收费全文 | 281479篇 |
免费 | 15966篇 |
国内免费 | 1405篇 |
林业 | 24302篇 |
农学 | 14468篇 |
基础科学 | 3227篇 |
45307篇 | |
综合类 | 30291篇 |
农作物 | 17552篇 |
水产渔业 | 17561篇 |
畜牧兽医 | 114756篇 |
园艺 | 6638篇 |
植物保护 | 24748篇 |
2021年 | 2746篇 |
2020年 | 3071篇 |
2019年 | 3851篇 |
2018年 | 4313篇 |
2017年 | 4746篇 |
2016年 | 5028篇 |
2015年 | 4642篇 |
2014年 | 5933篇 |
2013年 | 16650篇 |
2012年 | 7498篇 |
2011年 | 9706篇 |
2010年 | 8118篇 |
2009年 | 8479篇 |
2008年 | 8735篇 |
2007年 | 7973篇 |
2006年 | 8278篇 |
2005年 | 7573篇 |
2004年 | 7171篇 |
2003年 | 7004篇 |
2002年 | 6310篇 |
2001年 | 7195篇 |
2000年 | 6899篇 |
1999年 | 6139篇 |
1998年 | 4254篇 |
1997年 | 4276篇 |
1996年 | 4022篇 |
1995年 | 4530篇 |
1994年 | 3970篇 |
1993年 | 3702篇 |
1992年 | 4890篇 |
1991年 | 5254篇 |
1990年 | 4964篇 |
1989年 | 4863篇 |
1988年 | 4339篇 |
1987年 | 4436篇 |
1986年 | 4269篇 |
1985年 | 4482篇 |
1984年 | 4147篇 |
1983年 | 3771篇 |
1982年 | 3059篇 |
1981年 | 2926篇 |
1980年 | 2886篇 |
1979年 | 3615篇 |
1978年 | 3164篇 |
1977年 | 2849篇 |
1976年 | 2791篇 |
1975年 | 2638篇 |
1974年 | 2976篇 |
1973年 | 2883篇 |
1972年 | 2620篇 |
2. Hens were hypophysectomised at 6 intervals from 4.5 to 11.0 h before the expected time of ovulation. Ovulation occurred in the hens operated on from 4.5 to 7.3 h, but did not take place in birds operated on from 9.2 to 9.8 h before the expected time of ovulation.
3. When a single dose of P4 (2 mg/hen) was injected iv immediately after the removal of the anterior pituitary from 7.5 to 9.8 h before the expected time of ovulation, ovulation was induced. However, the percentage of hens responding decreased in proportion to the lapse of time between the hypophysectomy and the expected time of ovulation. No ovulation was induced in hens which were hypophysectomized and given P4 10.2 to 11.0 h before the expected time of ovulation.
4. It is suggested that ovulation is induced by P4 alone possibly in the absence of preovulatory gonadotrophins and that P4 acts directly on the ovary to induce follicle rupture. 相似文献
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