全文获取类型
收费全文 | 1404篇 |
免费 | 18篇 |
专业分类
公路运输 | 526篇 |
综合类 | 48篇 |
水路运输 | 420篇 |
铁路运输 | 48篇 |
综合运输 | 380篇 |
出版年
2022年 | 23篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 39篇 |
2017年 | 33篇 |
2016年 | 61篇 |
2015年 | 21篇 |
2014年 | 67篇 |
2013年 | 209篇 |
2012年 | 74篇 |
2011年 | 79篇 |
2010年 | 76篇 |
2009年 | 69篇 |
2008年 | 75篇 |
2007年 | 34篇 |
2006年 | 31篇 |
2005年 | 38篇 |
2004年 | 23篇 |
2003年 | 15篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 21篇 |
1980年 | 9篇 |
1979年 | 22篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有1422条查询结果,搜索用时 0 毫秒
81.
王渤洪 《变流技术与电力牵引》2006,(1):46-53
ICE 系列新动车ICE3、ICET、ICE TD采用了层级结构的诊断系统COBRA(Central On Board RailwayAssistant车载辅助中心),有各装置的自诊断和动车有关的上一级诊断.COBRA诊断系统有清晰的目标群取向,总是只向车务人员和维修人员提供重要的信息和可能的补救措施.在列车进段之前就对自动释放和经无线传输的诊断数据做了计算.列车一进段就准备好了维修人员和维修材料,例如更换损坏件和磨耗件,在进行清洁作业的同时为列车下一次运行准备好了良好的状态. 相似文献
82.
An analysis of the determinants of children’s weekend physical activity participation 总被引:1,自引:0,他引:1
This paper examines the out-of-home, weekend, time-use patterns of children aged 5–17 years, with a specific emphasis on their
physical activity participation. The impact of several types of factors, including individual and household demographics,
neighborhood demographics, built environment characteristics, and activity day variables, on physical activity participation
is analyzed using a joint nested multiple discrete–continuous extreme value-binary choice model. The sample for analysis is
drawn from the 2000 San Francisco Bay Area Travel Survey. The model developed in the paper can be used to assess the impacts
of changing demographics and built environment characteristics on children’s physical activity levels. 相似文献
83.
The need for acquiring the current-year traffic data is a problem for transport planners since such data may not be available
for on-going transport studies. A method is proposed in this paper to predict hourly traffic flows up to and into the near
future, using historical data collected from the Hong Kong Annual Traffic Census (ATC). Two parametric and two non-parametric
models have been employed and evaluated in this study. The results show that the non-parametric models (Non-Parametric Regression
(NPR) and Gaussian Maximum Likelihood (GML)) were more promising for predicting hourly traffic flows at the selected ATC station.
Further analysis encompassing 87 ATC stations revealed that the NPR is likely to react to unexpected changes more effectively
than the GML method, while the GML model performs better under steady traffic flows. Taking into consideration the dynamic
nature of the common traffic patterns in Hong Kong and the advantages/disadvantages of the various models, the NPR model is
recommended for predicting the hourly traffic flows in that region. 相似文献
84.
Neuro-Fuzzy Control of a Tracked Vehicle Featuring Semi-Active Electro-Rheological Suspension Units 总被引:3,自引:0,他引:3
S. B. Choi M. S. Suh D. W. Park M. J. Shin 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2001,35(3):141-162
This paper presents vibration control of a tracked vehicle installed with electro-rheological suspension units (ERSU). As a first step, an in-arm type ERSU is designed, and its spring and damping characteristics are evaluated with respect to the intensity of electric fields. Subsequently, a 16 degree-of-freedom model for a tracked vehicle equipped with the proposed ERSU is established followed by the formulation of a neuro-fuzzy controller. This controller takes account for both ride quality and steering stability by adopting a weighting parameter between two performance requirements. The parameter is appropriately determined by employing a fuzzy algorithm associated with two fuzzy variables: the vertical speed of the body and the rotational angular speed of the wheel. Control performances to isolate unwanted vibration from bump and random road excitations are evaluated through computer simulations. In addition, maximum speed of the vehicle with 6 Watt power absorption is investigated with respect to the road roughness. 相似文献
85.
H.K. Sachs 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1972,1(3):161-177
The influence of vehicle handling on the possible avoidance of accident situations is discussed. lit is shown that accident reconstruction at present does not provide the necessary information to relate the cause of accidents to the lack of road worthiness of vehicles. It follows that the vehicle behavior in proximity of its performance limit must be determined in order to infer its accident avoidance potential.
The paper presents a review of the state-of-the-art of vehicle modeling, simulation of vehicle maneuvers and full scale testing. The application of the direct method of the stability theory is suggested as a possible means of obtaining performance limit envelopes which are necessary for establishing standards of the performance of vehicles. 相似文献
The paper presents a review of the state-of-the-art of vehicle modeling, simulation of vehicle maneuvers and full scale testing. The application of the direct method of the stability theory is suggested as a possible means of obtaining performance limit envelopes which are necessary for establishing standards of the performance of vehicles. 相似文献
86.
李虎松 《西安交通大学学报(英文版)》1995,(2)
REGULATIONOFPRODUCTIONOFPARATHYROIDHORMONE-RELATEDPEPTIDE(PTHrP)ANDEXPRESSIONOFITSmRNAINAHUMANLIVER-DERIVEDCELLLINELiHusong;P... 相似文献
87.
88.
89.
Urban transportation is identified as a functional element in the broader context of urban facilities and services. From this point of view, the relative merits of separate information systems for transportation planning and general urban planning, as contrasted to unified systems for all urban management functions, are discussed. The overriding need to make the most effective use of urban resources argues strongly for the unification of urban information systems to the greatest possible extent consistent with the special data requirements of various functional programs. The need to identify and correlate data items for very small areal units and to keep current records of the constantly shifting patterns of social and economic activities in urban areas present difficult, but not insurmountable technical problems. However, the most serious barrier to the development and implementation of comprehensive urban information systems is concluded to be institutional, rather than technical, in nature. 相似文献
90.