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142.
Comparative analysis of the human type 1a and bovine type 1 papillomavirus genomes. 总被引:27,自引:17,他引:10 下载免费PDF全文
The DNA sequences of the genomes of the bovine type 1 and human type 1a papillomaviruses were compared. The overall organization of both genomes is very similar. Three areas of maximal homology were found in the L1 and E1/E2 genes, and at the beginning of L2. The conservation of homologous amino acid sequences encoded in the open reading frames argues that these segments represent real genes or exons. Within these segments, however, only certain domains of the putative proteins are preferentially conserved. Two polypeptide chains show homologous arrangement of the cysteine residue clusters Cys-X-X-Cys, despite a lack of conservation of the rest of the amino acid sequence. A significant sequence divergence in a region where the three reading frames are open suggests that papillomavirus genomes have evolved not solely by accumulation of point mutations. Conserved sequences were also found in the noncoding region, and their possible involvement in regulation of viral gene expression is discussed. 相似文献
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Absence of nucleosomes in a histone-containing nucleoprotein complex obtained by dissociation of purified SV40 virions 总被引:10,自引:0,他引:10
Reduction of disulfide bonds involving the major capsid protein with dithiothreitol and removal of the calcium ions by EGTA disrupts the simian virus 40 virions. This process yields normal circular viral minichromosomes containing the four core histones and traces of the capsid proteins at pH values higher than 8.5. However, when carried out at pH 7.5, this procedure yields nucleoprotein complexes that contain both histones and the viral structural proteins. These pH 7.5 complexes appear as circular structures with a mean of 93 +/- 17 beads with a diameter of 7 nm and no visible nucleosomes when observed by electron microscopy. In contrast to the compaction of the viral DNA in minichromosomes, the length of these beaded structures is roughly the same as free DNA. We suggest that VP1, the major capsid protein, can act as a nucleosome unfolding agent in neutral pH and low ionic strength. 相似文献
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M Yaniv O Croissant F Cuzin 《Biochemical and biophysical research communications》1974,57(4):1074-1079
Three easily denatured regions can be demonstrated in polyoma virus DNA. T4 gene 32 protein which binds to single stranded DNA, but not to duplex DNA, will specifically bind to any of these sites when viral DNA is in its superhelical configuration. These sites were mapped relative to a unique E. coli RI endonuclease cleavage site by electron microscopy. 相似文献
149.
A single mutational modification of a tryptophan-specific transfer RNA permits aminoacylation by glutamine and translation of the codon UAG 总被引:30,自引:0,他引:30
In this work we show that the wild-type (su?7) progenitor of the recessivelethal suppressors of UAG (su+7(UAG)) and of UAA/G (su+7(UAA/G)) is the structural gene for transfer RNATrp, the adaptor for translating the codon UGG. The su+7(UAG) suppressor form of the tRNA has a C for U substitution in the middle base of the anticodon; in the su+7(UAA/G) suppressor tRNA both C residues of the anticodon are replaced by U. Our data establish that the mutational change altering the tRNATrp to a UAG suppressor is accompanied by a loss of tryptophan-accepting specificity and the acquisition of glutamine-acceptor activity. 相似文献
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Serological Analysis of the Deoxyribonucleic Acid Polymerase of Avian Oncornaviruses II. Comparison of Avian Deoxyribonucleic Acid Polymerases 总被引:15,自引:7,他引:8 下载免费PDF全文
Monospecific antiserum prepared against the isolated deoxyribonucleic acid (DNA) polymerase of avian myeloblastosis virus (AMV) neutralized the endogenous ribonucleic acid-instructed DNA polymerase activity of detergent-disrupted virus. The viral polymerase was serologically unrelated to the seven major structural polypeptides of AMV. Furthermore, the viral enzyme was distinguished from normal cellular DNA polymerases by serological criteria; thus, antiserum against the viral enzyme neutralized its homologous antigen but not normal cellular DNA polymerases. Neutralization by antibody of viral DNA polymerase activity was observed with all avian leukemia-sarcoma viruses tested, irrespective of viral antigenic subtype. The DNA polymerase activity of avian reticuloendotheliosis virus, and of a variety of mammalian oncornaviruses, was not neutralized by antisera against the AMV polymerase. Immunological analysis of the RSValpha(O) mutant, which is deficient in DNA polymerase activity, shows this mutant to lack demonstrable polymerase antigen. Viral polymerase was identified by immunofluorescence as a cytoplasmic constituent in virus-producing chicken cells; polymerase antigen was not detected in uninfected (gs(-)) chicken cells. 相似文献