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1.
David Bellamy 《BMJ (Clinical research ed.)》1983,286(6375):1439-1440
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V T Forsyth A Mahendrasingam W J Pigram R J Greenall K Bellamy W Fuller S A Mason 《International journal of biological macromolecules》1989,11(4):236-240
Interactions with water are crucial to the conformation assumed by the DNA double helix. The location of water around the D conformation has been investigated in a neutron fibre diffraction study which shows that water is ordered in the minor groove of the DNA. The D conformation is important since its occurrence is limited to specific DNA base pair sequences which have been identified as functionally significant. This study is of particular interest because the D conformation has not been reported in single crystal studies of oligonucleotides. 相似文献
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Cytoplasmic delivery of ribozymes leads to efficient reduction in alpha-lactalbumin mRNA levels in C127I mouse cells. 总被引:4,自引:0,他引:4
Ribozymes targeted to five sites along the alpha-lactalbumin (alpha-lac) mRNA were delivered to the cytoplasm of mouse C127I mammary cells using the T7-vaccinia virus delivery system and the amount of alpha-lac mRNA was monitored 24-48 h post-transfection. Three target sites were selected in the alpha-lac coding region (nucleotides 15, 145 and 361) and two were located in the 3' non-coding region (nucleotides 442 and 694). Acting in trans and at a target:ribozyme ratio of 1:1000, ribozymes targeting sites 361 and 694 reduced alpha-lac mRNA by > 80%; another two ribozymes (targeting nucleotides 442 and 145) reduced mRNA levels by 80 and 60% respectively; the fifth ribozyme (targeting nucleotide 15, near the AUG) was largely ineffective. The kinetic activity (kcat) of each ribozyme in vitro was somewhat predictive of the activity of the two ribozymes that targeted nucleotides 361 and 694, but was not predictive of the in vivo activity of the other three ribozymes. Down-regulation of the intracellular levels of alpha-lac paralleled the ribozyme-dependent reduction achieved for mRNA. For site 442, the reduction in both mRNA and protein was attributed to the catalytic activity of the ribozyme rather than to the antisense effects of the flanking arms, because delivery of an engineered (catalytically-inactive) variant had no effect on mRNA levels and a minimal effect on the level of alpha-lac present in the cell. 相似文献
6.
Comparative sequence analysis of rotavirus genomic segment 6--the gene specifying viral subgroups 1 and 2 总被引:6,自引:3,他引:3 下载免费PDF全文
G W Both L J Siegman A R Bellamy N Ikegami A J Shatkin Y Furuichi 《Journal of virology》1984,51(1):97-101
Cloned DNA copies of rotavirus genomic segment 6 from simian 11 (subgroup 1) and human strain Wa (subgroup 2) rotaviruses have been used to determine the nucleotide sequences of the gene that determines viral subgroup specificity. Both genomic segments are 1,356 nucleotides in length and possess 5'- and 3'-terminal untranslated regions of 23 and 142 nucleotides, respectively. The inferred amino acid sequence reveals VP6 to be a polypeptide of 397 amino acids in which more than 90% of the amino acid sequence is conserved between the two viruses. There are 34 amino acid changes between the subgroup 1 and 2 polypeptides, most clustered in three regions of the molecule at residues 39 through 62, 80 through 122, and 281 through 315. 相似文献
7.
The immunogenicity of VP7, a rotavirus antigen resident in the endoplasmic reticulum, is enhanced by cell surface expression. 总被引:5,自引:2,他引:3 下载免费PDF全文
M E Andrew D B Boyle P L Whitfeld L J Lockett I D Anthony A R Bellamy G W Both 《Journal of virology》1990,64(10):4776-4783
The glycoprotein VP7, the major serotype antigen of rotaviruses, is localized to the endoplasmic reticulum (ER) of the cell, where it is retained as a membrane-associated protein before assembly into mature virus particles. Wild-type VP7 expressed by a recombinant vaccinia virus was also located internally and was poorly antigenic. Using recombinant techniques, a correctly processed, secreted form of VP7 (S.C. Stirzaker and G.W. Both, Cell 56:741-747, 1989) was modified by addition to its C terminus of the membrane anchor and cytoplasmic domains from the influenza virus hemagglutinin. The hybrid protein was directed to the surface of cells, where it was anchored in the plasma membrane. When expressed in mice and rabbits by a recombinant vaccinia virus, the surface-anchored antigen stimulated a level of rotavirus-specific antibodies that was greater than 100-fold above the level induced by wild-type VP7. T-cell responses to the novel antigen were also elevated in comparison with the wild-type, intracellular protein. Cell surface anchoring may provide a strategy to increase the immunogenicity of intracellular antigens from other parasites and viruses. 相似文献
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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
10.
Year-to-year turnover in bird species composition was recorded across, the whole size range (0 02-30 ha) of 146 woods studied The mean number of resident breeding species both lost and gained per wood between consecutive breeding seasons was 2 (range 0-8) No relationship was found between this absolute turnover rate and woodland area, or any other of 24 predictor variables (describing woodland structure, isolation, connectedness and surrounding land use) Extriction and colonisation rates (in terms of numbers of species lost and gained) were also unrelated to woodland area In all sizes of woods, the species most likely to show local extinctions and colonisations were those with small populations within those woods, but the identity of the species concerned changed as woodland area increased In the smallest woods, the majority of turnover involved common species, such as wren and dunnock, which occurred in only small numbers in these small woods As woodland area increased, these species attained sufficient numbers to usually avoid stochastic extinction The majority of turnover was then due to more specialist (and less numerous) woodland species, such as great-spotted woodpecker and marsh tit, which were usually lacking in small woods In Britain, much existing broadleaved woodland falls within the size range studied Thus the numbers of many bird species are liable to be small enough for yearly turnover in woodland bird communities to be appreciable, and for the long-term persistence of individual species in particular woods to depend on dispersal 相似文献