全文获取类型
收费全文 | 767篇 |
免费 | 107篇 |
国内免费 | 226篇 |
出版年
2024年 | 7篇 |
2023年 | 30篇 |
2022年 | 63篇 |
2021年 | 60篇 |
2020年 | 66篇 |
2019年 | 77篇 |
2018年 | 57篇 |
2017年 | 46篇 |
2016年 | 41篇 |
2015年 | 43篇 |
2014年 | 50篇 |
2013年 | 71篇 |
2012年 | 38篇 |
2011年 | 48篇 |
2010年 | 45篇 |
2009年 | 34篇 |
2008年 | 31篇 |
2007年 | 48篇 |
2006年 | 40篇 |
2005年 | 30篇 |
2004年 | 28篇 |
2003年 | 26篇 |
2002年 | 18篇 |
2001年 | 15篇 |
2000年 | 9篇 |
1999年 | 20篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1100条查询结果,搜索用时 15 毫秒
71.
Tea polyphenols for health promotion 总被引:18,自引:0,他引:18
People have been consuming brewed tea from the leaves of the Camellia sinensis plant for almost 50 centuries. Although health benefits have been attributed to tea, especially green tea consumption since the beginning of its history, scientific investigations of this beverage and its constituents have been underway for less than three decades. Currently, tea, in the form of green or black tea, next to water, is the most widely consumed beverage in the world. In vitro and animal studies provide strong evidence that polyphenols derived from tea may possess the bioactivity to affect the pathogenesis of several chronic diseases. Among all tea polyphenols, epigallocatechin-3-gallate has been shown to be responsible for much of the health promoting ability of green tea. Tea and tea preparations have been shown to inhibit tumorigenesis in a variety of animal models of carcinogenesis. However, with increasing interest in the health promoting properties of tea and a significant rise in scientific investigation, this review covers recent findings on the medicinal properties and health benefits of tea with special reference to cancer and cardiovascular diseases. 相似文献
72.
Vincent J. Tepedino Diane Gail Alston Brosi A. Bradley Trent R. Toler Terry L. Griswold 《Biodiversity and Conservation》2007,16(11):3083-3094
Capitol Reef National Park in central Utah, USA surrounds 22 managed fruit orchards started over a century ago by Mormon pioneers.
Honey bees are imported for pollination, although the area in which the Park is embedded has over 700 species of native bees,
many of which are potential orchard pollinators. We studied the visitation of native bees to apple, pear, apricot, and sweet
cherry over 2 years. Thirty species of bees visited the flowers but, except for pear flowers, most were uncommon compared
to honey bees. Evidence that honey bees prevented native bees from foraging on orchard crop flowers was equivocal: generally,
honey bee and native bee visitation rates to the flowers were not negatively correlated, nor were native bee visitation rates
positively correlated with distance of orchards from honey bee hives. Conversely, competition was tentatively suggested by
much larger numbers of honey bees than natives on the flowers of apples, apricots and cherry; and by the large increase of
native bees on pears, where honey bee numbers were low. At least one-third of the native bee species visiting the flowers
are potential pollinators, including cavity-nesting species such as Osmia lignaria propinqua, currently managed for small orchard pollination in the US, plus several fossorial species, including one rosaceous flower
specialist (Andrena milwaukiensis). We suggest that gradual withdrawal of honey bees from the Park would help conserve native bee populations without decreasing
orchard crop productivity, and would serve as a demonstration of the commercial value of native pollinators. 相似文献
73.
74.
Janice Newton 《The Australian journal of anthropology》2015,26(2):233-254
Recent senior anthropologists have heralded a new era where performative social and cultural kinship may eclipse procreational ‘biological kinship’ in contemporary western society. This article takes research on permanent residents in caravan parks as an extreme case that may act as an exemplar for future western contexts. Between 2003 and 2008, interviews with caravan‐park managers, 50 interviews with park residents and short field stays at 17 outer Melbourne and rural Victorian caravan parks, provided multi‐sited ethnographic material for analysis. I argue that contemporary contexts for relatedness give scope for creative development of social performative ties with ‘ex’ spouses and in‐laws, friends and pets. ‘Biological’ kin and family with a material dimension remain central, however, and a response to family need or rupture is often the broadening of the procreative kin links between grandparent and grandchild and between siblings. Childhood institutionalisation and divorce in particular, contributed to pathways towards caravan park housing. Other kin‐based motivations include finding safe accommodation for wives; providing housing for young adult males after injury and family divorce; and arranging for housing succession for children. Ideas of blood and folk biology demonstrate considerable resilience in contemporary kinship arrangements. 相似文献
75.
