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101.
Environmental impact assessment of sediment dumping in the southern Baltic Sea using meiofaunal indicators 总被引:1,自引:1,他引:0
Peter Frenzel Corinna Borrmann Beate Lauenburg Bjrn Bohling Jan Bartholdy 《Journal of Marine Systems》2009,75(3-4):430-440
An experimental sediment dumping was carried out in the southern part of the Mecklenburg Bight in June 2001. Foraminiferans and ostracods from superficial sandy sediment were studied in a time series from before dumping until March 2004 in order to assess changes in associations and recolonization patterns of both groups. Additionally, an area sampling covering the dumping site and its surroundings from 15.5 to 20.7 m water depth made it possible to compare associations inside and outside the dumping area as well as the water depth dependent distribution of foraminiferans and ostracods. Salinity values vary within the high alpha-mesohaline and low polyhaline range. The dominating species are Ammotium cassis (Foraminifera) and Sarsicytheridea bradii (Ostracoda). The diversity is low (Fisher alpha index from 0.4 to 3.2 for foraminiferans and 1.0 to 2.5 for ostracods), but higher within the dumping site samples. These higher values are explainable by input of allochthonous tests and valves representing additional species. After the sediment dumping it took two and a half years to re-establish the total foraminiferan association and the total foraminifer/ostracod ratio within the dumping site. Total foraminiferan abundance increases remarkably with water depth (mean 83 tests in 100 ml) driven by higher nutrient availability and more suitable salinity and temperature values within the zone of the oscillating halocline. The distribution of shallow water species such as Cribroelphidium excavatum, Eucythere argus and Hirschmannia viridis, within the transient water layer A. cassis, Nodulina dentaliniformis, S. bradii and Palmoconcha laevata and below Eggerella scabra indicate the depth position of the halocline. Water depth and sediment dumping influence are the main driving factors for the distribution of foraminifer and ostracod associations within the study area. However, a significant sedimentological difference between samples inside and outside the dumping area is not recognizable. 相似文献
102.
Peter Wang 《汽车杂志》2008,(8)
第四十三届世界通信大会于5月在北京举行,这是IEEE旗下通信领域最具权威的学术会议首次在我国举行。在我国,车载导航近年来取得了很好的市场效益。随着技术的进步,手机+GPS逐渐成为热点。 相似文献
103.
This paper addresses the issue of using before and after surveys to evaluate behavioural changes in response to transport
policies and investments, a procedure that, we argue is done far too rarely in this profession. Further, it demonstrates very
clearly that, in almost all conceivable cases, there are considerable economies to be obtained by using a panel (again, under-utilised
in our profession) to undertake evaluation, rather than successive independent cross-sectional surveys. The paper also addresses
the critical issue of sample size requirements for measuring changes of a relatively small magnitude in travel behaviour;
i.e., to state, with 95% confidence, that if there is a ∂ percent change in behaviour for the sample, there is a ∂ percent ± e
percent change in the behaviour of the population, where e is the sampling error. In this paper, we present a method for calculating such sample size requirements from first principles
and demonstrate the applicability both hypothetically and then empirically using data from the Puget Sound Transportation
Panel. The formulation enables designers of before and after surveys to investigate the trade-offs between the statistical
accuracy of their predictions and the sample size requirements systematically, without the need to specify ∂ a priori. This
latter point is crucial, we argue, because we have limited information on ∂, yet, as we explain here, it drives the sample
size requirements using alternative, well-cited approaches for calculating sample sizes to assess behavioural change. The
results have important ramifications both for those implementing transport policies intended to produce behavioural change,
especially when a cost-benefit evaluation of the policy is desired, and for those interpreting the results reported in previous
studies. 相似文献
104.
105.
The P-vector inverse method has been successfully used to invert the absolute velocity from hydrographic data for the extra-equatorial hemispheres, but not for the equatorial region since it is based on the geostrophic balance. A smooth interpolation scheme across the equator is developed in this study to bring together the two already known solutions (P-vectors) for the extra-equatorial hemispheres. This model contains four major components: (a) the P-vector inverse model to obtain the solutions for the two extra-equatorial hemispheres, (b) the objective method to determine the Ψ-values at individual islands, (c) the Poisson equation-solver to obtain the Π-values over the equatorial region from the volume transport vorticity equation, and (d) the Poisson equation-solver to obtain the Ψ and depth-integrated velocity field (U, V) over the globe from the Poisson Ψ-equation. The Poisson equation-solver is similar to the box model developed by Wunsch. Thus, this method combines the strength from both box and P-vector models. The calculated depth-integrated velocity and Ψ-field agree well with earlier studies. 相似文献
106.
