全文获取类型
收费全文 | 1442篇 |
免费 | 12篇 |
专业分类
公路运输 | 453篇 |
综合类 | 60篇 |
水路运输 | 466篇 |
铁路运输 | 42篇 |
综合运输 | 433篇 |
出版年
2023年 | 4篇 |
2022年 | 20篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 35篇 |
2017年 | 43篇 |
2016年 | 71篇 |
2015年 | 25篇 |
2014年 | 51篇 |
2013年 | 215篇 |
2012年 | 77篇 |
2011年 | 84篇 |
2010年 | 66篇 |
2009年 | 82篇 |
2008年 | 65篇 |
2007年 | 56篇 |
2006年 | 34篇 |
2005年 | 32篇 |
2004年 | 22篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 22篇 |
2000年 | 29篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 41篇 |
1994年 | 7篇 |
1993年 | 22篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有1454条查询结果,搜索用时 31 毫秒
991.
Sea level and Eddy Kinetic Energy variability in the Bay of Biscay, inferred from satellite altimeter data 总被引:1,自引:0,他引:1
Twelve years (1993–2005) of altimetric data, combining different missions (ERS-1/2, TOPEX/Poseidon, Jason-1 and Envisat), are used to analyse sea level and Eddy Kinetic Energy variability in the Bay of Biscay at different time-scales. A specific processing of coastal data has been applied, to remove erroneous artefacts. Likewise, an optimal interpolation has been used, to create a series of regional Sea Level Anomaly maps, merging data sets from two satellites.The sea level presents a trend of about 2.7 mm/year, which is within the averaged values of sea level rise in the global ocean. Frequency spectra show that the seasonal cycle is the main time-scale affecting the sea level and Eddy Kinetic Energy variability. The maximum sea level occurs in October, whilst the minimum is observed in April. The steric effect is the cause of this annual cycle. The Northern French shelf/slope presents intense variability which is likely due to internal tides. Some areas of the ocean basin are also characterised by intense variability, due to the presence of eddies.The Eddy Kinetic Energy, in turn, is higher from December to May, than during the rest of the year and presents a weak positive trend from April 1995 to April 2005. Several documented mesoscale events, occurring at the end of 1997 and during 1998, are analysed. Altimetry maps prove to be a useful tool to monitor swoddy-like eddies from their birth to their decay, as well as the inflow of seasonal slope water current into the southeastern corner of the Bay of Biscay. 相似文献
992.
S. Bazin C. Beckerich C. Blanquart M. Delaplace L. Vandenbossche 《Recherche - Transports - Sécurité》2011,27(3):215-238
Many high-speed rail (HSR) projects exist in Europe and elsewhere in the world and generate many expectations: economic development, location of new firms and new population, development of tourism, effect on real estate. But these expectations are not always fulfilled. For academic researchers, the myth of the existence of a linear causality between transport infrastructures and spatial, social and economic transformations, according to which automatic effects will occur, has been challenged for a long time. But sometimes, new economic dynamism can be observed. The aim of this paper is to present a review of academic and non-academic literature in order to understand why there is a gap between the academic literature and the regional stakeholders’ expectations. 相似文献
993.
994.
In this paper, an approach for integrating the data obtained from structural health monitoring (SHM) in the life-cycle performance assessment of ship structures under uncertainty is presented. Life-cycle performance of the ship structure is quantified in terms of the reliability with respect to first and ultimate failures and the system redundancy. The performance assessment of the structure is enhanced by incorporating prior design code-based knowledge and information obtained by SHM using Bayesian updating concepts. Advanced modeling techniques are used for the hull strength computations needed for the life-cycle performance analysis. SHM data obtained by testing a scaled model of a Joint High-speed Sealift Ship is used to update its life-cycle performance. 相似文献
995.
Paul R. Tétreault Ahmed M. El-Geneidy 《Transportation Research Part A: Policy and Practice》2010,44(6):390-402
In recent years, several transit agencies have been trying to be more competitive with the automobile to attract choice riders. Transit agencies can only be competitive if they can provide services that are reliable, have a short access and egress time, and have run times that are comparable to automobiles. Several transit agencies try to be competitive through offering faster service, such as limited-stop (express) bus service. This study uses AVL and APC data, in addition to a disaggregate data obtained from a travel behavior survey, to select stops and estimate run times for a new limited-stop service that will run parallel to a heavily used bus route (67 Saint-Michel) in Montréal, Canada. Three different scenarios are developed based on theory and practice to select stops to be incorporated in the new limited service. The time savings for each scenario are then evaluated as a range and a fourth scenario is developed. A limited-stop service is recommended based on selecting stops serving both directions of the route, major activity points and stop spacing. This study shows that implementing a limited-stop service would yield substantial time savings for both, the new limited service and the existing regular service running in parallel. 相似文献
996.
