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71.
Anna Siwertsson Rune Knudsen Kim Præbel Colin E. Adams Jason Newton Per-Arne Amundsen 《Evolutionary ecology》2013,27(3):547-564
Natural populations often vary in their degree of ecological, morphological and genetic divergence. This variation can be arranged along an ecological speciation continuum of increasingly discrete variation, with high inter-individual variation at one end and well defined species in the other. In postglacial fishes, evolutionary divergence has commonly resulted in the co-occurrence of a pelagic and a benthic specialist. We studied three replicate lakes supporting sympatric pelagic and benthic European whitefish (Coregonus lavaretus (L.)) morphs in search for early signs of possible further divergence into more specialized niches. Using stomach content data (recent diet) and stable isotope analyses (time-integrated measure of trophic niche use), we observed a split in the trophic niche within the benthic whitefish morph, with individuals specializing on either littoral or profundal resources. This divergence in resource use was accompanied by small but significant differences in an adaptive morphological trait (gill raker number) and significant genetic differences between fish exploiting littoral and profundal habitats and foraging resources. The same pattern of parallel divergence was found in all three lakes, suggesting similar natural selection pressures driving and/or maintaining the divergence. The two levels of divergence (a clear and robust benthic – pelagic and a more subtle littoral – profundal divergence) observed in this study apparently represent different stages in the process of ecological speciation. 相似文献
72.
Edna J. L. Barbosa Camilla A. M. Glad Anna G. Nilsson Niklas Bosaeus Helena Filipsson Nystr?m Per-Arne Svensson Bengt-?ke Bengtsson Staffan Nilsson Ingvar Bosaeus Cesar Luiz Boguszewski Gudmundur Johannsson 《PloS one》2014,9(8)
Objectives
Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br−).Design and Methods
Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br−, BIA, and BIS.Results
Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.Conclusion
The BIA and BIS are as accurate as Br− to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults. 相似文献73.
Kimmo?K.?KahilainenEmail author Anna?Siwertsson Karl??.?Gjelland Rune?Knudsen Thomas?B?hn Per-Arne?Amundsen 《Evolutionary ecology》2011,25(3):573-588
Gill raker divergence is a general pattern in adaptive radiations of postglacial fish, but few studies have addressed the
adaptive significance of this morphological trait in foraging and eco-evolutionary interactions among predator and prey. Here,
a set of subarctic lakes along a diversifying gradient of coregonids was used as the natural setting to explore correlations
between gill raker numbers and planktivory as well as the impact of coregonid radiation on zooplankton communities. Results
from 19 populations covering most of the total gill raker number gradient of the genus Coregonus, confirm that the number of gill rakers has a central role in determining the foraging ability towards zooplankton prey.
Both at the individual and population levels, gill raker number was correlated with pelagic niche use and the size of utilized
zooplankton prey. Furthermore, the average body size and the abundance and diversity of the zooplankton community decreased
with the increasing diversity of coregonids. We argue that zooplankton feeding leads to an eco-evolutionary feedback loop
that may further shape the gill raker morphology since natural selection intensifies under resource competition for depleted
prey communities. Eco-evolutionary interactions may thus have a central role creating and maintaining the divergence of coregonid
morphs in postglacial lakes. 相似文献
74.
Rune Knudsen Anna Siwertsson Colin E. Adams Monica Garduño-Paz Jason Newton Per-Arne Amundsen 《Evolutionary ecology》2011,25(3):589-604
There is now strong evidence that foraging niche specialisation plays a critical role in the very early stages of resource
driven speciation. Here we test critical elements of models defining this process using a known polymorphic population of
Arctic charr from subarctic Norway. We test the long-term stability of niche specialisation amongst foraging predators and
discuss the possibility that contrasting foraging specialists are exposed to differing selection regimes. Inter-individual
foraging niche stability was measured by combining two time-integrated ecological tracers of the foraging niche (each individual’s
δ13C and δ15N stable isotope (SI) signatures and their food borne parasite fauna) with a short-term measure of foraging niche use (stomach
contents composition). Three dietary subgroups of predators were identified, including zooplankton, gammarid and benthivore
specialists foragers. Zooplanktivorous specialists had muscle low in δ 13C, a high abundance of parasites transmitted from pelagic copepods, a smaller head, longer snout and a more slender body-form
than gammaridivorous specialist individuals which had muscle more enriched in δ 13C and high abundance of parasites transmitted from benthic Gammarus. Benthivorous individuals were intermediate between the other two foraging groups according to muscle SI-signals (δ13C) and loadings of parasites transmitted from both copepods and Gammarus. The close relationship between subgroups identified by stomach contents, time-integrated tracers of niche use (SI and parasites)
and functional trophic morphology (niche adaptations) demonstrate a long-term temporally stable niche use of each individual
predator. Differential habitat use and contrasting parasite communities and loadings, show differential exposure to different
suites of selection pressures for different foraging specialists. Results also show that individual specialisation in trophic
behaviour and thus exposure to different suites of selection pressures are stable over time, and thus provide a platform for
disruptive selection to operate within this sympatric system. 相似文献
75.