This paper explains the need for the application of cost-benefit analysis to the evaluation of alternative projects for investment in the transport field and outlines briefly the historical development of the technique. The results of a comparative survey of a number of cost-benefit studies which have been carried out in Britain and some conclusions as to their thoroughness and comprehensiveness (or otherwise) are presented. The article concludes with a number of specific and detailed recommendations to remedy apparent methodological weaknesses. Six of these recommendations seem to merit particular attention:
- The viewpoint of most studies should be extended so as to avoid confinement, for example, within an arbitrary local government boundary, and a wider range of “externalities” should be considered. Intangibles should be included explicitly in all such evaluation exercises.
- The actual incidence of costs and benefits should be examined in order to indicate the directional impact of the project and its implications in terms of equity. The elimination of transfer payments and double-counting should be postponed until the latest possible stage in the evaluation.
- Equity considerations should be investigated in any transportation plan, since most projects have considerable equity implications for particular areas or socio-economic groups.
- Discounted cash flow techniques, which are still used only in a minority of transportation studies, should become standard practice. Most evaluations are based on a single-year rate of return, or at best on simple trend forecasting. More resources should be devoted to proper evaluation of alternative plans which give due importance to the cost and benefit streams through time.
- Sensitivity analysis should be used in all transportation evaluations. Knowledge of the impact of different assignments, shadow prices, and discount rates are essential information for any decisionmaker.
- Last, but not least, much greater communication should exist between analyst and decisionmaker than has existed in the past.
107.
Yu Nie Xing WuJohn F. Dillenburg Peter C. Nelson 《Transportation Research Part A: Policy and Practice》2012,46(2):403-419
Reliable route guidance can be obtained by solving the reliable a priori shortest path problem, which finds paths that maximize the probability of arriving on time. The goal of this paper is to demonstrate the benefits and applicability of such route guidance using a case study. An adaptive discretization scheme is first proposed to improve the efficiency in computing convolution, a time-consuming step used in the reliable routing algorithm to obtain path travel time distributions. Methods to construct link travel time distributions from real data in the case study are then discussed. Particularly, the travel time distributions on arterial streets are estimated from linear regression models calibrated from expressway data. Numerical experiments demonstrate that optimal paths are substantially affected by the reliability requirement in rush hours, and that reliable route guidance could generate up to 5-15% of travel time savings. The study also verifies that existing algorithms can solve large-scale problems within a reasonable amount of time. 相似文献
108.
非洲铁路实施特许权转让已经有10多年的历史。加拿大CPCS Transcom公司曾帮助非洲9个国家铁实施了路私有化改造。今天的经验来自历史的教训。 相似文献
109.
Peter Wang 《汽车杂志》2009,(3)
经过2006年以来市场导入和培育,“导航”已经成为有车人士不再陌生的字眼,导航产品也拥有了数百万的用户群。随着用户逐步熟悉这个产品,“导航电子地图升级”成为越来越多用户关注的服务项目。 相似文献
110.
Huaguo Zhou Fatih Pirinccioglu Peter Hsu 《Transportation Research Part C: Emerging Technologies》2009,17(3):274-284
Past studies have shown that the level of roadway lighting is an important factor for nighttime roadway safety. To evaluate roadway lighting systems and maintain their functionality, it is essential to perform field lighting measurements. Currently, field measurements of roadway lighting systems are often conducted by handheld light meters using a short sample section. The evaluation of an entire corridor or a longer section is difficult when using the traditional manual measurement methods. This paper addresses this difficulty by developing a new lighting measurement system that can be used to collect massive amounts of lighting level data in an efficient, safe, and effective manner. The system consists of a light meter, a distance measurement instrument (DMI), a computer, software, and an electronic converter circuit to connect the computer and other hardware. Software was developed for the communication link between the computer and the light meter, and to record both the distance and illuminance data. The system was calibrated and validated with the field data. The new system will not only reduce future data collection costs, but also improve safety for field data collection personnel. The system has been approved for use to collect illuminance data on Florida state roads greater than or equal to 250-miles in length. 相似文献