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   2100篇
  免费   294篇
  国内免费   1篇
财政金融   361篇
工业经济   78篇
计划管理   223篇
经济学   837篇
综合类   27篇
运输经济   2篇
旅游经济   11篇
贸易经济   71篇
农业经济   468篇
经济概况   317篇
  2024年   1篇
  2023年   34篇
  2022年   26篇
  2021年   26篇
  2020年   100篇
  2019年   149篇
  2018年   114篇
  2017年   114篇
  2016年   108篇
  2015年   111篇
  2014年   147篇
  2013年   197篇
  2012年   217篇
  2011年   210篇
  2010年   151篇
  2009年   110篇
  2008年   142篇
  2007年   126篇
  2006年   104篇
  2005年   93篇
  2004年   25篇
  2003年   25篇
  2002年   19篇
  2001年   10篇
  2000年   10篇
  1999年   7篇
  1998年   1篇
  1997年   2篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1985年   4篇
  1984年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有2395条查询结果,搜索用时 15 毫秒
111.
Biofortification of maize with provitamin A carotenoids is a new approach to the alleviation of vitamin A deficiencies in Africa. Unfortunately these varieties are yellow or orange, while consumers generally prefer white. Consumer willingness to pay for yellow and fortified maize was compared in experimental auctions in three regions in Kenya. The premium that consumers are willing pay for fortified maize (24%) was higher than the discount they require to buy yellow maize (11%), and in one zone consumers prefer yellow. Yellow color is, therefore, not an impossible obstacle for biofortified maize, although it would clearly be easier to introduce this maize first in regions where yellow maize is currently grown.  相似文献   
112.
This study addresses the trade‐off between nutrition and taste in expenditure on breakfast cereal, milk, bread, and soft drinks. Within each category, products have similar cost and convenience, but have markedly different flavor and nutritional content. Using annual expenditure data for a large sample of households participating in the ACNielsen Homescan system, we regress a measure of “healthiness” on household demographics and market prices, and find that households with college‐educated heads and higher incomes made significantly healthier choices in all four categories. These effects are puzzling in that the nutritional differences between products were well known to consumers, and there are no cost or convenience differences between them. The presence of children was associated with less healthy choices, especially for cereal and bread, while older households made healthier choices in all categories except milk.  相似文献   
113.
This study considers the factors that explain the consumption of food and beverages with functional ingredients to avert or offset health problems. We use an instrumental variables Poisson regression model to deal with the endogeneity of perceived health status in functional ingredient use. The first stage results indicate that perceived health status is associated with attitude towards functional foods, food consumption motives and information seeking and being female. The second stage results suggest that individuals who consume more functional ingredients tend to have a positive attitude towards functional foods, are novelty‐seeking, female and older. As expected, consumption of functional ingredients is more likely when consumers’ self‐reports indicate that they are aware of functional foods’ nutritional value and the link with their own health. Consistent with previous research, most of the socio‐demographics are poor predictors of functional ingredient consumption.  相似文献   
114.
This paper proposes a nonparametric procedure to estimate market power for first‐price auction data and applies the procedure to cattle procurement markets. Most previous studies have used parametric methods, which require specific functional forms for retail demand, input supply and processors’ cost equations. However, researchers often find that market power estimates from parametric methods are sensitive to the choice of functional forms and specifications. An application to data from cattle procurement experiments shows that our nonparametric approach greatly outperforms commonly used parametric methods in estimating the degree of market power. While parametric estimates are sensitive to functional form specification and are at least 90% smaller than ‘true’ market power indices, estimates from our nonparametric procedure deviate from the actual value by no more than 25%.  相似文献   
115.
