全文获取类型
收费全文 | 237篇 |
免费 | 3篇 |
专业分类
公路运输 | 161篇 |
综合类 | 10篇 |
水路运输 | 40篇 |
铁路运输 | 2篇 |
综合运输 | 27篇 |
出版年
2022年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 27篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 20篇 |
2008年 | 13篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 46 毫秒
101.
High speed tensile test of steel sheets for the stress-strain curve at the intermediate strain rate 总被引:3,自引:0,他引:3
This paper presents stress-strain curves of steel sheets for an auto-body obtained at intermediate strain rates with a servo-hydraulic
type high speed tensile testing machine. The apparatus has the maximum stroke velocity of 7.8 m/sec to obtain the tensile
material properties at a strain rate of up to 500/sec. A special jig fixture is specially designed for accurate acquisition
of tensile loads with reduction of the load-ringing phenomenon induced by unstable stress wave propagation at high strain
rates. Tensile testing of steel sheets for an auto-body was carried out to obtain stress-strain curves of mild steel and advanced
high strength steels at strain rates ranged from 1/sec to 200/sec. The test results provide interesting information regarding
the stress-strain curves at intermediate strain rates ranged from 1/sec to 200/sec and demonstrate that strain rate hardening
is strongly coupled with strain hardening. 相似文献
102.
C. L. Myung K. H. Choi I. G. Hwang K. H. Lee S. Park 《International Journal of Automotive Technology》2009,10(2):161-166
In SI engines, valve events have a major influence on volumetric efficiency, fuel economy and exhaust emissions. Moreover,
swirl and tumble motions in the intake charge also improve combustion speed and quality by stratifying the mixture as well
as intensifying the mixing rate of air and fuel. This paper investigates the behaviors of an engine and the combustion phenomenon
for various intake valve timings and intake charge motions using CVVT system and port masking schemes. Test condition includes
a part load and a cold idle condition inclusive of a cold start of the engine. Time-resolved HC and NOx emissions were also
measured at an exhaust port to examine their formation mechanisms and behaviors with fast response HC/NOx analyzers. In conclusion,
the fast burning of fuel and improved combustion quality by enhanced charge motions reduced unburned HC emissions, and advancing
the intake valve opening reduced HC as well as NOx. Furthermore, HCs during the cold transient phase and idle conditions decreased
with recalibrated start parameters such as lean air-fuel ratio and spark retardation via the enhancement of intake charge
motions. 相似文献
103.
Y. T. Son B. Y. Kim K. J. Park H. Y. Lee H. J. Kim M. W. Suh 《International Journal of Automotive Technology》2009,10(5):635-644
To guarantee the efficiency of maintenance strategies for a complex structure, safety and cost limitations must be considered.
This research introduces RCM-based (Reliability Centered Maintenance) life cycle optimization for reasonable maintenance.
The design variable is the reliability of each part, which consists of a complex structure, while the objective is to minimize
the total cost function in order to maintain the system within the desired system reliability. This research constructs the
cost function that can reflect the current operating condition and maintenance characteristics of individual parts by generating
essential cost factors. To identify the optimal reliability of each component in a system, this paper uses a Neuro-Evolutionary
technique. Additionally, this research analyzes the reliability growth of a system by using the AMSAA (Army Material Systems
Analysis Activity) model to estimate the failure rate of each part. The MTBF (Mean Time Between Failure) and the failure rate
of the whole system, which is responding to the individual parts, are estimated based on the history data by using neural
networks. Finally, this paper presents the optimal life cycle of a complex structure by applying the optimal reliability and
the estimated MTBF to the RAMS (Reliability, Availability, Maintainability, and Safety) algorithm. 相似文献
104.
