全文获取类型
收费全文 | 235篇 |
免费 | 6篇 |
国内免费 | 5篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 26篇 |
2013年 | 21篇 |
2012年 | 17篇 |
2011年 | 30篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有246条查询结果,搜索用时 31 毫秒
11.
We have determined the full sequence of the ribosomal DNA intergenic spacer (IGS) of the swimming crab, Charybdis japonica, by long PCR for the first time in crustacean decapods. The IGS is 5376 bp long and contains two nonrepetitive regions separated
by one long repetitive region, which is composed mainly of four subrepeats (subrepeats I, II, III, and IV). Subrepeat I contains
nine copies of a 60-bp repeat unit, in which two similar repeat types (60 bp-a and 60 bp-b) occur alternatively. Subrepeat
II consists of nine successive repeat units with a consensus sequence length of 142 bp. Subrepeat III consists of seven copies
of another 60-bp repeat unit (60 bp-c) whose sequence is complementary to that of subrepeat I. Immediately downstream of subrepeat
III is subrepeat IV, consisting of three copies of a 391-bp repeat unit. Based on comparative analysis among the subrepeats
and repeat units, a possible evolutionary process responsible for the formation of the repetitive region is inferred, which
involves the duplication of a 60-bp subrepeat unit (60 bp-c) as a prototype.
Received: 13 April 1999 / Accepted: 2 August 1999 相似文献
12.
Chromosome terminal, complex repeats in the dipteran Chironomus pallidivittatus show rapid concerted evolution during which there is remarkably efficient homogenization of the repeat units within and between
chromosome ends. It has been shown previously that gene conversion is likely to be an important component during these changes.
The sequence evolution could be a result of different processes—exchanges between repeats in the tandem array as well as information
transfer between units in different chromosomes—and is therefore difficult to analyze in detail. In this study the concerted
evolution of a region present only once per chromosome, at the junction between the telomeric complex repeats and the subtelomeric
DNA was therefore investigated in the two sibling species C. pallidivittatus and C. tentans. Material from individual microdissected chromosome ends was used, as well as clones from bulk genomic DNA. On the telomeric
side of the border pronounced species-specific sequence differences were observed, the patterns being similar for clones of
different origin within each species. Mutations had been transmitted efficiently between chromosomes also when adjoining,
more distally localized DNA showed great differences in sequence, suggesting that gene conversion had taken place. The evolving
telomeric region bordered proximally to subtelomeric DNA with high evolutionary constancy. More proximally localized, subtelomeric
DNA evolved more rapidly and showed heterogeneity between species and chromosomes.
Received: 24 September 1997 / Accepted: 24 November 1997 相似文献
13.
M. Senda Y. Onodera T. Mikami 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):964-968
The mitochondrial atpA gene sequence of the normal fertile sugarbeet (cv ‘TK81-0’) exists in one full-length version and one truncated version,
both of which are present in normal stoichiometry and have a 406-bp segment in common. The PCR approach as well as prolonged
exposure of Southern blots indicates that the products of the recombination across the 406-bp repeat are present in substoichiometric
amounts in the ‘TK81-0’ genome. Intriguingly, one of these substoichiometric sequence arrangements was revealed to be preferentially
amplified in an evolutionary lineage that led to a cytoplasmic male-sterile variant [I-12CMS(2)] in wild beets. We also found
the 406-bp repeat to be part of a 6.5-kb repeat in the mitochondrial genome of I-12CMS(2). This 6.5-kb duplication is likely
to involve recombination between two sets of repeats (the above-mentioned 406-bp repeat and a 7-bp repeat) in an ancestral
beet mitochondria.
Received: 4 October 1997 / Accepted: 31 October 1997 相似文献
14.
