全文获取类型
收费全文 | 22872篇 |
免费 | 637篇 |
专业分类
财政金融 | 4057篇 |
工业经济 | 1620篇 |
计划管理 | 3971篇 |
经济学 | 5441篇 |
综合类 | 245篇 |
运输经济 | 179篇 |
旅游经济 | 347篇 |
贸易经济 | 3816篇 |
农业经济 | 1156篇 |
经济概况 | 2600篇 |
信息产业经济 | 3篇 |
邮电经济 | 74篇 |
出版年
2023年 | 108篇 |
2021年 | 152篇 |
2020年 | 295篇 |
2019年 | 460篇 |
2018年 | 510篇 |
2017年 | 535篇 |
2016年 | 527篇 |
2015年 | 364篇 |
2014年 | 584篇 |
2013年 | 2445篇 |
2012年 | 789篇 |
2011年 | 815篇 |
2010年 | 715篇 |
2009年 | 804篇 |
2008年 | 734篇 |
2007年 | 636篇 |
2006年 | 610篇 |
2005年 | 530篇 |
2004年 | 463篇 |
2003年 | 475篇 |
2002年 | 425篇 |
2001年 | 503篇 |
2000年 | 458篇 |
1999年 | 415篇 |
1998年 | 474篇 |
1997年 | 423篇 |
1996年 | 421篇 |
1995年 | 360篇 |
1994年 | 369篇 |
1993年 | 353篇 |
1992年 | 362篇 |
1991年 | 379篇 |
1990年 | 345篇 |
1989年 | 254篇 |
1988年 | 263篇 |
1987年 | 267篇 |
1986年 | 248篇 |
1985年 | 358篇 |
1984年 | 356篇 |
1983年 | 333篇 |
1982年 | 284篇 |
1981年 | 287篇 |
1980年 | 283篇 |
1979年 | 277篇 |
1978年 | 226篇 |
1977年 | 183篇 |
1976年 | 183篇 |
1975年 | 162篇 |
1974年 | 149篇 |
1973年 | 148篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Arega D. Alene Abebe Menkir S. O. Ajala B. Badu-Apraku A. S. Olanrewaju V. M. Manyong Abdou Ndiaye 《Agricultural Economics》2009,40(5):535-550
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
992.
Jon T. Biermacher B. Wade Brorsen Francis M. Epplin John B. Solie William R. Raun 《Agricultural Economics》2009,40(4):397-407
Plant-based precision nitrogen fertilizer application technologies have been developed as a way to predict and precisely meet nitrogen needs. Equipment necessary for precision application of nitrogen, based on sensing of growing wheat plants in late winter, is available commercially, but adoption has been slow. This article determines the expected profit from using a plant-sensing system to determine winter wheat nitrogen requirements. We find that plant-sensing systems have the potential to be more profitable than traditional nonprecise systems, but the existing system simulated was roughly breakeven with a traditional system. 相似文献
993.
This article explores demand-enhancing check-off programs and how such programs may influence both private programs as well as industry market structure. Under duopoly, a firm may increase its sales through privately funding product quality improvements. However, such endogenous sunk costs may also be used to exclude a rival. Industry-funded check-off programs affect firms' strategies and can be procompetitive. The rationale lies not only in how the check-off enhancement is perceived by consumers but also in the way the check-off's crowding-out effect reduces the ability of a firm to use its private expenditures to bar a rival's market access. 相似文献
994.
The future demand for land for mining and quarrying will be affected by a large number of economic, technological, environmental and social issues within the UK. Global developments also have a role to play. Although mining and quarrying account for only 0.9 per cent of the land area of England, the impact of this activity is considerable. Minerals are essential to the economy, for energy, construction, infrastructure and manufacturing, while their extraction has effects on the environment and on public perception. This paper examines current scientific understanding of the context of mining and quarrying, with particular reference to its impact on land use, along with the spatial relationship between minerals – which can only be worked where they occur – and other forms of land use and designation in the ‘post-industrial’ landscape of Britain. Looking out to 2060 and beyond, developments which may influence demand for minerals include climate change mitigation and adaptation; energy, food and raw material security; and new construction, manufacturing, recycling and re-use technologies. Factors influencing the supply side include the structure and ownership of the mining and quarrying industry, new extraction, processing and environmental technologies, ecosystem service provision, societal attitudes and land access. Although prediction carries a high level of uncertainty, continuous development of the regulatory framework is, and will remain, a major and pervasive factor in the relationship between mining and quarrying and land use. 相似文献
995.
