全文获取类型
收费全文 | 482篇 |
免费 | 31篇 |
专业分类
林业 | 49篇 |
农学 | 27篇 |
83篇 | |
综合类 | 12篇 |
农作物 | 38篇 |
水产渔业 | 79篇 |
畜牧兽医 | 178篇 |
园艺 | 8篇 |
植物保护 | 39篇 |
出版年
2023年 | 7篇 |
2022年 | 29篇 |
2021年 | 41篇 |
2020年 | 43篇 |
2019年 | 50篇 |
2018年 | 39篇 |
2017年 | 39篇 |
2016年 | 33篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 27篇 |
2012年 | 30篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 18篇 |
2006年 | 11篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
排序方式: 共有513条查询结果,搜索用时 0 毫秒
511.
Soil organic carbon and fractions of a Rhodic Ferralsol under the influence of tillage and crop rotation systems in southern Brazil 总被引:20,自引:0,他引:20
Alessandra A. Freixo Pedro Luiz O. de A. Machado Henrique. P. dos Santos Carlos A. Silva Francisco de S. Fadigas 《Soil & Tillage Research》2002,64(3-4):221-230
Soil organic matter (SOM) and its different pools have key importance in optimizing crop production, minimizing negative environmental impacts, and thus improving soil quality. The objective of this study was to evaluate the soil C and N contents in bulk soil and in different SOM pools (light and heavy fractions) of a clayey Rhodic Ferralsol after 13 years of different tillage and crop rotations in Passo Fundo, State of Rio Grande do Sul, Brazil. Soil samples were collected from no-tillage (no soil disturbance except for sowing; NT) and conventional tillage (disc plough followed by light disc harrowings; CT) applied to wheat/soybean (W/S) and wheat/soybean–vetch/maize (W/S–V/M) rotations. As reference, soil was sampled from a non-cultivated area adjacent to the field experiment. The greatest soil C and N contents were found in non-cultivated soils in the 0–5 cm depth (45 g C kg−1 soil and 3.6 g N kg−1 soil). Crop cultivation led to a decrease in SOM content which was higher for CT soils (approx. 60% decrease in C and N contents) than NT soils (approx. 43% decrease in C and N contents) at 0–5 cm. Tillage had the greatest impact on soil C and N storage. Soils under NT did not contain higher C and N storage than CT soils below 5 cm depth. Significantly, higher amounts of organic carbon of FLF in CT (0.5–0.7 g C kg−1 soil) than in NT soils (0.2 g C kg−1 soil) at 10–20 cm depth were also observed and the differences in C and N storage between CT and NT soils in the 0–30 cm layer were not significant. Silt and clay fractions contained the largest amount of organic carbon (60–95% of total organic carbon), and free light fraction was the most sensitive pool of organic carbon to detect changes in SOM due to soil tillage and crop rotations. 相似文献
512.
513.
Farias Nadja Naiara Pereira Freitas Ednardo Rodrigues do Nascimento Germano Augusto Jerônimo Xavier Regina Patrícia Souza de Melo Braz Nádia Dantas Francisco Diego Teixeira Figueiredo Carlos Weiber Silva Gomes Valter Luis Maia Watanabe Pedro Henrique 《Tropical animal health and production》2019,51(1):179-185
Tropical Animal Health and Production - The aim of the current study was to evaluate the addition of fresh and stored copra meal to the diet of meat quails. Two hundred eighty-seven-day-old male... 相似文献