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61.
62.
Tempo and mode of concerted evolution in the L1 repeat family of mice 总被引:10,自引:0,他引:10
Martin SL; Voliva CF; Hardies SC; Edgell MH; Hutchison CA d 《Molecular biology and evolution》1985,2(2):127-140
A 300-bp DNA sequence has been determined for 30 (10 from each of three
species of mice) random isolates of a subset of the long interspersed
repeat family L1. From these data we conclude that members of the L1 family
are evolving in concert at the DNA sequence level in Mus domesticus, Mus
caroli, and Mus platythrix. The mechanism responsible for this phenomenon
may be either duplicative transposition, gene conversion, or a combination
of the two. The amount of intraspecies divergence averages 4.4%, although
between species base substitutions accumulate at the rate of approximately
0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M.
domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix
L1 family has evolved into a distinct clade in the 10-12 Myr since M.
platythrix last shared a common ancestor with M. domesticus and M. caroli.
The parsimony tree also provides a means to derive the average half-life of
L1 sequences in the genome. The rates of gain and loss of individual copies
of L1 were estimated to be approximately equal, such that approximately
one-half of them turn over every 3.3 Myr.
相似文献
63.
Carl?Shooner Pierre-Luc?Caron Guylaine?Fréchette-Frigon Valérie?Leblanc Marie-Claude?Déry Eric?AsselinEmail author 《Reproductive biology and endocrinology : RB&E》2005,3(1):20
Background
During early rat pregnancy, trophoblast of the tiny embryo joins with the endometrium and epithelial cells undergo apoptosis. Near the end of pregnancy, regression of the decidua basalis (DB) is also observed (from day 14 to 20). However, little is known about the intra-cellular and molecular mechanisms involved in apoptosis regulation in the uterus during pregnancy. The objective of the present study was to investigate the presence and the developmental expression of transforming growth factor-beta isoforms (TGF-beta well known differentiation factor) in the rat endometrium throughout pregnancy and its action in vitro using cultured endometrial stromal cells. 相似文献64.
将化学合成的单链猪胰岛素前体(PIP)基因和用聚合酶链反应得到的α交配因子前导顺序(αMFL)基因插入质粒pVT102-U的醇脱氢酶基因ADH1的启动子和3’终止顺序之间而生成质粒pVT102-U/αMFL-PIP.被pVT102-U/αMFL-PIP转化的酵母(Saccharomyces cerevistae)可表达单链前体并分泌到培养基中.前体在纯化后可通过胰蛋白酶的转肽作用转变成人胰岛素.纯化的人胰岛素具有全部活力并可结晶.人胰岛素的总收率为每升培养液25mg. 相似文献
65.
The phylogenetic position of the Pedetidae, represented by a single species
Pedetes capensis, is controversial, reflecting in part the retention of
both Hystricomorphous and Sciurognathous characteristics in this rodent. In
an attempt to clarify the species evolutionary relationships, mtDNA gene
sequences from 10 rodent species (representing seven families) were
analyzed using phenetic, parsimony, and maximum-likelihood methods of
phylogenetic inference; the rabbit, Oryctolagus cuniculus (Order
Lagomorpha), and cow, Bos taurus (Order Artiodactyla), were used as
outgroups. Investigation of 714 base pairs of the protein-coding cytochrome
b gene indicate strong base bias at the third codon position with
significant rate heterogeneity evident between the three structural domains
of this gene. Similar analyses conducted on 816 base pairs of the 12S rRNA
gene revealed a transversion bias in the loop sections of all taxa. The
cytochrome b gene sequences proved useful in resolving associations between
closely related species but failed to produce consistent tree topologies at
the family level. In contrast, phylogenetic analysis of the 12S rRNA gene
resulted in strong support for the clustering of
Pedetidae/Heteromyidae/Geomyidae and Muridae in one clade to the exclusion
of the Hystricidae/Thryonomyidae and Sciuridae, a finding which is
concordant with studies of rodent fetal membranes as well as reproductive
and other anatomical features.
相似文献
66.
