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   4683篇
  免费   173篇
公路运输   1306篇
综合类   965篇
水路运输   1332篇
铁路运输   722篇
综合运输   531篇
  2024年   11篇
  2023年   31篇
  2022年   106篇
  2021年   177篇
  2020年   150篇
  2019年   64篇
  2018年   62篇
  2017年   85篇
  2016年   112篇
  2015年   137篇
  2014年   182篇
  2013年   427篇
  2012年   314篇
  2011年   349篇
  2010年   328篇
  2009年   334篇
  2008年   322篇
  2007年   322篇
  2006年   297篇
  2005年   185篇
  2004年   88篇
  2003年   72篇
  2002年   52篇
  2001年   76篇
  2000年   60篇
  1999年   44篇
  1998年   57篇
  1997年   32篇
  1996年   32篇
  1995年   31篇
  1994年   21篇
  1993年   22篇
  1992年   19篇
  1991年   18篇
  1990年   15篇
  1989年   16篇
  1988年   16篇
  1987年   16篇
  1986年   18篇
  1985年   11篇
  1984年   13篇
  1982年   13篇
  1981年   12篇
  1980年   15篇
  1979年   16篇
  1977年   12篇
  1976年   9篇
  1975年   17篇
  1974年   10篇
  1973年   9篇
排序方式: 共有4856条查询结果,搜索用时 15 毫秒
281.
以23 000 TEU大型集装箱船为例,进行尾轴分段建造工艺策划,论述尾轴分段施工计划管理,对尾轴分段建造工艺的关键路径进行优化,提升大型集装箱船的建造效率。  相似文献   
282.
Marine invertebrate species have usually been overlooked in favor of high-profile vertebrate species for facilitating dialogue towards area conservation. The northern abalone (Haliotis kamtschatkana) is proposed as a focal ("flagship") species whose protection and recovery could concentrate public concern for abalone and its associated kelp forest ecosystems in Haida Gwaii (Queen Charlotte Islands), British Columbia. I explain how issues of culture, commerce, and conservation unite to create a strong role for northern abalone in preparations for creating a large marine conservation area within Haida Gwaii. Culture is relevant, as local indigenous people (the Haida) are currently denied access to constitutionally established subsistence fishing rights for northern abalone. Commerce is involved as ongoing kelp forest-associated fisheries co-occur with northern abalone. Finally, this is a challenging precedent in Canadian marine conservation, as restoring two "listed" species- at risk (northern abalone and their predator, the sea otter (Enhydra lutris)) is potentially mutually exclusive. As part of the forthcoming public consultations towards establishing a marine conservation area, the opportunity provided by northern abalone to focus ideas and values should be seized.  相似文献   
283.
赵尚良 《中国水运》2006,4(5):52-53
打通钱塘江中游的七里垅航运瓶颈,发掘钱塘江全流域巨大的航运潜能,是浙江水运事业新构增长点。  相似文献   
284.
应力波法锚杆无损检测技术研究   总被引:3,自引:0,他引:3  
应力波法锚杆加固无损检测是一种快速、有效的无损检测方法,适合对锚杆质量进行大面积普查。文章结合衡阳-炎陵高速公路某隧道采用锚杆质量检测仪和分析处理软件进行质量检测的工程实践,探索了应力波无损检测技术的原理及其可行性。  相似文献   
285.
In previous publications the author has described a so-called first-order theory for the motion of a railway vehicle wheelset on a tangent track. In the present report the geometrical aspect of this theory is further evaluated and a method for solving the constraint equations between the coordinates of the wheelset is indicated.  相似文献   
286.
金良 《汽车技术》2001,(5):21-23
汽车转向拉杆及球头销是汽车上的重要部件,其强度和可靠性直接关系到汽车行驶安全,为满足该部件的产品要求,设计了一种转向拉杆及头销寿命试验台,介绍了试验台的试验技术参数,试验台的组成及原理,该试验台经工厂使用,效果良好。  相似文献   
287.
分析了膨胀土结构的分形行为,推导了膨胀土颗粒粒度的分维、颗粒质量的分形、孔隙分布的分维、孔隙表面分维计算公式,并结合实例进行验证,所获得的分析结果为铁路膨胀土路基稳定性的研究奠定了基础.  相似文献   
288.
The fatigue behaviour of longitudinal stiffeners of oil tankers and container ships, subjected to dynamic loads, is analysed. The following dynamic load components are considered: hull girder vertical wave bending moment, alone and combined with the horizontal wave bending moment, hydrodynamic pressure and inertial forces caused by cargo acceleration.

The spectral method was selected to calculate the fatigue damage, based on S—N curves and Miner's rule. Following this approach, the fatigue damage may be calculated as a function of a stress parameter Ωp, which represents the cumulative effect of wave induced loads in the unit of time and incorporates the combined effects of stress level and its occurring frequency.

Simple formulas for Ωp of oil tankers and container ships are given, obtained from the results of hydrodynamic analyses performed on several ships, in different wave environments.

Several examples show the applicability of the methods to real ship structures. The method, however, still needs to be calibrated because of the simplifying hypotheses introduced in the loading conditions.  相似文献   

289.
Road roughness and surface texture are known to affect tire rolling resistance; however, little emphasis has been placed on the consequent changes in total vehicle energy dissipation due to road roughness. Thus, tire rolling resistance, in isolation from vehicle contributed losses such as dissipation in the suspension, appears to be a weakness in present evaluation procedures as they relate to fuel economy and pollution level testing: Recent work by Funfsinn and Korst has shown that substantial and measurable increases in energy losses occur for vehicles traveling on rough roads. The present investigation uses vehicle axle accelerations as a means of examining various road surfaces. Correlation with computer simulations has allowed the development of a deterministic road roughness model which permits the prediction of energy dissipation in both the tire and suspension as functions of road roughness, tire pressure, and vehicle speed. Comparison to the experiments of Korst and Funfsinn results in good agreement and shows that total rolling loss increases of up to 20 percent compared to ideal smooth roads are possible. The aerodynamic drag coefficient is also found to increase while driving on rough roads.  相似文献   
290.
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