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161.
An acoustic vector sensor (AVS) can capture more information than a conventional acoustic pressure sensor (APS). As a result, more output channels are required when multiple AVS are formed into arrays, making processing the data stream computationally intense. This paper proposes a new algorithm based on the propagator method for wideband coherent sources that eliminates eigen-decomposition in order to reduce the computational burden. Data from simulations and lake trials showed that the new algorithm is valid: it resolves coherent sources, breaks left/right ambiguity, and allows inter element spacing to exceed a half-wavelength. 相似文献
162.
To evaluate the clinical outcome, effectiveness and safety of the surgical management of traumatic lumbar spondylolisthesis
with transforaminal lumbar interbody fusion (TLIF) with short segmental instrumentation fixation. A retrospective review of
a consecutive series of 24 patients with traumatic lumbar spondylolisthesis treated with TLIF procedure was carried out. Intraoperative
spinal cord monitoring was used to confirm the peripheral neural function intact during the reduction of the spondylolisthesis.
Preoperative clinical and radiographic evaluation of all cases were originally collected prospectively. Data regarding blood
loss, operative time, duration of hospital stay, radiographic fusion, instrumentation failure and clinical result were collected
and observed at regular follow-up periods. All patients were engaged in high-energy accidents in the lower back and 16 patients
had concomitant injuries. The mean operative time was 124 min, mean blood loss was 350 mL, and mean hospital stay was 6.5
days. There were no complications such as incision infection, cerebrospinal fluide (CSF) leakage and nerve root injury and
so on. All patients demonstrated a solid lumbar interbody fusion within 4 months, and no evidence of spondylolisthesis correction
loss, instrumentation failure and loosing. They all were completely asymptomatic, with normal neurologic findings, and had
resumed their previous level of physical activities on the final follow-up. Meticulous clinical examination and careful imaging
assessment could assist an early diagonosis in cases of traumatic lumbar spondylolisthesis. Performing open reduction and
the TLIF procedure as soon as possible could restore segmental stability and painless function. The TLIF procedure was a safe,
effective technique to treat traumatic lumbar spondylolisthesis. 相似文献
163.
Face recognition via adaptive image combination 总被引:1,自引:0,他引:1
于威威 《上海交通大学学报(英文版)》2010,15(5):600-603
Dimension reduction and manifold learning are the two most popular feature extraction methods. The two methods focus on spatial
locality as a guiding principle to find a low-dimensional basis for describing high-dimensional data, but no bases or features
are more spatially localized than the original image pixels. So, adaptive image combination is presented to represent a class
by a combined sample. The combined sample is a linear combination of original samples in the same class. Adaptive image combination
(AIC) find the best combination coefficients by minimizing the intrapersonal distance and maximizing the interpersonal distance.
Experimental results show that AIC is effective. 相似文献
164.
This paper establishes a link between an activity-based model for the Greater Toronto Area (GTA), dynamic traffic assignment,
emission modelling, and air quality simulation. This provides agent-based output that allows vehicle emissions to be tracked
back to individuals and households who are producing them. In addition, roadway emissions are dispersed and the resulting
ambient air concentrations are linked with individual time-activity patterns in order to assess population exposure to air
pollution. This framework is applied to evaluate the effects of a range of policy interventions and 2031 scenarios on the
generation of vehicle emissions and greenhouse gases in the GTA. Results show that the predicted increase of approximately
2.6 million people and 1.3 million jobs in the region by 2031 compared to 2001 levels poses a major challenge in achieving
meaningful reductions in GHGs and air pollution. 相似文献
165.
In an attempt to reduce CO2 emissions from motorized transport, the Taiwanese government introduced an idling stop policy for vehicles in early 2007.
This paper seeks to quantify the environmental benefits of the policy based on a stated preference analysis. Motorcyclists
were surveyed at urban intersections in Taiwan, to identify the amount of time they would be willing to turn off their engines
while waiting at traffic lights (the WTO). A contingent valuation framework based on stated preference questions was designed
to determine the WTO. Results obtained from the Spike model showed that the average motorcyclist’s WTO is 82 s. In another
analysis, in which other variables were taken into consideration, such as the possibility that the policy will be enacted
as legislation, the expected WTO increased to 101 s. In both cases, an idling stop policy would have positive environmental
effects, reducing gasoline usage by 1021 L per hour and reducing CO2 emissions by 0.56 metric tons per hour at the intersection studied during peak periods. 相似文献
166.
This paper seeks to improve our understanding of passengers’ behavioral intention by proposing an integrated framework from
the attitudinal perspective. According to the literature in marketing research, we establish a causal relationship model that
considers “service quality-satisfaction-behavioral intentions” paradigm, perceived value theory, and switching barrier theory.
Exploring passengers’ behavioral intention from satisfaction and perceived value help to understand how passengers are attracted
by the company, while switching barriers assist in realizing how passengers are “locked” into a relationship with the current
company. Furthermore, in order to capture the nature of service quality, we adopt a hierarchical factor structure which serves
service quality as the higher-order factor. In this study, coach industry is selected as our research subject. The empirical
results, as hypothesized, show that all causal relationships are statistically significant, and perceived value us the most
important predictor of satisfaction and passengers’ behavioral intention. In conclusion, the managerial implications and suggestions
for future research are discussed. 相似文献
167.
