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101.
102.
Controlling for P‐value inflation in allele frequency change in experimental evolution and artificial selection experiments
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Petri Kemppainen Bernt Rønning Thomas Kvalnes Ingerid J. Hagen Thor Harald Ringsby Anna M. Billing Henrik Pärn Sigbjørn Lien Arild Husby Bernt‐Erik Sæther Henrik Jensen 《Molecular ecology resources》2017,17(4):770-782
Experimental evolution studies can be used to explore genomic response to artificial and natural selection. In such studies, loci that display larger allele frequency change than expected by genetic drift alone are assumed to be directly or indirectly associated with traits under selection. However, such studies report surprisingly many loci under selection, suggesting that current tests for allele frequency change may be subject to P‐value inflation and hence be anticonservative. One factor known from genomewide association (GWA) studies to cause P‐value inflation is population stratification, such as relatedness among individuals. Here, we suggest that by treating presence of an individual in a population after selection as a binary response variable, existing GWA methods can be used to account for relatedness when estimating allele frequency change. We show that accounting for relatedness like this effectively reduces false‐positives in tests for allele frequency change in simulated data with varying levels of population structure. However, once relatedness has been accounted for, the power to detect causal loci under selection is low. Finally, we demonstrate the presence of P‐value inflation in allele frequency change in empirical data spanning multiple generations from an artificial selection experiment on tarsus length in two free‐living populations of house sparrow and correct for this using genomic control. Our results indicate that since allele frequencies in large parts of the genome may change when selection acts on a heritable trait, such selection is likely to have considerable and immediate consequences for the eco‐evolutionary dynamics of the affected populations. 相似文献
103.
Roel May Jiska van Dijk Jrn Magne Forland Roy Andersen Arild Landa 《Applied animal behaviour science》2008,112(1-2):58-67
In Norway domestic sheep Ovis aries range unattended in mountainous areas during the summer season. Wolverines Gulo gulo re-established in the alpine regions of southern Norway during recent decades and are viewed as a substantial predator on lambs. Reducing predation on sheep by wolverines would not only reduce the economic loss to farmers but also promote the acceptance of wolverines in their summer ranges. We hypothesized that male lambs would be more prone to wolverine predation, because of higher locomotor activity, lower behavioural ewe–lamb synchrony and larger ewe–lamb distance. We studied ewe and lamb behavioural patterns, synchrony and ewe–lamb distance on a summer range in Knutshøi, south-central Norway. Although no differences were found in ewe–lamb distance or locomotor activity in gender, female lambs synchronized their behaviour more with their mother than males. Only for female lambs, increased synchrony resulted in closer ewe–lamb distances. Overall losses to wolverines based on long-term data indicate that male lambs are more prone to predation than females later in the season. These sex-specific behavioural differences in lambs affect the spatial and social relationships between ewe and lamb, and are likely to increase with age eventually leading to sexual segregation. Male lambs can therefore be expected to be more prone to wolverine predation towards the end of the season, when lambs become independent from the ewe. 相似文献
104.
Wikan A 《Journal of mathematical biology》2001,43(6):471-500
Discrete age-structured density-dependent one-population models and discrete age-structured density-dependent prey–predator
models are considered. Regarding the former, we present formal proofs of the nature of bifurcations involved as well as presenting
some new results about the dynamics in unstable and chaotic parameter regions. Regarding the latter, we show that increased
predation may act both as a stabilizing and a destabilizing effect. Moreover, we find that possible periodic dynamics of low
period, either exact or approximate, may not be generated by the predator, but it may be generated by the prey. Finally, what
is most interesting from the biological point of view, is that given that the prey, in absence of the predator, exhibits periodic
or almost periodic oscillations of low period, then the introduction of the predator does not alter this periodicity in any
substantial way until the stabilizing effect of increased predation becomes so strong that a stable equilibrium is achieved.
Received: 16 June 2000 / Revised version: 18 January 2001 / Published online: 12 October 2001 相似文献
105.
Madsen L Guerre-Millo M Flindt EN Berge K Tronstad KJ Bergene E Sebokova E Rustan AC Jensen J Mandrup S Kristiansen K Klimes I Staels B Berge RK 《Journal of lipid research》2002,43(5):742-750
Tetradecylthioacetic acid (TTA) is a non-beta-oxidizable fatty acid analog, which potently regulates lipid homeostasis. Here we evaluate the ability of TTA to prevent diet-induced and genetically determined adiposity and insulin resistance. In Wistar rats fed a high fat diet, TTA administration completely prevented diet-induced insulin resistance and adiposity. In genetically obese Zucker (fa/fa) rats TTA treatment reduced the epididymal adipose tissue mass and improved insulin sensitivity. All three rodent peroxisome proliferator-activated receptor (PPAR) subtypes were activated by TTA in the ranking order PPARalpha > PPARdelta > PPARgamma. Expression of PPARgamma target genes in adipose tissue was unaffected by TTA treatment, whereas the hepatic expression of PPARalpha-responsive genes encoding enzymes involved in fatty acid uptake, transport, and oxidation was induced. This was accompanied by increased hepatic mitochondrial beta-oxidation and a decreased fatty acid/ketone body ratio in plasma. These findings indicate that PPARalpha-dependent mechanisms play a pivotal role, but additionally, the involvement of PPARalpha-independent pathways is conceivable. Taken together, our results suggest that a TTA-induced increase in hepatic fatty acid oxidation and ketogenesis drains fatty acids from blood and extrahepatic tissues and that this contributes significantly to the beneficial effects of TTA on fat mass accumulation and peripheral insulin sensitivity. 相似文献
106.
