全文获取类型
收费全文 | 2868篇 |
免费 | 160篇 |
国内免费 | 105篇 |
专业分类
林业 | 251篇 |
农学 | 262篇 |
基础科学 | 102篇 |
612篇 | |
综合类 | 373篇 |
农作物 | 307篇 |
水产渔业 | 218篇 |
畜牧兽医 | 593篇 |
园艺 | 111篇 |
植物保护 | 304篇 |
出版年
2024年 | 5篇 |
2023年 | 28篇 |
2022年 | 94篇 |
2021年 | 109篇 |
2020年 | 122篇 |
2019年 | 157篇 |
2018年 | 167篇 |
2017年 | 151篇 |
2016年 | 168篇 |
2015年 | 103篇 |
2014年 | 115篇 |
2013年 | 251篇 |
2012年 | 173篇 |
2011年 | 186篇 |
2010年 | 158篇 |
2009年 | 109篇 |
2008年 | 166篇 |
2007年 | 105篇 |
2006年 | 83篇 |
2005年 | 91篇 |
2004年 | 59篇 |
2003年 | 49篇 |
2002年 | 36篇 |
2001年 | 32篇 |
2000年 | 54篇 |
1999年 | 44篇 |
1998年 | 35篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 33篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有3133条查询结果,搜索用时 15 毫秒
31.
32.
33.
Effect of dietary probiotic,prebiotic and synbiotic supplementation on performance,immune responses,intestinal morphology and bacterial populations in broilers 下载免费PDF全文
A. Salehimanesh M. Mohammadi M. Roostaei‐Ali Mehr 《Journal of animal physiology and animal nutrition》2016,100(4):694-700
This study was conducted to investigate the effects of probiotic (Primalac), prebiotic (TechnoMos) and synbiotic (Primalac + TechnoMos) supplementation on performance, immune responses, intestinal morphology and bacterial populations of ileum in broilers. A total of 240 one‐day‐old broiler chicks were randomly divided into four treatment groups which included 60 birds. Control group did not receive any treatment. The chicks in the second, third and fourth groups were fed probiotic (0.9 g/kg), prebiotic (0.9 g/kg) and probiotic (0.9 g/kg) plus probiotic (0.9 g/kg; synbiotic), respectively, at entire period. Daily feed intake, daily weight gain and feed conversion ratio were evaluated. The birds were immunized by sheep red blood cell (SRBC) on days 12 and 29 of age and serum antibody titres were measured on days 28, 35 and 42. Newcastle vaccines administered on days 9, 18 and 27 to chicks and blood samples were collected on day 42. Intestinal morphometric assessment and enumeration of intestinal bacterial populations were performed on day 42. The results indicated that consumption of probiotic, prebiotic and synbiotic had no significant effect on daily feed intake, daily body weight gain, feed conversion ratio, carcass traits, intestinal morphology and bacterial populations of ileum (p > 0.05). Consumption of prebiotic increased total and IgM anti‐SRBC titres on days 28 and 42 and antibody titre against Newcastle virus disease on day 42 (p < 0.05). Synbiotic increased only total anti‐SRBC on day 28 (p < 0.05). It is concluded that consumption of prebiotic increased humoral immunity in broilers. Therefore, supplementation of diet with prebiotic for improvement of humoral immune responses is superior to synbiotic supplementation. 相似文献
34.
35.
36.
37.
By using RACE (rapid amplification ofcDNA ends) based homologous cloning strategy, we have successfully isolated the genomic and full-length cDNA sequences of a gene encoding typical DFR (dihydroflavonol-4-reductase) from black-seeded Brassica campestris L. var. oleifera DC.. The gene, designated BcDFR here, is 1 722bp in length and harbors 5 introns with typical splice sites of plant DFR genes. BcDFR cDNA is 1311bp in length with a 1 158bp ORF as well as a 25bp 5‘ UTR and a 128bp 3‘ UTR. The encoded BcDFR protein is 385 aa with a calculated Mw of 42.85kD and a pI value of 5.55. The nucleotide and amino acid sequences of this gene share extensive homologies to plant DFR genes of wide origins especially high similarities to Cruciferous DFR genes. Sequence analyses such as phylogenetic analysis, conserved domain search and substrate specificity region detection all indicated that BcDFR gene is a quite potentially biofunctional gene. Its cloning enables us to further dissect the possible relatedness between DFR gene and Brassica seed coat color traits and to create transgenic novel yellow-seeded rapeseed germplasm through antisense- or RNAi-suppression of DFR gene expression in black-seeded elite cultivars. 相似文献
38.
Aimed at soving the problem existing in the knowledge-acquisition directing-operation expert systems, a new method is proposed to acquire knowledge of expert-operation, excluding errors existed in examples and reinforce the accuracy of examples,the goal of knowledge acquisition can be achieved, the method presented in this paper solves the problem of self-enhancement of expert knowledge on line efficiently. 相似文献
39.
In the general directing-operation expert systems.the information of directingoperation is often shown after the subprocess has finished,The aim of the thesis is to enhance thefunction of directing-operation,and suggest that we add the self-tuning predictor in the expertsystems and use it to direct the present operation.We have shown the case oftemperature-predicting experiment made in the small wine distillatorv so that we can illustrate thatit is feasible to use the predictor to direct the operation. 相似文献
40.
地源热泵技术在中国温室设施中的应用探讨 总被引:3,自引:2,他引:3
当前在中国温室设施中应用和推广地源热泵技术尚存在诸多不利因素,大大限制了该项技术在设施农业领域中的发展。为探寻合理的解决途径,对地源热泵空调系统的关键技术和其在中国的发展概况进行了相关的阐述和分析,并以中国农业大学上庄实验站已经建成使用的地下水式温室地源热泵空调系统为实例,介绍该系统的组成、工作流程、性能参数和使用情况,探讨温室地源热泵空调系统在推广和使用中可能出现的投资较高,长时间运行性能不稳定等问题,分析其原因并提出相应的对策建议。 相似文献