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71.
Seven alleles of the alpha-Glycerophosphate dehydrogenase-1 (alphaGpdh-1) locus of Drosophila melanogaster have been described. These include two naturally occurring electrophoretic variants, one EMS-induced electrophoretic variant, and four EMS-induced "null" or "zero" mutants. With the electrophoretic variants, the locus was mapped to II-20.5 +/- 2.5. A complementation matrix was prepared utilizing the null mutants. Three of the four mutants and a deletion of the locus (Grell 1967) exhibit dosage dependency. The dosage independent mutant exhibits complementation with two of the other null alleles. Flies genetically deficient in alpha-glycerophosphate dehydrogenase are fertile, but their relative viability is severely diminished. Such flies also lose the ability to sustain flight, an observation consistent with the enzyme's function in energy production. The levels of mitochondrial alpha-glycerophosphate oxidase, measured in flies genetically deficient in the cytoplasmic enzyme, were normal. 相似文献
72.
73.
Can three incongruence tests predict when data should be combined? 总被引:31,自引:14,他引:17
Advocates of conditional combination have argued that testing for
incongruence between data partitions is an important step in data
exploration. Unless the partitions have had distinct histories, as in
horizontal gene transfer, incongruence means that one or more data support
the wrong phylogeny. This study examines the relationship between
incongruence and phylogenetic accuracy using three tests of incongruence.
These tests were applied to pairs of mitochondrial DNA data partitions from
two well-corroborated vertebrate phylogenies. Of the three tests, the most
useful was the incongruence length difference test (ILD, also called the
partition homogeneity test). This test distinguished between cases in which
combining the data generally improved phylogenetic accuracy (P > 0.01)
and cases in which accuracy of the combined data suffered relative to the
individual partitions (P < 0.001). In contrast, in several cases, the
Templeton and Rodrigo tests detected highly significant incongruence (P
< 0.001) even though combining the incongruent partitions actually
increased phylogenetic accuracy. All three tests identified cases in which
improving the reconstruction model would improve the phylogenetic accuracy
of the individual partitions.
相似文献
74.
75.
Organisms use circadian clocks to generate 24‐h rhythms in gene expression. However, the clock can interact with other pathways to generate shorter period oscillations. It remains unclear how these different frequencies are generated. Here, we examine this problem by studying the coupling of the clock to the alternative sigma factor sigC in the cyanobacterium Synechococcus elongatus. Using single‐cell microscopy, we find that psbAI, a key photosynthesis gene regulated by both sigC and the clock, is activated with two peaks of gene expression every circadian cycle under constant low light. This two‐peak oscillation is dependent on sigC, without which psbAI rhythms revert to one oscillatory peak per day. We also observe two circadian peaks of elongation rate, which are dependent on sigC, suggesting a role for the frequency doubling in modulating growth. We propose that the two‐peak rhythm in psbAI expression is generated by an incoherent feedforward loop between the clock, sigC and psbAI. Modelling and experiments suggest that this could be a general network motif to allow frequency doubling of outputs. 相似文献
76.
Nanotoxicity: the growing need for in vivo study 总被引:1,自引:0,他引:1
77.
CW Jonathan Edwards 《Arthritis research & therapy》2000,2(5):344-4
Synovial fibroblasts occur as two phenotypes - intimal and subintimal. The specialised intimal phenotype includes expression of uridine diphosphoglucose dehydrogenase (UDPGD), vascular cell adhesion molecule-1 (VCAM-1) and complement decay-accelerating factor (DAF). These gene products contribute to specialised functions relating to tissue movement and leucocyte traffic. 相似文献
78.
This study focuses on the cytotoxic effects of fumonisin B1 (FB1) on both immortalised and immortalised and subsequently transfected normal human bronchial epithelial (NHBE) cells of human
origin using four bioassays. While the MTT, Neutral Red and hexosaminidase colorimetric assays showed little difference between
the toxic effects on the two related cell lines, the clonogenic assay, measuring cell survival and proliferation, indicated
that FB1 had a more toxic effect on the nontransfected cells. This kind ofin vitro approach using cells which retain many characteristics of normal cell growth and differentiation can go some way to developing
evaluation models for food safety in the case of mycotoxin contamination without resorting totally to whole animal testing.
Nevertheless, one or two cytotoxicity tests may be inadequate for a complete appraisal of toxic potential: rather, as wide
a range of methodologies as feasible should be employed initially before meaningful conclusions may be drawn. 相似文献
79.
We previously reported experiments which led us to conclude that DNA synthesis in HeLa cells occurs in association with the nuclear membrane. Subsequent experiments which are reported here provide evidence that DNA synthesis occurs both in proximity to and at sites removed from the nuclear membrane. 相似文献
80.
1. The presence of xanthine was required for the inhibition of bovine milk xanthine oxidase by o-iodosobenzoate, iodoacetamide, hydrogen peroxide or p-chloromercuribenzoate. 2. Inactivation by p-chloromercuribenzoate was very rapid, was reversed by cysteine and was less in the presence of FAD. Lineweaver-Burk plots showed that the inactivation by p-chloromercuribenzoate was competitive with substrate. 3. Inactivation by o-iodosobenzoate, iodoacetamide or hydrogen peroxide could not be reversed by cysteine or xanthine. However, the presence of xanthine during the incubation with inhibitor protected the enzyme against o-iodosobenzoate but not against iodoacetamide or hydrogen peroxide. 4. p-Chloromercuribenzoate protected the enzyme against inactivation by hydrogen peroxide. 相似文献