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131.
132.
133.
Positive selection driving the evolution of a gene of male reproduction, Acp26Aa, of Drosophila: II. Divergence versus polymorphism 总被引:5,自引:1,他引:4
The evolution of the gene for a male ejaculatory protein, Acp26Aa, has been
shown to be driven by positive selection when nonsibling species in the
Drosophila melanogaster subgroup are compared. To know if selection has
been operating in the recent past and to understand the details of its
dynamics, we obtained DNA sequences of Acp26Aa and the nearby Acp26Ab gene
from 39 D. melanogaster chromosomes. Together with the 10 published
sequences, we analyzed 49 sequences from five populations in four
continents. The southern African population is somewhat differentiated from
all other populations, but its nucleotide diversity is lower at these two
loci. We find the following results for Acp26Aa: (1) The R: S (replacement
: silent changes) ratio is significantly higher in the between-species
comparisons than in the within-species data by the McDonald and Kreitman
test. Positive selection is probably responsible for the excess of amino
acid replacements between species. (2) However, within-species nucleotide
diversity is high. Neither the Tajima test nor the Fu and Li test indicates
a reduction in nucleotide diversity due to positive selection in the recent
past. (3) The newly derived nucleotides in D. melanogaster are at high
frequency significantly more often than predicted by the neutral
equilibrium. Since the nearby Acp26Ab gene does not show these patterns,
these observations cannot be attributed to the characteristics of this
chromosomal region. We suggest that positive selection is active, but may
be weak, for each amino acid change in the Acp26Aa gene.
相似文献
134.
135.
Yonekura H Sakurai S Liu X Migita H Wang H Yamagishi S Nomura M Abedin MJ Unoki H Yamamoto Y Yamamoto H 《The Journal of biological chemistry》1999,274(49):35172-35178
136.
Mitochondrial DNA (mtDNA) sequences that include (a) a part of the
cytochrome b gene, (b) two tRNA genes, and (c) a part of the noncoding
D-loop region of 31 Anguilla japonica (Japanese eel) and 1 A. marmorata
collected from Taiwan, Japan, and mainland China were determined to
evaluate the population structure of Japanese eel. Among 30 genotypes
identified from the 31 Japanese eel mtDNAs sequenced, there are 58 variable
sites, predominantly clustered at the D-loop region. The phylogenetic tree
constructed by the unweighted pair-group method with arithmetic mean shows
neither significant genealogical branches nor geographic clusters.
Furthermore, the sequence-statistics test reveals little, if any,
significant genetic differentiation. These results indicate that the 31
Japanese eels might come from a single population. Analysis of sequence
variation in mtDNA by using the relationship between the number of
segregating sites and the average number of nucleotide differences under
the neutral mutation hypothesis reveals that neutral mutation acts as a
major factor influencing the evolutionary divergence of the Japanese eel
mitochondrial genome sequenced, especially in the noncoding region.
相似文献
137.
Regeneration of Grateloupia acuminata Okamura from fragments of basal crusts and young upright thalli was studied in culture. The carpospores and tetraspores develop into basal crusts and these in turn produce upright thalli. When the crusts and the young upright thalli were cut into fragments, the fragments of basal crusts regenerated into new crusts, whereas those of upright thalli formed adventitious filaments. For cultivation in the sea, the cut fragments of basal crusts were inoculated onto oyster shells and synthetic twines of Nori-net and cultured for about one month in the laboratory. The oyster shells and the twines with regenerated crusts were then transferred into the sea from September to December. Many upright thalli developed and grew well during the cold season of the year (December to March).Author for correspondence 相似文献
138.
Mustafa G Migita CT Ishikawa Y Kobayashi K Tagawa S Yamada M 《The Journal of biological chemistry》2008,283(42):28169-28175
Escherichia coli membrane-bound glucose dehydrogenase (mGDH), which is one of quinoproteins containing pyrroloquinoline quinone (PQQ) as a coenzyme, is a good model for elucidating the function of bound quinone inside primary dehydrogenases in respiratory chains. Enzymatic analysis of purified mGDH from cells defective in synthesis of ubiquinone (UQ) and/or menaquinone (MQ) revealed that Q-free mGDH has very low levels of activity of glucose dehydrogenase and UQ2 reductase compared with those of UQ-bearing mGDH, and both activities were significantly increased by reconstitution with UQ1. On the other hand, MQ-bearing mGDH retains both catalytic abilities at the same levels as those of UQ-bearing mGDH. A radiolytically generated hydrated electron reacted with the bound MQ to form a semiquinone anion radical with an absorption maximum at 400 nm. Subsequently, decay of the absorbance at 400 nm was accompanied by an increase in the absorbance at 380 nm with a first order rate constant of 5.7 x 10(3) s(-1). This indicated that an intramolecular electron transfer from the bound MQ to the PQQ occurred. EPR analysis revealed that characteristics of the semiquinone radical of bound MQ are similar to those of the semiquinone radical of bound UQ and indicated an electron flow from PQQ to MQ as in the case of UQ. Taken together, the results suggest that MQ is incorporated into the same pocket as that for UQ to perform a function almost equivalent to that of UQ and that bound quinone is involved at least partially in the catalytic reaction and primarily in the intramolecular electron transfer of mGDH. 相似文献
139.
膝关节挫伤的磁共振影像表现 总被引:1,自引:1,他引:0
目的 :探讨磁共振短时的反转恢复序列 (STIR)在膝关节骨挫伤中的临床应用。方法 :通过 32例膝关节外伤病例在常规SE序列、FSE序列和STIR序列中的影像表现 ,分析STIR序列的优越性。结果 :32例共 45个骨挫伤病灶 ,T1W发现 38个 (占 84% ) ,T2W发现 37个 (占 82 % ) ,STIR序列病灶全部显示( 1 0 0 % )。结论 :STIR序列对骨挫伤的敏感性较高 ,能显示微小的骨髓水肿 ,充血及骨小梁的微骨折及其周围的骨软骨、关节囊的细微变化 ,对膝关节外伤具有较高价值。 相似文献
140.
Kawakami A Hida A Yamasaki S Miyashita T Nakashima K Tanaka F Ida H Furuyama M Migita K Origuchi T Eguchi K 《Biochemical and biophysical research communications》2002,296(1):26-31
1-Phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) is a synthetic inhibitor toward glucosyl transferase. Here, we showed the functional role of sphingolipids on CD54 expression of endothelial cells (ECs) by the use of PDMP. CD54 mRNA expression in human umbilical vein endothelial cells (HUVECs) was not changed by PDMP; however, PDMP treatment significantly enhanced the expression of membrane-bound CD54 (mCD54) on HUVECs. In contrast, the amount of soluble form of CD54 (sCD54) in the culture supernatants of HUVECs was diminished by PDMP. Similar results were obtained when HUVECs were incubated with metalloproteinase inhibitor, KB-R8301, or in the presence of C2-ceramide. The above effect of PDMP, KB-R8301, and C2-ceramide in HUVECs was commonly found in unstimulated, TNF-alpha-stimulated, and IL-1beta-stimulated HUVECs. These data provide the possibility that the shedding of mCD54 into sCD54 by metalloproteinase-like enzyme is inhibited by PDMP, in which PDMP-induced accumulation of ceramide may act as a second messenger. 相似文献