全文获取类型
| 收费全文 | 6844篇 |
| 免费 | 493篇 |
| 国内免费 | 205篇 |
专业分类
| 林业 | 396篇 |
| 农学 | 503篇 |
| 基础科学 | 68篇 |
| 1181篇 | |
| 综合类 | 813篇 |
| 农作物 | 445篇 |
| 水产渔业 | 505篇 |
| 畜牧兽医 | 2855篇 |
| 园艺 | 150篇 |
| 植物保护 | 626篇 |
出版年
| 2023年 | 61篇 |
| 2022年 | 84篇 |
| 2021年 | 178篇 |
| 2020年 | 174篇 |
| 2019年 | 190篇 |
| 2018年 | 228篇 |
| 2017年 | 248篇 |
| 2016年 | 236篇 |
| 2015年 | 188篇 |
| 2014年 | 232篇 |
| 2013年 | 331篇 |
| 2012年 | 371篇 |
| 2011年 | 415篇 |
| 2010年 | 293篇 |
| 2009年 | 272篇 |
| 2008年 | 349篇 |
| 2007年 | 354篇 |
| 2006年 | 304篇 |
| 2005年 | 258篇 |
| 2004年 | 239篇 |
| 2003年 | 289篇 |
| 2002年 | 356篇 |
| 2001年 | 344篇 |
| 2000年 | 203篇 |
| 1999年 | 157篇 |
| 1998年 | 50篇 |
| 1997年 | 54篇 |
| 1996年 | 39篇 |
| 1995年 | 52篇 |
| 1994年 | 46篇 |
| 1993年 | 38篇 |
| 1992年 | 48篇 |
| 1991年 | 43篇 |
| 1990年 | 55篇 |
| 1989年 | 55篇 |
| 1988年 | 35篇 |
| 1987年 | 40篇 |
| 1986年 | 30篇 |
| 1985年 | 37篇 |
| 1984年 | 51篇 |
| 1983年 | 28篇 |
| 1982年 | 26篇 |
| 1980年 | 25篇 |
| 1979年 | 29篇 |
| 1978年 | 28篇 |
| 1977年 | 27篇 |
| 1975年 | 25篇 |
| 1974年 | 37篇 |
| 1972年 | 30篇 |
| 1971年 | 37篇 |
排序方式： 共有7542条查询结果，搜索用时 138 毫秒
61.
Josiane C. Panisson Nathália C. Oliveira Cristina M. Sá-Fortes Adsos A. Passos Claudia C. da Silva Wagner A. G. Araújo Idael M. G. Lopes Gleison M. S. Costa Iara Q. Ataíde Bruno A. N. Silva 《Animal Science Journal》2021,92(1):e13592
Improvements in sow productivity have raised questions regarding dietary vitamin D recommendations. The present study aimed to evaluate the effects of the housing system with access to sunlight exposure and supplementation of 25-hydroxicholecalciferol on performance and serum levels of 25(OH)D3 in sows during gestation and lactation. Sows were distributed in an experimental design with two housing systems: gestation crates or gestation free-range system with external area for sunlight exposure; and two diets: 0 or 50 μg of 25-hydroxicholecalciferol kg−1. The use of 25-hydroxicholecalciferol tended (P = 0.052) to improve total born and influenced (P = 0.046) on number of born alive. Litter weight at birth was also increased (P = 0.01) by 25-hydroxicholecalciferol supplementation; 25-hydroxicholecalciferol supplementation and housing system (free-range with sunlight exposure) tended to increase weaning weight (P = 0.07) and litter daily gain (P = 0.051) during lactation. Exposure to sunlight and 25-hydroxicholecalciferol supplementation increased 25(OH)D3 serum levels when compared with control treatment during gestation (136.95 vs. 113.92 ng mL−1; P = 0.035) and lactation (120.29 vs. 88.93 ng mL−1; P = 0.026). In conclusion, the association of 25-hydroxicholecalciferol supplementation with exposure to sunlight during gestation improved significantly 25(OH)D3 serum levels and consequently performance traits in gestation and lactation. 相似文献
62.
