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   7811篇
  免费   104篇
公路运输   1663篇
综合类   581篇
水路运输   2519篇
铁路运输   764篇
综合运输   2388篇
  2023年   43篇
  2022年   112篇
  2021年   56篇
  2019年   80篇
  2018年   190篇
  2017年   105篇
  2016年   126篇
  2015年   90篇
  2014年   240篇
  2013年   1220篇
  2012年   316篇
  2011年   372篇
  2010年   224篇
  2009年   366篇
  2008年   298篇
  2007年   266篇
  2006年   230篇
  2005年   269篇
  2004年   288篇
  2003年   181篇
  2002年   146篇
  2001年   132篇
  2000年   138篇
  1999年   98篇
  1998年   129篇
  1997年   111篇
  1996年   138篇
  1995年   149篇
  1994年   84篇
  1993年   189篇
  1992年   160篇
  1991年   77篇
  1990年   83篇
  1989年   57篇
  1988年   74篇
  1987年   65篇
  1986年   59篇
  1985年   77篇
  1984年   73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
  1973年   45篇
排序方式: 共有7915条查询结果,搜索用时 15 毫秒
491.
The efficient integration of logistics modes is critical for international cargo shipping. The local transportation connecting to the export port then plays a vital role in such integration. This paper investigates the problems of carrier selection in the China Pearl River delta area, with respect to international shipping. The analytical hierarchy process (AHP) model is constructed based on a comprehensive industrial interviews and statistical analysis. Rather than simply ranking the given alternatives, we use AHP is used to analyse the weakness and strength of impacting factors in carrier selection. The model is implemented under different types of shipper. Seven criteria are statistically summarized from the questionnaire for evaluating eight different modes. The results are useful to those liner companies serving the PRD region in relationship to port selection and fleet deployment.  相似文献   
492.
493.
494.
This paper presents a new paradigm for choice set generation in the context of route choice model estimation. We assume that the choice sets contain all paths connecting each origin–destination pair. Although this is behaviorally questionable, we make this assumption in order to avoid bias in the econometric model. These sets are in general impossible to generate explicitly. Therefore, we propose an importance sampling approach to generate subsets of paths suitable for model estimation. Using only a subset of alternatives requires the path utilities to be corrected according to the sampling protocol in order to obtain unbiased parameter estimates. We derive such a sampling correction for the proposed algorithm.Estimating models based on samples of alternatives is straightforward for some types of models, in particular the multinomial logit (MNL) model. In order to apply MNL for route choice, the utilities should also be corrected to account for the correlation using, for instance, a path size (PS) formulation. We argue that the PS attribute should be computed based on the full choice set. Again, this is not feasible in general, and we propose a new version of the PS attribute derived from the sampling protocol, called Expanded PS.Numerical results based on synthetic data show that models including a sampling correction are remarkably better than the ones that do not. Moreover, the Expanded PS shows good results and outperforms models with the original PS formulation.  相似文献   
495.
今年关于太平洋航线有两个不确定因素,即美国进口量增长将会大大放缓,同时美国出口量会继续增加。因此,几乎所有其他的问题都是不确定的:进口量是否会增长还是会减少?航运公司是否会随着船只规模的增加,而为贸易业务分配更多运力,或者仅仅保持现有运力?他们是否能够成功增加运费以弥补成本的增长?发货人是否同意支付完全不固定的船舶燃油附加费?  相似文献   
496.
This paper argues for interval, rather than point, estimation when calibrating some variants of the trip distribution “gravity” models. Analytic expressions are derived for the approximate asymptotic covariances of least squares and maximum likelihood estimates of the parameters in the impedance function under a variety of conditions. A comparative numerical example, and an application using migration flows, are also presented.  相似文献   
497.
Environmental and qualify-of-life issues are taking on an increasing social and political significance the world over. Even in Japan, a country so often criticized for its economic-dominated outlook, talk is turning to these issues. Advances in telecommunications and a growing awareness of the need to change how we live and function in an increasingly threatened environment has brought telework to the forefront of the debate on the nature of work and how our cities function.After setting the broad Japanese social context, this paper will look at the progress of telework in Japan to date with especial emphasis on several current satellite and resort office pilots. It will summarize the findings and proposals of several available reports, and will also attempt to identify the overall outlook for telework in Japan.  相似文献   
498.
499.
The Pacific Halibut Catch Sharing Plan formalized the process for allocating halibut between the Alaska commercial and recreational charter sectors. It included a new program intended to allow for “flexibility” through inter-sectoral trading, permitting charter operators to lease commercial halibut pounds to relax client harvest restrictions. Here we evaluate the first two years of lease market activity and participation. Participation from some commercial quota holders in the lease market suggests that the program provided beneficial flexibility; in fact, the number of transfers to the charter sector was greater than transfers within the commercial sector for some quota types. We also identified a high proportion of self-leasers. However, transfers to the charter sector were on average smaller than within-sector commercial transfers, and total poundage leased by the charter sector was low compared with commercial transfers. Usage of leased quota by the recreational charter sector enables the harvest of larger fish or additional fish, and provides flexibility in catch composition on halibut closure days. Finally, the value-per-pound may be higher in the charter sector, as commercial-to-charter transfer prices approached the commercial ex-vessel price.  相似文献   
500.
The galvanic corrosion behavior of the metal combinations 15 CDV6/MDN138 and 15 CDV6/MDN250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN138, MDN250, and 15 CDV6 of the individual metal, the galvanic potential and galvanic current of the couples 15 CDV6/MDN138 and 15 CDV6/MDN250, were periodically monitored throughout the study period. The calcareous deposits on MDN138 and MDN250 in galvanic contact with 15 CDV6 were analyzed using XRD. The electrochemical behavior of MDN138, MDN250, and 15 CDV6 in seawater was studied using an electrochemical work station. The surface characteristics of MDN138 and MDN250 in galvanic contact with 15 CDV6 have been examined with a scanning electron microscope. The results of the study reveal that the galvanic protection offered by15 CDV6 to MDN250 and MDN138 in natural seawater amounts to 93% and 98%, respectively, implying that the galvanic protection offered by 15 CDV6 is continuous and effective, which has been further evinced from the adherent nature of the calcareous deposit film comprising compounds such as CaCO_3(calcite, aragonite, and vaterite), MgCO_3(magnesite),Mg(OH)_2(brucite), and MgO(brucite).  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