This article assembles the results of three multicountry surveys on variety performance and adoption patterns to measure the impacts of maize research in West and Central Africa from 1981 to 2005, and uses cost data since 1971 to compute social rates of return on public investments in maize research in the region. Adoption of modern varieties increased from less than 5% of the maize area in the 1970s to about 60% in 2005, yielding an aggregate rate of return on research and development (R&D) investment of 43%. The estimated number of people moved out of poverty through adoption of new maize varieties rose gradually in the 1980s to more than one million people per year since the mid 1990s. Over half of these impacts can be attributed to international maize research at IITA and CIMMYT. The article concludes with a discussion of strategic options to enhance the impacts of maize research in the region.  相似文献   
116.
The paper outlines EU policy on bioenergy, including biofuels, in the context of its policy initiatives to promote renewable energy to combat greenhouse gas emissions and climate change. The EU’s Member States are responsible for implementing EU policy: thus, the UK’s Renewables Obligation on electricity suppliers and its Renewable Transport Fuel Obligation and road‐fuel tax rebates are examined. It is unlikely that EU policy is in conflict with the WTO Agreement on Agriculture or that on Subsidies and Countervailing Measures, but its provisions on environmental sustainability criteria could be problematic.  相似文献   
117.
We estimate how much United States farms changed enterprise diversification in response to a marked increase in crop insurance coverage brought about by the 1994 Federal Crop Insurance Reform Act, which substantially increased insurance subsidies. The analysis exploits farm‐level panel census data to compare farm‐specific changes in enterprise diversification over time. By examining diversification decisions of the same farms over time, we control for time‐invariant unobserved individual heterogeneity. We then use pooled cross‐sectional data from the United States Department of Agriculture (USDA) Agricultural Resource Management Survey to estimate the relationship between farm diversification and average returns. We find that the insurance subsidies caused a modest increase in enterprise specialisation and production efficiency. Estimated efficiency gains are far less than the subsidies.  相似文献   
118.
The objective of this paper is to evaluate the effect of Plant Variety Protection (PVP) on the productive merit/yield increases of US seed varieties. As an example, we use wheat varieties, which are and have been available as both protected and unprotected under PVP from both the public and private sectors. We find evidence that PVP has contributed to the genetic improvement of wheat, using varietal trial data from Washington State. As the private open‐pollinated varieties exist only because of PVP and are higher yielding, these results indicate a clear public benefit from PVP.  相似文献   
119.
In this article, the potential impacts of Bt eggplant technology in Indian agriculture are analyzed. Several proprietary Bt hybrids are likely to be commercialized in the near future. Based on field trial data, it is shown that the technology can significantly reduce insecticide applications and increase effective yields. Comprehensive farm-survey data are used to project farm-level effects and future adoption rates. Simulations show that the aggregate economic surplus gains of Bt hybrids could be around US$108 million per year. Consumers will capture a large share of these gains, but farmers and the innovating company will benefit too. As the company has also shared its technology with the public sector, Bt open-pollinated varieties might become available with a certain time lag. This would make the technology more accessible, especially for resource-poor farmers, entailing further improvements in welfare and distribution effects. The wider implications of the private–public technology transfer are discussed. Furthermore, the potential benefits for farmers' health resulting from reduced insecticide applications are examined, using an econometric model and a cost-of-illness approach. These benefits are worth an additional $3–4 million per year, yet they constitute only a small fraction of the technology's environmental and health externalities. More research is needed for comprehensive impact analysis.  相似文献   
120.
Organic agriculture, which produces commodities that can be qualitatively differentiated from conventional food products, has grown into an important market in many countries. The dynamics of commodity prices in both sectors are partly interdependent, but are also shaped by independent determinants and have rarely been studied. We analyze organic food markets and their interdependencies with conventional markets in the context of wheat markets in Germany, which have been subject to a number of fundamental changes during the last two decades. Based on institutional market characteristics, we suggest a flexible Markov‐switching asymmetric time series model. We find a pronounced temporal sequence of market phases that differ in their asymmetric dynamics and the extent to which the organic price is influenced by the conventional price. Organic wheat prices tend to be increasingly connected to prices of conventional wheat.  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