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921.
The probability of capsize of purse seiners in irregular beam seas and the effect of freeboard height and metacentric height
on trapped water on the deck was investigated. The aim was to quantify a safety level that can be achieved by direct stability
assessment for this type of fishing vessel. The amount of trapped water on deck was numerically estimated using a hydraulic
flow assumption. The long-term capsizing probabilities were estimated using a piecewise linear approach together with wave
statistics from major Japanese fishing areas. The estimated safety level of capsizing probability was compared with that obtained
by the IMO weather criterion and by the water-on-deck criterion of the IMO Torremolinos Convention. Numerical results for
four typical Japanese purse seiners indicated that the effect of freeboard, on the amount of trapped water on deck, is more
important than that of the metacentric height. Besides the metacentric height and the freeboard, it was shown that the danger
of capsizing is a function of the rise of floor. The safety level obtained by the capsizing probability approach is generally
higher than that based on the IMO weather criterion. However, the water-on-deck criterion provides a higher safety level than
the capsizing probability approach for ships with a low rise of floor. 相似文献
922.
Alban Leroyer Sophie Barré Jean-Michel Kobus Michel Visonneau 《Journal of Marine Science and Technology》2008,13(1):1-15
This article aims at verifying the capabilities of a Reynolds-Averaged Navier-Stokes Equations (RANSE) solver (ISIS-CFD, developed
at the Fluid Mechanics Laboratory of Ecole Centrale de Nantes [LMF]) to accurately compute the flow around an oar blade and
to deduce the forces on it and other quantities such as efficiency. This solver is structurally capable of computing the flow
around any blade shape for any movement in six degrees of freedom, both when the blade pierces the free surface of the water
and when it does not. To attempt a first validation, a computation was performed for a simplified case chosen among those
for which experimental results are available at LMF. If results prove satisfactory for a simplified blade shape and for a
movement that respects the main characteristics of blade kinematics, then the solver could be used for real oars and more
realistic kinematics. First, the experimental setup is considered, and the objectives, methodologies, and procedures are elucidated.
The choice of the test case for numerical validation is explained, i.e., a plane rectangular blade with a constant immersion
and a specified movement deduced from analogy with tests on propellers. Next, the numerical framework is presented and the
Navier-Stokes solver and methods for handling multifluid flows and moving bodies are described. Lastly, numerical results
are compared with experimental data, highlighting an encouraging agreement and proving the relevance and the complementarity
of both approaches. 相似文献
923.
Timothy Lilienthal Akihiko Matsuda Giles Thomas 《Journal of Marine Science and Technology》2007,12(2):111-118
This article presents work based on the development of a performance-based stability assessment method. It describes a numerical
method used to determine the survival limit for a dynamic intact stability assessment procedure. The numerical method utilises
a time-domain vessel motion program to assess the limit for a range of vertical centres of gravity (KG). The appropriateness
of the numerical predictions was examined through comparison with model experiment results. Free-running model tests were
conducted in regular following waves at discrete KGs. A comparison between the survival limits determined through the numerical
and experimental methods is presented. The current International Maritime Organisation (IMO) stability criteria are also evaluated
against the numerical and experimental dynamic performance-based stability assessment methods. 相似文献
924.
This paper explores critical success conditions of collaborative planning projects in the area of urban transport, evaluating
the impact of new collaborative methods, instruments and processes on project performance. Hypothesis building is based on
a comparative, empirical research design, rather than on deductive theory construction. Potential critical success conditions
are derived from literature. Based on five urban transport planning projects in Gothenburg (Sweden), London (United Kingdom),
Milwaukee (United States), Tokyo (Japan) and Mexico City (Mexico), a rough set analysis of the five cases reveals validated
success conditions, which can be used for formulating hypotheses for further research or for policy and process improvement.
The results suggest that a dedicated management of the multi-actor network, a high diversity of actors, as well as an extensive
use of knowledge integration methods in combination with a high network density are critical success conditions of these planning
processes. Surprisingly, the extensive use of unilateral methods also showed to be an important success condition. The traditional
role of the planner will have to be complemented with the expertise of network and methodology management. The authors conclude
that rough set analysis can be a valuable addition to narrative, single-case analysis of collaborative urban transport planning
processes. 相似文献
925.
The paper presents a study on the incorporated probability that a tanker fleet meets a given permissible value of hull girder
strength loss. The analysis was based on a database of hull girder section modulus (HGSM) for as-gauged girth belts of tankers.
It was found that its mean value is below 5% over the entire life span of the analyzed tanker fleet. The Weibull probabilistic
distribution was found to best represent the time-varying HGSM loss. A method was developed for calculating the incorporated
safety of a fleet. As an example, the IMO requirement for a maximum HGSM reduction of 10% relative to its required value was
analyzed, accounting for time-variant HGSM loss and including a probabilistic model for coating longevity.
