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   11144篇
  免费   226篇
公路运输   2763篇
综合类   1404篇
水路运输   3358篇
铁路运输   1361篇
综合运输   2484篇
  2023年   64篇
  2022年   171篇
  2021年   178篇
  2020年   143篇
  2019年   113篇
  2018年   234篇
  2017年   156篇
  2016年   196篇
  2015年   186篇
  2014年   362篇
  2013年   1397篇
  2012年   532篇
  2011年   636篇
  2010年   503篇
  2009年   606篇
  2008年   546篇
  2007年   588篇
  2006年   523篇
  2005年   446篇
  2004年   359篇
  2003年   224篇
  2002年   186篇
  2001年   229篇
  2000年   197篇
  1999年   128篇
  1998年   154篇
  1997年   148篇
  1996年   165篇
  1995年   164篇
  1994年   101篇
  1993年   200篇
  1992年   166篇
  1991年   84篇
  1990年   87篇
  1989年   64篇
  1988年   79篇
  1987年   66篇
  1986年   61篇
  1985年   81篇
  1984年   74篇
  1983年   73篇
  1982年   73篇
  1981年   95篇
  1980年   68篇
  1979年   91篇
  1978年   56篇
  1977年   69篇
  1976年   53篇
  1975年   65篇
  1974年   50篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
61.
合成脂肪酸废水的厌氧处理   总被引:2,自引:0,他引:2  
对合成脂肪酸废水首先采用氧化钙处理,使其浓度降低到3000mg/L以下,再采用中温厌氧生物处理。在平均水力停留时间为5天时,废水的CODCr去除率达79.1%,沼气产率为0.41NM3/kgCoDCr试验还发现,的存在失使厌氧发酵的pH值上升。  相似文献   
62.
The Straits of Malacca and Singapore are an important trade route linking the Indian Ocean to the South China Sea and Pacific Ocean. They are also rich in resources and support a range of activities that benefit the economies of the littoral states (Indonesia, Malaysia and Singapore). This important shipping route is a very congested waterway and the authorities are keen to improve navigation facilities to promote ship safety and reduce the risk of groundings, collisions and accidents. This will also help to protect the marine environment from the effects of pollution and hence reduce its damaging impact on activities related to the Straits, e.g. fisheries and tourism. The Marine Electronic Highway (MEH) is an attempt to bring together maritime safety technologies and environmental management systems. The paper examines the costs of providing such a highway and considers some of the benefits which could accrue from its implementation. The analysis, conducted in the form of a cost-benefit study, clearly shows the economic viability of the scheme.  相似文献   
63.
卢戈梅  刘海澜 《中国水运》2007,7(6):210-211
随着经济全球化步伐的加快,航运市场不断夸张,竞争也日趋激烈,航运企业只有正确评价并发展其竞争力,才能持续的发展。本文运用TOPSIS的决策方法对航运企业竞争力的量化指标进行综合评价,具有重要意义。  相似文献   
64.
A linear theory for the physical fields in the water column under the action of large amplitude internal lee waves at the main sill of the Strait of Gibraltar is developed. The procedure is a combination of the perturbation and normal modes methods in order to study steady resonant conditions. The lowest order linear approach of the methodology resumes the Taylor–Goldstein equation, which can reconstruct the main features of the observed fields but the high order approach gives the finest structure and sometimes the largest contributions. The role of the non-linear terms is investigated up to the second order taking into account the non-linear interactions between modes, leading to an effective reconstruction of the whole water column for the velocity field.  相似文献   
65.
This paper presents a procedure for the estimation of origin‐destination (O‐D) matrices for a multimodal public transit network. The system consists of a number of favored public transit modes that are obtained from a modal split process in a traditional four‐step transportation model. The demand of each favored mode is assigned to the multimodal network, which is comprised of a set of connected links of different public transit modes. An entropy maximization procedure is proposed to simultaneously estimate the O‐D demand matrices of all favored modes, which are consistent with target data sets such as the boarding counts and line segment flows that are observed directly in the network. A case study of the Hong Kong multimodal transit network is used to demonstrate the effectiveness of the proposed methodology.  相似文献   
66.
This paper presents an off‐line forecasting system for short‐term travel time forecasting. These forecasts are based on the historical traffic count data provided by detectors installed on Annual Traffic Census (ATC) stations in Hong Kong. A traffic flow simulator (TFS) is developed for short‐term travel time forecasting (in terms of offline forecasting), in which the variation of perceived travel time error and the fluctuations of origin‐destination (O‐D) demand are considered explicitly. On the basis of prior O‐D demand and partial updated detector data, the TFS can estimate the link travel times and flows for the whole network together with their variances and covariances. The short‐term travel time forecasting by O‐D pair can also be assessed and the O‐D matrix can be updated simultaneously. The application of the proposed off‐line forecasting system is illustrated by a numerical example in Hong Kong.  相似文献   
67.
港口腹地划分的两种新方法探讨--以大连国际航运中心为例   总被引:11,自引:1,他引:10  
引入经济地理学的新理论成果———圈层结构法和点轴法,提出了圈层结构划分法和点轴结构划分法两种新的港口腹地划分方法,并应用这两种新方法对大连国际航运中心港口腹地范围的界定与划分进行实例分析。与以往的行政区划法、经济区域法等港口腹地划分方法相比,这两种方法更加注重对港口原有腹地的细分,更接近于港口腹地的实际状况,进而有利于港口企业的经营发展。  相似文献   
68.
众所周知,从90年代初起,美国经济一直以年均4%左右的速度高速增长着,并奇迹般地持续了近10个年头,成为美国经济史上最长的扩张时期.随着经济持续快速增长,美国经济实力已大大增强.美国已成为名副其实的世界经济"火车头",在自身高速成长的同时,也刺激了全球经济的快速发展.  相似文献   
69.
70.
Vehicle offtracking behavior at low speeds is closely approximated by a geometric entity called a tractrix. This paper presents differential equations for generalized coordinates of a planar multibody vehicle model based on tractrix behavior. The equations are exact, can be used with any type of input path, are valid for forward and backward movements, and are much simpler than previously published formulations used to compute transient offtracking. The differential equations can be integrated using conventional numerical integration algorithms to obtain plots of the low-speed tracking performance of articulated vehicles. The equations were formulated symbolically by a computer program used to analyze the kinematic and dynamic behavior of multibody systems. Example numerical results are plotted.  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