Catherine Jeandel Diana Ruiz-Pino Elvis Gjata Alain Poisson Christian Brunet Edwige Charriaud Frank Dehairs Daniel Delille Michel Fiala Charles Fravalo Juan Carlos Miquel Young-Hyang Park Philippe Pondaven Bernard Quguiner Suzanne Razouls Bernard Shauer Paul Trguer 《Journal of Marine Systems》1998,17(1-4)
Between January 1990 and March 1995, the research project KERFIX undertook the first regular noncoastal multiyear acquisition of parameters related to the carbon cycle in the Southern Ocean at a time series station located at 50°40′ S–68°25′ E, 60 miles southwest of the Kerguelen Islands. The objectives of KERFIX are (1) to monitor the ocean/atmosphere CO2 and O2 exchanges and to understand which processes govern these exchanges (2) to observe and interpret the seasonal and interannual variability of the production, flux, decomposition and dissolution of carbon and associated elements at this location. In addition, micropaleontological studies describe the present and past flux dynamics in this oceanic area, to improve the knowledge of the transfer functions of some oceanographic proxies. This paper presents a survey of the KERFIX program: scientific objectives, organization of the field operations and some main results obtained since the beginning of KERFIX program, as well as the results of the temporal evolution of hydrological, chemical and biological parameters. 相似文献
105.
Sung-Pil Hong Yun-Hong Min Myoung-Ju Park Kyung Min Kim Suk Mun Oh 《Transportation》2016,43(5):749-769
The aim of this study is to estimate both the physical and schedule-based connections of metro passengers from their entry and exit times at the gates and the stations, a data set available from Smart Card transactions in a majority of train networks. By examining the Smart Card data, we will observe a set of transit behaviors of metro passengers, which is manifested by the time intervals that identifies the boarding, transferring, or alighting train at a station. The authenticity of the time intervals is ensured by separating a set of passengers whose trip has a unique connection that is predominantly better by all respects than any alternative connection. Since the connections of such passengers, known as reference passengers, can be readily determined and hence their gate times and stations can be used to derive reliable time intervals. To detect an unknown path of a passenger, the proposed method checks, for each alternative connection, if it admits a sequence of boarding, middle train(s), and alighting trains, whose time intervals are all consistent with the gate times and stations of the passenger, a necessary condition of a true connection. Tested on weekly 32 million trips, the proposed method detected unique connections satisfying the necessary condition, which are, therefore, most likely true physical and schedule-based connections in 92.6 and 83.4 %, respectively, of the cases. 相似文献
106.
许筠被朝鲜学者称为朝鲜的李贽.李贽是阳明左派,许筠是儒学者徐敬德、李幌的左派,两人的思想和行为十分相似.当代韩国学术界在分析许筠的思想体系时,常将他与李贽相联系.许筠曾数次接待明廷使臣,又几度以使臣的身份出使明朝,期间购买许多书籍带回半岛.笔者在本文中对许筠何时、如何购得李贽的著作及其反应,进行集中考察. 相似文献
107.
Safety mechanism is required for an automotive battery pack to prevent thermal failure which could lead to catastrophic events. Passively cooled battery packs can prevent thermal failure by conducting adaptive control of battery power without any external cooling device. The key to this power control is how to secure battery safety while minimizing energy loss. This paper proposes a novel, adaptive power control strategy for automotive passive-cooling battery packs. Four different cases with electrochemical battery model are simulated and compared to each other according to a city driving profile. Driving simulation result confirmed that the present power control algorithm is an effective solution for preventing thermal failure along with improving energy efficiency of automotive battery packs. 相似文献
108.
Due to rapid progress in LED (Light Emitting Diode) technology, LEDs have become increasingly prevalent in applications to
automotive lighting. This paper studies recent trends of LED headlamps along with various experiments regarding photometric
characteristics, glare, and visibility. Experimental results are compared to those of halogen and HID (high intensity discharge)
headlamps. LED headlamps are found to be still inferior to conventional headlamps with respect to glare. However, many properties
of LED headlamps (luminous intensity, beam width, energy efficiency, and design) are competitive with halogen and HID headlamps.
The findings in this investigation will henceforth be reported to the Korean Motor Vehicle Safety Standard (KMVSS). 相似文献
109.
Transportation - Electric vehicles (EVs) are considered as a driving force behind the automotive industry’s transformation based on eco-friendliness and high energy efficiency. Unlike... 相似文献
110.