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41.
42.
In many bacterial genomes, the leading and lagging strands have different skews in base composition; for example, an excess
of guanosine compared to cytosine on the leading strand. We find that Chlamydia genes that have switched their orientation relative to the direction of replication, for example by inversion, acquire the
skew of their new ``host' strand. In contrast to most evolutionary processes, which have unpredictable effects on the sequence
of a gene, replication-related skews reflect a directional evolutionary force that causes predictable changes in the base
composition of switched genes, resulting in increased DNA and amino acid sequence divergence.
Received: 27 April 2000 / Accepted: 1 August 2000 相似文献
43.
Base Composition Skews, Replication Orientation, and Gene Orientation in 12 Prokaryote Genomes 总被引:21,自引:0,他引:21
Michael J. McLean Kenneth H. Wolfe Kevin M. Devine 《Journal of molecular evolution》1998,47(6):691-696
Variation in GC content, GC skew and AT skew along genomic regions was examined at third codon positions in completely sequenced
prokaryotes. Eight out of nine eubacteria studied show GC and AT skews that change sign at the origin of replication. The
leading strand in DNA replication is G-T rich at codon position 3 in six eubacteria, but C-T rich in two Mycoplasma species. In M. genitalium the AT and GC skews are symmetrical around the origin and terminus of replication, whereas its GC content variation has been
shown to have a centre of symmetry elsewhere in the genome. Borrelia burgdorferi and Treponema pallidum show extraordinary extents of base composition skew correlated with direction of DNA replication. Base composition skews
measured at third codon positions probably reflect mutational biases, whereas those measured over all bases in a sequence
(or at codon positions 1 and 2) can be strongly affected by protein considerations due to the tendency in some bacteria for
genes to be transcribed in the same direction that they are replicated. Consequently in some species the direction of skew
for total genomic DNA is opposite to that for codon position 3.
Received: 2 February 1998 / Accepted: 15 June 1998 相似文献
44.
目的:从HL-60细胞中获得了sTrail基因片段,优化蛋白表达条件,并研究其抗肿瘤活性。方法:培养HL-60细胞,提取总RNA,通过RT-PCR扩增sTRAIL蛋白基因片段,并将目的基因克隆至原核表达载体p ET28a上,并电击转化E.coli BL21(DE3),IPTG诱导表达,优化蛋白表达条件,Ni-IDA柱纯化重组蛋白,SDS-PAGE蛋白电泳,胶内酶解质谱鉴定。纯化后的重组蛋白作用HUVEC,He La,Hep-3B,HCT-116,MDA-MB-231,H460细胞检测蛋白生物学作用。结果:DNA测序结果证实成功构建了重组质粒p ET28a-sTrail,SDS-PAGE蛋白电泳,胶内酶解质谱检测显示成功表达sTRAIL蛋白,MTT法和流式细胞术结果显示,sTRAIL蛋白对肿瘤细胞包括He La,HCT-116,MDA-MB-231,H460,Hep-3B细胞有良好的生物活性,对正常的HUVEC细胞无毒性。结论:成功构建可以高效表达sTRAIL蛋白的原核表达载体,优化蛋白的表达和纯化后所得sTRAIL蛋白具有良好的抗肿瘤生物活性,为研究和发展利用sTRAIL蛋白作为临床治疗抗肿瘤药物提供了重要基础。 相似文献
45.
SP0306蛋白是肺炎链球菌TIGR4菌株中的一种假想的转录因子,但其蛋白三维结构及生物学功能尚未明了,生物信息学分析提示其可能调控碳水化合物代谢相关基因的表达。成功构建了SP0306蛋白的全长表达载体PET28a-sp0306,利用大肠杆菌BL21(DE3)菌株进行原核表达,获得了以可溶形式表达的目的蛋白。经Ni-NTA柱亲和层析及DEAE阴性离子交换层析纯化后,获得了高纯度的目的蛋白。采用悬滴气相扩散法获得了质量较好的SP0306蛋白晶体,并初步进行了晶体X射线衍射,为其最终的三维结构解析及生物学功能研究奠定了基础。 相似文献
46.
目的:构建s TACI-Fc-Myc重组质粒,并进行原核表达和纯化具有生物活性的融合蛋白。方法:通过PCR法获得s TACI-Fc-Myc重组片段,然后把融合基因片段与原核载体p ET28a连接在一起,并构建p ET28a-s TACI-Fc-Myc重组子,并转入BL21(DE3)中进行表达,用蛋白A凝胶亲和层析柱进行纯化及酶联免疫吸附剂(ELISA)法测定其生物学活性。结果:获得了s TACI-Fc-Myc重组质粒,且该质粒可以在BL21(DE3)中表达,亲和层析柱纯化后纯度可达到95%以上,与BAFF的结合活性具有剂量依赖性,浓度达到5 ng/μL时,两者的吸附达到饱和。结论:成功构建了s TACI-Fc-Myc原核表达载体,并使有生物学活性的融合蛋白在BL21(DE3)上获得了稳定表达,为进一步研究并筛选高活性BAFF拮抗肽奠定了基础。 相似文献
47.
48.
Rivers connect the carbon cycle in land with that in aquatic ecosystems by transporting and transforming terrestrial organic matter (TeOM). The Amazon River receives huge loads of TeOM from the surrounding rainforest, promoting a substantial microbial heterotrophic activity and consequently, CO2 outgassing. In the Amazon River, microbes degrade up to 55% of the lignin present in the TeOM. Yet, the main microbial genomes involved in TeOM degradation were unknown. Here, we characterize 51 population genomes (PGs) representing some of the most abundant microbes in the Amazon River deriving from 106 metagenomes. The 51 reconstructed PGs are among the most abundant microbes in the Amazon River, and 53% of them are not able to degrade TeOM. Among the PGs capable of degrading TeOM, 20% were exclusively cellulolytic, while the others could also oxidize lignin. The transport and consumption of lignin oxidation byproducts seemed to be decoupled from the oxidation process, being apparently performed by different groups of microorganisms. By connecting the genomic features of abundant microbes in the Amazon River with the degradation machinery of TeOM, we suggest that a complex microbial consortium could explain the quick turnover of TeOM previously observed in this ecosystem. 相似文献
49.
Improved white spruce (Picea glauca) genome assemblies and annotation of large gene families of conifer terpenoid and phenolic defense metabolism 下载免费PDF全文
René L. Warren Christopher I. Keeling Macaire Man Saint Yuen Anthony Raymond Greg A. Taylor Benjamin P. Vandervalk Hamid Mohamadi Daniel Paulino Readman Chiu Shaun D. Jackman Gordon Robertson Chen Yang Brian Boyle Margarete Hoffmann Detlef Weigel David R. Nelson Carol Ritland Nathalie Isabel Barry Jaquish Alvin Yanchuk Jean Bousquet Steven J. M. Jones John MacKay Inanc Birol Joerg Bohlmann 《The Plant journal : for cell and molecular biology》2015,83(2):189-212
50.
Ching-Hung Tseng Pei-Wen Chiang Hung-Chun Lai Fuh-Kwo Shiah Ting-Chang Hsu Yi-Lung Chen Liang-Saw Wen Chun-Mao Tseng Wung-Yang Shieh Isaam Saeed Saman Halgamuge Sen-Lin Tang 《BMC genomics》2015,16(1)