Statistical and dynamical analyses of propagation mechanisms of solitary internal waves in a two-layer stratification 总被引:2,自引:0,他引:2
Chen-Yuan Chen 《Journal of Marine Science and Technology》2011,16(1):100-114
The blocking effect of submarine ridges on the propagation of internal solitary waves (ISWs) over the topography of the seabed
results in the fission of the solitary waves that accompany the generation of reflected and transmitted waves. In this study,
multivariate analysis of variance (MANOVA) is used to investigate the inseparable relationship between the transmission and
reflection. An examination of the error sums of squares and cross-products (SSCP) matrix and the correction matrix shows that
the correlation between the transmission (at/ai) and reflection coefficients (ar/ai) is quite low (0.284). Moreover, from
multivariate testing, including Pillai’s trace, Wilks’ lambda, Hotelling’s trace and Roy’s largest root, we conclude that
the ridge height has a large effect (η = 0.456) on both the amplitude of the transmitted and reflected waves, as well as large (η = 0.411) and very large (η = 0.469) effects on the amplitudes of the transmitted and reflected waves, respectively. In conclusion, the results in the
present study highlight the importance of the role played by ridge height in coherent ISW transmission and reflection during
oceanic wave–ridge interactions. 相似文献
168.
Hirotada Hashimoto Naoya Umeda Akihiko Matsuda 《Journal of Marine Science and Technology》2011,16(4):448-461
The new intact stability criteria which are under development at the International Maritime Organization (IMO) are required
to cover a broaching phenomenon, well known as a great threat to high-speed vessels which can lead to capsizing. Some reports
exist which demonstrate that their numerical models can predict a highly nonlinear phenomenon of broaching. However, additional
validation studies are needed for unconventional vessels, in addition to conventional ones, to develop direct stability assessment
methods for the new intact stability criteria. In this research, we selected as the subject ship a wave-piercing tumblehome
vessel with twin screws and twin rudders, a design expected to be one of a new generation of high-speed monohull ships. Firstly,
a series of captive model tests were conducted to measure the resistance, the manoeuvring forces, the wave-exciting forces,
the heel-induced hydrodynamic forces, and the roll restoring variation for the unconventional tumblehome vessel. Secondly,
the existing mathematical model which had been developed for broaching prediction of conventional vessels with a single propeller
and a single rudder was extended to unconventional vessels with twin propellers and twin rudders. Finally, comparisons between
numerical simulations and the existing free running model experiments were conducted. As a result, it was demonstrated that
fair quantitative prediction of broaching is realised when the rudder force variation, the roll restoring variation and the
heel-induced hydrodynamic force for large heel angles are taken into account. 相似文献
169.
Parametric rolling prediction in irregular seas using combination of deterministic ship dynamics and probabilistic wave theory 总被引:1,自引:0,他引:1
Atsuo Maki Naoya Umeda Shigeaki Shiotani Eiichi Kobayashi 《Journal of Marine Science and Technology》2011,16(3):294-310
In recent years there have been reports of serious accidents of parametric rolling for modern container ships and car carriers.
For avoiding such accidents, a prediction method of parametric rolling in irregular seas is required. Since parametric rolling
is practically non-ergodic, repetitions of numerical simulations or experiments could be not feasible to ascertain the behaviour.
Therefore, in this paper, a method combining a stochastic approach with a deterministic approach in order to estimate the
probabilistic index without such simple repetitions is developed. The ship's response in regular seas is estimated by solving
an averaged system of the original 1-DoF roll model, and random waves necessary for occurrence of parametric rolling is achieved
by using Longuet-Higgins’s or Kimura’s wave group theory. As a result, a fast and robust computation method of the probabilistic
index is established. Finally, it is concluded that the proposed method is considered to be one of the useful tools for discussing
the new IMO Intact Stability Code. 相似文献
170.
Kazuhiro Iijima Kazuhiro Kimura Weijun Xu Masahiko Fujikubo 《Journal of Marine Science and Technology》2011,16(4):379-389
Dynamic collapse behavior of a ship’s hull girder in waves is investigated; post-ultimate strength behavior is the focus.
Firstly, a simulation method is proposed. Assuming that a plastic hinge is formed during the collapse of the hull girder,
the whole ship is modeled as two rigid bodies connected amidship via a nonlinear rotational spring. The post-ultimate strength
behavior, such as the reduction of load carrying capacity due to buckling and yielding, is reflected in the model. Hydrodynamic
loads are evaluated by using nonlinear strip theory to account for the effect of large plastic deformations on the loads.
A scaled model for validation of the simulation is designed and fabricated. Then a series of tank tests is conducted using
the scaled model to validate the simulation results. Post-ultimate strength behavior characteristics in waves are clarified
by using the numerical and tank test results. It is shown that the hull girder collapses rapidly after reaching ultimate strength,
and then the plastic deformation grows until unloading starts at the collapsed section. Finally, several parametric dependencies
of the extent of the collapse behavior are discussed based on a series of the simulations. 相似文献