Kristina Noreikiene Gábor Herczeg Abigél Gonda Gergely Balázs Arild Husby Juha Meril? 《Proceedings. Biological sciences / The Royal Society》2015,282(1810)
The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback (Gasterosteus aculeatus). We found that heritabilities were low (average h2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average rG = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high (rG = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks. 相似文献
107.
Silje L. Rekdal Jarl Andreas Anmarkrud Jan T. Lifjeld Arild Johnsen 《Molecular ecology》2019,28(23):5133-5144
Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen‐mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra‐pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra‐pair males in a nonrandom, self‐matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra‐pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade‐off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra‐pair mating is adaptive through altered genetic constitution in offspring. 相似文献
108.
Sexually dimorphic plumage coloration is widespread in birds and is generally thought to be a result of sexual selection for more ornamented males. Although many studies find an association between coloration and fitness related traits, few of these simultaneously examine selection and inheritance. Theory predicts that sex‐linked genetic variation can facilitate the evolution of dimorphism, and some empirical work supports this, but we still know very little about the extent of sex linkage of sexually dimorphic traits. We used a longitudinal study on juvenile Florida scrub‐jays (Aphelocoma coerulescens) to estimate strength of selection and autosomal and Z‐linked heritability of mean brightness, UV chroma, and hue. Although plumage coloration signals dominance in juveniles, there was no indication that plumage coloration was related to whether or not an individual bred or its lifetime reproductive success. While mean brightness and UV chroma are moderately heritable, hue is not. There was no evidence for sex‐linked inheritance of any trait with most of the variation explained by maternal effects. The genetic correlation between the sexes was high and not significantly different from unity. These results indicate that evolution of sexual dimorphism in this species is constrained by low sex‐linked heritability and high intersexual genetic correlation. 相似文献
109.
Parental Care and Sexual Selection in the Bluethroat, Luscinia s. svecica: A Field-experimental Test of the Differential Allocation Hypothesis 总被引:1,自引:0,他引:1
Percy A. Rohde Arild Johnsen & Jan T. Lifjeld 《Ethology : formerly Zeitschrift fur Tierpsychologie》1999,105(8):651-663
One of the processes by which secondary sexual characters in monogamous species with biparental care may evolve is described by the differential allocation hypothesis. It predicts that mates adjust their parental effort to the attractiveness of their partner. The more attractive sex is expected to withhold parental effort while the less attractive sex is expected to compensate for the partner's decreased effort thus preventing a reduction in breeding success. Asymmetry in attractiveness then imposes costs on the less attractive sex which are thought to be exceeded by the indirect (i.e. genetic) benefits which result from sharing offspring with a highly attractive partner. This idea was tested with bluethroats, Luscinia s. svecica , a bird species in which the male is characterized by a complex multiple-coloured plumage ornament on the throat and chest. We manipulated male attractiveness by attaching conspicuous coloured leg bands which matched the blue and chestnut components of the male ornament. Control males were banded with green and yellow bands. The results from another field experiment on mate-guarding behaviour demonstrate the effectiveness of this treatment. As measures of parental effort we determined: 1. clutch size; 2. feeding rates by video recording feeding activity of both parents; and 3. brood mass up to day 9. The results do not support the differential allocation hypothesis. The experimental and control groups differed in none of the above variables. On the basis of these results we discuss the ecological factors which may influence the differential allocation process in monogamous birds. 相似文献
110.
cDNA representational difference analysis of ileal Peyer's patches in lambs after oral inoculation with scrapie 总被引:3,自引:0,他引:3
Skretting G Espenes A Ulvund MJ Olsaker I 《Biochemical and biophysical research communications》2004,316(1):272-279
cDNA representational difference analysis (RDA) was used to study gene expression profiles in the ileal Peyer's patch of a lamb 1 week after oral inoculation with the scrapie agent. Twenty-five differentially expressed cDNA fragments were identified and cloned. Sequence analysis indicated seven novel gene sequences. Other clones shared sequence homology with genes encoding ribosomal and mitochondrial proteins, the translation initiation factor EIF4GII and the bovine pancreatic thread protein. Reverse Northern was used to confirm the differential expression in another four lambs inoculated with scrapie and the tissue distribution of the novel genes was examined using Northern blot analysis. 相似文献