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11.
12.
B.G. Barrell H.L. Weith J.E. Donelson H.D. Robertson 《Journal of molecular biology》1975,92(3):377-393
The nucleotide sequence of the principal bacteriophage φX174 ribosome-protected DNA fragment has been determined. Details of the approaches and methods used for direct DNA sequence analysis are described, The resulting sequence allows prediction of the first nine amino acids at the amino terminus of a protein which has been identified as the product of φX174 gene G. The sequence has several features of biological relevance including two termination codons to the left of the initiator triplet. 相似文献
13.
Nucleotide sequences of two fragments from the coat-protein cistron of bacteriophage R17 ribonucleic acid 总被引:2,自引:2,他引:0
P. G. N. Jeppesen B. G. Barrell F. Sanger A. R. Coulson 《The Biochemical journal》1972,128(5):993-1006
Bacteriophage R17 RNA was labelled with 32P and was subjected to partial digestion with ribonuclease T1. The products were fractionated by ionophoresis on polyacrylamide gel. Two fragments were purified and their nucleotide sequences determined by methods involving complete and further partial digestion with ribonucleases A and T1. Fragment 20 had a sequence that coded for the amino acids in positions 32–53 of the coat protein of the bacteriophage. Fragment 20X, on further purification in 7m-urea, gave rise to two smaller nucleotides whose sequences coded for the amino acids in positions 56–66 and 67–76 of the coat protein. The sequence of the two fragments was such that they could be written in the form of loops stabilized by base-pairing. 相似文献
14.
The psu1+ amber suppressor gene of bacteriophage T4: identification of its amino acid and transfer RNA 总被引:9,自引:0,他引:9
Previous work identified the psu+1 amber suppressor gene of bacteriophage T4. Analysis of protein arising from suppression now shows that psu+1 specifies the insertion of serine in response to the amber triplet. The efficiency of suppression is 70%.The psu1+ gene affects a serine transfer RNA coded by bacteriophage T4. Comparative ribonuclease T1 fingerprint analysis of the serine transfer RNAs made by wild type T4 and psu+1 strains shows a specific alteration in the patterns, presumably reflecting a mutational alteration in the anticodon of the transfer RNA. Mutations which result in the loss of suppressor activity define two genes: one is apparently the structural gene for the serine transfer RNA; the function of the second gene, M1, is less clear. Mutational inactivation of either gene prevents the appearance of the serine transfer RNA and a second transfer RNA, which has not yet been associated with its cognate amino acid. M1 mutants are also deficient in the production of several additional transfer RNA species, as well as several larger RNAs. The significance of these results in relation to transfer RNA biosynthesis is discussed. 相似文献
15.
16.
Facilitating the recovery of phenotypically normal transgenic lines in clonal crops: a new strategy illustrated in potato 总被引:1,自引:0,他引:1
Barrell PJ Conner AJ 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,122(6):1171-1177
Transgenic plants frequently exhibit altered phenotypes, unrelated to transgene expression, which are attributed to tissue
culture-induced variation and/or insertional mutagenesis. Distinguishing between these possibilities has been difficult in
clonal crops such as potato, due to their highly heterozygous background and the resulting inherent phenotypic variability
associated with segregation. This study reports the use of transgene integration as a molecular marker to trace the clonal
origin of single cells in tissue culture. Following transformation, multiple shoots have been regenerated from cell colonies
of potato (Solanum tuberosum L.) and Southern analysis used to confirm their derivation from a single transformed cell. Analysis of phenotypic variation
in field trials has demonstrated marked differences between these multiple regeneration events, the origin of which must have
occurred after T-DNA insertion, and consequently during the tissue culture phase. This result unequivocally demonstrates that
somaclonal variation occurs during tissue culture and independent of transgene insertion. Furthermore, the first shoots recovered
do not necessarily exhibit less somaclonal variation, since later regeneration events can give rise to plants that are more
phenotypically normal. Therefore, when developing transgenic lines for genetic improvement of clonal crops, multiple shoots
should be regenerated and evaluated from each transformation event to facilitate the recovery of phenotypically normal transgenic
lines. 相似文献
17.