M. Muoz‐Rojas A. Jordn L. M. Zavala D. De la Rosa S. K. Abd‐Elmabod M. Anaya‐Romero 《Land Degradation \u0026amp; Development》2015,26(2):168-179
During the last few decades, land use changes have largely affected the global warming process through emissions of CO2. However, C sequestration in terrestrial ecosystems could contribute to the decrease of atmospheric CO2 rates. Although Mediterranean areas show a high potential for C sequestration, only a few studies have been carried out in these systems. In this study, we propose a methodology to assess the impact of land use and land cover change dynamics on soil organic C stocks at different depths. Soil C sequestration rates are provided for different land cover changes and soil types in Andalusia (southern Spain). Our research is based on the analysis of detailed soil databases containing data from 1357 soil profiles, the Soil Map of Andalusia and the Land Use and Land Cover Map of Andalusia. Land use and land cover changes between 1956 and 2007 implied soil organic C losses in all soil groups, resulting in a total loss of 16·8 Tg (approximately 0·33 Tg y−1). Afforestation increased soil organic C mostly in the topsoil, and forest contributed to sequestration of 8·62 Mg ha−1 of soil organic C (25·4 per cent). Deforestation processes implied important C losses, particularly in Cambisols, Luvisols and Vertisols. The information generated in this study will be a useful basis for designing management strategies for stabilizing the increasing atmospheric CO2 concentrations by preservation of C stocks and C sequestration. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
63.
Effects of dietary lysozyme levels on growth performance,intestinal morphology,non‐specific immunity and mRNA expression in weanling piglets 
下载免费PDF全文
下载免费PDF全文 Jiatao Zhu Xiaoxue Pang Zhengfeng Fang Yan Lin Lianqiang Che Shengyu Xu Jian Li Yiming Huang Xiang Su De Wu 《Animal Science Journal》2016,87(3):411-418
The aim of the present study was to determine the effect of dietary lysozyme levels on growth performance, gut health and non‐specific immunity of weanling piglets. A total of 150 weanling piglets were allocated to six treatments. The piglets were fed the same basel diet supplemented with 0, 30, 60, 90 and 120 mg/kg lysozyme as well as antibiotics for 28 days. From day 14 to day 28 of dietary treatment, piglets fed 90 mg/kg lysozyme had greater average daily gain than piglets fed control diet. During the whole experimental period, piglets fed 120 mg/kg lysozyme tended to have greater average daily gain than piglets fed control diet. Compared with piglets fed control diet, piglets fed diets containing antibiotics and 90 mg/kg lysozyme had greater villus height to crypt depth ratio in duodenum and jejunum. Additionally, dietary supplementation of 60 and 90 mg/kg lysozyme as well as antibiotics enhanced the phagocytic activity of peritoneal macrophages in piglets. In conclusion, dietary lysozyme can accelerate the growth of weanling piglets by improving gut health and non‐specific immunity and supplementing 90 mg/kg lysozyme is as effective as antibiotics (20 mg/kg colistin sulphate + 50 mg/kg kitasamycin) in improving the growth performance of weanling piglets. 相似文献
64.
Composition and fatty acid profile of milk from cows supplemented with pressed oilseed cake 下载免费PDF全文
下载免费PDF全文 Ronaldo Lopes Oliveira Severino Gonzaga Neto Francisco Helton Sa de Lima Ariosvaldo Nunes de Medeiros Leilson Rocha Bezerra Elzania Sales Pereira Adriana Regina Bagaldo Caius Barcellos de Pellegrini Braulio Rocha Correia 《Animal Science Journal》2016,87(10):1225-1232
This study compared the productive and nutritional parameters of milk from crossbred lactating cows managed on Panicum maximum Jacq. cv. Tanzania and with a diet supplemented with different pressed oilseed cakes. The supplements used were as follows: peanut cake, sunflower cake and palm kernel cake for replacement of soybean meal. Sixteen cows with an average weight of 544 ± 57 kg and producing 8 ± 1.4 L of milk per day were used in this study. The animals were randomly assigned to the treatments according to a Latin square design repeated over time, with four treatments, 16 animals and four experimental periods. Supplementation of the diet with peanut cake, sunflower cake and palm kernel cake compared with soybean meal in the diet of cows did not affect the average daily production or composition of the milk. The palm kernel cake promoted an increase in lauric fatty acids (C12:0) and palmitoleic acids (C16:1) (5.02 and 1.65%, respectively) compared with peanut cake and sunflower cake (4.13 and 4.01%, respectively). The levels of oleic fatty acids (C18:1) were higher for the sunflower cake and palm kernel cake supplements (26.01 and 25.01%, respectively) compared with peanut cake (23.11%). The replacement of soybean meal with sunflower cake and palm kernel cake improved the nutritional quality of the milk, with lower concentrations of saturated fatty acids and higher concentrations of unsaturated fatty acids, without compromising the production or nutritional composition of the milk. © 2015 Japanese Society of Animal Science 相似文献
65.
