首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1460篇
  免费   15篇
公路运输   674篇
综合类   39篇
水路运输   331篇
铁路运输   28篇
综合运输   403篇
  2022年   11篇
  2021年   9篇
  2020年   10篇
  2019年   6篇
  2018年   65篇
  2017年   75篇
  2016年   156篇
  2015年   12篇
  2014年   46篇
  2013年   137篇
  2012年   95篇
  2011年   164篇
  2010年   150篇
  2009年   68篇
  2008年   119篇
  2007年   53篇
  2006年   21篇
  2005年   28篇
  2004年   22篇
  2003年   12篇
  2002年   16篇
  2001年   17篇
  2000年   6篇
  1999年   14篇
  1998年   9篇
  1997年   5篇
  1996年   8篇
  1995年   12篇
  1994年   9篇
  1993年   11篇
  1992年   7篇
  1991年   4篇
  1990年   4篇
  1989年   4篇
  1988年   6篇
  1987年   3篇
  1986年   7篇
  1985年   4篇
  1984年   9篇
  1983年   7篇
  1982年   6篇
  1981年   10篇
  1980年   6篇
  1979年   9篇
  1977年   2篇
  1976年   2篇
  1975年   5篇
  1974年   5篇
  1973年   2篇
  1972年   4篇
排序方式: 共有1475条查询结果,搜索用时 375 毫秒
301.
Lane-changing events are often related with safety concern and traffic operational efficiency due to complex interactions with neighboring vehicles. In particular, lane changes in stop-and-go traffic conditions are of keen interest because these events lead to higher risk of crash occurrence caused by more frequent and abrupt vehicle acceleration and deceleration. From these perspectives, in-depth understanding of lane changes would be of keen interest in developing in-vehicle driving assistance systems. The purpose of this study is to analyze vehicle interactions using vehicle trajectories and to identify factors affecting lane changes with stop-and-go traffic conditions. This study used vehicle trajectory data obtained from a segment of the US-101 freeway in Southern California, as a part of the Next Generation Simulation (NGSIM) project. Vehicle trajectories were divided into two groups; with stop-and-go and without stop-and-go traffic conditions. Binary logistic regression (BLR), a well-known technique for dealing with the binary choice condition, was adopted to establish lane-changing decision models. Regarding lane changes without stop-and-go traffic conditions, it was identified based on the odd ratio investigation that he subject vehicle driver is more likely to pay attention to the movement of vehicles ahead, regardless of vehicle positions such as current and target lanes. On the other hand, the subject vehicle driver in stop-and-go traffic conditions is more likely to be affected by vehicles traveling on the target lane when deciding lane changes. The two BLR models are adequate for lane-changing decisions in normal and stop-and-go traffic conditions with about 80 % accuracy. A possible reason for this finding is that the subject vehicle driver has a tendency to pay greater attention to avoiding sideswipe or rear-end collision with vehicles on the target lane. These findings are expected to be used for better understanding of driver’s lane changing behavior associated with congested stop-and-go traffic conditions, and give valuable insights in developing algorithms to process sensor data in designing safer lateral maneuvering assistance systems, which include, for example, blind spot detection systems (BSDS) and lane keeping assistance systems (LKAS).  相似文献   
302.
The measurement of accessibility: Some preliminary results   总被引:4,自引:0,他引:4  
This paper presents an analysis of accessibility by private transport, using a Hansen type measure of accessibility. The data base is the 1962 London Travel Survey. The study is confined to car-owning households residing in inner London. A comparison of the patterns of accessibility associated with four measures of areal attractiveness - total employment, retail employment, households and population - is presented. The sensitivity of relative accessibilities to marginal changes in parameter values is analysed. Two aspects of the effect of the zoning system on the measurement of accessibility are investigated: the effects of zonal configuration and zonal aggregation. First, the implications of increasing the size of central area zones is analysed. Second, a comparison of patterns of accessibility calculated at the zonal and district levels is undertaken.[/p]  相似文献   
303.
Research purposes: Based on an engineering of traffic tunnel, anti-breaking model experiment of large-scale 1 :30 is carried out under fault dislocation. Reduction effect of three working conditions(working condition A of no reducing joint, B of staggered setting of reducing joint and dislocation surface, C of reducing joint set at dislocation position) is comparatively analyzed by analysis of contact pressure, lining strain and lining stress. The optimal location of reduction joint is explored. Research conclusions:(1)The reduction effect of different position of reducing joint is different, such as A相似文献   
304.
A novel intelligent drug delivery system potential for the more effective therapy of the diabeticswas proposed, and the composition of system was analyzed. Based on the design of micro-electro-mechanicalsystems (MEMS), an iterative modeling process was introduced. Unified modeling language (UML) was em-ployed to describe the function requirement, and different diagrams were built up to explore the static model,the dynamic model and the employment model. The mapping analysis of different diagrams can simply verifythe consistency and completeness of the system model.  相似文献   
305.
In 2006, a review of maritime accidents found that non-technical skills (NTSs) are the single largest contributing factor towards such incidents. NTSs are composed of both interpersonal and cognitive elements. These include things such as situational awareness, teamwork, decision making, leadership, management and communication skills. In a crisis situation, good NTSs allow a deck officer to quickly recognise that a problem exists and then harness the resources that are at their disposal to safely and efficiently bring the situation back under control. This paper has two aims. The first is to develop a methodology which will enable educators to quantitatively assess the impact of Maritime and Coastguard Agency (MCA)-approved Human Element, Leadership and Management (HELM) training on deck officer’s NTSs with a view to identifying further training requirements. The second is to determine whether the HELM training provided to develop the NTSs of trainee deck officers is fit for purpose. To achieve these aims, a three-phase approach was adopted. Initially, a taxonomy for deck officer’s NTSs is established, behavioural markers are identified and the relative importance of each attribute is calculated using the analytical hierarchy process (AHP). Subsequently, a set of scenarios were identified for the assessment of deck officer’s NTSs in a ship bridge simulator environment. A random selection of students that have completed the Chief Mate (CM) programme was performed, and data regarding their NTS-related performance in the scenarios was collected. Finally, the collected data was fed into the evidential reasoning (ER) algorithm, utility values were produced and, having established these values, the effectiveness of the HELM training that the students have received was then evaluated.  相似文献   
306.
