全文获取类型
收费全文 | 17618篇 |
免费 | 819篇 |
国内免费 | 1033篇 |
专业分类
林业 | 943篇 |
农学 | 1039篇 |
基础科学 | 1117篇 |
1902篇 | |
综合类 | 9358篇 |
农作物 | 1085篇 |
水产渔业 | 528篇 |
畜牧兽医 | 2664篇 |
园艺 | 451篇 |
植物保护 | 383篇 |
出版年
2024年 | 92篇 |
2023年 | 220篇 |
2022年 | 421篇 |
2021年 | 513篇 |
2020年 | 550篇 |
2019年 | 612篇 |
2018年 | 323篇 |
2017年 | 519篇 |
2016年 | 764篇 |
2015年 | 684篇 |
2014年 | 1116篇 |
2013年 | 1192篇 |
2012年 | 1453篇 |
2011年 | 1536篇 |
2010年 | 1197篇 |
2009年 | 1213篇 |
2008年 | 1061篇 |
2007年 | 1111篇 |
2006年 | 873篇 |
2005年 | 705篇 |
2004年 | 459篇 |
2003年 | 455篇 |
2002年 | 283篇 |
2001年 | 250篇 |
2000年 | 260篇 |
1999年 | 209篇 |
1998年 | 190篇 |
1997年 | 200篇 |
1996年 | 150篇 |
1995年 | 156篇 |
1994年 | 107篇 |
1993年 | 152篇 |
1992年 | 87篇 |
1991年 | 89篇 |
1990年 | 68篇 |
1989年 | 46篇 |
1988年 | 46篇 |
1987年 | 42篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1962年 | 1篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 843 毫秒
171.
《The Journal of Applied Poultry Research》2016,25(3):422-427
Xinyang green-shell laying hens (n = 720), 32 wk of age were allocated to 5 dietary treatments groups, each of which included 6 replicates of 24 hens. The control group was given a basal corn-peanut-soybean meal diet containing 0.47% L-threonine (L-Thr). L-Thr levels of the experimental groups were 0.57, 0.67, 0.77, and 0.87%, respectively. The trial lasted 10 wk. Serum concentrations of total superoxide dismutases (T-SOD) and superoxide dismutases (SOD) were maximized at 0.67% L-Thr group. The 0.57% L-Thr group had the highest serum total antioxidative capacity (T-AOC), while the 0.67% L-Thr group had the lowest serum malondialdehyde (MDA) concentration. Hens fed 0.67% L-Thr of the diet resulted in the highest SOD and T-AOC levels in the liver. The activity of amylase and lipase in the jejunum was maximized at 0.77% L-Thr level. Hens fed 0.77% L-Thr in the diet resulted in the highest IgM and IgG levels in the jejunum. In conclusion, we suggest that a L-Thr level above 0.67% may have had an antioxidant capacity and positive effect on digestive enzyme activities and antibody production in the jejunum of Xinyang green-shell laying hens. 相似文献
172.
173.
A. Wallenbeck S. Wilhelmsson L. Jönsson S. Gunnarsson J. Yngvesson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2016,66(3):168-176
This study compared behavioural time budgets, presence of comfort behaviours and social behaviours in two different broiler genotypes (the fast-growing Ross 308 (R) and the slower-growing Rowan Ranger (RR)) fed organic diets with high (17.0% crude protein (CP)) or low (14.5% CP) protein content during a 10-week rearing period. 429-day-old chicks (218 R and 211 RR, respectively) were included in the study and behaviour was recorded at 2, 6 and 9 weeks of age. The results showed no effect of diet treatments but that R broilers were less active and sat, ate and drank more frequently than RR broilers, which stood and perched more frequently. However, both hybrids showed decreasing activity and foraging behaviour with increasing age, while time spent eating and sleeping was approximately similar over the entire rearing period. 相似文献
174.
