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   282篇
  免费   12篇
财政金融   29篇
工业经济   25篇
计划管理   126篇
经济学   31篇
综合类   14篇
运输经济   6篇
旅游经济   1篇
贸易经济   29篇
农业经济   14篇
经济概况   19篇
  2023年   10篇
  2022年   3篇
  2021年   11篇
  2020年   5篇
  2019年   8篇
  2018年   5篇
  2017年   14篇
  2016年   7篇
  2015年   24篇
  2014年   40篇
  2013年   22篇
  2012年   28篇
  2011年   28篇
  2010年   14篇
  2009年   12篇
  2008年   8篇
  2007年   9篇
  2006年   11篇
  2005年   5篇
  2004年   4篇
  2003年   3篇
  2002年   1篇
  2001年   3篇
  2000年   1篇
  1999年   5篇
  1998年   3篇
  1997年   2篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
排序方式: 共有294条查询结果,搜索用时 15 毫秒
1.
Agricultural applications of nanotechnology are at a relatively early stage and little is known about consumer responses to the technology. Canadian consumer responses to food nanotechnology are examined through the lens of the Food Value Scale. Data from a survey of Canadian consumers are used to evaluate the relative importance of eleven food values to food purchase decisions. We find that taste, safety, nutrition, and price are among the most important food values to Canadians, however, consumers exhibit considerable heterogeneity with respect to the priority placed on these values. A discrete choice experiment (DCE) explores the effect of food values on choice behavior. The DCE is positioned as a sliced apple product with non-browning and antioxidant-enhanced features introduced through the use of nanocoating or a conventional coating method. Random parameters logit (RPL) and latent class models (LCM) confirm the existence of significant preference heterogeneity. The LCM identifies three classes of consumers: “supporters,” “doubters,” and “opponents” who differ in their reaction to nanotechnology and in the relative importance placed on food values such as naturalness, novelty, and convenience. The analysis shows that food values provide additional insights into consumers’ food choices and their attitudes toward novel food technologies.  相似文献   
2.
碳酸盐岩储层岩性组成复杂,仅仅依靠少量的岩心、岩屑和几条常规的测井曲线资料很难准确地展现储层岩性的纵向及横向分布特征,从而影响对储层空间分布的预测。本文以上余家坝石炭系石炭系地层的岩心、岩屑录井资料为分析样本,结合对应的常规测井资料并对其进行数学处理,处理后共有12个参数供逐步判别函数筛选,经过多次的引入与剔除,建立了各类岩石的判别函数。其中灰岩、灰质云岩、云岩选择了9个参数;云质灰岩选择了10个参数。将岩性判别结果与取心井段的岩性对照,每类岩性的判别符合率都在85.39%以上,综合符合率为91.49%。说明本方法对目的层段碳酸盐岩储层岩性的识别是可行的。  相似文献   
3.
王龙  陶晓杰  李龙胜 《价值工程》2015,(10):153-154
文章以断面法在胶东某金矿的应用为例,对断面法计算储量进行了详细的介绍。实例说明断面法是一种应用比较方便的储量计算方法,也能保证计算精度。分析总结断面法的优缺点,并从理论上分析了储量计算误差来源及储量计算的精度。  相似文献   
4.
结合本矿的开采技术条件,拟选用砂浆锚索进行预加固。该支护方式能通过砂浆、杆体把岩体连成一体,从而提高了顶板的稳定性,可以有效的防治冒落。被加固矿岩与钢绞线通过水泥砂浆结合成稳固的整体,借助杆体的悬吊作用,来提高采场顶板的岩体稳定性,从而为回采提供安全的作业环境。  相似文献   
5.
In the conventional economic wisdom, the notion of unique equilibria that are efficient and Pareto optimal dominates the modeling discourse. Hebert Simon proposed an alternative analytical framework where the notion of multiple and sustainable equilibria is critical. Multiple equilibrium is the crucial stylized fact of economic life that requires better understanding and modeling. Of particular significance, Simon touched on the importance of institutions and differential power relationships in affecting economic outcomes. But this modeling approach was not well developed by Simon. Following from his contributions, further develop the notion of multiple equilibria especially in the realm of production with an emphasis on x-efficiency theory. I bring to bear the importance of institutional parameters (including power relationships), culture, norms, ethics, and moral sentiments to the determination of economic outcomes. In the model developed here, boundedly rational decision-makers’ choices are contextualized and constrained by complex environmental factors. No one choice is either inevitable or economically efficient. A multiplicity of outcomes is possible and sustainable inclusive of those that are suboptimal. Much depends on individual preferences and institutional design. This has significant implication for institutional design and policy.  相似文献   
6.
