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   63篇
  免费   5篇
  国内免费   1篇
林业   7篇
农学   2篇
  8篇
综合类   21篇
农作物   7篇
水产渔业   9篇
畜牧兽医   13篇
园艺   1篇
植物保护   1篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2017年   2篇
  2016年   1篇
  2015年   5篇
  2014年   1篇
  2013年   5篇
  2012年   4篇
  2011年   3篇
  2009年   1篇
  2008年   4篇
  2007年   5篇
  2006年   3篇
  2005年   4篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  2000年   1篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1986年   1篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1976年   5篇
  1974年   1篇
排序方式: 共有69条查询结果,搜索用时 15 毫秒
51.
White and red wines spiked with catechin-rich green tea extract and grape seed extract were assessed for phenolic content, antioxidant activity, and cross-cultural consumer rejection thresholds in relation to wine as a functional food. Health functionality is an important factor in functional foods, and spiking pure compounds or plant extracts is an effective method to increase or control functionality. The total phenolic content and antioxidant activity were measured in wines spiked to different extract concentrations, namely, control and 50, 100, 200, 400, and 800 mg/L, to confirm the dose-response curves in both white and red wines. Consumer rejection thresholds (CRTs) were established for spiked wines in a Korean and in an Australian population. Our results showed that the green tea extract and grape seed extract increased the antioxidant activity dose dependently, and the CRTs varied considerably between the Korean and the Australian groups, with Koreans preferring wines spiked with green tea extract and Australians showing a preference for wines spiked with grape seed extract. These results have implications for producing wine products that are enhanced in phenolic compounds and targeted to different cultural groups.  相似文献   
52.
Studies are reported on two small lakes at Sudbury, Ontario located close to a nickel-copper smelter which closed in 1972. At that stage, Baby Lake had a pH of 4.0–4.2 while the adjacent Alice Lake had a pH 5.9–6.3. Both lakes were almost entirely devoid of algae and had neither Zooplankton nor fish. Soon after the closure of the smelter, with its large airborne volume of sulphur dioxide and of copper and nickel containing particulates, the chemistry of the lakes began to change. By 1985, Baby Lake had changed from pH 4.0 to 6.8 and is now at pH 7.2. The pH of Alice Lake increased from a low of 5.9 in the early 1970s to 6.9–7.4 in the mid 1980s and is now at 7.3. Copper and nickel concentrations also decreased in both lakes during this period. The first biota found in the lakes in the post-smelter stage in the early 1980s were benthic red chironomids, planktonic rotifers, and a limited number of phytoplankton species, of which Rhizosolenia was the most common. By the 1990s, 13 phytoplankton species were present in each lake, with a substantial Zooplankton fauna (14 species) of rotifers, copepods, and cladocerans. There are now numerous insect larvae in the sediment and some small fish in both lakes. The biological recovery, which followed substantial reductions in acidity and in soluble nickel and copper concentrations in the waters, is a slower process than chemical recovery and is initially characterized by the dominance of a few species.  相似文献   
53.
54.
55.
56.
Dust concentrations in ice of the last glacial maximum (LGM) are high in ice cores from Greenland and Antarctica. The magnitude of the enhancements can be explained if the strength of the hydrologic cycle during the LGM was about half of that at present. This notion is consistent with a large decrease (5 degrees Celsius) in ocean temperature during the LGM, as recently deduced from measurements of strontium and calcium in corals.  相似文献   
57.
An ecological perspective on the valuation of ecosystem services   总被引:31,自引:0,他引:31  
Ecosystem services are the conditions and processes through which natural ecosystems and the species that make them up, sustain and fulfil human life. Ecosystem service valuation is being developed as a vehicle to integrate ecological understanding and economic considerations to redress the traditional neglect of ecosystem services in policy decisions. This paper presents a critical review on the neoclassical economic framework, tools used for economic valuation of ecosystem services and the economic welfare approach to collective decision-making, from an ecological perspective. The applicability of the framework and techniques for valuing ecosystem services are evaluated in light of the challenges posed by the complex, non-linear nature of many ecosystem services. Decisions concerning ecosystem management are often complex, socially contentious and fraught with uncertainty. Although judicious application of economic valuation techniques to ecosystem services can provide valuable information for conceptualizing decision choices and evaluating management options, there are serious limitations in the economic welfare approach to decision-making. These shortcomings and their implications for ecosystem management are elucidated and alternative approaches that emphasize participation, explicit treatment of uncertainty and transparent decision-making processes are discussed.  相似文献   
58.
59.
刘向之《诗经》学家法,前人每有论及。然其论据及研究方法,均仍有可改善之处。本文从家学、异文比较、《诗》说比较三方面,考论刘向之《诗》学家法,以图全面分析刘向《诗》学家法的问题,并希望由此而于两汉《诗》学研究有所裨益。  相似文献   
60.
高产蛋鸡按吨饲料添加150克该植物提取物(5%),能降低饲料消耗,提高产蛋率,降低死淘率,本实验表明,投入产出比为1:3.51。  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