66.
Rearing conditions affected responses of weaned pigs to organic acids showing a positive effect on digestibility,microflora and immunity 下载免费PDF全文
下载免费PDF全文 Yalin Zhang Yumo Song Xiaoling Zhang Yan Lin Lianqiang Che Shengyu Xu De. Wu Bai Xue Zhengfeng Fang 《Animal Science Journal》2016,87(10):1267-1280
Three experiments were conducted to assess the response of weaned pigs to organic acid SF3, which contains 34% calcium formate, 16% calcium lactate, 7% citric acid and 13% medium chain fatty acids. Dietary treatments had no effect on growth performance of piglets (21‐day weaning) fed the commercial prestart diet for 1 week before receiving the experimental diets supplemented with SF3 at 0, 3 or 5 g/kg diet (Exp. 1), whereas diarrhea frequency averaged across a week was decreased by SF3 supplementation (5 g/kg diet) in piglets fed the experimental diets immediately after weaning (Exp. 2). In Exp. 3, piglets (28‐day weaning) were fed the control (containing pure colistin sulfate and enramycin, respectively, at 20 mg/kg diet) for 1 week and then were fed the control or SF3‐supplemented (5 g/kg diet) diet for 2 weeks. The SF3‐fed piglets had greater apparent ileal digestibility of calcium and dry matter, while also demonstrating greater overall gross energy, up‐regulated jejunal expression of sodium‐glucose cotransporter‐1 and transforming growth factor‐β, down‐regulated jejunal expression of tumor necrosis factor (TNF)‐α, higher ileal Lactobacillus, with lower total bacteria content, lower plasma TNF‐α but higher IgG levels than the control‐fed piglets. Collectively, SF3 consumption improved diarrhea resistance of weaned pigs by improving nutrient digestibility, piglet immunity and intestinal bacteria profile. © 2016 Japanese Society of Animal Science 相似文献
67.
68.
S. Sartore P. Sacchi D. Soglia S. Maione A. Schiavone M. De Marco 《British poultry science》2016,57(4):435-443
The objective of this study was to determine the genetic structure and variability of Bionda Piemontese and Bianca di Saluzzo (Piedmont, Northwest Italy) using an international set of microsatellite loci (AVIANDIV-FAO). Differences compared with commercial lines and other Italian breeds were verified to justify the implementation of conservation programmes.
Flock contribution to genetic variability was assessed following the approach implemented in the MolKin software. Comparison was performed using the fixation index and the Reynolds genetic distance. The most likely number of different populations was estimated using the clustering procedure implemented in STRUCTURE.
The molecular information suggests that management practices could have prevented random mating and produced inbreeding and heterogeneity across flocks. In this respect, Bionda and Bianca show substructuring and are more similar to British breeds than other continental European breeds.
Bionda and Bianca fit into the European breeds provided with the highest number of alleles and expected heterozygosity. There is a clear distinction between the Piedmont breeds and the other populations. The Piedmont poultry differ from both commercial lines and other Italian breeds and retain a high level of genetic variability.
As for other indigenous breeds, Bionda and Bianca could make an original contribution to the industry in the future. A collective planned approach to restoration is essential, because the flocks are managed with poor regulation. Enhancing connection between breeders with an efficient replacement interchange and mating plan is the right way of controlling inbreeding, preventing substructuring and increasing variability within the flocks.
69.
70.
Alana Batista dos Santos Mara Lúcia Albuquerque Pereira Herymá Giovane de Oliveira Silva Gleidson Giordano Pinto de Carvalho Taiala Cristina de Jesus Pereira Leandro Sampaio Oliveira Ribeiro José Augusto Gomes Azevêdo Maria das Graças Conceição Parada Costa Silva Larisse Borges Sousa Leandro Borges Sousa Daiane de Oliveira Alencar 《Tropical animal health and production》2016,48(3):509-515