《DNA Repair》2015
DNA repair normally protects the genome against mutations that threaten genome integrity and thus cell viability. However, growing evidence suggests that in the case of the Repeat Expansion Diseases, disorders that result from an increase in the size of a disease-specific microsatellite, the disease-causing mutation is actually the result of aberrant DNA repair. A variety of proteins from different DNA repair pathways have thus far been implicated in this process. This review will summarize recent findings from patients and from mouse models of these diseases that shed light on how these pathways may interact to cause repeat expansion. 相似文献
15.
16.
The aim of this study was to determine the prevalence and risk factors for subclinical endometritis (SE) and its effects on fertility in repeat breeder dairy cows. Dairy cows of parity 1 to 5 that were artificially inseminated (AI) 3 or more times (selected cows were artificially inseminated an average of 3.9 times) were examined at 190 ± 40 days in milk, and clinically normal cows (n = 77) were selected based on the absence of abnormal discharges on external inspection and the absence of abnormal findings on transrectal palpation and ultrasonographic examination. Endometrial samples were collected from the uterus by using the lavage technique in the luteal phase of the estrus cycle. Collected samples were centrifuged and a drop of sediment was streaked on to a clean microscopic slide and stained with Giemsa. The percentage of polymorphonuclear cells (neutrophils) was counted for each specimen. The analysed data showed that the average amount of neutrophils was 3.1% (0-9) in the selected cows. Abnormal calving (dystocia, twin births, and abortion), retained placenta, and postpartum uterine infections were associated with an increase in prevalence of SE. Subsequently, SE was significantly associated with a decrease in conception rate in the next AI. Conception rate in the next AI was 5% for cows (n = 38) with SE (≥ 3% neutrophil), and 47% for cows (n = 34) without SE (< 3% neutrophil) (P = 0.001). The prevalence of cytologically diagnosed SE (≥ 3% neutrophil) was 52.7% (n = 38). In conclusion, abnormal calving, retained placenta, and postpartum uterine infections may be associated with an increase in prevalence of SE and subsequently, SE may decrease reproductive performance and increase the incidence of repeat breeder syndrome. 相似文献
17.
Emmanuel S. Burgos Carola Wilczek Takashi Onikubo Jeffrey B. Bonanno Janina Jansong Ulf Reimer David Shechter 《The Journal of biological chemistry》2015,290(15):9674-9689
The protein arginine methyltransferase PRMT5 is complexed with the WD repeat protein MEP50 (also known as Wdr77 or androgen coactivator p44) in vertebrates in a tetramer of heterodimers. MEP50 is hypothesized to be required for protein substrate recruitment to the catalytic domain of PRMT5. Here we demonstrate that the cross-dimer MEP50 is paired with its cognate PRMT5 molecule to promote histone methylation. We employed qualitative methylation assays and a novel ultrasensitive continuous assay to measure enzyme kinetics. We demonstrate that neither full-length human PRMT5 nor the Xenopus laevis PRMT5 catalytic domain has appreciable protein methyltransferase activity. We show that histones H4 and H3 bind PRMT5-MEP50 more efficiently compared with histone H2A(1–20) and H4(1–20) peptides. Histone binding is mediated through histone fold interactions as determined by competition experiments and by high density histone peptide array interaction studies. Nucleosomes are not a substrate for PRMT5-MEP50, consistent with the primary mode of interaction via the histone fold of H3-H4, obscured by DNA in the nucleosome. Mutation of a conserved arginine (Arg-42) on the MEP50 insertion loop impaired the PRMT5-MEP50 enzymatic efficiency by increasing its histone substrate Km, comparable with that of Caenorhabditis elegans PRMT5. We show that PRMT5-MEP50 prefers unmethylated substrates, consistent with a distributive model for dimethylation and suggesting discrete biological roles for mono- and dimethylarginine-modified proteins. We propose a model in which MEP50 and PRMT5 simultaneously engage the protein substrate, orienting its targeted arginine to the catalytic site. 相似文献
18.
