全文获取类型
收费全文 | 1352篇 |
免费 | 19篇 |
专业分类
公路运输 | 575篇 |
综合类 | 45篇 |
水路运输 | 343篇 |
铁路运输 | 26篇 |
综合运输 | 382篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 42篇 |
2017年 | 41篇 |
2016年 | 87篇 |
2015年 | 19篇 |
2014年 | 72篇 |
2013年 | 222篇 |
2012年 | 76篇 |
2011年 | 85篇 |
2010年 | 82篇 |
2009年 | 66篇 |
2008年 | 80篇 |
2007年 | 36篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 21篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 17篇 |
2000年 | 29篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 17篇 |
1996年 | 22篇 |
1995年 | 24篇 |
1994年 | 9篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有1371条查询结果,搜索用时 15 毫秒
871.
872.
Sovereignty claims over insular features and maritime jurisdiction in the South China Sea have been disputed for decades, and a governance regime to address ocean-related issues is urgently needed. This article first introduces the notion of a regime, and examines details of cooperation mechanisms in the Polar Regions. Lessons that can be applied to the South China Sea include that both soft and hard law regimes work to bring States concerned together to cooperate on the “commons” issues even when military conflicts or sovereignty disputes still exist. Consensus among bordering States would be necessary to make the South China Sea a “zone of peace.” Mechanisms that accommodate the various sovereignty claims and freeze existing and new claims to, as well as to prohibit military activities in, the South China Sea are recommended. Lastly, if a cooperative mechanism were to be established in the future, the Arctic regime would be more applicable to the South China Sea than the Antarctic regime due to their geographic nature. Thus, only States bordering the South China Sea should have voting and decision-making rights in the cooperative mechanism. As always, the political will of all parties is paramount to the success of such an endeavor. 相似文献
873.
A new index, namely the overall motion induced interruptions (OMII), is proposed as a seakeeping criterion for fishing vessels, to compare ships having different hull forms and dimensions by means of an only parameter, in a human centred approach, mainly related to the onboard risk level. Therefore, the first aim of the paper is to investigate the factors affecting fishing vessels’ seakeeping performances to improve them to reduce the high number of injuries occurring during fishing operations, mainly related to both risk perception and harsh weather conditions. Despite the classical approach, where motion induced interruption is determined for a certain sea state with regard to several location points, the new index accounts for all crew members’ positions on the working deck, all heading angles the vessel may experience during fishing operations, based on relevant operating scenario, and all sea states the ship may encounter in the fishing area. The influence of position, heading angles and sea states on the attained risk level is fully investigated, analysing seakeeping performances of four fishing vessels with different hull forms and dimensions. Finally, a new operability criterion is proposed, based on OMII, to investigate the influence of ship size and operating scenario on the risk of injuries during fishing operations. Main factors affecting fishing vessels’ seakeeping performances are fully discussed, paying attention to relevant correlation with ship roll natural period. 相似文献
874.
This paper presents a comprehensive review of the literature on off-peak hour deliveries (OPHD). The review identifies different approaches and policy levers used in the past, such as the laissez-faire approach, a road pricing approach, an incentives approach, and a regulatory approach. The paper also identifies different delivery reception schemes discussed in the literature. The authors complement the theory with a synthesis of pilot tests and the analysis of a set of interviews with practitioners (from the public sector and other organisations) in charge of OPHD programmes. The results from this review show the potential benefits that these programmes could bring about, the challenges faced in the early stages – along with potential solutions – and the significant progress that has been made in this domain in the last decade. According to the review, the results from the pilot tests tend to be positive, suggesting the importance of these programmes to reach more efficient and sustainable transportation systems. 相似文献
875.
Konstantin I. Matveev Nicholaus I. Perry Alexander W. Mattson Christopher S. Chaney 《船舶与海洋工程学报》2015,(1)
This paper addresses the development and testing of a remotely controlled boat platform with an innovative air-ventilated hull. The application of air cavities on the underside of ship hulls is a promi... 相似文献
876.