M. T. Addico 《Maritime Policy and Management》2013,40(2):121-132
This paper looks at how the Shippers‘ Council could operate to make shipping cost-effective and to play its role as a servant of trade—a servant of the shippers. It looks at the key problems that confront the shipper requiring intervention by a Shippers‘ Council and surveys how the organization of the Shippers’ Council effectively handles problems. The final sections draw conclusions which could contribute to increasing the efficiency of Shippers' Councils, as well as improving the understanding of the Councils as managers of the demand side of shipping. 相似文献
997.
The present study aims to make a thermodynamic analysis of an ethylene cascade re-liquefaction system that consists of the following two subsystems: a liquefaction cycle using ethylene as the working fluid and a refrigeration cycle operating with a hydrocarbon refrigerant. The hydrocarbon refrigerants considered are propane (R290), butane (R600), isobutane (R600a), and propylene (R1270). A computer program written in FORTRAN is developed to compute parameters for characteristic points of the cycles and the system’s performance, which is determined and analyzed using numerical solutions for the refrigerant condensation temperature, temperature in tank, and temperature difference in the cascade condenser. Results show that R600a gives the best performance, followed by (in order) R600, R290, and R1270. Furthermore, it is found that an increase in tank temperature improves system performance but that an increase in refrigerant condensation temperature causes deterioration. In addition, it is found that running the system at a low temperature difference in the cascade condenser is advantageous. 相似文献
998.
Abstract Over 90 percent of British Columbia's annual log harvest enters into complex water‐based systems of transportation, storage, and handling. These systems have considerable impacts on a wide range of coastal resources and uses. A number of site‐specific conflicts have arisen between forestry and preexisting or emerging values including fisheries, mariculture, recreational boating, and harbor redevelopment. Specific data on the impacts leading to conflict are often fragmentary. However, concerns about highly valued and fragile areas‐particularly estuariesalong with industrial concerns regarding log losses and handling efficiency, have prompted changes in log handling. These include moves to dryland sorting, log bundling, and a redistribution of forestry activities in estuaries to accommodate other values. Conflict adjustments and responses have in the past been largely ad hoc and attempted in a jurisdictional vacuum concerning control of coastal management. A more inclusive strategy is now slowly emerging, which involves the coordinated participation of federal, provincial, and industrial interests. 相似文献
999.
Brenda M. Katon Robert S. Pomeroy Len R. Garces Marshall W. Ring 《Coastal management》2013,41(1):29-37
The local management of mangrove resources in Cogtong Bay, Philippines, dates back to the 1940s and 1950s when some families informally designated mangrove areas under their care and management. The 1960s and 1970s saw several exogenous events that led to the progressive denudation of mangrove stands and the decline in fish catch per fishing trip. This article draws attention to the forces that prompted coastal villages and external agents to collaborate with the national and local government units in resource rehabilitation. It also assesses the performance of a coastal resources comanagement project at Cogtong Bay. 相似文献
1000.
Abstract An analysis of ecological systems that both sustain and are sustained by coastal waters provides the key to a biophysical procedure for delineating inland coastal management boundaries. This analysis entails two basic tasks: (1) mapping the ecosystems that compose coastal waters and adjacent areas, and (2) charting sustaining flows among these systems. The resulting boundary encompasses all environments of coastal waters (subaqueous areas containing a measurable quantity of seawater) and all shore‐lands (either emergent or submergent environments that interchange sustaining materials, energy, or biota with coastal waters). As this biophysical procedure depends on the precise location of, and functional transfers among, coastal ecosystems, it provides a means both for assessing the consequences of human actions and for establishing a landward boundary for a management program. Alternative boundaries not based on locations and operations of coastal ecosystems would probably be either arbitrary or of undue extent, nor would such “alternative”; boundaries be an integral part of an ongoing management process. 相似文献