收费全文 | 164589篇 |
免费 | 8870篇 |
国内免费 | 105篇 |
林业 | 6576篇 |
农学 | 4743篇 |
基础科学 | 1130篇 |
18582篇 | |
综合类 | 31688篇 |
农作物 | 6398篇 |
水产渔业 | 7513篇 |
畜牧兽医 | 85231篇 |
园艺 | 1892篇 |
植物保护 | 9811篇 |
2018年 | 1952篇 |
2017年 | 2169篇 |
2016年 | 2085篇 |
2015年 | 1776篇 |
2014年 | 2146篇 |
2013年 | 6108篇 |
2012年 | 4088篇 |
2011年 | 5059篇 |
2010年 | 3292篇 |
2009年 | 3329篇 |
2008年 | 5040篇 |
2007年 | 4638篇 |
2006年 | 4530篇 |
2005年 | 4163篇 |
2004年 | 4178篇 |
2003年 | 4139篇 |
2002年 | 3993篇 |
2001年 | 5120篇 |
2000年 | 5145篇 |
1999年 | 3894篇 |
1998年 | 1636篇 |
1997年 | 1665篇 |
1995年 | 1944篇 |
1994年 | 1801篇 |
1993年 | 1711篇 |
1992年 | 3603篇 |
1991年 | 3881篇 |
1990年 | 3708篇 |
1989年 | 3787篇 |
1988年 | 3498篇 |
1987年 | 3667篇 |
1986年 | 3808篇 |
1985年 | 3661篇 |
1984年 | 2927篇 |
1983年 | 2652篇 |
1982年 | 1798篇 |
1981年 | 1675篇 |
1979年 | 2699篇 |
1978年 | 2244篇 |
1977年 | 1846篇 |
1976年 | 1811篇 |
1975年 | 1852篇 |
1974年 | 2401篇 |
1973年 | 2510篇 |
1972年 | 2481篇 |
1971年 | 2332篇 |
1970年 | 2177篇 |
1969年 | 1999篇 |
1968年 | 1640篇 |
1967年 | 1744篇 |
2. In the first experiment, removal of food for 8 h/d from 42 to 56 d of age significantly improved food conversion efficiency of broilers on deep litter. Removal of food for 16 h/d or on alternate days tended to cause slower growth and also improved conversion efficiency.
3. In the second experiment, denial of food for 8 h/d did not significantly affect either growth rate or conversion efficiency of caged broilers. Denial of food on alternate days, from 28 d of age, depressed food intake and growth rate. Food restriction decreased dressing percentage regardless of the age of introduction. With 32, 40 or 48 h food denial each 72 h there was a large depression in growth rate and dressing percentage. Carcass dry matter was also less, indicating less carcass fat, when food was denied for 48 h each 72 h.
4. In the third experiment, growth rate of broilers on deep litter was significantly improved by denying food for 8 h/d from 28 d of age, and was significantly depressed by food denial on alternate days. This depression was significantly more severe if restriction started at 28 d rather than at 42 d of age. Conversion efficiency was not significantly improved by denial for 8 h/d.
5. In the last two experiments conversion efficiency was much worse in severe restriction. 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. Realised heritability estimates calculated after five generations of selection were : 0–37 + 0.04 for weight gain (WG); 0.44 + 0.05 for food consumption (FC); 0.21 + 0.04 for food conversion ratio (FCR).
3. Realised genetic correlation estimates were: WG and FC, +0.71 ±006; WG and FCR, ‐0.40±0.09; FC and FCR, +0.27 + 0.09.
4. Zero‐generation heritability and genetic correlation estimates were greater than the realised estimates, and sex linkage appeared to be important in the expression of all three traits.
5. The genetic correlation between FC and FCR was asymmetrical with considerable positive response in FCR in line F (rg = +0.79) but negligible response in FC in line E (rg = —0.01).
6. There was an apparent plateau in response in FCR in line E from the third to the fifth selected generations. 相似文献