全文获取类型
收费全文 | 18652篇 |
免费 | 134篇 |
专业分类
林业 | 3789篇 |
农学 | 1547篇 |
基础科学 | 167篇 |
3265篇 | |
综合类 | 824篇 |
农作物 | 2264篇 |
水产渔业 | 2057篇 |
畜牧兽医 | 1655篇 |
园艺 | 1178篇 |
植物保护 | 2040篇 |
出版年
2023年 | 36篇 |
2022年 | 73篇 |
2021年 | 83篇 |
2020年 | 101篇 |
2019年 | 126篇 |
2018年 | 2847篇 |
2017年 | 2804篇 |
2016年 | 1274篇 |
2015年 | 144篇 |
2014年 | 130篇 |
2013年 | 231篇 |
2012年 | 949篇 |
2011年 | 2247篇 |
2010年 | 2198篇 |
2009年 | 1330篇 |
2008年 | 1402篇 |
2007年 | 1657篇 |
2006年 | 113篇 |
2005年 | 153篇 |
2004年 | 151篇 |
2003年 | 196篇 |
2002年 | 89篇 |
2001年 | 45篇 |
2000年 | 74篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1981年 | 9篇 |
1979年 | 14篇 |
1977年 | 6篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1971年 | 7篇 |
1969年 | 7篇 |
1968年 | 8篇 |
1967年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The economics of harvesting wheat based on input management zones in the northern wheatbelt of Western Australia was studied
using a simulated field of regular dimensions with varying zone sizes and layouts. Fertilizer application rates and crop yield
and quality data from field trials of input management were used to estimate the gross crop revenue and harvesting costs from
the different field layouts and zone combinations. As a general observation there was no consistency in the results; harvesting
by zone generated more gross income in some combinations of field layout and yield quantity scenarios, but not in others.
However, there were key factors in determining whether it was profitable to harvest by zone. These were prior knowledge of
the potential yield and quality characteristics of grain from each zone in a field, and the layout of zones within a field. 相似文献
994.
Alison Hope Alkon 《Agriculture and Human Values》2008,25(4):487-498
Advocates of environmental sustainability and social justice increasingly pursue their goals through the promotion of so-called
“green” products such as locally grown organic produce. While many scholars support this strategy, others criticize it harshly,
arguing that environmental degradation and social injustice are inherent results of capitalism and that positive social change
must be achieved through collective action. This study draws upon 18 months of ethnographic fieldwork at two farmers markets
located in demographically different parts of the San Francisco Bay Area to examine how market managers, vendors, and regular
customers negotiate tensions between their economic strategies and environmental sustainability and social justice goals.
Managers, vendors, and customers emphasize the ethical rather than financial motivations of their markets through comparisons
to capitalist, industrial agriculture and through attention to perceived economic sacrifices made by market vendors. They
also portray economic strategies as a pragmatic choice, pointing to failed efforts to achieve justice and sustainability through
policy change as well as difficulties funding and sustaining non-profit organizations. While market managers, vendors, and
customers deny any difficulties pursuing justice and sustainability through local economics, the need for vendors to sustain
their livelihoods does sometimes interfere with their social justice goals. This has consequences for the function of each
market.
Alison Hope Alkon is a Ph.D. candidate in the Department of Sociology at the University of California, Davis. Her research examines how efforts to create environmental protection and social justice operate in a market context. 相似文献
Alison Hope AlkonEmail: |
Alison Hope Alkon is a Ph.D. candidate in the Department of Sociology at the University of California, Davis. Her research examines how efforts to create environmental protection and social justice operate in a market context. 相似文献
995.
