Hasselt in Belgium, using 26 young adults as respondents. Response data are used
to apply the Association Rules, a fairly common technique in machine learning. Results highlight different interrelated contexts,
instruments and values considered when planning a trip. These findings can give feedback to current AB models to raise their
behavioral realism and to improve modeling accuracy. 相似文献