全文获取类型
收费全文 | 5231篇 |
免费 | 288篇 |
国内免费 | 412篇 |
专业分类
林业 | 208篇 |
农学 | 632篇 |
基础科学 | 10篇 |
326篇 | |
综合类 | 2177篇 |
农作物 | 356篇 |
水产渔业 | 533篇 |
畜牧兽医 | 1093篇 |
园艺 | 292篇 |
植物保护 | 304篇 |
出版年
2024年 | 9篇 |
2023年 | 42篇 |
2022年 | 74篇 |
2021年 | 115篇 |
2020年 | 107篇 |
2019年 | 113篇 |
2018年 | 98篇 |
2017年 | 151篇 |
2016年 | 192篇 |
2015年 | 147篇 |
2014年 | 224篇 |
2013年 | 234篇 |
2012年 | 312篇 |
2011年 | 404篇 |
2010年 | 360篇 |
2009年 | 379篇 |
2008年 | 391篇 |
2007年 | 398篇 |
2006年 | 353篇 |
2005年 | 277篇 |
2004年 | 252篇 |
2003年 | 223篇 |
2002年 | 170篇 |
2001年 | 154篇 |
2000年 | 149篇 |
1999年 | 114篇 |
1998年 | 82篇 |
1997年 | 76篇 |
1996年 | 57篇 |
1995年 | 71篇 |
1994年 | 55篇 |
1993年 | 26篇 |
1992年 | 41篇 |
1991年 | 33篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1962年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有5931条查询结果,搜索用时 93 毫秒
121.
AIM: To investigate the correlation of gene modification between histone H3 lysine 4 (H3K4) trimethylation and DNA methylation in IgA nephropathy patients. METHODS: H3K4 trimethylation variations were analyzed in peripheral blood mononuclear cells (PBMCs) from 40 IgAN patients and 40 healthy controls by the method of chromatin immunoprecipitation linked to microarrays (ChIP-chip). ChIP real-time PCR was used to validate the microarray results. Quantitative real-time PCR (qRT-PCR) was employed to analyze mRNA expression. DNA methylation in 4 selected positive genes was analyzed by the method of methylated DNA immunoprecipitation-quantitative PCR (MeDIP-qPCR). RESULTS: IgAN patients displayed higher H3K4 trimethylation level and lower DNA methylation level than those of the healthy controls. There were significant differences in DNA methylation and H3K4 trimethylation of 4 selected genes between IgAN patients and the healthy controls (P<0.05). CONCLUSION: Our studies indicate that significant alterations of H3K4 trimethylation and DNA methylation exist in IgAN patients. There is a correlation of gene modification between DNA mathylation and histone H3 lysine 4 trimethylation in IgAN patients. 相似文献
122.
两种林木总DNA提取效果的比较 总被引:2,自引:0,他引:2
试验以刺槐(Robiniapseudoacacia)和华北落叶松(Larixprincipis-rupprechti)为DNA提取材料,采用2种提取DNA方法,紫外光检测林木DNA提取纯度,并计算DNA收率。实验结果表明,不同林木总DNA提取的效果存在一定差异,从刺槐和落叶松两树种的生理特性和生长特点等方面对试验结果作了比较和分析。 相似文献
123.
平菇不同菌株核DNA的提取及RAPD分析 总被引:2,自引:0,他引:2
采用改进的微量SDS裂解法,对平菇2026、2019、CCEF89这3个菌株的子实体进行了核DNA的提取和纯化,并以提取的DNA为模板,进行RAPD分析,鉴定3个平菇菌株核DNA在分子水平上的差异。对19个随机引物的扩增结果表明,13个引物有扩增产物.共得到208条带。这13个引物所扩增出来的产物在3个菌株之间都存在差异,根据扩增指纹的不同,可将3个菌株区分开。对3个菌株的扩增产物两两进行比较,证明这3个平菇菌株确实属于不同品种,与菌丝拮抗实验结果一致。研究结果表明,RAPD技术可用于平菇品种的快速鉴定。 相似文献
124.
将 M D C C M S B1 48 小时培养物 1000r/m in 离心的上清液分别用 R N A 酶、 D N A 酶和蛋白酶 K 处理后,进行体外试验。结果表明,只有 D N A 酶处理后的上清液失去了体外抑制 M D V“814”增殖的作用。将该上清液 10000r/m in 离心所得的沉淀分别用上述酶处理后进行体内试验。结果表明,只有 D N A 酶处理的样品失去了体内促进 M D V 京1 株致瘤的作用。同时,电泳分析结果证明,该上清液中确实存在 D N A。 相似文献
125.
Abstract: Heterosigma akashiwo virus (HaV) is a large icosahedral virus (∼0.2 μm) harboring a double-stranded DNA (dsDNA) genome (∼294 kbp). The virus is the only member of the genus Raphidovirus in the family Phycodnaviridae. Since its first discovery, a number of ecologic, physiologic and genetic studies about HaV have been conducted; especially, the relationship between H. akashiwo and HaV in nature was studied and viral infection is now regarded as a significant factor influencing the dynamics and termination of H. akashiwo blooms. HaV infection has considerable impacts on H. akashiwo populations in both aspects of fluctuation in biomass (quantity) and changes in clonal composition (quality). Partial sequencing of the HaV genome revealed that a number of genes showed considerable similarity to those of other protist-infecting viruses; still, the phylogenetic position of HaV suggested a number of enigmas in host–virus coevolution. Here are summarized the ecology, physiology and genetics of HaV especially from the viewpoint of the host–virus relationship. 相似文献
126.
127.
128.
采用随机扩增多态性DNA技术对产气荚膜杆菌进行PCR扩增。结果产气荚膜杆菌A,B,C,D4个型均可扩增出约430bp的条带,B,C型还扩增出约210bp条带,B,D型还扩增出约1210bp条带,A型还扩增出约240bp和690bp条带,各型之间的条带差别明显,从而为产气荚膜杆菌的基因分型、PCR快速诊断提供可靠的依据。 相似文献
129.
AIM and METHODS: The ratio of mitochondrial DNA (mtDNA) deletion was measured to find the relationship between mtDNA deletion and aged learning and memory deficit. The aged rats were divided into two groups, aged learning and memory deficit group and aged learning and memory normal group. The ratio of mtDNA deletion was measured by dilution polymerase chain reaction. RESULTS: There are deleted mtDNA (about 4834 bp) in the cerebral cortex, hippocampus and cerebellum of both young and aged rats. The ratios of deleted mtDNA were similar in the cerebral cortex,hippocampus and cerebellum of young rats (about 0.00018%). The ratio mtDNA of aged learning and memory normal rats had increased by five-fold in the cerebral cortex and hippocampus, or one-fold in the cerebellum over young rats. The ratio of aged learning and memory dificit rats had increased by one-fold in the cerebral cortex or 0.8-fold in the hippocampus or two-fold in the cerebellum over aged learning and memory normal rats.CONCLUSIONS: There was really the increase of mtDNA in aging rat brain. And this increase was double in amount in aged learning and memory deficit rats compared to the normal learning and memory aged rats. It is suggested that the mtDNA deletions in the brain regions associated with learning and memory may be contributed to the cellular and molecular mechanism of learning and memory deicit with aged rats. 相似文献
130.