张建 《价值工程》2014,(3):60-61
阐述了车削用量与实际生产的联系,提供了部分在保证机械产品性能和质量的基础上提高生产率和缩减成本的可靠性解决办法。在仔细分析了当前机加工行业的情况下,预测了车削加工的发展方向。  相似文献   
7.
Runway incursions are an important aviation safety concern; between 2002 and 2015 there were 16,785 runway incursions at United States airports ranging in size from small general aviation (GA) to large commercial airline hubs. When examining airports with the 50 highest incursion count over the past 5 years, the predominant categories were large hubs, which accounted for 21 airports and general aviation (GA) airports which accounted for 16 airports. In June 2015, the Federal Aviation Administration (FAA) announced the Runway Incursion Mitigation (RIM) program to identify airport risk factors that might contribute to a runway incursion and develop strategies to help airport stakeholders mitigate those risks. Different size airports serve different aircraft fleets, serve different operating volumes, and have different resources available (both funds and technologies) for incursion mitigation. Therefore, it is valuable to determine the correlating factors that affect incursions at different size airports. This paper uses econometrics based modelling techniques to identify statistically significant factors in data provided by the (FAA) public web sites on runway incursions. The model identified statistically significant variables that correlate with incursions, based on severity, for airports categories defined by the National Plan of Integrated Airport Systems (NPIAS).The model results indicate that operational incidents (OI) are more likely at large hub airports. In contrast, at GA/non-hub airports, pilot deviations (PD) were significant for less severe incursions (severity C and D). Only one variable, “number of years since 2002”, was found to be significant for all the three airport categories; this variable was correlated with severity A incursions and indicated a statistically significant reduction in severity A incursions, despite an overall 80% increase in incursions between 2002 and 2015.  相似文献   
8.
In Rational Econometric Man, Edward Nell and Karim Errouaki present a welcome and timely case for the view that econometrics and econometric model-building may not be the magic tools to solve all empirical questions despite what many seem to have thought they were in the 1960s. Here I examine some possible problems with econometric models that have to do with their usually taking the form of equilibrium models. Some of these problems were recognized by Trygve Haavelmo decades ago. And as Aris Spanos has recently discussed, the problems are often the result of what we say in our textbooks. Some problems have to do with what we mean by econometric parameters and others with how we use probabilities.  相似文献   
9.
This paper discusses an optimal investment, consumption, and life insurance purchase problem for a wage earner in a complete market with Brownian information. Specifically, we assume that the parameters governing the market model and the wage earner, including the interest rate, appreciation rate, volatility, force of mortality, premium-insurance ratio, income and discount rate, are all random processes adapted to the Brownian motion filtration. Our modeling framework is very general, which allows these random parameters to be unbounded, non-Markovian functionals of the underlying Brownian motion. Suppose that the wage earner’s preference is described by a power utility. The wage earner’s problem is then to choose an optimal investment-consumption-insurance strategy so as to maximize the expected, discounted utilities from intertemporal consumption, legacy and terminal wealth over an uncertain lifetime horizon. We use a novel approach, which combines the Hamilton–Jacobi–Bellman equation and backward stochastic differential equation (BSDE) to solve this problem. In general, we give explicit expressions for the optimal investment-consumption-insurance strategy and the value function in terms of the solutions to two BSDEs. To illustrate our results, we provide closed-form solutions to the problem with stochastic income, stochastic mortality, and stochastic appreciation rate, respectively.  相似文献   
10.
Statistical issues arising in modelling univariate extremes of a random sample have been successfully used in the most diverse fields, such as biometrics, finance, insurance and risk theory. Statistics of univariate extremes (SUE), the subject to be dealt with in this review paper, has recently faced a huge development, partially because rare events can have catastrophic consequences for human activities, through their impact on the natural and constructed environments. In the last decades, there has been a shift from the area of parametric SUE, based on probabilistic asymptotic results in extreme value theory, towards semi‐parametric approaches. After a brief reference to Gumbel's block methodology and more recent improvements in the parametric framework, we present an overview of the developments on the estimation of parameters of extreme events and on the testing of extreme value conditions under a semi‐parametric framework. We further discuss a few challenging topics in the area of SUE. © 2014 The Authors. International Statistical Review © 2014 International Statistical Institute  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