全文获取类型
收费全文 | 539篇 |
免费 | 22篇 |
专业分类
林业 | 12篇 |
农学 | 4篇 |
基础科学 | 1篇 |
76篇 | |
综合类 | 172篇 |
农作物 | 15篇 |
水产渔业 | 13篇 |
畜牧兽医 | 232篇 |
园艺 | 2篇 |
植物保护 | 34篇 |
出版年
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2015年 | 7篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1970年 | 6篇 |
1969年 | 7篇 |
1968年 | 6篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1920年 | 5篇 |
1918年 | 5篇 |
1915年 | 8篇 |
1911年 | 4篇 |
1909年 | 5篇 |
1908年 | 5篇 |
排序方式: 共有561条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
Summary The Andigena potatoes (Solanum tuberosum ssp.andigena) of the Commonwealth Potato Collection (C.P.C.) were screened for resistance to non-pathotype A populations ofHeterodera rostochiensis. Three populations were used: Duddingston (pathotype B), Nocton (pathotype C) and Changed Little Ouse (pathotype C). Resistance was found in C.P.C. 2775, 2802 and 2805. C.P.C. 2775 also had resistance to pathotype A (Feltwell population) and appeared to have two dominant genes,H
1 giving resistance to pathotype A andH
3 giving resistance to pathotypes B and C. C.P.C. 2802 was susceptible to pathotype A and appeared to have only anH
3-type gene. C.P.C. 2805, which has not been investigated thoroughly because the plants lacked vigour, may also have anH
1 and anH
3 gene. The value of C.P.C. 2775, 2802 and 2805 for breeding nematode-resistant potatoes will only be known when they have been tested with further non-pathotype A populations and when the genetics of resistance have been investigated thoroughly. 相似文献
35.
OBJECTIVE: To determine the prevalence of overweight and obesity in British young people (4-18 years) in 1997. DESIGN: Cross-sectional analysis of the National Diet and Nutrition Survey of young people. SETTING: Great Britain. SUBJECTS: Nationally representative sample of 1836 young people (age 4-18 years). RESULTS: The prevalence of obesity based on body mass index (weight/height(2)) and the International Obesity Task Force cut-offs was 4.0%, with a further 15.4% identified as overweight. Asians were almost four times as likely to be obese as white subjects (13.6 vs. 3.5%, P<0.001). Among white subjects there was no significant difference in the prevalence of obesity between girls and boys, or with age. The risk of obesity was significantly higher in subjects from social classes IV and V than from social classes I-III (6.5 vs. 2.7%, P=0.003). Subjects living in Scotland and Wales were significantly more likely to be obese than those in England (7.6 and 6.5 vs. 2.9%, respectively, P<0.01). Multiple logistic regression showed that, among white subjects, those in social classes IV and V living in Wales and Scotland were three times more likely to be obese than the other children in the survey (odds ratio 3.3, 95% confidence interval 1.1-9.8). CONCLUSION: These data provide information on the national prevalence of overweight and obesity in Great Britain and baseline data from which to monitor future trends. This analysis provides important demographic information on those most at risk of obesity, which may be used to inform public health strategies to prevent obesity in young people. 相似文献
36.
37.
38.
The effect of acidic precipitation on cation leaching in a second-growth Douglas-fir ecosystem at the Thompson Research Center is reviewed. Sulfate mobility and soil pH buffering power were tested by applications of heavy doses of H2SO4 to the study plot. Sulfate at high concentrations proved to be immobilized, presumably by adsorption to soil sesquioxide surfaces. Soil sulfate adsorption was determined at varying sulfate concentrations, and two mechanisms of adsorption are implied by the shapes of the isotherms. 相似文献
39.
40.
Histone structure: asymmetric distribution of lysine residues in lysine-rich histone 总被引:8,自引:0,他引:8
Structural studies on a very lysine-rich histone show that the carboxyl-terminal half of the molecule is enriched in lysine (and proline). which suggests that it is a site for binding to DNA. The amino-terminal half. containing most of the acidic residues. resembles small, nonhistone proteins and so might have specificity for factors other than DNA. 相似文献