The winter feeding ecology of Avocets Recurvirostra avosetta on intertidal areas. II. Diet and feeding mechanisms 总被引:1,自引:1,他引:0
FRANCISCO MOREIRA 《Ibis》1995,137(1):99-108
The diet and feeding methods of Avocets Recurvirostra avosetta using the most common feeding strategy (Normal Feeding Strategy) on emerged intertidal areas in the Tagus estuary, Portugal, were studied during two winters.
Avocets using the Normal Feeding Strategy fed non-selectively in the top 20 mm of sediment, ingesting prey bigger than a minimum threshold dimension of around 1.5 mm. Some mud was also ingested whilst feeding. Prey were captured by the mechanical action of the bill, and the estimated number of items captured per sweep was quite high (mean = 10.9 worms). Most of the biomass ingested by Avocets consisted of oligochaetes, spionid worms, Capitella capitata and small ragworms Nereis diversicolor.
The estimated intake rate of Avocets suggested that the energy ingested during daylight hours did not represent a significant percentage of the daily requirements. Thus, feeding on emerged intertidal areas is probably a secondary component of their daily gross food intake, unless night feeding yields higher intake rates due to increased prey availability. 相似文献
Avocets using the Normal Feeding Strategy fed non-selectively in the top 20 mm of sediment, ingesting prey bigger than a minimum threshold dimension of around 1.5 mm. Some mud was also ingested whilst feeding. Prey were captured by the mechanical action of the bill, and the estimated number of items captured per sweep was quite high (mean = 10.9 worms). Most of the biomass ingested by Avocets consisted of oligochaetes, spionid worms, Capitella capitata and small ragworms Nereis diversicolor.
The estimated intake rate of Avocets suggested that the energy ingested during daylight hours did not represent a significant percentage of the daily requirements. Thus, feeding on emerged intertidal areas is probably a secondary component of their daily gross food intake, unless night feeding yields higher intake rates due to increased prey availability. 相似文献
67.
FRANCISCO MOREIRA 《Ibis》1995,137(1):92-98
The behaviour of Avocets Recurvirostra avosetta feeding on emerged intertidal areas in a major wintering area, the Tagus estuary (Portugal), was studied during 2 years.
Avocets used four different feeding strategies. By far the most common was the Normal Feeding Strategy, in which the median sweeping rate was 28 sweeps per min and the percentage of swallowing movements (ingestions) was very high (median = 90%). No prey were visible in the bill while birds were using this strategy. Another less common feeding strategy was the Worm Feeding Strategy, in which the sweeping rate was higher (median = 46 sweeps/min) and the percentage of swallowing movements was much lower (median = 6%). While using the Worm Feeding Strategy, Avocets preyed on ragworms Nereis diversicolor. The Mixed Feeding Strategy and Scrobicularia plana Siphons Feeding Strategy were rarely observed.
In a detailed study on the use of the mudflats by Avocets, it was found that the density of birds on the upper shore was much higher than on the lower shore. There were differences in feeding behaviour between these two areas, although the same feeding strategy was used. On the lower shore, where there was a lower biomass of prey available, sweeping rates were higher and aggressive behaviour did not occur. On the upper shore, sweeping rates were lower and aggressive behaviour was frequent, with some birds defending territories. Nevertheless, estimated food intake rates were 1.5 times higher on the upper shore. 相似文献
Avocets used four different feeding strategies. By far the most common was the Normal Feeding Strategy, in which the median sweeping rate was 28 sweeps per min and the percentage of swallowing movements (ingestions) was very high (median = 90%). No prey were visible in the bill while birds were using this strategy. Another less common feeding strategy was the Worm Feeding Strategy, in which the sweeping rate was higher (median = 46 sweeps/min) and the percentage of swallowing movements was much lower (median = 6%). While using the Worm Feeding Strategy, Avocets preyed on ragworms Nereis diversicolor. The Mixed Feeding Strategy and Scrobicularia plana Siphons Feeding Strategy were rarely observed.
In a detailed study on the use of the mudflats by Avocets, it was found that the density of birds on the upper shore was much higher than on the lower shore. There were differences in feeding behaviour between these two areas, although the same feeding strategy was used. On the lower shore, where there was a lower biomass of prey available, sweeping rates were higher and aggressive behaviour did not occur. On the upper shore, sweeping rates were lower and aggressive behaviour was frequent, with some birds defending territories. Nevertheless, estimated food intake rates were 1.5 times higher on the upper shore. 相似文献
68.