Identification and procaryotic expression of the gene coding for the highly immunogenic 28-kilodalton structural phosphoprotein (pp28) of human cytomegalovirus. 总被引:23,自引:17,他引:6
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H Meyer A T Bankier M P Landini C M Brown B G Barrell B Rüger M Mach 《Journal of virology》1988,62(7):2243-2250
Human cytomegalovirus contains a structural polypeptide that is 28 kilodaltons in apparent molecular size and is reactive in Western blot (immunoblot) analysis with the majority of human sera. The gene coding for this polypeptide was mapped on the genome of human cytomegalovirus strain AD169. A monoclonal antibody specific for the 28-kilodalton polypeptide was used to screen a cDNA library constructed from poly(A)+ RNA of human cytomegalovirus-infected cells in the procaryotic expression vector lambda gt11. Hybridization of cDNA with cosmid and plasmid clones mapped the gene to the HindIII R fragment. The gene was transcribed into a late 1.3-kilobase RNA. The nucleotide sequence of the coding region was determined. Parts of the 28-kilodalton polypeptide were expressed in Escherichia coli as hybrid proteins fused to beta-galactosidase. In Western blots these proteins were recognized by human sera. Antibodies raised against the hybrid proteins reacted specifically with the viral antigen in immunoprecipitations and Western blots. In vitro phosphorylation of HCMV virions and immunoprecipitation showed that the 28-kilodalton polypeptide was phosphorylated. 相似文献
18.
The evolutionary origin of the pinnipeds (seals, sea lions, and walruses)
is still uncertain. Most authors support a hypothesis of a monophyletic
origin of the pinnipeds from a caniform carnivore. A minority view suggests
a diphyletic origin with true seals being related to the mustelids (otters
and ferrets). The phylogenetic relationships of the walrus to other
pinniped and carnivore families are also still particularly problematic.
Here we examined the relative support for mono- and diphyletic hypotheses
using DNA sequence data from the mitochondrial small subunit (12S) rRNA and
cytochrome b genes. We first analyzed a small group of taxa representing
the three pinniped families (Phocidae, Otariidae, and Odobenidae) and
caniform carnivore families thought to be related to them. We inferred
phylogenetic reconstructions from DNA sequence data using standard
parsimony and neighbor-joining algorithms for phylogenetic inference as
well as a new method called spectral analysis (Hendy and Penny) in which
phylogenetic information is displayed independently of any selected tree.
We identified and compensated for potential sources of error known to lead
to selection of incorrect phylogenetic trees. These include sampling error,
unequal evolutionary rates on lineages, unequal nucleotide composition
among lineages, unequal rates of change at different sites, and
inappropriate tree selection criteria. To correct for these errors, we
performed additional transformations of the observed substitution patterns
in the sequence data, applied more stringent structural constraints to the
analyses, and included several additional taxa to help resolve long,
unbranched lineages in the tree. We find that there is strong support for a
monophyletic origin of the pinnipeds from within the caniform carnivores,
close to the bear/raccoon/panda radiation. Evidence for a diphyletic origin
was very weak and can be partially attributed to unequal nucleotide
compositions among the taxa analyzed. Subsequently, there is slightly more
evidence for grouping the walrus with the eared seals versus the true
seals. A more conservative interpretation, however, is that the walrus is
an early, but not the first, independent divergence from the common
pinniped ancestor.
相似文献
19.
Induction of host nuclear DNA synthesis in coccidia-infected chicken intestinal cells 总被引:1,自引:0,他引:1
M A Fernando J Pasternak R Barrell P H Stockdale 《International journal for parasitology》1974,4(3):267-276
When Eimeria maxima (gamonts) infects villus epithelial cells of the chicken duodenum there is extensive cellular enlargement with no alteration in nuclear size. Feulgen DNA microspectrophotometric measurements indicated that the infected host-cell nucleus contains the same amount of DNA as an uninfected cell nucleus. Evidence is presented to indicate that second generation schizonts of E. necatrix develop in crypt epithelial cells that are displaced/migrate into the lamina propria. The developing parasite causes cellular and nuclear hypertrophy in these cells as does E. tenella in cecal cells of the chicken. In these two cases nuclear enlargement is accompanied by induced rounds of DNA synthesis in the host-cell. Analyses indicated that the DNA content of enlarged nuclei does not fall into classes that correspond to a geometric series 2:4:6:8:16: etc. times the DNA content of a 2C equivalent, and that nuclear size and DNA content in infected cells are not significantly correlated. Autoradiographic studies on E. necatrix infected chicks administered 3H-thymidine show that DNA synthesis takes place in the nuclei of cells containing all developing stages but not mature schizonts, and that this synthesis is not a continuous process. The data suggest that intestinal cells that are capable of undergoing cell division and therefore additional rounds of DNA synthesis, can be induced by coccidial infection in the absence of concomitant cell division. 相似文献
20.
The sequence of phenylalanine tRNA from E. coli 总被引:28,自引:0,他引:28