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51.
Giles Thomas Stefan Winkler Michael Davis Damien Holloway Shinsuke Matsubara Jason Lavroff Ben French 《Journal of Marine Science and Technology》2011,16(1):8-21
Slam events experienced by high-speed catamarans in irregular waves were characterised through experiments using a hydroelastic
segmented model. The model was designed to represent the dynamic behaviour of the full-scale Incat 112 m vessel and to allow
the measurement of the slam load on the centrebow and wet deck. It was tested in irregular head seas at two speeds relating
to Froude numbers of 0.32 and 0.60. Nearly 300 slams were identified in the test data and analysed with respect to kinematic
parameters. Slams were found to have a large range of magnitudes, with the largest equivalent to 1785 tonnes full scale (approximately
70% of vessel displacement); however, the majority of events were of relatively low severity. Differences in slam characteristics
were found for the two model speeds tested; slams at the slower speed generally occurred further forward on the hull, prior
to the wave crest and with a bow down pitch angle. Immersion of the centrebow to the two-dimensional filling height of the
cross-section between the centrebow and demihulls is shown to be a better indicator of slam occurrence than immersion to the
top of the archway. 相似文献
52.
为了提高城市交叉口通行能力和减少机动车尾气排放,提出了利用遗传算法实现多目标优化的方法,开发了基于遗传优化的城市交通微观仿真模型,并进行了仿真试验.仿真结果表明:这种多目标优化方法可以获得更好的交通信号控制效果和改善环境. 相似文献
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针对爆炸场温度和冲击波存储测试系统设计了基于以太网传输的数据回收方案,完成存储测试系统中以太网接入模块的硬件和软件设计,并对TCP/IP协议进行裁剪,简单高效地实现了嵌入式系统接入以太网。 相似文献
57.
Zina Armi Elbahri Trabelsi Souad Turki Béchir Béjaoui Naceur Ben Maïz 《Journal of Marine Science and Technology》2010,15(4):417-426
Phytoplankton community structure was investigated in a 1-year study period from January to December 2006 in the Tunis North
Lagoon (South Mediterranean). Twice a month, sampling was carried out from the whole water column. Phytoplankton species composition
showed seasonal dynamics following the general environmental variable trends in the study area, with variation in species
abundance levels within each season characterised by the presence of different phytoplankton communities. Analysis of environmental
variables indicated that phytoplankton-dominant communities were associated with various water physicochemical characteristics,
especially water temperature and salinity. Accordingly, significant correlation was recorded between water temperature and
dinoflagellates (r = 0.35; p < 0.05) in summer and diatoms (r = 0.69; p < 0.05) in autumn, whereas euglenophytes, cyanophytes and chlorophytes were slightly correlated with temperature in autumn.
Salinity was positively correlated with dichtyophytes (r = 0.41; p < 0.05) in winter and with diatoms (r = 0.65; p < 0.05) and euglenophytes (r = 0.57; p < 0.05) in autumn. On the other hand, relationships between high nitrogen nutrient concentration and phytoplankton concentration
were recorded for diatoms (r = 0.43; p < 0.05 with NO2; r = 0.49; p < 0.05 with NO3) in winter. Silicate concentration supported proliferation of diatoms (r = 0.58; p < 0.05) in autumn in our study period. In contrast, increase of dinoflagellate concentration was associated with the decrease
of these parameters in spring and summer. 相似文献
58.
Routing and scheduling software is part of the information and technology systems available to support the transport industry, and uses complex algorithms along with geographical representations of the road network to allow better planning of daily collection and delivery schedules. This paper reviews the evolution of routing and scheduling software, the algorithms used along with reported barriers to wider take-up and potential industry-driven improvements that could be made. A survey of transport companies in the U.K. was conducted in order to validate and prioritise the software capabilities that require the most development according to the new challenges that the industry is facing. Responses suggested that companies required improved route optimisation to tackle congestion based on time-dependent data and models, and greater accuracy in the representation of the road network. Not considering congestion leads to the underestimation of travel times and the production of inaccurate schedules. Literature shows that operational research techniques are available to solve problems that represent real-world conditions, but research into the relative merits of using time-dependent models needs to be undertaken. Data might be improved by cooperation between government and private sector. 相似文献
59.
Queues are often associated with uncertainty or unreliability, which can arise from chance or climatic events, phase changes in system behaviour, or inherent randomness. Knowing the probability distribution of the number of customers in a queue is important for estimating the risk of stress or disruption to routine services and upstream blocking, potentially leading to exceeding critical limits, gridlock or incidents. The present paper focuses on time-varying queues produced by transient oversaturation during demand peaks where there is randomness in arrivals and service. The objective is to present practical methods for estimating a probability distribution from knowledge of the mean, variance and utilisation (degree of saturation) of a queue available from computationally efficient, if approximate, time-dependent calculation. This is made possible by a novel expression for time-dependent queue variance. The queue processes considered are those commonly used to represent isolated priority (M/M/1) and signal-like (M/D/1) systems, plus some statistical variations within the common Pollaczek-Khinchin framework. Results are verified by comparison with Markov simulation based on recurrence relations. 相似文献
60.
目前我国隧道大规模快速的发展,而钻爆法以其高效、经济的特点在隧道建设过程中起着至关重要的作用。然而,施工期隧道钻孔、爆破、喷射混凝土、出渣等施工工艺都会扬起大量粉尘颗粒物,严重危害现场人员的身体健康,降低施工现场的能见度影响施工效率和安全,同时大量颗粒物加剧机械设备磨损,在一定程度上影响了设备的使用寿命。结合隧道开挖过程,根据粉尘在隧道内分布规律,粉尘产生因素及运移机理,通过比较隧道减尘、降尘、排尘、除尘、阻尘五种控制措施的特点,提出与现场相适应的粉尘颗粒物综合防治措施,从而减小粉尘的危害,提高现场施工环境质量。 相似文献