收费全文 | 270677篇 |
免费 | 15992篇 |
国内免费 | 927篇 |
林业 | 24102篇 |
农学 | 14208篇 |
基础科学 | 3043篇 |
44716篇 | |
综合类 | 26526篇 |
农作物 | 17645篇 |
水产渔业 | 17406篇 |
畜牧兽医 | 109127篇 |
园艺 | 6346篇 |
植物保护 | 24477篇 |
2021年 | 2600篇 |
2020年 | 2994篇 |
2019年 | 3786篇 |
2018年 | 4360篇 |
2017年 | 4778篇 |
2016年 | 5062篇 |
2015年 | 4512篇 |
2014年 | 5860篇 |
2013年 | 16414篇 |
2012年 | 7077篇 |
2011年 | 9197篇 |
2010年 | 7846篇 |
2009年 | 8327篇 |
2008年 | 8573篇 |
2007年 | 7520篇 |
2006年 | 7929篇 |
2005年 | 7034篇 |
2004年 | 6881篇 |
2003年 | 6655篇 |
2002年 | 5954篇 |
2001年 | 7102篇 |
2000年 | 6749篇 |
1999年 | 6071篇 |
1998年 | 4231篇 |
1997年 | 4305篇 |
1996年 | 4018篇 |
1995年 | 4574篇 |
1994年 | 3969篇 |
1993年 | 3634篇 |
1992年 | 4708篇 |
1991年 | 4897篇 |
1990年 | 4588篇 |
1989年 | 4593篇 |
1988年 | 3994篇 |
1987年 | 4042篇 |
1986年 | 3959篇 |
1985年 | 4197篇 |
1984年 | 3803篇 |
1983年 | 3556篇 |
1982年 | 2933篇 |
1981年 | 2866篇 |
1980年 | 2803篇 |
1979年 | 3396篇 |
1978年 | 3052篇 |
1977年 | 2739篇 |
1976年 | 2625篇 |
1975年 | 2571篇 |
1974年 | 2744篇 |
1973年 | 2667篇 |
1972年 | 2367篇 |
A Colour Atlas of Avian Anatomy, by J. McLelland. 1990. 127 pp. illustrated. London, Wolfe Publishing Ltd. £30. ISBN 0–7234–1575–7.
The Tropical Agriculturalist—Poultry, by A. J. Smith, 1990. vi + 218 pp. CTA/Macmillan, London. ISBN 0–333–52306–7. 相似文献
2. The correlated relative genetic responses for 5 traits of the period between 41 and 60 weeks of age for the two lines were: 4.3% and 5.2% in egg number, 5.8% and 7.4% in egg weight, 8.4% and 10.8% in egg mass, ‐2.7% and ‐0.6% in body weight at 60 weeks, and ‐5.2% and ‐6.3% in food efficiency.
3. The estimated heritabilities of these 5 traits from the whole data set were 0.36, 0.75, 0.34, 0.71 and 0.17. The estimated genetic correlations between SECR and the same 5 traits were 0.30, 0.46, 0.61, ‐0.22 and ‐0.49.
4. A high genetic correlation of income minus food cost with egg weight and a low one with egg number were found in pullets, but the relationships were reversed in older hens. 相似文献
2. A 5 x 5 factorial approach was employed where 5 concentrations of dietary methionine were obtained (ranging from 3.9 to 12.15 g/kg diet dry matter) by the addition of DL‐methionine, and 5 concentrations of condensed tannins (ranging from 0.5 to 19.7 g/kg diet dry matter) by altering the ratio of tannin‐free and tannin‐containing faba bean hulls added to a basal diet.
3. The intake of condensed tannins had a significant, depressive effect on apparent available nitrogen (P< 0.001) and nitrogen corrected apparent metabolisable energy (AMEn ) (P< 0.001). There was no interaction between methionine and tannin (P>0.05). Thus the depressive effect of tannin was independent of methionine levels in the diet.
4. Methionine does not act as a specific detoxifier of faba bean condensed tannins. 相似文献
2. Chicks fed on diets containing 400 g/kg of the low (1.3 g BOAA/kg seed) and medium (2.2 g BOAA/kg seed) BOAA lines did not differ (P>0.05) in weight gain (WG) or in apparent fat and protein digestibilities compared to birds fed on a wheat‐based diet.
3. Consumption of 600 g low BOAA lathyrus/kg diet caused a slight, but significant (P< 0.05), decrease in WG. Food efficiency decreased as the amount of dietary lathyrus was increased, suggesting that lathyrus may contain an antinutritive factor(s) other than BOAA.
4. Removal of the hull (70 g hull/kg seed) from the seed did not affect chick performance (P> 0.05).
5. Pre‐adapting chicks for 7 d to diets containing up to 600 g medium line lathyrus/kg diet did not reduce the detrimental effects of the lathyrus.
6. Although dehulling and pre‐adaptation of chicks to lathyrus were not beneficial, the low and medium lines of lathyrus tested show potential for use in chick diets up to at least 400 g lathyrus/kg diet. 相似文献
Egg and Eggshell Quality. Sally E. Solomon, 1991, 149 pp., illustrated. London, Wolfe Publishing Ltd., £35.00, ISBN 0 7234 1647 8.
Aleen Cust, Veterinary Surgeon, Britain's First Woman Vet. Connie M. Ford, 1990, 109 pp., £5.99, Bristol, Biopress Ltd., The Orchard, Clanage Road, ISBN 0 948737 11 5.
Avian Incubation. Edited by S. G. Tullett, 1991, xiv + 335 pp., illustrated. London, Butterworth‐Heinemann. £00.00, $00.00. ISBN 0–7506–1002–6.
A Colour Atlas of Diseases & Disorders of the Domestic Fowl & Turkey. Edited by C. J. Randall, second edition, 1991, 175 pages, 432 illustrations in colour. London, Wolfe Publishing Ltd, £35, ISBN 0723416281. 相似文献
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The response (cooperation) rate among the eligible producers initially contacted was 70%. Approximately two-thirds of producers maintained individual animal records, primarily calving season records. Approximately 40% recorded disease occurrences.
The advantages, disadvantages, and interpretation of “on-farm” observational studies are discussed.
相似文献