全文获取类型
收费全文 | 325篇 |
免费 | 50篇 |
国内免费 | 32篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 17篇 |
2011年 | 24篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 23篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1992年 | 8篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1968年 | 2篇 |
1963年 | 2篇 |
1959年 | 2篇 |
1958年 | 3篇 |
1957年 | 2篇 |
1955年 | 3篇 |
1949年 | 5篇 |
1948年 | 2篇 |
排序方式: 共有407条查询结果,搜索用时 15 毫秒
1.
Identification of an amber nonsense mutation in the rosy516 gene by germline transformation of an amber suppressor tRNA gene. 总被引:7,自引:0,他引:7
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Seven xanthine dehydrogenase and cross-reacting material negative Drosophila melanogaster rosy stocks were screened for amber and ochre nonsense mutations. Amber and ochre nonsense suppressors were created by site-directed mutagenesis starting from a wild-type tRNA(Tyr) gene. The suppressor tRNA genes were subcloned into a pUChsneo transformation vector providing heat-shock controlled neomycin resistance. The seven rosy stocks were germline transformed with amber and ochre tDNA(Tyr), and the G1 generation was screened for Geneticin resistance. Surviving rosy516 flies transformed with the amber suppressor showed an eye colour intermediate between the original ry516 stock and the wild-type, suggesting that ry516 is an amber nonsense mutant. This was confirmed by sequencing the relevant part of the ry516 gene; the analysis revealed a C-to-T transition in a CAG glutamine codon at nucleotide 1522 of the wild-type rosy gene. 相似文献
2.
Payant V; Abukashawa S; Sasseville M; Benkel BF; Hickey DA; David J 《Molecular biology and evolution》1988,5(5):560-567
Nuclear DNA was extracted from each of the eight species comprising the
Drosophila melanogaster species subgroup. Southern hybridization of this
DNA by using a molecular probe specific for the alpha-amylase coding region
showed that the duplicated structure of the amylase locus, first found in
D. melanogaster, is conserved among all species of the melanogaster
subgroup. Evidence is also presented for the concerted evolution of the
duplicated genes within each species. In addition, it is shown that the
glucose repression of amylase gene expression, which has been extensively
studied in D. melanogaster, is not confined to this species but occurs in
all eight members of the species subgroup. Thus, both the duplicated gene
structure and the glucose repression of Drosophila amylase gene activity
are stable over extended periods of evolutionary time.
相似文献
3.
Queuosine modification of the wobble base in tRNAHis influences ''in vivo'' decoding properties. 总被引:5,自引:1,他引:4
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The 'in vivo' decoding properties of four tRNAHis isoacceptors, two from Drosophila melanogaster and two from brewer's yeast, were studied after their microinjection, along with turnip yellow mosaic virus (TYMV) coat protein mRNA, into Xenopus laevis oocytes. The two Drosophila isoacceptors are identical besides containing either a guanosine (G) or the hypermodified nucleoside queuosine (Q) in the wobble position. The brewer's yeast isoacceptors differ by four bases in the anticodon stem, and by one base in the amino acceptor stem. Our results show that, under competing 'in vivo' conditions, the Drosophila tRNAHis with the anticodon GUG clearly prefers the histidine codon CAC to the codon CAU, whereas little preference is observed for the tRNAHis with the anticodon QUG for the codon CAU, and no preference for either codon by the two yeast isoacceptors. Hence, it can be concluded that the presence of the Q-base clearly affects the choice of the codon. This is the first demonstration of an 'in vivo' codon preference by tRNA isoacceptors differing in the modification of the wobble base during the elongation step of protein synthesis. These results imply that one function of the Q-base is at the translational level. 相似文献
4.
The primary structure of wheat germ tRNAArg--the substrate for arginyl-tRNAArg:protein transferase 总被引:1,自引:0,他引:1
Besides its major role in protein synthesis, wheat germ arginyl-tRNAArg can serve as an amino acid donor in an enzymatic reaction to bovine serum albumin catalysed by the enzyme arginyl-tRNAArg: protein transferase. The nucleotide sequence of the tRNAArg involved in this reaction was determined to be: pG-A-C-U-C-C-G-U-m1G-m2G-C-C-C-A-A-D-Gm-G-A-X-A-A-G-G-C-m2(2) G-C-U-G-G-U-Cm-U-I-C-G-m2A-A-A-C-C-A-G-A-G-A-D-U-m5C-U-G-G-G-T-psi -C-G-m1 A-U-C-C-C-C-A-G-C-G-G-A-G-U-C-G-C-C-AOH. We suggest that the decapentanucleotide 5'-G-U-Pu-m2G-C-N-C-A-A-D-Gm-G-A-X-A-3', localized in the D-region, interacts specifically with the protein transferase. 相似文献
5.
The genes coding for 4 snRNAs of Drosophila melanogaster: localization and determination of gene numbers. 总被引:7,自引:5,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
H P Saluz T Schmidt R Dudler M Altwegg E Stumm-Zollinger E Kubli P S Chen 《Nucleic acids research》1983,11(1):77-90
Four small nuclear RNAs (snRNAs) have been isolated from Drosophila melanogaster flies. They have been characterized by base analysis, fingerprinting, and injection into Axolotl oocytes. The size of the molecules and the modified base composition suggest that the following correlations can be made: snRNA1 approximately U2-snRNA; snRNA2 approximately U3-snRNA; snRNA3 approximately U4-snRNA; snRNA4 approximately U6-snRNA. The snRNAs injected into Axolotl oocytes move into the nuclei, where they are protected from degradation. The genes coding for these snRNAs have been localized by "in situ" hybridization of 125-I-snRNAs to salivary gland chromosomes. Most of the snRNAs hybridize to different regions of the genome: snRNA1 to the cytological regions 39B and 40AB; snRNA2 to 22A, 82E, and 95C; snRNA3 to 14B, 23D, 34A, 35EF, 39B, and 63A; snRNA4 to 96A. The estimated gene numbers (Southern-blot analysis) are: snRNA1:3; snRNA2:7; snRNA3:7; snRNA4:1-3. The gene numbers correspond to the number of sites labeled on the polytene salivary gland chromosomes. 相似文献
6.
JOÃO BATISTA TAVARES DA SILVA ISAAC ROITMAN 《The Journal of eukaryotic microbiology》1990,37(6):521-523
ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme. 相似文献
7.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm-
blooded hosts by ixodid ticks. Frequency-dependent selection for variant
outer-surface proteins might be expected to arise in this species, since
rare variants are more likely to avoid immune surveillance in previously
infected hosts. We sequenced the OspA and OspB genes of nine North American
strains and compared them with nine strains previously described. For each
gene, the mean number of synonymous substitutions per synonymous site and
the mean number of nonsynonymous substitutions per nonsynonymous site show
only a twofold excess of silent mutations. Synonymous rates vary widely
along the OspB protein. Some regions show a significant excess of silent
substitutions, while divergence in other regions is constrained by biased
base composition or selection. The presence, in antigenically important
regions of the protein, of significant variation among strains, as well as
evidence for recombination among strains, should be considered in attempts
to develop vaccines against this disease.
相似文献
8.
M P ROBINSON G BUTCHER R H CURTIS K G DA VIES K EVANS 《The Annals of applied biology》1993,123(2):337-347
Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations. 相似文献
9.
10.