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   1825篇
  免费   70篇
公路运输   506篇
综合类   453篇
水路运输   438篇
铁路运输   391篇
综合运输   107篇
  2024年   6篇
  2023年   8篇
  2022年   42篇
  2021年   62篇
  2020年   73篇
  2019年   41篇
  2018年   36篇
  2017年   55篇
  2016年   63篇
  2015年   79篇
  2014年   157篇
  2013年   92篇
  2012年   189篇
  2011年   148篇
  2010年   126篇
  2009年   110篇
  2008年   114篇
  2007年   102篇
  2006年   108篇
  2005年   81篇
  2004年   57篇
  2003年   40篇
  2002年   30篇
  2001年   20篇
  2000年   16篇
  1999年   7篇
  1998年   6篇
  1997年   7篇
  1996年   4篇
  1995年   4篇
  1994年   1篇
  1993年   2篇
  1992年   3篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1984年   2篇
排序方式: 共有1895条查询结果,搜索用时 234 毫秒
781.
This paper introduces a methodology for the characterization of ports, employing specifically defined eco-efficiency indicators and combining typically available data (handled cargo, containers and passengers) with ship exhaust pollutants values (mainly NOx, SOx and PM) and anticipated external costs (ECs) due to emitted air pollutants to provide a collective overview of all port-related economic and environmental activities. The results from an applied case study allow a comparative evaluation of 16 selected ports based on 17 different evaluation criteria and denote that the employment of such an overall approach can allow port authorities to improve managerial aspects, potentially lower operational costs and promote reduced environmental effects.  相似文献   
782.
One of the major drawbacks of conventional air quality models is their inability in accurately predicting extreme air pollutant concentrations. Hybrid modelling is one of the techniques that estimates/predicts the ‘entire range’ of the distribution of pollutant concentrations by combining the deterministic based models (capable in predicting average range) with suitable statistical (probability) distribution models (capable in predicting extreme range). This research paper describes system based approach in developing hybrid model to predict hourly averages as well as extreme percentile ranges of NOx and PM2.5 concentrations at two urban locations having complex traffic heterogeneity, highly variable tropical meteorology and different geographical characteristics. At one of the selected locations i.e. Delhi megacity, during winters, hybridization of AERMOD and Lognormal predicts NOx and PM2.5 concentrations satisfactorily with index of agreement ‘d’ values of 0.98–0.99, respectively; however, during summers, AERMOD-Log-logistic and AERMOD-Lognormal are best predicting NOx and PM2.5 concentrations with d values of 0.98–0.96, respectively. In another, i.e., Chennai, a coastal megacity, AERMOD-Lognormal predicts PM2.5 concentrations satisfactorily with d values of 0.98 and 0.99 during winter and summer seasons, respectively. Further, hybrid model has also been used to evaluate regulatory compliance.  相似文献   
783.
Ports are under increasing pressures to increase sustainability and reduce the local and global emissions impacts associated with their operations. Due to limits on their jurisdictional authority, ports may design effective voluntary programs and appropriately motivate participation from global shipping companies that visit their ports. This paper investigates the success of the Vessel Speed Reduction Program at the Ports of Los Angeles and Long Beach and uses qualitative methods to analyze the factors that contributed to the success of the program at reducing local air quality pollutants. In particular, why did individual private firms participate in a non-required, voluntary effort? This research found that external pressures such as community concerns about emissions and regulatory threats are important to motivating voluntary behavior and may even be more important than financial incentives. Furthermore, simplicity of program design, clear goals and presence of a monitoring mechanism are important in influencing participation. These findings broaden our understanding of the business strategy behind slow steaming and its applicability as an operational practice as much work to date is focused on how fuel prices and financial incentives influence the choice for shipping companies to slow their speeds. While the VSR program led to significant emission reductions, an additional lesson for voluntary programs is the need for them to evolve and strive for continuous improvement.  相似文献   
784.
航空摄影新技术推动数字摄影测量的发展   总被引:3,自引:0,他引:3  
本文介绍了国内航空摄影新技术的发展及应用情况,并对航空摄影技术进行了具体的应用前景分析。  相似文献   
785.
通过对R407C制冷剂进行理论分析和性能试验,研究其在列车空调机组上替代R22制冷剂的可行性及应注意的问题。  相似文献   
786.
通过将各空气污染因子区分为物理性、化学性和生物性等因子,分别分析了它们对人体的医学危害性,揭示了目前影响室内空气品质的一些主要因素,并讨论了在空调工况下空气污染对室内空气品质的影响问题.  相似文献   
787.
李东江 《汽车技术》1997,(10):43-48
97新款“现代”轿车上,安装了一套自动温控式空调系统,它设计新颖,操作简单,由ECU控制所需的温度。详细地介绍了该系统的系统的组成,以及各主要部件的功用;同时分析了该系统常见故障原因,并提出了相应的检修措施。  相似文献   
788.
文丘里型末端变风量阀弹簧设计探讨   总被引:2,自引:0,他引:2  
文章提出了当量直径概念,根据量纲分析理论对绕圆球充动的绕流阻力公式进行了修改,从而得出文丘里型末端变风量瘩中阀芯绕流阻力与其所处位置的关系,在理论上提出了设计主等节距弹簧的方案,这对建立数学模型进行数值计算有着启发性的意义。  相似文献   
789.
This paper examines air traffic patterns among China’s scheduled airlines in January 2006 and January 2011, using Official Airline Guide data on carrier schedules. The author classifies Chinese carriers into one of four classes. Airports are also organized into a classification scheme based on several criteria related to the total volume of traffic, the carriers serving the airports and the nature of the airports to which they are connected. Counts, sums, percentage shares and changes in these calculations between 2006 and 2011 are presented in tabular form. Inferences about the fundamental structure and future patterns of capacity growth for the yet not fully emerged Chinese air traffic system can be drawn.  相似文献   
790.
通风空调系统运行能耗巨大,其设计是城市轨道交通系统总体设计中的重中之重。基于相关标准和节能减排要求,确定了上海轨道交通12号线工程通风空调系统的运行模式,并对区间隧道(含辅助线)通风系统兼排烟系统、车站车轨区排热兼排烟系统、车站公共区通风空调系统、设备管理用房通风空调系统、空调冷源及水系统的设计进行了详细阐述。  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