Daniel R. Block Michael Thompson Jill Euken Toni Liquori Frank Fear Sherill Baldwin 《Agriculture and Human Values》2008,25(3):379-388
Engagement happens when academics and non-academics form partnerships to create mutual understanding, and then take action
together. An example is the “value web” work associated with W. K. Kellogg Foundation’s Food Systems Higher Education–Community
Partnership. Partners nationally work on local food systems development by building value webs. “Value chains,” a concept
with considerable currency in the private sector, involves creating non-hierarchical relationships among otherwise disparate
actors and entities to achieve collective common goals. The value web concept is extended herein by separating the values
of the web itself, such as the value of collaboration, from values “in” the web, such as credence values associated with a
product or service. By sharing and discussing case examples of work underway around the United States, the authors make a
case for employing the value webs concept to represent a strategy for local food systems development, specifically, and for
higher education–community partnerships, generally.
Daniel R. Block is an associate professor of geography and coordinator of the Frederick Blum Neighborhood Assistance Center at Chicago State University. His current research focuses on food access issues in urban environments, particularly in Chicago. Michael Thompson is an assistant professor at Oregon State University, and a Seafood and Fisheries specialist for Oregon Sea Grant Extension. Primary areas of research include fisheries management, seafood quality/handling, and seafood product development. Jill Euken is an industrial specialist for biobased products for Iowa State University Extension/CIRAS, and deputy director, ISU Bioeconomy Institute. She was part of the steering team for the Iowa Value Chain Partnership for Sustainable Agriculture and led the Bioeconomy Working Group. Toni Liquori is a nutritionist, teacher and food activist with a long time interest in the design, implementation, and evaluation of school-based intervention programs and coalition building for activism around food related issues, as well as teaching and training in public health. Frank Fear is senior associate dean, College of Agriculture and Natural Resources; and professor, in the Department of Community, Agriculture, Recreation and Resources Studies; and Senior Outreach Fellow at Michigan State University. He is lead author of Coming to Critical Engagement (University Press of America, 2006), an analysis of the engagement movement in higher education; and recently completed two terms as president of the Greater Lansing Food Bank. Sherill Baldwin is ecology director at Mercy Center at Madison, Connecticut, a spiritual retreat and conference center. She previously provided consulting services to CitySeed, Inc. in New Haven (CT) and to Frank Fear and the W. K. Kellogg Foundation for a community learning project related to sustainable food systems. She has an MS in Resource Development from Michigan State University and a BA in Solid Waste Management from the University of Massachusetts. 相似文献
Daniel R. BlockEmail: |
Daniel R. Block is an associate professor of geography and coordinator of the Frederick Blum Neighborhood Assistance Center at Chicago State University. His current research focuses on food access issues in urban environments, particularly in Chicago. Michael Thompson is an assistant professor at Oregon State University, and a Seafood and Fisheries specialist for Oregon Sea Grant Extension. Primary areas of research include fisheries management, seafood quality/handling, and seafood product development. Jill Euken is an industrial specialist for biobased products for Iowa State University Extension/CIRAS, and deputy director, ISU Bioeconomy Institute. She was part of the steering team for the Iowa Value Chain Partnership for Sustainable Agriculture and led the Bioeconomy Working Group. Toni Liquori is a nutritionist, teacher and food activist with a long time interest in the design, implementation, and evaluation of school-based intervention programs and coalition building for activism around food related issues, as well as teaching and training in public health. Frank Fear is senior associate dean, College of Agriculture and Natural Resources; and professor, in the Department of Community, Agriculture, Recreation and Resources Studies; and Senior Outreach Fellow at Michigan State University. He is lead author of Coming to Critical Engagement (University Press of America, 2006), an analysis of the engagement movement in higher education; and recently completed two terms as president of the Greater Lansing Food Bank. Sherill Baldwin is ecology director at Mercy Center at Madison, Connecticut, a spiritual retreat and conference center. She previously provided consulting services to CitySeed, Inc. in New Haven (CT) and to Frank Fear and the W. K. Kellogg Foundation for a community learning project related to sustainable food systems. She has an MS in Resource Development from Michigan State University and a BA in Solid Waste Management from the University of Massachusetts. 相似文献
996.
