全文获取类型
收费全文 | 1787篇 |
免费 | 163篇 |
国内免费 | 11篇 |
专业分类
财政金融 | 153篇 |
工业经济 | 176篇 |
计划管理 | 743篇 |
经济学 | 207篇 |
综合类 | 137篇 |
运输经济 | 43篇 |
旅游经济 | 11篇 |
贸易经济 | 260篇 |
农业经济 | 105篇 |
经济概况 | 124篇 |
信息产业经济 | 2篇 |
出版年
2024年 | 8篇 |
2023年 | 47篇 |
2022年 | 56篇 |
2021年 | 43篇 |
2020年 | 72篇 |
2019年 | 63篇 |
2018年 | 40篇 |
2017年 | 46篇 |
2016年 | 60篇 |
2015年 | 85篇 |
2014年 | 167篇 |
2013年 | 193篇 |
2012年 | 172篇 |
2011年 | 196篇 |
2010年 | 121篇 |
2009年 | 68篇 |
2008年 | 115篇 |
2007年 | 94篇 |
2006年 | 63篇 |
2005年 | 51篇 |
2004年 | 37篇 |
2003年 | 39篇 |
2002年 | 23篇 |
2001年 | 28篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1991年 | 4篇 |
排序方式: 共有1961条查询结果,搜索用时 15 毫秒
1.
为了提高双离合变速器在车辆上的换挡品质,提升电气化换挡执行机构的工作效率,给出执行机构性能与换挡品质评价准则;通过两种不同双离合变速器电控电动执行机构的工作原理与性能分析,基于MATLAB数值仿真方法优化出最高效率进行试验.基于车辆6个维度的换挡工况对二者所搭载的变速器分别进行试验与CAN线数据采集,对比研究两种机构优缺点,通过雷达图的方式进行优劣说明.结果表明,两种执行机构传动效率可达70%且换挡品质相当.可见Tip in tip out工况对二者要求最为严格. 相似文献
2.
《Journal of Retailing》2022,98(2):277-293
This research examines how consumers’ intentions to purchase food change depending on the visualisation mode (3D vs. AR) and product format (served vs. packaged). In three studies, we demonstrate that mental simulation of eating experiences (process and outcome) mediate these effects. Study 1 shows that AR visualisation of a served food improves simulation of the eating process over 3D visualisation, with a positive effect on purchase intention. Study 2 reveals that 3D visualisation improves purchase intention for packaged products (high instrumental properties) over served products (low instrumental properties) while the opposite is true for AR visualisation. In addition, interactivity and immersion mediate the effects of 3D (vs. AR) on mental simulation of the eating process for packaged products. Study 3 extends these results by showing that 3D increases purchase intention by eliciting mental simulation of the eating outcome, when the food is visible due to transparent (vs. opaque) packaging (displaying both sensory and instrumental properties), but that no such differences emerge for AR. This research highlights the importance of using different visualisation modes to promote food depending on the product format. The findings have important implications for both offline and online retailers. 相似文献
3.
In the context of personal income tax (PIT) reform in China in 2018, this paper examines some of the major issues of concern regarding the reform and income distribution. Using the China Personal Income Tax Micro‐simulation model, the paper compares the differences between the 2011 and 2018 PIT systems, and finds that residents relying on different income sources may face a large degree of real tax rate change. Once the tax system is altered to PIT 2018, the coverage of PIT for wage earners will decrease from 46.9 to 23.4 percent, the income redistributive effect will drop from 1.95 to 1.22 percent and the PIT's role in fiscal revenue will also be negatively affected. Nevertheless, if individual income continues to grow, the share of PIT in fiscal revenue is expected to return to the 2018 level in 2022, but its income redistribution function is difficult to recover in the short term. The paper finds that the effect of PIT on income distribution depends on the tax structure. Gradual transition to an “entirely comprehensive” tax system when conditions are appropriate will achieve better income redistribution results at a lower average tax rate. 相似文献
4.
Jaehyun So Nassim Motamedidehkordi Yingjie Wu Fritz Busch Keechoo Choi 《International Journal of Sustainable Transportation》2018,12(4):286-298
This study proposes an integrated simulation approach, which consists of a microscopic traffic simulation model, a vehicle dynamics model, and an emission estimation model, in order to estimate emissions based on more reliable vehicle performance measures. The vehicle performance measures such as engine power and engine speed significantly relate to the amount of emissions, and road curvatures and inclinations are the core inputs affecting these vehicle performance measures. Therefore, providing reliable vehicle performance measures reflecting the road geometric attributes is critical for a reliable emission estimation. This study proposes to use the microscopic traffic simulation model for generating vehicle trajectories, which is advantageous in modeling various traffic situations, and the vehicle dynamics model for producing the vehicle performance measures based on the vehicle trajectories. Finally, the outputs from the vehicle dynamics model are fed into the emission estimation model to compute emission measures. This study conducted a case-study using two road sections, one is a hypothesized road section, including various curvatures and inclinations with regular variations, and the other is a Kesselberg road section, which is an actual geometry in Bayern, Germany. The emission measures are estimated in these case-study road sections using both an existing simulation approach and the proposed integrated simulation approach. The difference between these two emission estimation approaches is discussed in terms of the emission measures, including fuel consumption, nitrogen oxides, and particulate matters. 相似文献
5.
