全文获取类型
收费全文 | 251篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
林业 | 20篇 |
农学 | 2篇 |
70篇 | |
综合类 | 49篇 |
农作物 | 12篇 |
水产渔业 | 22篇 |
畜牧兽医 | 31篇 |
园艺 | 1篇 |
植物保护 | 60篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 23篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 13篇 |
2005年 | 13篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 5篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1964年 | 5篇 |
1963年 | 2篇 |
排序方式: 共有267条查询结果,搜索用时 468 毫秒
71.
在田间的小麦丛矮病非典型病株申常常分离到北方禾谷花叶病毒(NCMV)及玉米粗缩病毒(MRDV)两种病原物。单独用前者接种,仅表现小麦丛矮症,单独用后者接种,仅表现小麦蓝矮症,即植株矮化、暗绿、分蘖减少,叶坚挺。两者混合侵染时,往往表现两者的混合症状,但以何种病毒占优势而倾向于优势病毒的症状。典型丛矮症植株中电镜检出弹状病毒粒体,40—70×270—400nm尺度与日本报导的稍异。典型丛矮病株中不存在玉米粗缩病毒的粒体。小麦丛矮病毒很可能是北方禾谷花叶病毒的一种地方性株系。 相似文献
72.
Infectious bursal disease virus (IBDV) causes a contagious immunosuppressive disease in chickens. The aim of the present study is to develop an enzyme-linked immunosorbent assay (ELISA) using the expressed VP2 or VP3 protein of IBDV as the coating antigen for detecting antibodies to IBDV. Experimental results were compared with virus neutralization assay and a commercial-available ELISA. These assays were used to examine the sera from farm chickens and chickens vaccinated experimentally. The VP3-based ELISA had a higher correlation coefficient (R(2)) of 0.812 with a commercial ELISA kit at a serum dilution of 1:500 than that of VP2-based ELISA (R(2)) of 0.671. The relative sensitivity between virus neutralization and VP2-ELISA and VP3-ELISA was 96% (251/262) and 100% (262/262), respectively, and that between virus neutralization and a commercial ELISA was 99% (257/261). Additionally, compared with virus neutralization assay, the reference technique for diagnosing IBDV, VP3-based ELISA had an agreement value of 99%, superior to that of VP2-based ELISA (95%) or the commercial kit (89%). These results revealed that the capability of either VP2-ELISA or VP3-ELISA in detecting the field chicken sera was comparable to the commercial one, which is generally used to replace the virus neutralization assay. However, the preparation of VP3 is derived from an Escherichia coli expression system with a high yield and purification efficiency by Ni(2+)-NTA gels, which is more favorable to the insect cell-derived particles formed by VP2. Therefore, VP3-ELISA could be developed as an efficient and low cost diagnostic method for IBDV infection in field chickens. 相似文献
73.
74.
75.
76.
棉苗黑斑病的致病菌在关中棉区初步认为是 Alternaria tenuis Nees 与棉成株期叶片上的致病菌不同。病菌孢子借气流传布。种子带菌率虽然很高,但诱发苗病率却很低,因此,种子消毒或采用轮栽来控制这个病害,是不能达到预期效果的。病害发生与棉苗受冻、强风对棉苗的伤害以及棉苗阶段发育有密切的关系。各年发病期有早有晚,但以真叶出现时为易感阶段。本文阐述了棉苗生育阶段、气候条件与发病的关系,为预测病害发生的物候与气象参考条件提供了资料。棉株伤害与发病有关系,建议在生产上适当降低播种量,提高播种质量,适期早疏苗、早间苗;以减轻由于伤损而导致病害侵染。品种与病害发生的关系不显著。试验证明,使用波尔多液加1059于降温前喷射效果较好。 相似文献
77.
78.
Human endothelial cell growth factor: cloning, nucleotide sequence, and chromosome localization 总被引:78,自引:0,他引:78
M Jaye R Howk W Burgess G A Ricca I M Chiu M W Ravera S J O'Brien W S Modi T Maciag W N Drohan 《Science (New York, N.Y.)》1986,233(4763):541-545
Several of the endothelial cell polypeptide mitogens that have been described probably play a role in blood vessel homeostasis. Two overlapping complementary DNA clones encoding human endothelial cell growth factor (ECGF) were isolated from a human brain stem complementary DNA library. Southern blot analysis suggested that there is a single copy of the ECGF gene and that it maps to human chromosome 5 at bands 5q31.3 to 33.2 A 4.8-kilobase messenger RNA was present in human brain stem messenger RNA. The complete amino acid sequence of human ECGF was deduced from the nucleic acid sequence of these clones; it encompasses all the well-characterized acidic endothelial cell polypeptide mitogens described by several laboratories. The ECGF-encoding open reading frame is flanked by translation stop codons and provides no signal peptide or internal hydrophobic domain for the secretion of ECGF. This property is shared by human interleukin-1, which is approximately 30 percent homologous to ECGF. 相似文献
79.
Pang PC Chiu PC Lee CL Chang LY Panico M Morris HR Haslam SM Khoo KH Clark GF Yeung WS Dell A 《Science (New York, N.Y.)》2011,333(6050):1761-1764
Human fertilization begins when spermatozoa bind to the extracellular matrix coating of the oocyte, known as the zona pellucida (ZP). One spermatozoan then penetrates this matrix and fuses with the egg cell, generating a zygote. Although carbohydrate sequences on the ZP have been implicated in sperm binding, the nature of the ligand was unknown. Here, ultrasensitive mass spectrometric analyses revealed that the sialyl-Lewis(x) sequence [NeuAcα2-3Galβ1-4(Fucα1-3)GlcNAc], a well-known selectin ligand, is the most abundant terminal sequence on the N- and O-glycans of human ZP. Sperm-ZP binding was largely inhibited by glycoconjugates terminated with sialyl-Lewis(x) sequences or by antibodies directed against this sequence. Thus, the sialyl-Lewis(x) sequence represents the major carbohydrate ligand for human sperm-egg binding. 相似文献
80.
K Muegge T M Williams J Kant M Karin R Chiu A Schmidt U Siebenlist H A Young S K Durum 《Science (New York, N.Y.)》1989,246(4927):249-251