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991.
Since cargo capacity increases faster than fuel consumption, the significantly larger capacity fleets which will accompany expansion of the Panama Canal will introduce additional fuel economies and cost savings. Enabling larger, more fuel-efficient vessels to carry cargo the entire distance from Asia to US east-coast ports allows vessel operators to realize significant and meaningful savings compared with the alternatives of using smaller Panamax vessels for the whole distance, or sending the cargo over the US land bridge by train or truck. Fuel savings are quantified along with the monetary savings based on various assumptions for the price of fuel. These savings are dramatic and will increase directly with the price of crude petroleum. Finally, microeconomic theory is deployed to determine how cost savings will be distributed between shipping customers and vessel operators. 相似文献
992.
Successful co-deposition of fine particulate matter within an Electroless Nickel-Phosphorous (ENi-P) matrix is dependent on various factors like bath composition, particle compatibility with metallic matrix, bath reactivity (pH), particle size and their distribution. ENi-P deposits incorporating Al2O3/Alumina in a disperse phase have varied effects on properties and attributes like surface roughness (Ra), microhardness, wear resistance, corrosion resistance and surface morphology of the deposits obtained. This paper experimentally investigates the effect of alumina (1.55 g/L) on Ra, microhardness, surface morphology, deposition rate, wettability, wear resistance and corrosion resistance of ENi-P-Al2O3 composite deposits on mild steel substrates at bath pH 5, 7 and 9. Study reveals that optimum deposit parameters and deposition rates are achieved with bath pH. However, not much study has been undertaken concerning composite deposits obtained from higher bath pH or basic bath. This is attributable to the fact that at higher bath pH or alkaline baths, the bath gets unstable and eventually degrades or decomposes, thereby resulting in sub optimal or poor deposition. Hence, experimental investigations carried out by preparing suitable baths, operating under optimum conditions, and enabling successful composite deposition in acidic and alkaline baths have revealed that there is a significant improvement in the above mentioned properties of the as-deposited composite deposits, as the pH is increased from pH 5 to pH 9. This aspect can therefore be advantageously utilized for preparing various marine components like fasteners, nuts, bolts, washers, pipes, cables, components having relative motion etc. 相似文献
993.
Optimal toll design from a network reliability point of view is addressed in this paper. Improving network reliability is proposed as a policy objective of road pricing. A reliability‐based optimal toll design model, where on the upper level network performance including travel time reliability is optimized, while on the lower level a dynamic user‐equilibrium is achieved, is presented. Road authorities aim to optimize network travel time reliability by setting tolls in a network design problem. Travelers are influenced by these tolls and make route and trip decisions by considering travel times and tolls. Network performance reliability is analyzed for a degradable network with elastic and fluctuated travel demand, which integrates reliability and uncertainty, dynamic network equilibrium models, and Monte Carlo methods. The proposed model is applied to a small hypothesized network for which optimal tolls are derived. The network travel time reliability is indeed improved after implementing optimal tolling system. Trips may have a somewhat higher, but more reliable, travel time. 相似文献
994.
Despite the widespread use of synthetic data in discrete choice analysis, little is known about how the methodology used to
generate synthetic datasets influences the properties of parameter estimates and the validity of results based on these estimates.
That is, there are two potential sources of biases when using synthetic discrete choice data: (1) bias due to the method used
to generate the dataset; and, (2) bias due to parameter estimation. The primary objective of this study is to examine bias
due to the underlying data generation method. This study compares three methods for generating synthetic datasets and uses
design of experiments and analysis of variance methods to investigate the ability to recover estimates for “true” logsum parameters
for nested logit models. The method that uses nested logit probabilities to generate the chosen alternative results in unbiased
parameter estimates. The method that is based on Gumbel error component approximations reveals that while the error components
themselves are unbiased, subtle empirical identification problems can arise when these error components are combined with
synthetically generated utility functions. The method that is based on normal error component approximations reveals that
all logsum coefficients are biased upwards; the bias dramatically increases for those nests that have a low choice frequency
and is most pronounced for those nests with high correlations among alternatives. Based on the results of the analysis, several
recommendations for the generation of synthetic datasets for discrete choice analyses are provided. 相似文献
995.
Modeling the interaction between the built environment and travel behavior is of much interest to transportation planning
professionals due to the desire to curb vehicular travel demand through modifications to built environment attributes. However,
such models need to take into account self-selection effects in residential location choice, wherein households choose to
reside in neighborhoods and built environments that are conducive to their lifestyle preferences and attitudes. This phenomenon,
well-recognized in the literature, calls for the specification and estimation of joint models of multi-dimensional land use
and travel choice processes. However, the estimation of such model systems that explicitly account for the presence of unobserved
factors that jointly impact multiple choice dimensions is extremely complex and computationally intensive. This paper presents
a joint GEV-based logit regression model of residential location choice, vehicle count by type choice, and vehicle usage (vehicle
miles of travel) using a copula-based framework that facilitates the estimation of joint equations systems with error dependence
structures within a simple and flexible closed-form analytic framework. The model system is estimated on a sample derived
from the 2000 San Francisco Bay Area Household Travel Survey. Estimation results show that there is significant dependency
among the choice dimensions and that self-selection effects cannot be ignored when modeling land use-travel behavior interactions. 相似文献
996.
