全文获取类型
收费全文 | 9848篇 |
免费 | 266篇 |
专业分类
公路运输 | 2625篇 |
综合类 | 2366篇 |
水路运输 | 2765篇 |
铁路运输 | 1124篇 |
综合运输 | 1234篇 |
出版年
2023年 | 47篇 |
2022年 | 253篇 |
2021年 | 261篇 |
2020年 | 208篇 |
2019年 | 100篇 |
2018年 | 487篇 |
2017年 | 407篇 |
2016年 | 437篇 |
2015年 | 181篇 |
2014年 | 334篇 |
2013年 | 687篇 |
2012年 | 563篇 |
2011年 | 715篇 |
2010年 | 726篇 |
2009年 | 605篇 |
2008年 | 699篇 |
2007年 | 683篇 |
2006年 | 550篇 |
2005年 | 431篇 |
2004年 | 200篇 |
2003年 | 184篇 |
2002年 | 144篇 |
2001年 | 131篇 |
2000年 | 136篇 |
1999年 | 76篇 |
1998年 | 76篇 |
1997年 | 64篇 |
1996年 | 64篇 |
1995年 | 69篇 |
1994年 | 37篇 |
1993年 | 42篇 |
1992年 | 34篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 27篇 |
1983年 | 23篇 |
1982年 | 26篇 |
1981年 | 39篇 |
1980年 | 26篇 |
1979年 | 43篇 |
1978年 | 13篇 |
1977年 | 30篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
781.
D. H. Kim J. M. Lee E. H. Park J. H. Song S. I. Park 《International Journal of Automotive Technology》2011,12(3):409-416
A comprehensive study evaluating the performance of biobutanol-blended gasoline in passenger cars was conducted because biobutanol
is considered a better biofuel than bioethanol as it has no water solubility and it has a higher caloric value, giving it
a higher energy value. Several kinds of samples—suboctane gasoline, 8 volume percentage and 16 volume percentage biobutanol—blended
gasoline, and a 10 volume percentage MTBE-blended market sample (as the oxygencontaining gasoline)-were tested to evaluate
the engine performance in terms of the detergency of the intake valves and combustion chambers, power, emissions, and fuel
efficiency. Additionally, the toxicity of the emissions from these biobutanolblended samples was tested in order to assess
the viability of biobutanol as one of the competitive potential substitutes for MTBE as an oxygenator in the near future.
The results show that biobutanol-blended gasoline samples had relatively better detergency, relatively higher power, and similar
levels of emissions compared with those of MTBE-blended gasoline. Formaldehyde was emitted from all of the samples at almost
the same levels and within the error range, whereas biobutanolblended gasoline samples emitted approximately three times the
amount of acetaldehyde than did the suboctane gasoline. This study shows that biobutanol is one of the best alternative bioalcohol
fuels for use in the near future. 相似文献
782.
W.-H. Cho J.-G. Ih S.-H. Shin J.-W. Kim 《International Journal of Automotive Technology》2011,12(3):443-450
In this paper, a method to establish a decision criterion to evaluate the quality of small window motors using sound quality
(SQ) metrics is suggested. Although the sound level radiated from the motor is relatively small compared to other sounds in
a car, the sound from an abnormal motor gives an uncomfortable feeling and the impression of abnormal operation, which can
lead to customer complaints. To construct an objective decision criterion, the correlation between the SQ metrics and the
subjective decision on the passing or failure of the motor were investigated. Four representative SQ metrics, viz., loudness,
sharpness, roughness, and fluctuation strength, were calculated for the collected samples. It was observed that the loudness
and roughness of the motor sample group classified as abnormal was higher than those of the normal motors. For a single figure
rating for motor quality, an evaluation index for the motor sound was generated by combining the correlated SQ metrics with
proper weightings. Evaluation results on the specimens that were not employed in generating the quality evaluation index showed
a reasonable agreement with the subjective test at 73%. The suggested quality check method can replace the current subjective
decision procedure to identify the faulty motors. 相似文献
783.
Y. Kim S. Choi J. Lee W. Yoo J. Sohn 《International Journal of Automotive Technology》2011,12(4):521-527
In this study, a large bus is tested to measure its dynamic response by the single-lane change test and the rapid stop test.
A full car model is established by ADAMS/Car for computer simulation. For multibody modeling of a large bus, user-defined
templates are used in the simulation. Simulation results of the single-lane change test and the rapid braking test are compared
to the results of the physical experiments, in which several sensors are installed to measure the vehicle’s responses. The
results obtained from the simulation show good agreement with the tests’ results. A dynamic model for the MR(magnetic-rheological)
damper is also developed by employing the Magic Formula model, which is widely used in the nonlinear modeling of a tire. Bump
simulation of a full car with the MR damper is carried out to verify the performance of the MR damper. The comparison of the
simulation results obtained with the MR damper model to the results obtained with the traditional passive damper model showed
improved response of the vehicle with the MR damper. 相似文献
784.
This paper discusses the final investigation into the effect of fuel stratification on flame propagation. In previous works,
the characteristics under the no port-generated swirl condition and the low-swirl condition were considered. For this purpose,
the initial flame development and propagation were visualized under different axially stratified states in a modified optical
single-cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the
piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged
and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area
and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and
through the mean absolute deviation of the propagation direction. The results show that the LML is expanded remarkably under
the high-swirl cases up to the highest relative AFRs of 1.71 and 1.75 between 140 and 160CA. In addition, similar to the low-swirl
condition, the flame-flow interaction determines the direction of flame propagation, and the governing roles of the two factors
vary according to the swirl level; the flow is more important at the higher swirl conditions, and the flame is more important
at the lower swirl condition. Finally, fast and stable flame propagation can be achieved under the preferably stratified condition,
which is induced by the suitable combination of the high swirl and injection timing. 相似文献
785.
786.
介绍了京杭运河苏北段船闸电气控制系统的现状及存在问题,提出了船闸电气控制系统标准化的概念,并针对Quantum PLC系统在实现船闸电气控制标准化中的难点和解决方法进行了阐述. 相似文献
787.
788.
789.
790.