全文获取类型
收费全文 | 200篇 |
免费 | 9篇 |
专业分类
林业 | 33篇 |
农学 | 1篇 |
基础科学 | 1篇 |
12篇 | |
综合类 | 27篇 |
农作物 | 31篇 |
水产渔业 | 2篇 |
畜牧兽医 | 80篇 |
植物保护 | 22篇 |
出版年
2020年 | 2篇 |
2018年 | 4篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 3篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1983年 | 2篇 |
1979年 | 7篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1968年 | 2篇 |
1958年 | 2篇 |
1957年 | 4篇 |
1932年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1928年 | 2篇 |
1926年 | 1篇 |
1924年 | 2篇 |
1923年 | 1篇 |
1919年 | 1篇 |
1898年 | 1篇 |
1895年 | 1篇 |
1891年 | 1篇 |
1887年 | 1篇 |
1885年 | 1篇 |
1883年 | 2篇 |
排序方式: 共有209条查询结果,搜索用时 46 毫秒
1.
2.
Robert A. Slesak Stephen H. SchoenholtzTimothy B. Harrington 《Forest Ecology and Management》2011,262(9):1722-1728
We assessed changes in mineral soil total carbon (C) and nutrient (exchangeable Ca, K, Mg, and total N) pools to 60 cm depth 5 years after manipulating biomass and competing vegetation at two contrasting Douglas-fir plantations (Matlock, WA, and Molalla, OR). Biomass treatments included whole-tree (WT) and bole-only (BO) harvest, and competing vegetation control (VC) treatments were applied as either initial or annual herbicide applications. There were main effects of biomass removal and VC on the absolute change in soil pools of some elements at both sites, but significant effects were more prevalent at the lower soil quality Matlock site than the Molalla site, and were generally confined to the top 15 cm of soil. In all cases, treatment effects were associated with increases in C and nutrients following BO and initial VC treatments combined with little change in soil pools following WT and annual VC treatments. At the Matlock site, total soil pools (0-60 cm) of C, N, and Ca significantly increased in the BO and initial VC treatments, and Mg increased and K decreased regardless of treatment. At the Molalla site, soil C and nutrient pools did not change in response to treatments, but total soil Mg increased in all treatments during the study period. Correlation analyses indicated little influence of soil nutrient pools on early growth at Matlock likely because soil water is more limiting than nutrient availability at that site, but vegetation growth was correlated to nutrient pools at Molalla indicating changes in pools associated with harvesting and treatment could influence crop development in the future. These early results indicate low potential for intensive management practices to reduce mineral soil pools of C and nutrients, but there is uncertainty on the long-term growth response because treatments may have influenced nutrient storage in pools other than mineral soil. 相似文献
3.
Three cutting heights, 2±5, 7±6 and 12±7 cm (1, 2±5 and 5 in.) and three levels of fertilizer N, 168, 280 and 392 kg N/ha (150, 250 and 350 Ib N/ac) were imposed on a sward of Italian ryegrass (Lolium multiflorum) cv. Irish. Lowering the cutting height and increasing the level of applied N increased the yield of herhage DM. Increasing the level of applied N had a greater effect on the chemical composition of the herbage than altering the cutting height 相似文献
4.
5.
6.
7.
8.
Diane Murdaugh DVM PhD Richard I. Miller BVSc PhD David R. Harrington DVM Louis L. Martin DVM 《Journal of Equine Veterinary Science》1985,5(4):189-191
An in utero tibial fracture was examined at necropsy in a seven-month-old male aborted Thoroughbred fetus. Grossly the healed fracture had a smooth cortical surface. Histologically there was no callus formation or excessive osteoclastic or osteoblastic activity. 相似文献
9.
10.