全文获取类型
收费全文 | 279篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
林业 | 11篇 |
农学 | 5篇 |
41篇 | |
综合类 | 33篇 |
农作物 | 28篇 |
水产渔业 | 26篇 |
畜牧兽医 | 112篇 |
植物保护 | 33篇 |
出版年
2020年 | 5篇 |
2019年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2010年 | 13篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2002年 | 3篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1968年 | 3篇 |
1965年 | 3篇 |
1963年 | 6篇 |
1961年 | 3篇 |
1960年 | 3篇 |
1958年 | 10篇 |
1957年 | 6篇 |
1956年 | 9篇 |
1955年 | 4篇 |
1954年 | 6篇 |
1953年 | 6篇 |
排序方式: 共有289条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
87.
The provision of analgesia at the time of marking has been adopted by the Australian sheep industry, but data on production benefits are lacking. In the current study, alternate lambs were provided with either meloxicam (non‐steroidal anti‐inflammatory drug [NSAID], n = 781) or no analgesia (NONE, n = 822) at the time of ring castration and tail docking. Six distinct management groups of lambs were studied. Lambs were weighed immediately before marking and then again at weaning. There was no significant effect of treatment on average daily gain between marking and weaning in cross‐bred lambs. In Merino lambs, average daily gain was 5 g/day lower (P < 0.005) in lambs receiving NSAID, but this may not be biologically significant. Lamb losses were significantly (P < 0.05) lower in the NSAID group (1.1%) than in the NONE group (2.7%). This observation is worth validating in larger studies, particularly considering that lamb mortality is a significant cost to production and welfare concern. 相似文献
88.
The catchment of the Kingston Brook has an area of 57 km2, mainly under pasture (56%) and arable crops (36%). Changes of soil water content, measured with a neutron probe from April 1969 to March 1973, were analysed to determine evaporation (summer only) and drainage. From measurements of rainfall and runoff, supplemented by Penman estimates of evaporation (in winter), water storage is estimated month by month. Annual mean values (mm) were: rainfall (559), evaporation (398), runoff (157). During the summer, the measured decrease in soil water storage contributed ca 100 mm to evaporation and drainage and there is evidence of delayed recharge (about 30 mm) during the winter. A linear relation between annual rainfall and annual runoff is interpreted in terms of (i) a fixed catchment storage (125 mm); (ii) a small and nearly constant winter evaporation (ca 49mm); (iii) summer evaporation of 125 mm from storage plus a constant fraction (0.57) of contemporary precipitation. Summer evaporation was restricted by the supply of rain in every year from 1969 to 1976. By estimation, 500 mm of summer rain is needed to maintain potential evaporation, and the deficit at which actual evaporation falls below the potential rate was about 40 mm. Replacing the pasture by cereals would increase runoff by about 10% because of the shorter growing season. 相似文献
89.
Aspects of litter movement were looked at in a variety of ways. River bank clearances provided valuable information on litter accumulation and movement, showing a distinctive correlation between flood events and litter movement. Introduction of litter outside of channel deposition (diffuse sources) were limited in the study area in South Wales, UK. A rise in litter deposition occurred for some time after flood events, with the main accumulation occurring in the mid-bank zone. As only some litter types have an increased input during flood events e.g. sewage-derived material from combined sewer outfalls (CSO), accumulation of other litter types, e.g. plastic sheeting could be due to their distribution throughout the catchment. A positive correlation between litter stranding and vegetation was found. During high flows, (75.59 cumecs) litter is removed from sites with little restraining vegetation and deposited where stranding potential is high. Smaller items such as feminine hygiene products were more susceptible to stranding than larger plastic sheeting. 相似文献
90.