Effects of cerium oxide supplementation to laying hen diets on performance,egg quality,some antioxidant enzymes in serum and lipid oxidation in egg yolk 下载免费PDF全文
S. C. Bölükbaşı A. A. Al‐sagan H. Ürüşan M. K. Erhan O. Durmuş N. Kurt 《Journal of animal physiology and animal nutrition》2016,100(4):686-693
This study was conducted to determine the effects of dietary cerium oxide levels (0, 100, 200, 300 or 400 mg/kg) on the laying performance, egg quality, some blood serum parameters and egg lipid peroxidation of laying hen. In total, one hundred and twenty 22‐week‐old brown Lohman LSL laying hens were randomly assigned to five groups equally (n = 24). Each treatment was replicated six times. Dietary supplementation of cerium oxide had no significant effect on feed intake and egg weight. The addition of cerium oxide to the laying hens' feed improved feed conversion ratio and increased (p < 0.05) egg production. Quality criteria of egg for except shell breaking strength were not affected by supplementing cerium oxide. In particular, supplementation of 200 and 300 mg/kg cerium oxide to the laying hens feed led to a significant (p < 0. 01) increase in egg shell breaking strength. Calcium and phosphorus concentration of serum increased significantly (p < 0.05) with supplementation of 100 mg/kg cerium oxide to laying hen diets. It was also observed that serum superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration decreased significantly with supplementation of cerium oxide in diets. Inclusion of cerium oxide resulted in a significant reduction in thiobarbituric acid reactive substance (TBARS) values in egg yolk in this study. It can be concluded that the addition of cerium oxide had positive effects on egg production, feed conversion ratio and egg shelf life. Based on the results of this study, it could be advised to supplement laying hens feed with cerium oxide as feed additives. 相似文献
175.
176.
社会主义新农村建设目标及实现 总被引:2,自引:1,他引:1
曾庆学 《信阳农业高等专科学校学报》2007,17(1):32-33
“生产发展、生活宽裕、乡风文明、村容整洁、管理民主”是社会主义新农村建设的主要目标,它是物质文明、精神文明和政治文明的具体体现。这些目标的实现,有赖于党的坚强领导,农民生活条件的改善和自身素质的提高。 相似文献
177.
本研究旨在比较不同生长阶段隔日限饲(早期限饲:1~14日龄限饲,后期限饲:50~63日龄限饲)对肉鸡肌肉生长及相关激素水平的影响,并探讨早期限饲对肉鸡肌肉生长的程序化作用。试验结果:1)早期限饲组整个试验阶段体重均极显著低于对照组,后期限饲组限饲一周后体重显著低于对照组并于63日龄实现完全补偿生长;2)早期限饲组14日龄和63日龄胸肌、腓肠肌重均显著低于对照组;后期限饲组63日龄胸肌、腓肠肌重均显著低于对照组,且二者与早期限饲组均差异不显著;3)早期限饲显著降低了14日龄肉鸡肌肉中DNA、RNA和蛋白含量,63日龄恢复至正常水平,且核酸、蛋白水平在胸肌和腓肠肌内的趋势表现不一致;4)早期限饲组14日龄血清中T3、T4水平均显著低于对照组,63日龄血清T3水平仍显著低于对照组;后期限饲组63日龄血清T3水平显著低于对照组,T4水平与对照组差异不显著。结果表明:1)限饲可显著阻碍肉鸡肌肉的生长;2)不同部位的肌肉对限饲的敏感度不同;3)早期营养因子对肉鸡肌肉的生长具有"程序化"作用,甲状腺激素可能参与这些过程的调节。 相似文献
178.
《The Journal of Applied Poultry Research》2007,16(3):365-380
A study involving 7 white-egg and 3 brown-egg commercial layer strains was conducted at the North Carolina Piedmont Research Station to assess the effects cage population 3-bird vs. 4-bird cages and alternative molt programs on performance through 113 wk of age (791 d). The flock was divided into 3 groups; not molted (NM), maintained in continuous production; molted using feed restriction (FR), an industry-type 14-d feed withdrawal molting program initiated at 463 d of age; and molted using a nonfasted/anorexic program (NF), in which an ad libitum supply of a low protein, low energy molt feed was provided. Productivity, egg size, and egg quality were monitored at 28-d periods throughout the test providing the performance data for the white-egg and brown-egg strains with regard to these management factors. Detailed results by strain are available on the following Web site: http://www.ces.ncsu.edu/depts/poulsci/tech_info.html#layer. The performance for the 3-bird or 4-bird cage groups for either type of layer was similar, except that birds in 4-bird cages had higher feed consumption in the first production phase than did the birds in 3-bird cages. In the same time period the white-egg birds in the 3-bird cages had a greater percentage of cracked eggs and a smaller percentage of Grade A large eggs than those in 4-bird cages. No differences were observed in egg income for the 2 population sizes for either type of layer. However, due to their higher feed consumption, the white egg birds in the 4-bird cages had higher feed cost per hen for the first cycle, which was offset by the egg income component due to their increased production rate. The molted layers outperformed the nonmolted layers for both types of layers in terms of overall income over feed costs. The FR molted hens, under a program that has traditionally been used by commercial producers, outperformed NF-molted hens, indicating that further refinements are needed to make the NF program economically competitive with the FR molting program. 相似文献
179.
180.