全文获取类型
收费全文 | 70篇 |
免费 | 28篇 |
专业分类
1篇 | |
农作物 | 24篇 |
畜牧兽医 | 73篇 |
出版年
2011年 | 1篇 |
2006年 | 1篇 |
2005年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1963年 | 3篇 |
1962年 | 2篇 |
1960年 | 1篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1954年 | 3篇 |
1953年 | 3篇 |
1950年 | 1篇 |
1948年 | 2篇 |
1947年 | 1篇 |
1946年 | 4篇 |
1945年 | 2篇 |
1944年 | 9篇 |
1943年 | 4篇 |
1942年 | 3篇 |
1941年 | 3篇 |
1940年 | 7篇 |
1939年 | 11篇 |
1938年 | 11篇 |
1937年 | 4篇 |
1936年 | 1篇 |
1935年 | 2篇 |
1934年 | 1篇 |
1928年 | 1篇 |
1926年 | 1篇 |
排序方式: 共有98条查询结果,搜索用时 0 毫秒
1.
2.
E. Marx C. H. Metzger B. A. Brown Eugene W. Whitman H. R. Talmage Frank W. Hussey H. A. Reiley Marx Koehnke J. C. Campbell E. V. Hardenburg Karl H. Fernow Earl B. Tussing E. R. Jackman C. A. Henderson O. D. Burke K. W. Lauer John Noonan H. L. Bailey Chas D. Gaines W. N. Keenan R. E. Goodin 《American Journal of Potato Research》1943,20(8):224-236
3.
4.
5.
6.
Birds in woodland can be affected by increasing deer populations through changes to vegetation structure and potential impacts on foraging resources; these effects need to be better understood. Effects of deer browsing are reported from a replicated split-plot exclusion experiment in English coppiced woodland. All stages of growth were examined up to eight years after felling. We used standardised mist-netting (totaling 1920 h) to sample birds in breeding and post-breeding periods. Deer browsing strongly altered vegetation structure by reducing canopy cover and shrub layer foliage density. However deer did not affect invertebrate density per unit of foliage, providing no evidence of an ungulate-mediated plant chemical response affecting forage quality for invertebrate herbivores. At avian guild level, significantly more ground and understorey foraging birds were captured where deer were excluded, and negative responses to browsing were more marked for pooled migrants than pooled residents. At the species level, especially pronounced negative effects were evident for dunnock (Prunella modularis) and garden warbler (Sylvia borin); approximately five times more dunnocks were captured in deer exclosures than in browsed vegetation. We also detected negative responses to browsing by nightingale (Luscinia megarhynchos) and long-tailed tit (Aegithalos caudatus). No significant positive responses to browsing were detected. For some species the use of young re-growth increased post breeding relative to the breeding period, including a marked shift by pooled residents that involved a disproportionate number of juveniles. Previous studies in North America have shown that, through vegetation modification, ungulate activity can alter woodland bird assemblages; as far as we are aware this is the first experimental demonstration of effects in Europe, and at low to moderate browsing intensity typical of the wider landscape scale. 相似文献
7.
8.
9.
10.
Chas. A. Mitchell L. F. Guerin John Robillard 《Canadian journal of veterinary research》1968,32(4):544-546
The decay rate of six strains of Influenza virus Type A of human origin and eight strains of avian origin were examined in aerosol form under fixed conditions of temperature and humidity. Strains of avian origin were demonstrated to have greater resistance to decay of viability. 相似文献