Scrutinizing individuals’ leisure-shopping travel decisions to appraise activity-based models of travel demand 总被引:1,自引:0,他引:1
Diana Kusumastuti Els Hannes Davy Janssens Geert Wets Benedict G. C. Dellaert 《Transportation》2010,37(4):647-661
Activity-based models for modeling individuals’ travel demand have come to a new era in addressing individuals’ and households’
travel behavior on a disaggregate level. Quantitative data are mainly used in this domain to enable a realistic representation
of individual choices and a true assessment of the impact of different Travel Demand Management measures. However, qualitative
approaches in data collection are believed to be able to capture aspects of individuals’ travel behavior that cannot be obtained
using quantitative studies, such as detailed decision making process information. Therefore, qualitative methods may deepen
the insight into human’s travel behavior from an agent-based perspective. This paper reports on the application of a qualitative
semi-structured interview method, namely the Causal Network Elicitation Technique (CNET), for eliciting individuals’ thoughts
regarding fun-shopping related travel decisions, i.e. timing, shopping location and transport mode choices. The CNET protocol
encourages participants to think aloud about their considerations when making decisions. These different elicited aspects
are linked with causal relationships and thus, individuals’ mental representations of the task at hand are recorded. This
protocol is tested in the city centre of Hasselt in Belgium, using 26 young adults as respondents. Response data are used
to apply the Association Rules, a fairly common technique in machine learning. Results highlight different interrelated contexts,
instruments and values considered when planning a trip. These findings can give feedback to current AB models to raise their
behavioral realism and to improve modeling accuracy. 相似文献
997.
Ron N. Buliung Kalina Soltys Randy Bui Catherine Habel Ryan Lanyon 《Transportation》2010,37(6):849-873
Fluctuating fuel prices, rising congestion, longer commutes, and related environmental and human health effects have combined
to once more draw the interest of governments, commuters, and firms toward the concept of travel demand management (TDM).
While TDM is not new, the proliferation of mobile telephony, fixed Internet, and associated applications has created fresh
prospects for the implementation of commuter focused TDM strategies. One recent example is Carpool Zone, an on-line carpool-matching
tool deployed and managed by the TDM group at Metrolinx, the regional transportation planning agency within Canada’s largest
metropolitan region, the Greater Toronto and Hamilton Area. Using data provided by Metrolinx, this paper broadens current
thinking on carpool formation and use. The main hypothesis guiding this work is that the carpool formation and use process
is sensitive to personal and household characteristics, space, time, travel cost, and workplace TDM policies. Results from
a logistic regression analysis suggest that geographical proximity to other users; workplace TDM policies; the scheduling
of work; and commuter role preference increase the odds of successfully carpooling. Importantly, findings regarding the positive
influence of workplace TDM policies suggest that Internet based TDM tools will likely require critically important investment
in human capital at the back-end to ensure program participation. 相似文献
998.
The application of social marginal cost pricing (SMCP) in PPP's in the railway sector faces several challenges. We examine in detail the practical applicability of SMCP in railway PPPs from the perspectives of cost accounting and effectiveness of SMCP towards the allocative efficiency goal, addressing the likely drawbacks in conciliating the welfare objectives of SMCP with the objectives of project financing (cost recovery) and value for money that justify the realization of PPP's. To this end, we combine theoretical analysis with the observation of empirical results of a case study. We split the analysis per type of private service provision, which can be for service operation or infrastructure management. For infrastructure management, we recommend splitting the operator remuneration and the track access charges. For service operation, we argue that the correct decision on source of funding of the service operator should depend on the characteristics of the contract. 相似文献
999.
The maximum specific sludge activity of granular sludge from large-scale UASB, IC and Biobed anaerobic reactors were investigated by batch tests. The limitation factors related to maximum specific sludge activity (diffusion, substrate sort, substrate concentration and granular size) were studied. The general principle and procedure for the precise measurement of maximum specific sludge activity were suggested. The potential capacity of loading rate of the IC and Biobed anaerobic reactors were analyzed and compared by use of the batch tests results. 相似文献
1000.
在对高尔夫A4型轿车行李箱盖的使用材料性能进行实验研究的基础上,建立了三维数学模型,利用I-deas工程软件对其有限元计算,计算与实验结果相吻合.并通过对不同应用材料的有限元计算结果的分析,为生产厂家合理选材和正确使用材料提供了较准确的计算前提. 相似文献