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1.
2.
A synthesis of adenosine-5′-d (4), and its p.m.r. spectral characteristics, are described. The presence of deuterium in 4 gives rise to a 2:1 mixture of R and S configurations at C-5, thereby permitting specific assignments for the resonances of the residual 5′-protons. From the observed spin-spin coupling between the latter and H-4′, and estimate has been made of the rotamer population of the exocyclic 5′-carbinol group. It is shown that the gauche-gauche rotamer is preponderant (≈70%) and the gauche-trans one of minor importance (≈20%) in aqueous solution, which contrasts markedly with the preference for the latter rotamer exhibited by adenosine in the solid state. 相似文献
3.
Effect of introducing genetically engineered microorganisms on soil microbial community diversity 总被引:4,自引:0,他引:4
Abstract Introducing the genetically engineered microorganism Pseudomonas cepacia AC1100 into soil microcosms resulted in elevated taxonomic diversity determined by phenotypic analyses of culturable isolates and genetic diversity determined by analysis of the heterogeneity of total microbial community DNA reannealing kinetics. The greatest impact occurred when P. cepacia AC1100 was introduced along with the herbicide 2,4,5-T, which P. cepacia AC1100 can degrade. The data suggests that both changes in the balance of populations and genetic recombination contributed to the increased diversity. 相似文献
4.
Functional effects and cross-reactivity of antibody to purified subunit b (uncF protein) of Escherichia coli proton-ATPase 总被引:2,自引:0,他引:2
Subunit b (uncF protein) of the proton-ATPase (F1F0) of Escherichia coli was purified from membranes of strain AN1460 (unc+). Antibody to purified subunit b was raised in rabbits. It reacted with F1-depleted membranes and blocked F1 binding. Bound antibody had no effect on proton transport through F0. F1-Depleted membranes competed with purified subunit b for antibody in an enzyme-linked immunosorbent assay. F1-Depleted membranes which had been pretreated with trypsin or preincubated with saturating amounts of soluble F1 competed poorly with purified subunit b for antibody. The antibody to subunit b was used to further evaluate the trypsin-cleavage data previously reported [D. S. Perlin, D. N. Cox, and A. E. Senior (1983) J. Biol. Chem. 258, 9793-9800]. The results indicated that trypsin proteolysis of F1-depleted membranes resulted in the transient appearance of three fragments of subunit b (Mr = 16,400, 15,700, and 15,500) that remained tightly bound to the membrane. A water-soluble fragment (Mr 14,800), previously thought to be derived from subunit b, was not detected by the antibody. The antibody to subunit b did not cross-react with any subunit of mitochondrial, chloroplast, or other bacterial proton-ATPase, or with the proton-ATPase of clathrin-coated vesicles, plant microsomal membranes, or Neurospora crassa plasma membranes. 相似文献
5.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
6.
A high efficiency transformation system for the basidiomycete Ustilago violacea employing hygromycin resistance and lithium-acetate treatment 总被引:1,自引:0,他引:1
A basidiomycete phytopathogenic fungus, Ustilago violacea, was transformed with pUCH1, a bacterial plasmid containing the hygromycin (Hyg)-resistance hygB gene fused to a promoter from the ascomycete Cochliobolus heterostrophus. After lithium acetate/polyethylene glycol treatment of whole sporidial cells, U. violacea transformants appeared on Hyg-agar at a frequency of 60-80 per microgram pUCH1 DNA. The Hyg phenotype was 100% stable in these transformants for at least 30 generations of mitotic growth under non-selective conditions. Southern DNA-DNA hybridization revealed multiple integrations of the pUCH1 plasmid into the U. violacea nuclear DNA. In addition, Escherichia coli transformants appeared at a frequency of 12 per microgram nuclear fraction DNA from Hyg U. violacea transformants; these E. coli consistently contained a deleted pUCH1 plasmid. This latter result suggested the low-frequency production of circular molecules by recombination within the integrated sequences. 相似文献
7.
Defective H(+)-ATPase of hygromycin B-resistant pma1 mutants fromSaccharomyces cerevisiae 总被引:5,自引:0,他引:5
D S Perlin S L Harris D Seto-Young J E Haber 《The Journal of biological chemistry》1989,264(36):21857-21864
Mutations in the plasma membrane H(+)-ATPase gene (PMA1) of Saccharomyces cerevisiae that confer growth resistance to hygromycin B have been shown recently to cause a marked depolarization of whole cell membrane potential (Perlin, D. S., Brown, C. L., and Haber, J. E. (1988) J. Biol. Chem. 263, 18118-18122). In this report, the biochemical and genetic properties of H+-ATPases from four prominent hygromycin B-resistant pma1 mutants, pma1-105, pma1-114, pma1-147, and pma1-155, are described. Single base pair changes were identified in pma1-105, pma1-114, and pma1-147 that resulted in amino acid substitutions of Ser-368----Phe, Gly-158----Asp, Pro-640----Leu, respectively. An A----G transition mutation at -39 in the 5'-untranslated region of the mRNA of pma1-155 was also found. This mutation creates an out-of-Frame upstream AUG initiation codon that apparently reduces normal translation of PMA1. DNA sequence analysis of PMA1 from strain Y55 identified 9 base pair substitutions that resulted in 6 amino acid changes in nonconserved regions when compared to the published sequence for strain S288C. Plasma membranes of three of the four pma1 mutants contained normal amounts of H(+)-ATPase; membranes from pma1-155 contained enzyme at 62% of the wild-type level. The kinetics of ATP hydrolysis were most strongly altered for enzymes from pma1-105 and pma1-147 which showed changes in both Km and Vmax. A striking pH dependence for these parameters was found for enzyme from pma1-105 which resulted in a precipitous decline in Km and Vmax below pH 6.5. ATP hydrolysis by enzymes from pma1-105 and pma1-147 was insensitive to inhibition by vanadate. These enzymes, in contrast to wild-type and vanadate-sensitive mutant enzymes, were poorly protected from trypsin-induced inactivation by MgATP and vanadate or Pi alone. These results are pertinent to the mechanism of vanadate-induced enzyme inhibition and suggest that Ser-368 and Pro-640 influence the affinity of the phosphate-binding site for Pi. All mutant enzymes catalyzed ATP-induced pH gradient formation following purification and reconstitution into liposomes. Finally, these results further demonstrate the usefulness of hygromycin B as a generalized screening tool for isolating diverse plasma membrane ATPase mutants. 相似文献
8.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
9.