For at least the past two decades, eco‐industrial parks (EIPs) have been promoted as policy and commercial instruments for achieving industrial sustainable development. Yet, few EIPs have seen successful operational implementation, especially if they begin as standard industrial parks. Rapid economic growth, commensurate with increasing environmental damage in China, has resulted in officials’ further pursuing EIP policy as a significant element of the broader circular economy and ecological modernization efforts. This article examines the barriers for EIP development from industrial park senior manager perspectives. Using resource dependence theory and the resource‐based view as theoretical lenses, we investigate the external and internal barriers for EIP development in 51 Chinese industrial parks. A number of barriers are identified and grouped through a factor analysis. Cluster analysis is utilized to help categorize and evaluate the perceived levels of barriers and hardships experienced by various senior officials that manage the EIPs. It is found that few respondents encounter no significant barriers. Barriers related to technological development and capacity building are the most prevalent. These results highlight the relative importance of various activities that may be necessary by policy makers and other stakeholders to overcome the barriers. For example, cooperation in developing technological solutions for EIPs seems to be a major thrust that should be pursued by EIP development stakeholders. Other policy and managerial insights based on the general findings of this study are also presented. 相似文献
76.
Reducing Urban Disaster Risk by Improving Resilience in China from a Planning Perspective 总被引:1,自引:0,他引:1
ABSTRACTThis article aims to examine the implications of improving urban resilience that emerge from Chinese practices for reducing urban disaster risk. First, the concept of urban resilience is discussed, the goal of which is to shape a “culture of resilience” to the largest extent possible in order to reduce urban risk. Urban resilience encompasses broad and diverse areas, and thus can be improved in many ways. This article primarily discusses the planning process. Second, the main focus of the discussion on planning process to improve urban resilience is that of the urban risk management planning of Shenzhen, China. This was the first local urban government project in China to have comprehensively and broadly assessed and reduced urban risk, and it is covered along with the Chinese legislation system and current urban resilience programs in China. The findings show that both the Chinese central government and local governments are paying more and more attention to urban resilience through various legislation and programs, even if they are not using the same terminology as other countries. 相似文献
77.
Aeroterrestrial green algae form conspicuous biofilms on man-made surfaces. The self-cleaning properties of photocatalytic coatings prevent their growth and can probably replace biocides. The aim of this study was to develop a laboratory method to investigate the efficiency of photocatalytic materials against algal growth. Two algal isolates (“Chlorella” luteoviridis, SAG 2196, and Coccomyxa sp., SAG 2040) functioned well as model organisms because they grew on almost all test specimens at 100% humidity and low UVA radiation. With these species, we examined algal growth prevention using photocatalytic glass. No effects on algal growth were detected, although the coated surfaces were photocatalytically active and degraded methylene blue. Because their cells are protected well against photocatalytically generated hydroxyl radicals, aeroterrestrial algae survive various stress factors. Nevertheless, the newly developed experimental design may be useful for assessing the biological function of other photocatalytic materials or stress factors. 相似文献
78.
C. Block B. Van Praet T. Windels I. Vermeulen G. Dangreau A. Overmeire E. D’Hooge T. Maes G. Van Eetvelde C. Vandecasteele 《Journal of Industrial Ecology》2011,15(4):584-596
The industrial park of Herdersbrug (Brugge, Flanders, Belgium) comprises 92 small and medium‐sized enterprises, a waste‐to‐energy incinerator, and a power plant (not included in the study) on its site. To study the carbon dioxide (CO2) neutrality of the park, we made a park‐wide inventory for 2007 of the CO2 emissions due to energy consumption (electricity and fossil fuel) and waste incineration, as well as an inventory of the existing renewable electricity and heat generation. The definition of CO2 neutrality in Flanders only considers CO2 released as a consequence of consumption or generation of electricity, not the CO2 emitted when fossil fuel is consumed for heat generation. To further decrease or avoid CO2 emissions, we project and evaluate measures to increase renewable energy generation. The 21 kilotons (kt) of CO2 emitted due to electricity consumption are more than compensated by the 25 kt of CO2 avoided by generation of renewable electricity. Herdersbrug Industrial Park is thus CO2 neutral, according to the definition of the Flemish government. Only a small fraction (6.6%) of the CO2 emitted as a consequence of fossil fuel consumption (heat generation) and waste incineration is compensated by existing and projected measures for renewable heat generation. Of the total CO2 emission (149 kt) due to energy consumption (electricity + heat generation) and waste incineration on the Herdersbrug Industrial Park in 2007, 70.5% is compensated by existing and projected renewable energy generated in the park. Forty‐seven percent of the yearly avoided CO2 corresponds to renewable energy generated from waste incineration and biomass fermentation. 相似文献
79.
80.