FERNANDO GÓMEZ PURIFICACIÓN LÓPEZ-GARCÍA DAVID MOREIRA 《The Journal of eukaryotic microbiology》2009,56(5):440-445
ABSTRACT. Members of the family Warnowiaceae are unarmored phagotrophic dinoflagellates that possess an ocelloid. The genus Erythropsidinium (= Erythropsis ) has also developed a unique dynamic appendage, the piston, which is able to independently retract and extend for at least 2 min after the cell lyses. We provide the first small subunit ribosomal RNA gene sequences of warnowiid dinoflagellates, those of the type Erythropsidinium agile and one species of Warnowia . Phylogenetic analyses show that warnowiid dinoflagellates branch within the Gymnodinium sensu stricto group, forming a cluster separated from the Polykrikos clade and with autotrophic Pheopolykrikos beauchampii as closest relative. This reinforces their classification as unarmored dinoflagellates based on the shape of the apical groove, despite the strong ecological and ultrastructural diversity of the Gymnodinium s.s. group. Other structures, such as the ocelloid and piston, have no systematic value above the genus level. 相似文献
69.
JUAN ANTONIO DÍAZ‐PENDÓN M. CARMEN CAÑIZARES ENRIQUE MORIONES EDUARDO R. BEJARANO HENRYK CZOSNEK JESÚS NAVAS‐CASTILLO 《Molecular Plant Pathology》2010,11(4):441-450
Tomato yellow leaf curl disease (TYLCD) is one of the most devastating viral diseases affecting tomato crops in tropical, subtropical and temperate regions of the world. Here, we focus on the interactions through recombination between the different begomovirus species causing TYLCD, provide an overview of the interactions with the cellular genes involved in viral replication, and highlight recent progress on the relationships between these viruses and their vector, the whitefly Bemisia tabaci. Taxonomy: The tomato yellow leaf curl virus‐like viruses (TYLCVs) are a complex of begomoviruses (family Geminiviridae, genus Begomovirus) including 10 accepted species: Tomato yellow leaf curl Axarquia virus (TYLCAxV), Tomato yellow leaf curl China virus (TYLCCNV), Tomato yellow leaf curl Guangdong virus (TYLCGuV), Tomato yellow leaf curl Indonesia virus (TYLCIDV), Tomato yellow leaf curl Kanchanaburi virus (TYLVKaV), Tomato yellow leaf curl Malaga virus (TYLCMalV), Tomato yellow leaf curl Mali virus (TYLCMLV), Tomato yellow leaf curl Sardinia virus (TYLCSV), Tomato yellow leaf curl Thailand virus (TYLCTHV), Tomato yellow leaf curl Vietnam virus (TYLCVNV) and Tomato yellow leaf curl virus(TYLCV). We follow the species demarcation criteria of the International Committee on Taxonomy of Viruses (ICTV), the most important of which is an 89% nucleotide identity threshold between full‐length DNA‐A component nucleotide sequences for begomovirus species. Strains of a species are defined by a 93% nucleotide identity threshold. Host range: The primary host of TYLCVs is tomato (Solanum lycopersicum), but they can also naturally infect other crops [common bean (Phaseolus vulgaris), sweet pepper (Capsicum annuum), chilli pepper (C. chinense) and tobacco (Nicotiana tabacum)], a number of ornamentals [petunia (Petunia×hybrida) and lisianthus (Eustoma grandiflora)], as well as common weeds (Solanum nigrum and Datura stramonium). TYLCVs also infect the experimental host Nicotiana benthamiana. Disease symptoms: Infected tomato plants are stunted or dwarfed, with leaflets rolled upwards and inwards; young leaves are slightly chlorotic; in recently infected plants, fruits might not be produced or, if produced, are small and unmarketable. In common bean, some TYLCVs produce the bean leaf crumple disease, with thickening, epinasty, crumpling, blade reduction and upward curling of leaves, as well as abnormal shoot proliferation and internode reduction; the very small leaves result in a bushy appearance. 相似文献
70.
Simon Brooker Archie CA Clements Peter J Hotez Simon I Hay Andrew J Tatem Donald AP Bundy Robert W Snow 《Malaria journal》2006,5(1):1-8