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   2164篇
  免费   18篇
公路运输   686篇
综合类   92篇
水路运输   710篇
铁路运输   73篇
综合运输   621篇
  2023年   13篇
  2022年   36篇
  2021年   20篇
  2020年   20篇
  2019年   19篇
  2018年   63篇
  2017年   54篇
  2016年   92篇
  2015年   29篇
  2014年   74篇
  2013年   323篇
  2012年   105篇
  2011年   120篇
  2010年   87篇
  2009年   120篇
  2008年   105篇
  2007年   72篇
  2006年   41篇
  2005年   47篇
  2004年   40篇
  2003年   26篇
  2002年   38篇
  2001年   28篇
  2000年   41篇
  1999年   28篇
  1998年   44篇
  1997年   35篇
  1996年   39篇
  1995年   51篇
  1994年   12篇
  1993年   27篇
  1992年   25篇
  1991年   19篇
  1990年   18篇
  1989年   12篇
  1988年   11篇
  1987年   19篇
  1986年   16篇
  1985年   15篇
  1984年   19篇
  1983年   19篇
  1982年   12篇
  1981年   18篇
  1980年   18篇
  1979年   28篇
  1978年   12篇
  1977年   19篇
  1976年   13篇
  1975年   17篇
  1974年   13篇
排序方式: 共有2182条查询结果,搜索用时 15 毫秒
991.
Huang  Yantao  Kockelman  Kara M. 《Transportation》2020,47(5):2529-2556
Transportation - This study anticipates changes in U.S. highway and rail trade patterns following widespread availability of self-driving or autonomous trucks (Atrucks). It uses a...  相似文献   
992.

R&D in the field of driver support systems is increasingly paid attention to. These systems can contribute significantly to public traffic goals. However, there is much uncertainty about future technology developments, market introduction, and impacts on driver and traffic behaviour. An international Delphi study collecting expert opinions on these issues is partly described here. The Delphi study was organized in three rounds. Opinions of 50 experts from the USA, Japan and Europe were collected. The paper is limited to market introduction, and technological and driver-behavioural barriers. The main conclusion is that future developments are less obvious than often assumed.  相似文献   
993.
Thie paper re-examines the link between shipping investment and investment incentives, first explored in this journal by Marlow, and subsequently developed by mcWilliams et al. in the July–September issue. Examination of the ststistical properties of the data reveals that some of McWilliams' results may be flawed. A modified version of the Marlow model is estimated. checking for statistical and economic consistency, using cointegration, checking for statistical and economic consistency, using cointegration techniques. The estimated model resolves marlow's original challenge, but does not appear to be as robust as could be wished.  相似文献   
994.
The performance and safety of the rear wing and spoiler employed on the National Association of Stock Car Auto Racing (NASCAR) COT (car of tomorrow) racecar are experimentally studied using 10 % scale models in a water channel. Particle image velocimetry is used to qualitatively examine the differences in flow structures between the two downforce-generating devices under 0 and 180-degree yaw cases. The latter is important due to an issue with the COT flipping into the air when at extreme yaw (i.e. during a crash). At zero yaw, it is observed that smaller length scales of the flow structures in the wake of the wing compared to those in the wake of the spoiler, provide more predictable handling for racecars in close proximity and may allow more safe and competitive racing. At 180-degree yaw, it is observed that wake-structure interactions may not allow proper operation of anti-flipping devices (roof flaps) on the winged car. In the extreme yaw case, local flow scales are examined and show much stronger Reynolds number (Re) dependence for the wing than the spoiler.  相似文献   
995.
A new type of electromechanical continuously variable transmission (EMCVT) was investigated. The EMCVT uses a direct current (DC) motor to push the driving pulley, which in turn changes the transmission ratio without a hydraulic system. This paper introduces the principle of the EMCVT and establishes a dynamic ratio control model. Ratio control strategies using both position and speed closed-loop control are proposed. Simulation results show that the simulation ratio curves of the EMCVT follow pre-designed ratios well for ramp and sine curves. Control software is based on MATLAB/Simulink/Stateflow and MotoHawk platforms. A prototype vehicle equipped with an EMCVT has been developed. Vehicle test results show that the control performance of the EMCVT satisfies the requirements of vehicle operation. The effectiveness of the EMCVT ratio control strategy proposed in this paper is validated with test data for the prototype vehicle.  相似文献   
996.
In this two-part paper, a topological analysis of powertrains for refuse-collecting vehicles (RCVs) based on simulation of different architectures (internal combustion engine, hybrid electric, and hybrid hydraulic) on real routes is proposed. In this second part, three different hybrid electric powertrain architectures are proposed and modeled. These architectures are based on the use of fuel cells, ultracapacitors, and batteries. A calculation engine, which is specifically designed to estimate energy consumption, respecting the original performance as the original internal combustion engine (ICE), is presented and used for simulations and component sizing. Finally, the overall performance of the different architectures (hybrid hydraulic, taken from the first paper part, and hybrid electric, estimated in this second part) and control strategies are summarized in a fuel and energy consumption table. Based on this table, an analysis of the different architecture performance results is carried out. From this analysis, a technological evolution of these vehicles in the medium- and long terms is proposed.  相似文献   
997.

