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   374篇
  免费   5篇
公路运输   21篇
综合类   36篇
水路运输   289篇
铁路运输   16篇
综合运输   17篇
  2023年   4篇
  2022年   1篇
  2021年   3篇
  2020年   6篇
  2019年   2篇
  2018年   7篇
  2017年   9篇
  2016年   7篇
  2015年   8篇
  2014年   17篇
  2013年   28篇
  2012年   8篇
  2011年   13篇
  2010年   13篇
  2009年   29篇
  2008年   38篇
  2007年   52篇
  2006年   24篇
  2005年   18篇
  2004年   10篇
  2003年   12篇
  2002年   13篇
  2001年   8篇
  2000年   14篇
  1999年   9篇
  1998年   11篇
  1997年   10篇
  1996年   4篇
  1994年   1篇
排序方式: 共有379条查询结果,搜索用时 31 毫秒
121.
The methodology to achieve a real time inter-comparison of five state-of-the-art operational forecast systems for the North Atlantic and Mediterranean basins is presented. All systems provide analysis and near real-time prediction of the three-dimensional ocean through Opendap servers. A standard set of diagnostics called metrics, is described. Definition and examples of metrics are given. An inter-comparison of the five systems is conducted over a 1 year period using those metrics. It is shown that the methodology developed allows a successful inter-comparison. It has been adopted by the GODAE community. It is also shown that the systems are consistent with the current knowledge of the ocean circulation and climatologies. Systems are deficient in the representation of specific water masses characteristics as Mode waters. Data assimilation of vertical profiles of temperature and salinity solve such deficiencies. Metrics also allow a monitoring of the system's North Atlantic overturning stream function and will allow detecting any changes in the coming year system's thermohaline circulation.  相似文献   
122.
Sea level time series derived from TOPEX altimeter and from tide gauge measurements in the Bay of Biscay (Eastern North Atlantic Ocean) are used to investigate the regional sea level rise. Altimetry sea level anomalies are computed from TOPEX measurements and resampled into fixed along track bins in order to obtain consistent records and to approach as close as possible to the coast. Tidal corrections are critical in the estimation of sea level trends; therefore an additional analysis has been carried out in order to identify and correct for residual tidal signals. The obtained mean sea level rise in the region is + 3.09 ± 0.21 mm/year over the period 1993–2002. Tide gauges have been corrected for vertical land motions by means of collocated GPS measurements. GPS-corrected tide gauges and nearby altimetry trends are found to be statistically consistent. The relationship with the atmospheric forcing is also investigated revealing that 15% of this sea level rise is attributed to the atmospheric pressure effects.  相似文献   
123.
Sampling of the near-bottom calanoid copepods was performed on board of the research vessel Polarstern in 1993 in the Laptev Sea (Siberian Arctic). Three new species of Xanthocalanus were identified as such, and are described and figured here: X. spinodenticulatus sp. nov., X. laptevorum sp. nov. and X. polarsternae sp. nov.  相似文献   
124.
根据航海日志及碰撞事故报告中可能提供的船舶运动过程等资料及其精度,建立各参数物理意义鲜明、并可从船舶资料中直接或间接获取的船舶运动数学模型,利用计算机,直观显示或绘制船舶运动轨迹,供有关人员分析和处理碰撞海事参考。  相似文献   
125.
The species composition, abundance, and biomass of micro- (>15 μm) and nano- (<15 μm) phytoplankton were studied along the southern Black Sea during June–July 1996 and March–April and September 1998. A total of 150 species were identified, 50% of them being dinoflagellates. The average total phytoplankton abundance changed from 77×103 cells l−1 in spring to 110×103 cells l−1 in autumn and biomass from 250 μg l−1 in summer to 1370 μg l−1 in spring. Based on the extensive sampling grid from June–July 1996, phytoplankton seemed to have a rather homogeneous biomass distribution in the southern Black Sea. In all periods, the coccolithophorid Emiliania huxleyi was the most abundant species, its contribution to the total abundance ranging from 73% in autumn to 43% in spring. However, in terms of biomass, diatoms made up the bulk of phytoplankton in spring (97%, majority being Proboscia alata) and autumn (73%, majority being Pseudosolenia calcar-avis), and dinoflagellates in summer (74%, Gymnodinium sp.). There was a remarkable similarity in the dominant species between the western and eastern regions of the southern Black Sea, indicating transport of phytoplankton within the basin.  相似文献   
126.
