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   131篇
  免费   67篇
化学   3篇
综合类   7篇
数学   176篇
物理学   12篇
  2023年   1篇
  2022年   20篇
  2021年   18篇
  2020年   15篇
  2019年   17篇
  2018年   8篇
  2017年   12篇
  2016年   10篇
  2015年   3篇
  2014年   12篇
  2013年   9篇
  2012年   12篇
  2011年   4篇
  2010年   5篇
  2009年   5篇
  2008年   8篇
  2007年   6篇
  2006年   5篇
  2005年   8篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   4篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1990年   1篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
排序方式: 共有198条查询结果,搜索用时 140 毫秒
41.
企业职工养老基金的收支平衡,关系到社会稳定和向老龄化社会的顺利过渡.利用微分方程、高阶函数建立了预测远期社会平均工资及职工在职时的工资模型,并经分析对比,选用与实际吻合较好的模型,以3种年龄段为例,计算分析了它们的养老金、替代率、收支等情况.结果表明:职工年平均工资高、退休年龄迟于60岁、缴费年数多于20年,则替代率高,能接近目标值;若基础养老金按现收现付方式管理,且按目前法定年龄退休,则缺口较大.因此,要从政策与管理等多方面采取有效措施,保障养老金保险制度顺利实施.  相似文献   
42.
依据一个经济时期内能源需求、能源供应和政府调控之间相互依存、相互制约的演化关系为背景建立了一个新的能源供需模型.模型中引入市场自身调节的闽值,政府调控的阈值,政府调控对能源需求和能源供应的影响系数等参数,通过参数的调整,分析了政府调控在能源供需中的作用.通过平衡点稳定性、系统的耗散性、Lyapunov指数谱等的分析,研究了系统的基本动力学行为,利用数值模拟的方法给出了系统的动力演化行为;给出了模型中参数估计的方式,对模型所反映的现实意义进行了解释,给出了数值模拟结果,验证了理论分析的正确性.  相似文献   
43.
建立了一个考虑税收腐败和公共支出腐败的经济增长模型,从理论上探讨财政腐败行为及其影响.主要结论归纳:第一,财政腐败降低私人资本的回报率,使厂商的生产力下降,就整体而言阻碍了经济增长.第二,最优税率可能大于或小于Barro的最优税率,取决于征税效率和寻租引发的行政成本,第三,两种类型的公共支出隐含着不同程度的腐败机会,以...  相似文献   
44.
Japan’s National Project for Earthquake Prediction has been conducted since 1965 without success. An earthquake prediction should be a short-term prediction based on observable physical phenomena or precursors. The main reason of no success is the failure to capture precursors. Most of the financial resources and manpower of the National Project have been devoted to strengthening the seismographs networks, which are not generally effective for detecting precursors since many of precursors are non-seismic. The precursor research has never been supported appropriately because the project has always been run by a group of seismologists who, in the present author’s view, are mainly interested in securing funds for seismology — on pretense of prediction. After the 1995 Kobe disaster, the project decided to give up short-term prediction and this decision has been further fortified by the 2011 M9 Tohoku Mega-quake. On top of the National Project, there are other government projects, not formally but vaguely related to earthquake prediction, that consume many orders of magnitude more funds. They are also un-interested in short-term prediction. Financially, they are giants and the National Project is a dwarf. Thus, in Japan now, there is practically no support for short-term prediction research. Recently, however, substantial progress has been made in real short-term prediction by scientists of diverse disciplines. Some promising signs are also arising even from cooperation with private sectors.  相似文献   
45.
We study the operational implications from competition in the provision of healthcare services, in the context of national public healthcare systems in Europe. Specifically, we study the potential impact of two alternative ways through which policy makers have introduced such competition: (i) via the introduction of private hospitals to operate alongside public hospitals and (ii) via the introduction of increased patient choice to grant European patients the freedom to choose the country they receive treatment at. We use a game-theoretic framework with a queueing component to capture the interactions among the patients, the hospitals and the healthcare funders. Specifically, we analyze two different sequential games and obtain closed form expressions for the patients’ waiting time and the funders’ reimbursement cost in equilibrium. We show that the presence of a private provider can be beneficial to the public system: the patients’ waiting time will decrease and the funders’ cost can decrease under certain conditions. Also, we show that the cross-border healthcare policy, which increases patient mobility, can also be beneficial to the public systems: when welfare requirements across countries are sufficiently close, all funders can reduce their costs without increasing the patients’ waiting time. Our analysis implies that in border regions, where the cost of crossing the border is low, “outsourcing” the high-cost country’s elective care services to the low-cost country is a viable strategy from which both countries’ systems can benefit.  相似文献   
46.
