首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   79560篇
  免费   5220篇
  国内免费   181篇
财政金融   6087篇
工业经济   3474篇
计划管理   18498篇
经济学   13455篇
综合类   15585篇
运输经济   482篇
旅游经济   1254篇
贸易经济   10134篇
农业经济   5372篇
经济概况   10617篇
信息产业经济   3篇
  2024年   18篇
  2023年   788篇
  2022年   1049篇
  2021年   1473篇
  2020年   1899篇
  2019年   1219篇
  2018年   1123篇
  2017年   1337篇
  2016年   1446篇
  2015年   2049篇
  2014年   5062篇
  2013年   5546篇
  2012年   6808篇
  2011年   8877篇
  2010年   6691篇
  2009年   5653篇
  2008年   6271篇
  2007年   5850篇
  2006年   5763篇
  2005年   4161篇
  2004年   2988篇
  2003年   2443篇
  2002年   1572篇
  2001年   1410篇
  2000年   942篇
  1999年   459篇
  1998年   254篇
  1997年   244篇
  1996年   172篇
  1995年   99篇
  1994年   81篇
  1993年   95篇
  1992年   61篇
  1991年   42篇
  1990年   53篇
  1989年   30篇
  1988年   23篇
  1987年   15篇
  1986年   17篇
  1985年   185篇
  1984年   201篇
  1983年   145篇
  1982年   104篇
  1981年   58篇
  1980年   75篇
  1979年   47篇
  1978年   37篇
  1977年   23篇
  1975年   1篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
This paper examines the cost structures of the leading integrated air cargo carriers, FedEx Express and UPS Airlines. A total cost model is estimated for the two carriers using quarterly data on domestic operations and costs over a nine-year period (2003–2011). The estimated model indicates that the integrated industry exhibits increasing returns to traffic density and constant returns to scale. Accounting for carrier-specific differences in cost structure and network size, FedEx Express is found to be more cost-efficient than UPS Airlines. Looking at the carriers individually, UPS Airlines exhibits substantial economies of traffic density and constant returns to scale while FedEx Express' cost structure is characterized by weak economies of density and constant returns to scale. The combined effect of returns to density and returns to scale on the cost structures of integrated carriers is captured by economies of size. Both FedEx Express and UPS Airlines exhibit economies of size, indicating that carriers in the integrated industry can be more cost efficient by making appropriate adjustments to their network size as their output grows. Moreover, the relative cost-efficiencies of the carriers are reversed when their network-size differences are not controlled.  相似文献   
2.
Methods for the road network design problem, typically, are based on optimization of the network efficiency measures (e.g. network-wide travel time) under a predefined budget. In these approaches, equity issues are not taken into account and, consequently, most of the road improvements are planned next to large cities. Thus, disparities between large and small cities increase, which does not conform to sustainable development objectives. In this paper, to overcome concerns associated with traditional methods, equity is incorporated into the interurban road network design problem. To this end, accessibility concepts are employed. However, unlike previous studies, instead of maximizing the total accessibility, a new definition is proposed for inaccessibility, and total inaccessibility is minimized throughout the network. Using this new definition not only is more compatible with the equity issue, but also helps to eliminate the nonlinearity of the problem. Average travel time to neighboring opportunities is utilized to propose this definition for inaccessibility, which captures the reality more effectively. With the aim of this definition, equity is incorporated into the road network design problem implicitly. This is another improvement over previous methods, where a new term in the objective function or a new constraint is added to include the equity. The proposed model is formulated as a mixed integer linear programming (MILP) problem, where the objective is to minimize the aggregate inaccessibility over all the population centers in the network. To illustrate the application of the model, the Northwest region of the United States is used as the case study. The respective exact solution of the example is found using a commercial solver (CPLEX). This new solution is also compared with the solutions from the traditional methods.  相似文献   
3.
This article studies a container drayage problem with flexible orders defined by using requiring and releasing attributes as a unified formulation of various order types. A determined-activities-on-vertex (DAOV) graph introduces a temporary vertex set to formulate different truck statuses. The problem is formulated as a mixed-integer nonlinear programming model based on the DAOV graph. Four strategies including a window partition based (WPB) strategy are presented and evaluated extensively to solve the problem. Results indicate that the WPB method could solve the problem effectively and efficiently. Furthermore, this method is robust considering the operating time biases compared to other algorithms.  相似文献   
4.