Social-ethical issues concerning the control strategy of animal diseases in the European Union: A survey 总被引:1,自引:0,他引:1
Nina E. Cohen Marcel A.P.M. van Asseldonk Elsbeth N. Stassen 《Agriculture and Human Values》2007,24(4):499-510
In 2004 a survey was conducted in the member states of the European Union designed to gain greater insight into the views
on control strategies for foot and mouth disease, classical swine fever, and avian influenza with respect to the epidemiological,
economic and social-ethical consequences of each of these animal diseases. This article presents the results of the social-ethical
survey. A selection of stakeholders from each member state was asked to prioritize issues for the prevention and control of
these diseases. A majority of stakeholders chose preventive measures as the preferred issue. An analysis was done to determine
whether there were differences in views expressed by stakeholders from member states with a history of recent epidemics and
ones without such a history, and whether there were regional differences. There were no differences between member states
with or without a history of recent epidemics. There were indeed regional differences between the priority orders from Northern
and Southern Europe on the one hand, and from Eastern Europe on the other.
Nina
E. Cohen
is a biologist and is a researcher at the Wageningen University. She is specialized in societal and ethical issues in human–animal
relationships. Her current research is focused on the social-ethical issues concerning the prevention and control of foot
and mouth disease, classical swine fever and avian influenza.
Marcel A.P.M. van Asseldonk
has studied animal science. Currently he works at the Institute for Risk Management in Agriculture (IRMA) of the Wageningen
University. He is specialized in the design and pricing of insurance policies and animal health funds for the main livestock
epidemics.
Elsbeth N. Stassen
is a veterinarian and professor of Animals and Society at the Wageningen University. Elsbeth Stassen is specialized in animal
health, animal welfare and human–animal relationships. She was a member of a governmental welfare committee during the avian
influenza epidemic in the Netherlands in 2003. 相似文献
997.
Gap junction membrane channels mediate electrical and metabolic coupling between adjacent cells. The structure of a recombinant cardiac gap junction channel was determined by electron crystallography at resolutions of 7.5 angstroms in the membrane plane and 21 angstroms in the vertical direction. The dodecameric channel was formed by the end-to-end docking of two hexamers, each of which displayed 24 rods of density in the membrane interior, which is consistent with an alpha-helical conformation for the four transmembrane domains of each connexin subunit. The transmembrane alpha-helical rods contrasted with the double-layered appearance of the extracellular domains. Although not indicative for a particular type of secondary structure, the protein density that formed the extracellular vestibule provided a tight seal to exclude the exchange of substances with the extracellular milieu. 相似文献
998.
The trace water content of salt in six Louisiana salt domes has been determined and has been found to be the lowest of any terrestrial rock type. The average water content of normal domal salt is on the order of 0.003 percent by weight, but anomalous zones within salt stocks can have more than ten times this amount. From the average value, the minimum amount of water in liters, W, available to collect around a radioactive waste repository is given as W = 0.28 r(3), where r is the radius in meters of the sphere in which water may be thermally activated to migrate completely to the repository. 相似文献
999.
1000.
Elizabeth Finnis 《Agriculture and Human Values》2007,24(3):343-353
Using a case study from the Kolli Hills, India, I suggest that political ecology provides a useful theoretical basis for considering
localized dietary transitions in rural, agricultural communities in developing countries. By examining the reasons for the
near-disappearance of local minor millets as staple foods in three small-farmer communities, I argue that an explicit, actor-oriented
analysis allows for an integration of food issues with considerations of environmental circumstances, local aspirations, and
labor concerns. That is, an agricultural shift that abandons minor millets as a food resource reflects environmental changes
and household economic aspirations. Such an analysis has implications for the creation of practical food security projects
through the recognition and incorporation of small-farmer experiences, voices, and priorities. This research was undertaken
through ethnographic fieldwork, using semi-structured interviews and participant observation as the primary methods.
Elizabeth
Finnis obtained her PhD from McMaster University in Canada and is currently a post-doctoral fellow in the Department of Anthropology
and the Centre for Society, Technology, and Development at McGill University. 相似文献