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1.
A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
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Sulfate reduction, methanogenesis, and methane oxidation in the upper sediments of the Vistula and Curonian Lagoons, Baltic Sea 总被引:1,自引:0,他引:1
N. V. Pimenov M. O. Ul’yanova T. A. Kanapatskii I. N. Mitskevich I. I. Rusanov P. A. Sigalevich I. A. Nemirovskaya V. V. Sivkov 《Microbiology》2013,82(2):224-233
Microbiological, biogeochemical, and isotope geochemical investigations of the upper sediments of the Vistula and Curonian lagoons, Baltic Sea, were carried out. High content of organic matter in the sediments was responsible for the high numbers (over 1010 cells cm?3) and activity of heterotrophic microorganisms. The calculated integral rates of dark CO2 assimilation for the upper 30 cm of the sediments varied 12.5 to 38.8 mmol m?2 day?1 and were somewhat higher in the Curonian Lagoon than in the Vistula Lagoon. Integral rates of sulfate reduction were higher in the more saline Vistula Lagoon. Rapid consumption of sulfates of the pore water resulted in intensified methanogenesis, with significantly higher rates detected in the silts of the Curonian Lagoon. High rates of methanogenesis in the Curonian Lagoon correlated with higher methane levels in its upper sediments and near-bottom water. The highest rates of methane oxidation were detected in the uppermost sediment horizons (oxidized or slightly reduced), which was an indication of the barrier role of aerobic methanotrophic bacteria. The calculated methane flows from the sediments into the water column were 0.45 and 0.007 mmol m?2 day?1 for the Vistula and Curonian Lagoons, respectively. Low methane flow from the sediments of the Curonian Lagoon resulted probably from the specific weather (wind) conditions during sampling. The near-stormy conditions in the Curonian Lagoon caused sediment detachment, resulting in methane release into the water column. 相似文献
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Fedurkina NV Belousova LV Mitskevich LG Zhou HM Chang Z Kurganov BI 《Biochemistry. Biokhimii?a》2006,71(3):325-331
Creatine kinase thermal aggregation kinetics has been studied in 30 mM Hepes-NaOH buffer, pH 8.0, at two temperatures: 50.6
and 60°C. Aggregation kinetics was analyzed by measuring the growth of apparent absorption (A) at 400 nm. It was found that the limiting value of apparent absorption (A
lim) is proportional to protein concentration at both temperatures. The first order rate constant (k
I) does not depend on protein concentration in the range 0.05–0.2 mg/ml at temperature 50.6°C, but at temperature 60°C it increases
with the growth of protein concentration in the range 0.1–0.4 mg/ml. Kinetic curves, shown in coordinates {A/A
lim; t}, in experiments at 50.6°C fuse to a common curve, which coincides with the theoretical curve of creatine kinase denaturation
calculated using the denaturation rate constant determined from differential scanning calorimetry. At temperature 60°C, half-transformation
time t
1/2 = ln2/k
I decreases when protein concentration grows. We conclude that when temperature increased from 50.6 to 60°C, change in the
kinetic regime of thermal creatine kinase aggregation took place: at 50.6°C aggregation rate is limited by the stage of protein
molecule denaturation, but at 60°C it is limited by the stage of protein aggregate growth, which proceeds as a reaction of
pseudo-first order. Small heat shock protein Hsp 16.3 Mycobacterium tuberculosis suppresses the creatine kinase aggregation.
Published in Russian in Biokhimiya, 2006, Vol. 71, No. 3, pp. 408–416. 相似文献
8.
E V Proshliakova O N Rumiantseva M S Mitskevich 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(5):616-619
Brain hypothalamus region was removed by encephalectomy in utero in 21-23-day-old rabbit fetuses to find out when hypothalamic control over testicular androgenous function was set up during rabbit prenatal development. Testosterone concentration in testicular tissue was measured by radioimmunoassay at different terms after the operation. Encephalectomy resulted in a reliable decrease of testosterone concentration in 29- and 25-day-old fetuses, however, no significant changes were observed in 23-day-old fetuses. The greatest reduction in hormone gland concentration was noted in 25-day-old fetuses, encephalectomized on day 23 of their development. Introduction of LH-RH to 25-day-old encephalectomized fetuses 30 min before fixation significantly increased androgen concentration in the gland. The data obtained indicate that hypothalamic control over testicular androgenous function is set up on days 23-25 of prenatal development. 相似文献
9.
We studied different genetic models and evaluation systems to select against a genetic disease with additive, recessive or polygenic inheritance in genetic conservation schemes. When using optimum contribution selection with a restriction on the rate of inbreeding (ΔF) to select against a disease allele, selection directly on DNA-genotypes is, as expected, the most efficient strategy. Selection for BLUP or segregation analysis breeding value estimates both need 1–2 generations more to halve the frequency of the disease allele, while these methods do not require knowledge of the disease mutation at the DNA level. BLUP and segregation analysis methods were equally efficient when selecting against a disease with single gene or complex polygene inheritance, i.e. knowledge about the mode of inheritance of the disease was not needed for efficient selection against the disease. Smaller schemes or schemes with a more stringent restriction on ΔF needed more generations to halve the frequency of the disease alleles or the fraction of diseased animals. Optimum contribution selection maintained ΔF at its predefined level, even when selection of females was at random. It is argued that in the investigated small conservation schemes with selection against a genetic defect, control of ΔF is very important. 相似文献
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