Gilbert T. Rowe Gregory S. Boland Elva G. Escobar Briones Marta Elizabeth Cruz-Kaegi Adrian Newton Dieter Piepenburg Ian Walsh Jody Deming 《Journal of Marine Systems》1997,10(1-4)
Sediment community metabolism (oxygen demand) was measured in the Northeast Water (NEW) polynya off Greenland employing two methods: in situ benthic chambers deployed with a benthic (GOMEX) lander and shipboard laboratory Batch Micro-Incubation Chambers (BMICs) utilizing ‘cores’ recovered from USNEL box cores. The mean benthic respiration rate measured with the lander was 0.057 mM O2 m−2 h−1 (n = 5); whereas the mean measured with the BMICs was 0.11 mM O2 m−2 h−1 (n = 21; p < 0.01 that the means were the same). In terms of carbon fluxes (14 and 27 mg C m−2 d−1), these respiration rates represent ca. 5–15% of the average net primary production measured in the euphotic zone in 1992. The biomass of the bacteria, meiofauna and macrofauna were measured at each location to quantify the relationship between total community respiration and total community biomass (mean 1.42 g C m−2). Average carbon residence time in the biota, calculated by dividing the biomass by the respiration, was on the order of 50–100 days, which is comparable to relatively oligotrophic continental margins at temperate latitudes.The biomass and respiration data for the aerobic heterotrophic bacteria, the infaunal invertebrates (meiofauna and macrofauna), and the epifaunal megabenthos (two species of brittle stars) are summarized in a ‘steady-state’ solution of a sediment food chain model, in terms of carbon. This carbon budget illustrates the relative importance of the sediment-dwelling invertebrates in the benthic subsystem, compared to the bacteria and the epibenthos, during the summer open-water period in mud-lined troughs at depths of about 300 m. The input needed to drive heterotrophic respiratory processes was within the range of the input of organic matter recorded in moored, time-sequencing sediment traps.A time-dependent numerical simulation of the model was run to investigate the potential responses of the three size groups of benthos to abrupt seasonal pulses of particulate organic matter. The model suggests that there is a time lag in the increase in bottom community biomass and respiration following the POC pulse, and provides hypothetical estimates for the potential carbon storage in the summer (open water), followed by catabolic losses during each ensuing winter (ice covered).This sequence of storage and respiration may contribute to the process of seasonal CO2 ‘rectification’ (sensu Yager et al., 1995) in some Arctic ecosystems. 相似文献
877.
The setation patterns of female antennules of some Paracyclops species are analysed with reference to the hypothetical 28-segmented antennule of ancestral copepod proposed by Huys and Boxshall in 1991. Comparison between Paracyclops species has revealed a setation pattern common to all species thus far examined. Several modifications of the female antennules have been identified as apomorphic states and can be used in phylogenetic studies. P. waiariki has 12-segmented antennules and exhibits more plesiomorphic characters than the reduced 8-segmented antennules of other species, such as P. fimbriatus. The results confirm that simple segment numbers are unusable as characters in cladistic analysis. Both P. affinis and P. yeatmani, for example, have 11-segmented antennules but analysis of segmental homologies has revealed that the 11-segmented state is convergent in these two species. 相似文献
878.
We consider a city region with several facilities that are competing for customers of different classes. Within the city region, the road network is dense, and can be represented as a continuum. Customers are continuously distributed over space, and they choose a facility by considering both the transportation cost and market externalities. More importantly, the model takes into account the different transportation cost functions and market externalities to which different customer classes are subjected. A logit‐type distribution of demand is specified to model the decision‐making process of users' facility choice. We develop a sequential optimization approach to decompose the complex multi‐class and multi‐facility problem into a series of smaller single‐class and single‐facility sub‐problems. An efficient solution algorithm is then proposed to solve the resultant problem. A numerical example is given to demonstrate the effectiveness and potential applicability of the proposed methodology. 相似文献
879.
Understanding individual travel decisions: results from a commuters survey in Geneva 总被引:1,自引:0,他引:1
In this paper, we present the results of an extended traveler behavior survey conducted in Geneva (Switzerland) in March 1994. In this survey, commuters were asked about the impact of various factors, related to individual or household characteristics and situational, contextual and environmental constraints on their basic travel decisions. In particular, the issues of mode, route and departure time choice were investigated, together with the diversion from normal patterns in response to adverse weather conditions. Some cross cultural comparisons are discussed with respect to the results of a similar survey conducted in Brussels (Belgium) in 1992 (Khattak & de Palma 1995, 1997). 相似文献
880.
PRADYA PREMPRANEERACH FRANZ S. HOVER MICHAEL S. TRIANTAFYLLOU TIMOTHY J. MCCOY CHRYSSOSTOMOS CHRYSSOSTOMIDIS GEORGE E. KARNIADAKIS 《Naval Engineers Journal》2008,120(1):109-121
Stochastic sensitivity analysis is a valuable tool in ranking inputs and in investigating the degree of interaction of its components. In this paper, we present stochastic simulation results for a shipboard integrated power system and study its sensitivity. Specifically, we apply sensitivity analysis to two high-fidelity models of shipboard subsystems, investigating open- and closed-loop control of the propulsion system. The results show that different inputs are most important for the open- and closed-loop control, with sensitivities that change dramatically in time as they reflect the transition from the fast electrical scales to slower mechanical scales. We also demonstrate how sensitivity analysis can be used to establish the robustness of the AC drive. 相似文献