The views expressed in the paper are those of the authors and not necessary those of ABS. 相似文献
926.
José María López Felipe Jiménez Francisco Aparicio Nuria Flores 《Transportation Research Part D: Transport and Environment》2009,14(1):1-5
Due to growing concerns about NOx and particulate matter (PM) emissions from diesel engines, stricter regulations are being introduced requiring advanced emission control technology. In response the diesel industry has begun testing various emission control technologies and applying them. To assess vehicle renewal policies of bus companies, two exhaust after-treatment technologies are compared: the combination of a diesel particulate filter and an exhaust gas re-circulation system and the combination of a selective catalytic reduction and urea. On-board emission measurements were conducted under real-world driving conditions on a specific bus route in the city of Madrid. 相似文献
927.
LI Tie-shan YAN Shu-jia QIAO Wen-ming 《船舶与海洋工程学报》2007,6(4):1-7
This paper focuses on the problem of linear track keeping for marine surface vessels. The influence exerted by sea currents on the kinematic equation of ships is considered first. The input-to-state stability (ISS) theory used to verify the system is input-to-state stable. Combining the Nussbaum gain with backstepping techniques, a robust adaptive fuzzy algorithm is presented by employing fuzzy systems as an approximator for unknown nonlinearities in the system. It is proved that the proposed algorithm that guarantees all signals in the closed-loop system are ultimately bounded. Consequently, a ship's linear track-keeping control can be implemented. Simulation results using Dalian Maritime University's ocean-going training ship 'YULONG' are presented to validate the effectiveness of the proposed algorithm. 相似文献
928.
Qin Xia Jianli Duan Feng Gao Qiuxia Hu Yingdong He 《International Journal of Automotive Technology》2018,19(4):751-758
Intelligent vehicle greatly benefits traffic safety, efficiency and driving comfortable. With the development of intelligent driving technology and its application, it is becoming increasingly important to do effective and comprehensive tests before putting on the market. Comprehensively considering the cost of test, an automatic generation method of test scenarios is proposed to ensure both coverage and effectiveness. Based on the analyzed key infuence factors of an intelligent driving system, the analytic hierarchy process (AHP) is used to determine their importance and accordingly an complex index is defined, based on which an improved test case generation algorithm based on the pairwise independent combinatorial testing tool (PICT) is proposed to ensuring both combinational coverage and complexity of test cases. Finally, the test scenario is generated by clustering these discrete test cases considering similarity and complexity. The high complex test cases are preferred to be combined together and conducted preferentially to increase the test efficiency. The effectiveness of this method is validated by applying it on a lane departure warning system (LDW). 相似文献
929.
930.
The influence of intrusions of eastern North Atlantic central water (ENACW) in the north and northwestern Iberian shelf on phytoplankton composition and abundance and on particle-size distributions of seston was analyzed using data collected on three extensive cruises during spring 1991 and 1992. Water with temperature and salinity values between 12.20 and 13.86 °C and between 35.66 and 35.98 psu, respectively, characteristics of the subtropical type of ENACW (ENACWt), was detected in the upper 100 m of the water-column in all cruises, but particularly in the western coast in 1992. The highest salinity values of this water were found near the surface (0–100-m depth) and in early spring 1992, while minimum salinity values, and also minimum geographical extension, were found in late spring in both years. Phytoplankton blooms concentrated in frontal areas between different water types, with maximum intensity and extension in early spring.Using temperature and salinity characteristics, samples were classified in four groups corresponding to the major water types found in the region: Bay of Biscay central water (BBCW), two segments of ENACW of different salinity and surface water influenced by continental runoff. This classification was significantly confirmed by three independent discriminant analyses using hydrographic and chemical (dissolved nutrients and chlorophyll) variables, phytoplankton species abundance variables and particle-size concentration of seston variables. Phytoplankton blooms related to the presence of saline waters were characterized by the dominance of either chain-forming diatoms or a mixture of diatoms and phytoflagellates and high concentrations of seston. The diatom species dominating in saline waters were typical of upwelling-induced blooms occurring generally during summer. Blooms occurring in waters influenced by runoff also contained diatoms but in lower numbers than those of saline waters. Nutrients were not exhausted in the region, suggesting that phytoplankton populations were still in active growth. These results are interpreted taking into account the known variability in water-mass formation and in the poleward current driving ENACWt along the shelf, and indicate that saline intrusions are a major feature affecting the distribution and composition of plankton in the spring in the southern Bay of Biscay, thus enlarging to a wider spatial scale their reported influence on the pelagic ecosystem. 相似文献