Air–sea fluxes in the Caribbean Sea are presented based on measurements of partial pressure of CO2 in surface seawater, pCO2sw, from an automated system onboard the cruise ship Explorer of the Seas for 2002 through 2004. The pCO2sw values are used to develop algorithms of pCO2sw based on sea surface temperature (SST) and position. The algorithms are applied to assimilated SST data and remotely sensed winds on a 1° by 1° grid to estimate the fluxes on weekly timescales in the region. The positive relationship between pCO2sw and SST is lower than the isochemical trend suggesting counteracting effects from biological processes. The relationship varies systematically with location with a stronger dependence further south. Furthermore, the southern area shows significantly lower pCO2sw in the fall compared to the spring at the same SST, which is attributed to differences in salinity. The annual algorithms for the entire region show a slight trend between 2002 and 2004 suggesting an increase of pCO2sw over time. This is in accord with the increasing pCO2sw due the invasion of anthropogenic CO2. The annual fluxes of CO2 yield a net invasion of CO2 to the ocean that ranges from − 0.04 to − 1.2 mol m− 2 year− 1 over the 3 years. There is a seasonal reversal in the direction of the flux with CO2 entering into the ocean during the winter and an evasion during the summer. Year-to-year differences in flux are primarily caused by temperature anomalies in the late winter and spring period resulting in changes in invasion during these seasons. An analysis of pCO2sw before and after hurricane Frances (September 4–6, 2004), and wind records during the storm suggest a large local enhancement of the flux but minimal influence on annual fluxes in the region.  相似文献   
127.
游艇业——福建海洋经济的朝阳产业   总被引:3,自引:0,他引:3  
钟惠萍 《中国水运》2006,6(12):192-194
充分利用福建船艇工业现有基础和区位优势发展游艇产业,将是福建海洋经济的新增长点,可带动海洋经济其他产业可持续发展能力的全面提升,缓解就业压力,优化产业结构,有利于形成特色鲜明、辐射面广、竞争力强的海洋产业聚集区和产业集群,为建设海峡西岸经济区提供强有力的产业支撑。  相似文献   
128.
城市交叉口的闯红灯违规分析研究   总被引:1,自引:0,他引:1  
王金梅 《中南公路工程》2006,31(4):123-126,130
闯红灯冲突比起交叉路口所有冲突占有比较高的伤害百比率。通过对西安部分城市交叉路口机动车辆违规行为的调查分析,对设置有全红灯间隔、没有设置全红灯间隔以及是否安装闯红灯自动检测系统的交叉口进行了比较研究,分析了闯红灯违规的特点,研究分析表明在信号灯相位及其间隔设置合理的前提下,实施安装自动闯红灯监测系统可以明显减少闯红灯行为的发生,闯红灯自动检测系统机动车驾驶员的行为规范得到改善。还给出了黄灯信号期通过交叉口车辆的微观仿真建模及其实验结果,初步探讨了减少闯红灯违规的有效措施。  相似文献   
129.
赵琳  孙枫 《中国航海》1996,(1):69-70
该文研究了推算船位/罗兰C(GPS)组合导航系统的组合模式和推广的非线性卡尔曼滤波算法在该组合模式中的应用,详细推导了舰船运动的七状态数学模型及其机械编排。该文还给出了该组合系统在南海进行试验时的舰船轨迹及定位误差曲线,并进行了比较分析。结果表明:组合系统克服了推位系统的积累误差,抑制了罗兰C(GPS)的随机定位误差,有效地改善了导航定位精度,滤波方案正确,算法稳定。该组合系统已成功地装备于多种型号的舰船上。  相似文献   
130.
本文在预测了本世纪本我国铁矿石进口的基础上构筑了其海运网络。运用网络流模糊规划方法按最大最小费用流问题对矿石货流进行了合理安排。  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