[目的]探讨经济发达地区土地利用变化时空规律,为城市发展提供合理土地利用政策,同时优化土地利用结构以支持经济可持续发展。[方法]通过遥感影像获取长时间序列的土地利用数据,探讨近30多年来绍兴市的土地利用变化,进一步利用土地利用动态变化模型,对绍兴市土地利用变化过程、趋势、变化轨迹进行了深入分析。[结果](1)绍兴市土地利用在1980~2000年相对稳定,在2000年后变化强度逐年增强,2005~2015年土地利用转化量增多和类型多样。绍兴市东北部平原和县区核心区域是经济发达地区土地利用变化的活跃区域,主要是其他类型土地向建设用地转移;(2)1980~2015年绍兴市土地利用变化轨迹主要受到人口增长和GDP增长的影响。[结论]城市化的发展和人口的迅速增长,使城市人口和土地面积迅速增加,造成城市边缘的农业用地转化成了建设用地。经济的发展、科技的进步及政府政策的制定,改变了人们的生活和工作方式,进而影响土地利用类型。 相似文献
6.
Reinhard Sellmair Tom Schelo 《International Journal of Sustainable Transportation》2019,13(7):479-496
Replacing conventional vehicle taxis with electric vehicles would be an efficient measure to reduce greenhouse gas emissions. Due to the limited range and long charging times of current battery electric vehicles, it is of utmost importance to provide sufficient charging facilities. This article analyses the impact of the placement and charging power of charging stations on potential mileage and revenue of electric taxis on the example of Singapore. Therefore, we developed an agent-based electric taxi simulation model to investigate electric taxis’ driving profiles with respect to different vehicle types and charging infrastructure designs. This model is also capable of simulating conventional taxi driving profiles. The validation of these simulation results with real taxi data showed that the model is reproducing taxi driving profiles with high accuracy in great detail. We found out that electric taxis could reach the same mileage and revenue as conventional taxis if charging with a power of 160?kW is possible. Furthermore, we discovered that waiting times for available charging stations have a stronger effect on revenue than the length of detours to reach charging stations. Based on these findings, we concluded that it is more important to reduce waiting times by placing sufficient numbers of charging stations at each location before expanding the charging network by installing small numbers of charging stations at many locations. 相似文献
7.
针对空战目标识别中机型自动识别比较困难的问题,提出了采用航迹特征的智能目标识别方法。利用卷积神经网络(Convolutional Neural Network,CNN)分层学习特征的能力,训练CNN算法模型自动地从航迹数据中学习有用的特征并分类。利用沿海实地采集的15个类别的飞机航迹数据,经一系列数据预处理后作为智能识别算法的训练和测试数据,在验证实验中描述了算法网络的相关配置,对比了CNN与其他分类器的识别结果。实验结果表明,CNN具有很好的识别性能。 相似文献
8.
Marcin Maleszka 《Enterprise Information Systems》2019,13(7-8):1120-1142
ABSTRACTWe present a group dynamics model that shows knowledge integration as a process occurring over time. As each individual in the group contact others, his own knowledge changes, and over time the collective knowledge is obtained. This allows modeling knowledge diffusion in a social network and while the models presented in this paper are not competitive in that area, they approach the problem from previously unconsidered direction. We test the behavior of the model in a multi-agent simulation and we test a simple advertisement campaign in a social network. We provide discussion of elements needed for making model more competitive. 相似文献
9.
10.
The credit risk contagion of Internet peer-to-peer (P2P) lending platforms is an important part of Internet financial risk management and supervision. This study analyzes the contagion path of credit risk in Internet P2P lending. Based on complex network theory and the theory of infectious disease dynamics, the characteristics of Internet P2P lending development are combined to construct a SEIR model of credit risk transmission among Internet P2P lending platforms with time lag, and the robustness of the model is analyzed and proven. The influence of platform correlations, the susceptible immune rate, the platform elimination rate, contagion latency, the saturation coefficient, and the susceptibility input rate on credit risk contagion behavior among Internet P2P lending platforms is analyzed, using the equilibrium point and threshold value. The impact of each variable is analyzed by simulation. Corresponding countermeasures and suggestions are proposed to prevent and control credit risk contagion among these platforms. 相似文献