政府补贴方式下排放许可交易生产优化   总被引:1,自引:0,他引:1  
从学术上探讨了政府补贴方式下有排放许可交易的生产优化问题.分析了配额和补贴方式效果在管理上的差异,给出了补贴方式下的各经济核算关系及模型,给出了最低净化水平定理的证明;给出优化计算,求解了最优净化水平,并探讨了其与最优产量和企业最优收益间的关系;给出仿真计算,并对企业生产在这种支持方式下的优化管理进行了分析.研究表明:企业将对生产中产生的全部排放物进行相同净化水平α的处理时,所需要的处理费用最低;在线性反需求函数下,最优产量的变化量只与净化成本函数、排放交易价格、补助价格等几个量相关,最优收益与最优产量的平方成正比.  相似文献   
47.
This paper attempts to measure the efficiency of provinces in the Philippines in utilizing public resources for health and education where only 1% of the total budget is spent for health and 3% is allocated for education. With such budget constraints, it is important to examine the efficiency of spending on social services as small changes can have a major impact in achieving the Millennium Development Goals. Efficiency is defined as the deviation from the frontier which represents the maximum output attainable from each input level. This efficiency frontier is estimated using the data envelopment analysis, free disposal hull and Malmquist-DEA. We use expenditures for social services for input and primary and secondary enrollment rates, literacy rate per province, and life expectancy for outputs. An analysis of efficiency scores shows that provinces where the level of inequality is higher (as measured by the Gini coefficient) as well as those who receive a larger portion of their budget as grants are among the least efficient. This research can help in the budget allocation and rationalization among Philippine provinces.  相似文献   
48.
张健  廖梦洁  齐林 《运筹与管理》2019,28(7):133-143
服务化转型是传统制造企业实现向价值链两端高收益空间演化的重要驱动,却受到转型成本高、转型难度大等多重阻碍。推动制造业服务化政策设置的合理与否,关乎制造企业产业优化升级的成败。本文以由有限理性的寡头与一般企业组成的传统制造集群为研究对象,依据演化博弈理论建立了政府差异化激励条件下集群服务化转型策略的演化博弈模型,利用可视化系统仿真演释了制造集群寡头企业群体与一般企业群体的服务化策略选择过程。研究表明,政策激励设置的合理性直接影响制造集群服务化转型升级的成败,政策制定者应避免陷入无法使制造企业选择服务化策略的政策困境。本文为制造集群服务化激励水平的设定提供了理论依据和解决思路。  相似文献   
49.
为推动城市开发与基础设施建设,满足城市新增人口的公共服务需求,地方隐性债务规模快速增长,经济下行加剧了地方政府所面临的债务风险。利用2007—2018年我国285个地级市隐性债务数据,采用固定效应模型,从债务规模与发债主体特征两个视角评估隐性债务对城市空间扩张的驱动机制。主要结论有:(1)隐性债务规模对城市空间扩张有显著正向影响,上期隐性债务规模的增加将推动当期城市建成区扩张。发债规模增加1亿元,城市建成区面积增加0.192 km2,“借债建城”成为地方政府推动城市空间扩张的主要模式。(2)发债企业数和发债企业质量对城市空间扩张有显著正向影响,发债企业数增加,且信用评级为AA+及以上,发债主体的比例提高推动城市建成区面积的增加。信用等级高的发债企业越多,城市扩张能力越强。(3)发债企业数对城市空间扩张的影响存在区域异质性,发债企业数对中西部地区的城市空间扩张具有显著正向影响,对东部地区则无显著影响。  相似文献   
50.
一种包含递归的核回归估计的回归预测模型   总被引:1,自引:0,他引:1  
本文首先构造了包含递归的核回归的回归模型 ,然后将其应用于湖南省城镇居民消费性支出 ,提高了拟合度 ,减少了预测误差  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