全文获取类型
收费全文 | 974篇 |
免费 | 74篇 |
国内免费 | 14篇 |
专业分类
林业 | 37篇 |
农学 | 24篇 |
基础科学 | 5篇 |
119篇 | |
综合类 | 233篇 |
农作物 | 23篇 |
水产渔业 | 61篇 |
畜牧兽医 | 477篇 |
园艺 | 29篇 |
植物保护 | 54篇 |
出版年
2023年 | 10篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 28篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 48篇 |
2012年 | 44篇 |
2011年 | 59篇 |
2010年 | 54篇 |
2009年 | 46篇 |
2008年 | 34篇 |
2007年 | 51篇 |
2006年 | 44篇 |
2005年 | 32篇 |
2004年 | 50篇 |
2003年 | 27篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1992年 | 22篇 |
1991年 | 10篇 |
1990年 | 22篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 12篇 |
1971年 | 14篇 |
1970年 | 10篇 |
1969年 | 5篇 |
1966年 | 6篇 |
排序方式: 共有1062条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
OBJECTIVE: To examine the pattern of intake of key foods and beverages of children aged 4-12 years and the association with weight status. DESIGN AND SETTING: A computer-assisted telephone interview was used to determine the intake of fruit, vegetables, packaged snacks, fast foods and sweetened drinks 'yesterday' and 'usually' as reported by parents/guardians of a representative sample of 2184 children from the Barwon South-Western region of Victoria, Australia. RESULTS: Children who consumed >2-3, >3-4 and >4 servings of fruit juice/drinks 'yesterday' were, respectively, 1.7 (95% confidence interval (CI) 1.2-2.2), 1.7 (95% CI 1.2-2.5) and 2.1 (95% CI 1.5-2.9) times more likely to be overweight/obese compared with those who had no servings of fruit juice/drink 'yesterday', adjusted for age, gender and socio-economic status (SES). Further, children who had > or = 3 servings of soft drink 'yesterday' were 2.2 (95% CI 1.3-3.9) times more likely to be overweight/obese compared with those who had no servings of soft drink 'yesterday', adjusted for age, gender and SES. In addition, children who 'usually' drank fruit juice/drinks twice or more per day were 1.7 (95% CI 1.2-2.4) times more likely to be overweight/obese compared with those who drank these beverages once or less per week, adjusted for age, gender and SES. Although fast foods and packaged snacks were regularly eaten, there were no associations between weight status and consumption of these foods. CONCLUSIONS: Intake of sweetened beverages was associated with overweight and obesity in this population of Australian schoolchildren and should be a target for intervention programmes aimed at preventing unhealthy weight gain in children. 相似文献
56.
Infectivity studies of infectious hypodermal and hematopoietic necrosis virus (IHHNV) were conducted on Penaeus stylirostris and P. vannamei (representing species highly susceptible and highly refractory to the disease) via intramuscular injections of the virus. Distinctive histological lesion patterns were observed between species. Six target organ systems were compared interspecifically. The gills and nerve cord/ganglia were shown to undergo significantly higher degrees of tissue damage in infected P. stylirostris compared with infected P. vannamei. Pathogenetic differences correlated well with observed differences in epizootiology between the two species.The infectivity study confirmed that IHHN disease is virus-caused. Cell-free extracts from IHHNV-infected shrimp, when injected into healthy, susceptible shrimp, produced mortalities and Cowdry type A intranuclear eosinophilic inclusion bodies presently considered pathognomonic for the disease. 相似文献
57.
58.
59.