Before embarking on the development of rural areas or regions it seems necessary to answer the following key questions: what goals of the parties involved can be realized, and where, when and how? To tackle these questions we have developed a ‘roadmap’, as part of an overall sustainable development procedure for physical planning and spatial management in rural areas. The roadmap is a tool for the process manager and the people involved. It helps to find the way in the exploration of the potential social, economic and ecological benefits of developing the area or region. The purpose of using the roadmap is to alleviate doubts about the advantages of cooperating in pursuit of sustainable development. A back-casting approach is applied to create appealing visions of the future and visualize mutual opportunities worth implementing. In this article we first describe the need for this new roadmap. We then describe its use, step by step and in some detail. An example of the exploration process is described and the strengths and weaknesses of the roadmap are discussed. 相似文献
996.
This paper reviews the relationships between land use and climate change. It explores how land use decisions will be affected by future changes in the climate, but also the feedbacks from land use change to the global climate system through greenhouse gas (GHG) fluxes. Past changes in land use were characterised by decreasing areas of agricultural use and increasing areas of forested and urbanised land. This has led to UK land use being a net sink for GHGs, mostly due to forestation. However, existing forests have on average passed their age for maximum net removals of carbon from the atmosphere. In the next decade at least, net removals from UK forests are likely to decrease significantly.Longer term scenarios of future land use change are consistent in their expectation of further declines in the agricultural area used for food production – offset to some extent by increased bioenergy cropping – along with increases in forested and urban areas. These trends are broadly consistent with the observed past land use change, but are calculated from various assumptions about future changes in drivers rather than by extrapolation from the past. Socio-economic and technological changes are likely to be the most important drivers for land use, with climate change having a smaller influence. The land use changes represented in these scenarios would likely reduce GHG emissions and enhance carbon sinks. These trends would be reinforced by small future changes in the climate, but large climatic changes are likely to cause net GHG fluxes to switch from being a sink to a source. Land use change will also be moderated by potential policy goals that seek to reduce GHG emissions from land and/or increase the size of land-based sinks. This includes strategies to reduce carbon and nitrogen emissions through increased efficiency, afforestation and biofuel production. 相似文献
997.
998.
Seonghee Cho Misty M. Johanson Priyanko Guchait 《International Journal of Hospitality Management》2009
The purpose of the study is to examine whether the predictors that decrease employee intention to leave will also increase employees’ intention to stay. Therefore, the objective of the study is twofold: (1) to examine the influence of perceived organizational support, perceived supervisors’ support, and organizational commitment regarding intent to leave and (2) to investigate the influence of the same variables on intent to stay. A total of 416 hospitality employees in the U.S. participated. The results suggest that perceived organizational support and organizational commitment decreased intent to leave while only perceived organizational support had a positive impact on intention to stay. Implications detail ways that hospitality organizations can focus on increasing their employees’ commitment through perceived organizational support as a critical component of turnover culture. 相似文献
999.
Airport stops and flights on small airplanes as inhibitors of tourism-related air travel: A case study 总被引:2,自引:0,他引:2
This article discusses the extent to which prospective tourists' concerns about airport stops and flights on small airplanes inhibit air travel to tourist destinations, drawing on data from telephone surveys conducted in the Dallas–Fort Worth, Texas area. Respondents were queried about the extent to which one airport stop, two airport stops, and one airport stop followed by a flight on a small, propeller-powered airplane, respectively, would deter them from flying to a destination 1096 miles (1764 km) away. Findings suggest that marketers of similar destinations in similarly distant markets that are accessible by air only after two airport stops risk having their promotional appeals ignored by roughly half those who would prefer to reach such destinations by air. Moreover, those most concerned about such flight schedules were more likely than other respondents to have high incomes and to use the Internet to obtain vacation or travel information. 相似文献
1000.
Ines Engelmann M.A. 《Publizistik》2009,54(1):82-102
While framing theory is concerned with the way media content is presented, news bias theory concentrates on the evaluative aspect. The study integrates both approaches of news structuring. A detailed argument analysis of two German quality newspapers, Die Welt and Frankfurter Rundschau, representative for two opposite editorial viewpoints, was conducted to test the assumptions of both theories. The examination of news coverage related to the accession of Poland, Czech Republic, Bulgaria and Romania to the EU contradicts previous results of framing and news bias research. Apart from finding a pronounced focus on economical topics in both newspapers, they clearly differ in their frames of reference and political positions on the issues, staying in line with their editorial orientation. A comparison of the different accession times reveals a change in the frames of reference and the advocates of these frames. 相似文献