Development of awareness and capacity is a central component to the delivery of ICM and spans from local communities to national-level politicians. Education and training activities associated with ICM must be extremely varied to match both the existing capacity and role that the stakeholders play within the process of ICM. Consequently, there cannot be considered any effective “generic” ICM training; training must be tailored to match the requirements of target groups. The transfer and uptake of good-practice thus becomes an important aspect of quality enhancement in ICM capacity development. Six case studies from the Asia-Pacific region are presented that show diverse and innovative examples of good practice. A comparative analysis of these case studies is carried out in terms of institutional level of impact. In addition a generic systems-based evaluation framework is used to determine the extent to which the training impacts upon ICM implementation indicators. It is concluded that the exchange, transfer, and translation to local conditions of appropriate good practice in ICM capacity development can be an important element in enhancing the impact of ICM programs on the coastal environments and societies. Furthermore, there appears to be a positive link between the involvement of national/state/regional stakeholders in capacity-building initiatives and impacting a wider variety of indicators of ICM delivery.  相似文献   
998.
The article is divided into three clearly defined sections. The first outlines the Brazilian National Coastal Zone Management Plan. The second offers a critical assessment of its introduction. To conclude, some general considerations are made. In this way, the author aims to achieve two objectives: to disseminate the aforementioned plan and offer a critical opinion of it.  相似文献   
999.
Abstract

The use of fossil fuels in transportation is an important topic as a result of growing concerns over global warming. Automobile petrol demand has been of particular interest to researchers and policy-makers, given that the automobile is a major contributor to the enhanced greenhouse effect. This paper forecasts Australia's automobile petrol demand up to the year 2020 based on the best performing forecasting model selected out of eight models. In order to establish ways to reduce the demand for petrol, and the consequent by-product of reducing the amount of greenhouse gas emissions, we have estimated the impact on CO2 for several potential policy instruments, using Transportation and Environment Strategy Impact Simulator (an integrated transport, land use and environmental strategy impact simulation programme). We find that a carbon tax of AU$0.50/kg can reduce automobile kilometres by 5.9%, resulting in reduced demand for petrol and a reduction in CO2 of 1.5%.  相似文献   
1000.
Using data collected from May 1978 to November 1996, this article assesses the effects of fluctuating water levels on the beach and shoreline at the Northeast Beach, Point Pelee, Lake Erie, Canada. To compare the serial dynamics of lake levels with net shoreline positional changes and beach net sediment flux, the data are transformed to standard scores to deal with the differences in the units and in the scale associated with each variable. The results demonstrate that over the 18-year period, fluctuating lake levels are associated with shifts in shoreline position and the development of various aggradational and degradational states at the beach. A sustained rapid rise in lake levels will initiate an erosional sequence which will persist even with declining water levels. With a persistent decline in water levels the beach and shoreline will adjust very gradually from unstable, erosional states to an aggradational state. Other results emphasize that those beach sectors directly governed by artificial structures suffered disproportionately higher erosion during high-water levels. Coastal managers must, therefore, be cognizant of the fact that shore protection devices must be carefully designed in order to be effective against the influence of fluctuating lake levels.  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