Background
Transposable Elements (TEs) are key components that shape the organization and evolution of genomes. Fungi have developed defense mechanisms against TE invasion such as RIP (Repeat-Induced Point mutation), MIP (Methylation Induced Premeiotically) and Quelling (RNA interference). RIP inactivates repeated sequences by promoting Cytosine to Thymine mutations, whereas MIP only methylates TEs at C residues. Both mechanisms require specific cytosine DNA Methyltransferases (RID1/Masc1) of the Dnmt1 superfamily.Results
We annotated TE sequences from 10 fungal genomes with different TE content (1-70%). We then used these TE sequences to carry out a genome-wide analysis of C to T mutations biases. Genomes from either Ascomycota or Basidiomycota that were massively invaded by TEs (Blumeria, Melampsora, Puccinia) were characterized by a low frequency of C to T mutation bias (10-20%), whereas other genomes displayed intermediate to high frequencies (25-75%). We identified several dinucleotide signatures at these C to T mutation sites (CpA, CpT, and CpG). Phylogenomic analysis of fungal Dnmt1 MTases revealed a previously unreported association between these dinucleotide signatures and the presence/absence of sub-classes of Dnmt1.Conclusions
We identified fungal genomes containing large numbers of TEs with many C to T mutations associated with species-specific dinucleotide signatures. This bias suggests that a basic defense mechanism against TE invasion similar to RIP is widespread in fungi, although the efficiency and specificity of this mechanism differs between species. Our analysis revealed that dinucleotide signatures are associated with the presence/absence of specific Dnmt1 subfamilies. In particular, an RID1-dependent RIP mechanism was found only in Ascomycota.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1347-1) contains supplementary material, which is available to authorized users. 相似文献19.
紫、红黄肉甘薯种质遗传多样性的ISSR分析 总被引:2,自引:0,他引:2
采用ISSR分子标记,分析了21份紫肉、28份红黄肉甘薯种质遗传多样性。结果表明:17对引物共扩增出154条谱带,其中多态性谱带138条,占89.6%,平均每个引物扩增出8.12条多态性谱带,表现出丰富的多态性。聚类分析和主成分分析将49份甘薯种质聚为4大类,类型间遗传差异较大,将红黄薯单独聚为1类,说明紫薯和红黄薯分别具有明显不同的来源和系统演化关系。种质间的遗传相似系数变幅为0.58~0.93,其中,0.61~0.70之间的种质占51.4%,0.71~0.80之间的占44.0%。而邻近地域育种单位或同一育种单位的品种亲缘关系较近。文章对如何在育种中利用这些优异种质进行了讨论。 相似文献
20.
Complete sequence determination of the brachiopod Lingula anatina mtDNA (28,818 bp) revealed an organization that is remarkably atypical for an animal mt-genome. In addition to the usual set of 37 animal mitochondrial genes, which make up only 57% (16,555 bp) of the entire sequence, the genome contains lengthy unassigned sequences. All the genes are encoded in the same DNA strand, generally in a compact way, whereas the overall gene order is highly divergent in comparison with known animal mtDNA. Individual genes are generally longer and deviate considerably in sequence from their homologues in other animals. The genome contains two major repeat regions, in which 11 units of unassigned sequences and six genes (atp8, trnM, trnQ, trnV, and part of cox2 and nad2) are found in repetition, in the form of nested direct repeats of unparalleled complexity. One of the repeat regions contains unassigned repeat units dispersed among several unique sequences, novel repetitive structure for animal mtDNAs. Each of those unique sequences contains an open reading frame for a polypeptide between 80 and 357 amino acids long, potentially encoding a functional molecule, but none of them has been identified with known proteins. In both repeat regions, tRNA genes or tRNA gene-like sequences flank major repeated units, supporting the view that those structures play a role in the mitochondrial gene rearrangements. Although the intricate repeated organization of this genome can be explained by recurrent tandem duplications and subsequent deletions mediated by replication errors, other mechanisms, such as nonhomologous recombinations, appear to explain certain structures more easily. 相似文献