Stephanie A. Blain Dolph Schluter Colin E. Adams Per-Arne Amundsen Rune Knudsen Louise Chavarie 《Global Ecology and Biogeography》2023,32(12):2257-2270
Aim
High repeatability among assemblages of closely related but ecologically distinct ecotypes implies predictability in evolution and assembly of communities. The conditions under which ecotype assemblages form predictably, and the reasons, have been little investigated. Here, we test whether repeatability declines as the number of ecotypes builds.Location
Postglacial lakes with a circumboreal distribution.Time Period
Data were extracted from studies published between 1982 and 2019.Major Taxa Studied
Ecotype assemblages from two Salmonid genera – Salvelinus and Coregonus. Fish in postglacial lakes commonly occur as pairs of ecotypes, typically with a pelagic and a littoral/benthic form, but in Salvelinus and Coregonus, assemblages commonly contain multiple sympatric ecotypes.Methods
We used a meta-analysis of Salvelinus and Coregonus to empirically assess how repeatability varies across assemblages of two to seven ecotypes. We examined repeatability of use of broad niche categories as well as underlying phenotypic traits.Results
Within Coregonus, repeatability across multi-ecotype assemblages did not break down with the addition of a third or fourth ecotype. However, in Salvelinus, repeatability was largely absent and independent of the number of ecotypes. Repeatability of trait frequency distributions was absent in both genera, yet associations between trait means and niche categories were evident, especially in Coregonus.Main Conclusions
These results show that repeatability can vary greatly between lineages; that repeatability need not break down as the number of ecotypes builds; and that high repeatability of broad niche categories may result despite marked differences in the underlying frequency distribution of trait means. These findings not only affirm the presence of repeatable ecotype assembly and early stages of divergence in postglacial fishes at a global scale, but also highlight variability among taxa and underlying phenotypic traits. 相似文献76.
We scrutinised the seasonal food-niche utilisation of river dwelling Atlantic salmon parr and alpine bullhead in order to
examine potential mechanisms that may facilitate coexistence of species with similar niches. Fish were sampled monthly during
the ice-free season, and diet composition and feeding strategy of the two species were compared by analyses of stomach contents.
The dietary niches and feeding strategy of salmon parr and bullheads were highly similar both at the individual and population
levels, with high within-phenotype contributions to niche width and pronounced generalisation observed during time periods
with severe resource limitations. Our findings suggest that competitive coexistence with similar niches may be facilitated
by a generalisation of niche width as predicted by optimal foraging theory, rather than the specialised niche width predicted
by classic niche theory as a response to interspecific competition. Competitive coexistence may be particularly widespread
in spatially and temporally dynamic habitats such as northern lotic systems, which thus may select for generalisation and
convergence of ecological niches. 相似文献
77.
The aim of this study was to investigate the effects of
elevated glucose concentrations on complement receptor–
and Fcγ receptor–mediated phagocytosis in normal human
neutrophils. D-Glucose at 15 or 25 mM dose-dependently
inhibited both complement receptor– and Fcγ receptor–
mediated phagocytosis, as compared to that at a normal
physiological glucose concentration. The protein kinase
C (PKC) inhibitors GF109203X and Go6976 both dose dependently
and completely reversed the inhibitory effect of
25 mM D-glucose on phagocytosis. Complement receptor–
mediated phagocytosis was dose-dependently inhibited by
the cell permeable diacylglycerol analogue 1,2-dioctanoylsn-
glycerol (DAG), an effect that was abolished by PKC
inhibitors. Furthermore, suboptimal inhibitory concentrations
of DAG and glucose showed an additive inhibitory effect
on complement receptor–mediated phagocytosis. The
authors conclude that elevated glucose concentrations can
inhibit complement receptor and Fcγ receptor–mediated
phagocytosis in normal human neutrophils by activating
PKCα and/or PKCβ, an effect possibly mediated by DAG. 相似文献