This paper describes an integrated model that jointly optimizes the strategic and tactical decisions of a closed-loop supply chain (CLSC). The strategic level decisions relate to the amounts of goods flowing on the forward and reverse chains. The tactical level decisions concern balancing disassembly lines in the reverse chain. The objective is to minimize costs of transportation, purchasing, refurbishing, and operating the disassembly workstations. A nonlinear mixed integer programming formulation is described for the problem. Numerical examples are presented using the proposed model.  相似文献   
5.
HPLC 法测定豆腐黄浆水中有机酸质量浓度   总被引:1,自引:0,他引:1  
建立利用反相高效液相色谱法同时快速的测定豆腐黄浆水中柠檬酸、苹果酸、酒石酸、草酸、富马酸、琥珀酸6种有机酸的方法.采用Agilent Eclipse XDB-C18色谱柱;紫外检测器,检测波长为210 nm;流动相为甲醇∶0.01 mol/L KH2PO4-H3PO4缓冲溶液(3∶97,pH值为2.85);流速为0.8 mL/min;柱温为25℃;进样量为20μL.在最佳色谱条件下,柠檬酸、苹果酸、草酸等6种有机酸能同时、快速的分离.线性相关系数r>0.9824,检出限为0.5558~1.2948μg/mL,相对标准偏差0.13%~4.2%,该方法具有分析速度快,重现性好,精密度高,定量准确等特点.适用于豆腐黄浆水中有机酸的定量分析,对黄浆水开发利用有重要意义.  相似文献   
6.
为了探索适合高职学生学习特点的教学方法,提高教学质量,本文就研学结合教学理念的内涵、实施路径、特征和目的进行了探索和研究,并在微观经济学课程中进行试验。结果显示教学效果良好,教学质量得到提升,学生的学习兴趣得以提高,主动参与的积极性增加,培养了学生分析问题和解决问题的能力,为专业训练和实践打好基础。论文最后就研学结合教学理念在微观经济学课程实施中存在的问题进行了剖析,并提出了进一步探索和努力地方向。  相似文献   
7.
物流配送“最后一公里”是个复杂系统,具有不确定性,已经成为影响京城物流行业发展的瓶颈.“最后一公里”配送是物流活动得以顺畅进行的根本保证,是京城物流发展的重要环节之一.如今在物流配送末端相对滞后的情况下,物流成本不断增加,而“最后一公里”又是导致物流成本上升的主要因素,一方面,在短时间内物流的末端配送难以摆脱对成本的控制,另一方面,高额的人力资源制约着物流行业利润上升空间.本文运用复杂系统理论,并结合物联网信息技术对物流配送“最后一公里”中存在的问题提出对策及实施方案,期望对京城物流行业的发展有所裨益.  相似文献   
8.
新兴商业模式的出现,对物流模式创新提出了前所未有的挑战.本文通过分析第三方物流、连锁物流等传统物流的困境和挑战,对在零售变革时代大背景下,对物流产业创新进行了探索.  相似文献   
9.
教育本该不一样,因材施教、有教无类,说的就是不同。教育不从根本上由“批发”改为“零售”,我们就培养不出创新人才、杰出人才,甚至于培养不出我们常说的有用人才。为了培养创新人才,教育内容要力求全面,教育目标要力求明确,教育的方法要务求得当。  相似文献   
10.
We construct and compare three distinct measures of household asset wealth that complement traditional income‐ or expenditure‐based measures of socioeconomic status. We apply these measures to longitudinal household survey data from China and demonstrate that household asset wealth has been increasing over time, a theme consistent with many previous studies on the process of development in China. Unlike other studies that have shown rising income inequality over time, however, we show that asset wealth inequality has actually been declining in recent years, indicating widespread participation in the benefits of economic reforms. Furthermore, the evolution in the cumulative distribution of household welfare is such that social welfare has been increasing with the passage of time, despite rising inequality in the early years of the survey.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号