A novel high-voltage electrostatics corona ions pre-charger apparatus and methods were invented earlier by Hamade related to treat various types of receptors such as but not limited to electret polymer, air filters, particulates, catalytic converters, bioaerosols, fluids, pollutants, virus, and bacteria. It is shown in this article that his work led to the construction of various prototype chargers, customized differently for each type of a receptor. In particular his recent development of biological matter corona charger (BMCC) prototype related to expose, treat, sanitize, and disinfect bioaerosols, virus, bacteria, and contaminated fluids and blood such as human immunodeficiency virus (HIV) - acquired immune deficiency syndrome (AIDS). It is shown in this paper that each previous investigated research contemplated ionized corona charger attendant to a charging process and the corona, imparts and provides enough treatment charges to receptors including the aforementioned receptors. Researchers often relied on adopting prior corona charger methods that do not necessarily and effectively solve the problems associated with them or utilize them for optimum treatment effect. The inventor exhaustively studied the characteristics of corona discharge, and has found that the greatest difficulty in corona discharge has to do with the maintenance of the corona, particularly when the receptor is being charged. This is due to variations in either the dielectric value between the corona electrode and a grounded base or flaws in the design as the receptor passes there between suppressing or hindering corona and its effectiveness. What is needed in-the-art is an apparatus and method to achieve maximum possible charge on a receptor, a charge order of magnitude greater than that used by other investigators. This often requires customizing each apparatus and method and does not just merely use one type of a charger to satisfy all applications. To satisfy this need, we build a low cost prototype BMCC that generates self-sustaining charge corona, eliminates many previous design flaws such as spark over, and make it ready for testing remotely or with apparatus.  相似文献   
307.
Abstract

Part 1 elicited major research issues and opportunities in the transport sector in the EEC from an examination of a range of planning scenarios. This article relates those issues and opportunities to the needs of the EEC transport sector policy formation and derives a set of research recommendations. The respective roles of the EEC and other institutions in developing and meeting the research needs are then discussed, concluding with some institutional proposals for the strengthening of the organization of the strategic research effort of the EEC in the transport sector.  相似文献   
308.
Peter K. Else 《运输评论》2013,33(4):291-309
Governments have rarely been content to leave the provision of public transport services entirely to the market. Competition has been regulated and increasingly services have been subsidized from public funds. However, the criteria for such subsidies have been a continuing source of debate. Economists have tended to emphasize efficiency criteria and advocated the use of cost‐benefit analysis, but, for a variety of reasons, in the U.K. at least, this approach does not seem to have played a major role in the allocation of subsidies. Others have advocated more needs‐based approaches. Whilst these have been tried, they also have their limitations. The first few sections of the paper, therefore, review the development of these approaches in the U.K. and consider their shortcomings from the point of view of deciding on transport subsidies. In the latter part of the paper it is suggested that developments in the appraisal of health care procedures, particularly in the use of cost‐utility techniques, indicate a possible alternative approach. The approach in the health context is outlined and it is demonstrated how it might be applied to the appraisal of local transport services.  相似文献   
309.
This paper presents a differential evolution algorithm (DEA) to solve a vehicle routing problem with backhauls and time windows (VRPBTW) and applied for a catering firm. VRPBTW is an extension of the vehicle routing problem, which includes capacity and time window constraints. In this problem, customers are divided into two subsets: linehaul and backhaul. Each vehicle starts from a depot and goods are delivered from the depot to the linehaul customers. Goods are subsequently brought back to the depot from the backhaul customers. The objective is to minimize the total distance that satisfies all of the constraints. The problem is formulated using mixed integer programming and solved using DEA. Proposed algorithm is tested with several benchmark problems to demonstrate effectiveness and efficiency of the algorithm and results show that our proposed algorithm can find superior solutions for most of the problems in comparison with the best known solutions. Hence, DEA was carried out for catering firm to minimize total transportation costs. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
310.
The Fuel-Injection Pump (FIP) used in diesel engine has a higher-pair cam-mechanism to pressurize the fuel for injection. This paper proposes a methodology to model FIP from a multibody Dynamics (MBD) perspective. The results from the model include the temporal behavior of driving torque, contact Hertz stress and reaction forces at various joints. The model helps the designer to assess the effect of various cam profiles, link parameters and other design variables. It is necessary that these parameters be optimized for future high pressure applications. For this purpose, a cam-mechanism with offset follower axis is analysed. Decoupled Natural Orthogonal Complement (DeNOC) matrices based algorithm is used to model FIP without and with offset cam-mechanism. The study shows that, the offset cam-mechanism allows reduction in the side-thrust, reaction forces, and the contact Hertz stress acting on the cam-follower interface. As a typical case, for an FIP working around a pressure value of 600 bar, an optimum offset value is found to be 9.5 mm and it shows a reduction of about 45% in side thrust values. To validate the modeling approach, experimental studies are performed on pump without and with offset cam-mechanism. Experimental results are in qualitative agreement with the theoretical model results.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号