收费全文 | 7450篇 |
免费 | 3529篇 |
国内免费 | 1篇 |
林业 | 242篇 |
农学 | 460篇 |
基础科学 | 4篇 |
1529篇 | |
综合类 | 146篇 |
农作物 | 143篇 |
水产渔业 | 2569篇 |
畜牧兽医 | 4516篇 |
园艺 | 31篇 |
植物保护 | 1340篇 |
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 147篇 |
2020年 | 499篇 |
2019年 | 1061篇 |
2018年 | 922篇 |
2017年 | 955篇 |
2016年 | 959篇 |
2015年 | 829篇 |
2014年 | 831篇 |
2013年 | 1022篇 |
2012年 | 518篇 |
2011年 | 571篇 |
2010年 | 641篇 |
2009年 | 274篇 |
2008年 | 305篇 |
2007年 | 161篇 |
2006年 | 190篇 |
2005年 | 170篇 |
2004年 | 172篇 |
2003年 | 162篇 |
2002年 | 165篇 |
2001年 | 79篇 |
2000年 | 109篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1970年 | 6篇 |
1968年 | 3篇 |
1966年 | 3篇 |
2. The effect of the pelleting process on AMEn was inconsistent and was dependent on the cereal included and the addition of enzyme.
3. The growth trial showed a significant effect of enzyme addition to pelleted diets over the whole growth period (0 to 42 d). Addition of TVE improved weight gain and food efficiency by 1.3% and 2.9%, respectively and decreased food intake by 1.6% between 0 and 22 d. In the finisher period (23 to 42 d) TVE improved efficiency by 2.8% and reduced food intake by 2.9%.
4. The incidence of sticky droppings was related to the viscosity of barley used, and enzyme supplementation reduced it. Both pelleting and enzyme addition increased dry matter content of excreta.
5. At the end of the experiment, 14 animals per treatment were slaughtered and carcass yield, viscera weight and abdominal fat were determined. 相似文献
2. When this treated meal was fed to susceptible ("tainting") hens the concentration of trimethylamine in the eggs was decreased to much less than that required to cause taint. 相似文献
2. Age at first egg, body‐weight gain and egg production were affected by energy allowance. Birds on the lower energy allowances came into lay later than birds on the higher energy allowances and at a lower body weight.
3. Body‐weight gain decreased with decreasing energy allowance. The decrease in egg output in response to decreasing energy allowance resulted from more birds ceasing to lay and fewer birds laying on more than 3 d per week. Similar changes in the distribution of rates of lay were observed on each treatment as the flock aged.
4. The relationship between body‐weight gain and egg number on each treatment was negative from 21 to 36 weeks, but became less consistent with age.
5. Protein intake had little effect on body weight. At the lowest energy allowance, egg number and egg weight decreased with increasing protein allowance. This effect was not observed on the higher energy allowances. 相似文献
2. Injecting the growing embryo with amino acids equivalent to the amount of protein used resulted in higher weight of chicks at all stages up to 56 d. 相似文献
2. Body‐weight gain and carcass fat and water content increased and fertility decreased with increasing energy allowance. Maximum egg production occurred at an energy intake of 1.73 MJ AME/bird d.
3. Differences in egg weight and hatchability were related to differences in both energy and protein intake. The highest egg weight occurred at the highest allowance of energy and protein. Hatchability was depressed where the daily allowances of protein and energy were in a ratio of more than 15 g protein: 1 MJ AME.
4. Apart from egg size no significant effects on reproductive performance were observed when dietary protein intake was varied from 27 to 19.5 g/bird d.
5. Requirements of broiler breeder hens for protein during lay may be lower than previously thought. For the strain used a protein intake of 19.5 g/bird d appeared adequate provided essential amino acid concentrations were maintained.
6. The close relationships between body weight and energy allowance and the latter and egg production make body‐weight gain a useful guide to management. A body‐weight gain of about 1.1 kg from 21 to 36 weeks of age was associated with optimum performance in this study. 相似文献
2. A 20% reduction in energy allowance from 23 to 34 weeks was associated with reduced body‐weight gain, egg weight and carcass constituents except ash, but had no significant effect on egg production or hatchability.
3. Increases in nutrient intake after 34 weeks were associated with an increase in body‐weight gain and carcass fat.
4. Moderate decreases in energy intake after 34 weeks were associated with reduced body‐weight gain, and a 15% reduction in nutrient intake resulted in a decrease in body weight and egg weight.
5. It is suggested that a feeding allowance which controls body‐weight gain during early lay, and then allows for a gradual increase in body weight over the breeding period may be the most efficient way of feeding the broiler breeder hen. 相似文献
2. Differences in weight gain between birds in cooled and uncooled houses ranged from 101.5 g at eight birds/m2 to 385 g at 16 birds/m2. Food consumption increased gradually with increasing bird density. Food conversion efficiency, meat yield and carcass conformation were much better in the cooled house than under conventional conditions.
3. The financial return/m2 ranged from 2.30 to 4.51 ID1 in the cooled house, compared with 2.01 to 2.77 ID in the uncooled house at different floor densities. 相似文献
2. Legs cut from the whole birds after removal from store, unpacking and thawing, and legs from the portions were compared in odour preference at four times of examination.
3. After only 1 d the odour of the legs stored as parts at —12 °C was less preferred than that of the reference group; this was also true for legs cut from whole birds after 3 months at the same temperature.
4. After 3 months at — 12 °C the odour of the legs stored as parts was less preferred than the odour of legs obtained from whole birds.
5. Storage of legs as parts at —18 °C resulted in a comparatively less preferred odour after 3 months, while the same was true after 9 months for legs cut from the carcasses. 相似文献