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Some of the mitochondria in the free-living giant ameba Pelomyxa carolinensis (Chaos chaos) exhibit unusual and strikingly complex morphological patterns. A study of serial sections of these mitochondria reveals that the patterns are formed by the organization and packing of minute villi (cristae mitochondriales). The form of the individual villus is a regular soft zigzag (or wave) with a bulbous enlargement at each point of inflection ("elbow") on the wave. The pattern of the mitochondria may become increasingly complex as a result of branching and fusing of the wavy villi. Densely packed fibrillar material is sometimes present in the stroma of the mitochondria. 相似文献
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STEVEN A. POTHOVEN HENRY A. VANDERPLOEG JOANN F. CAVALETTO DAMON M. KRUEGER DORAN M. MASON STEPHEN B. BRANDT 《Freshwater Biology》2007,52(3):561-573
1. We sampled along a nearshore transect (10-m bathymetric contour) in Lake Michigan to determine diet, 24-h feeding periodicity, daily ration and food requirements of an invasive fish, the alewife, Alosa pseudoharengus , relative to zooplankton abundance and production. Our objective was to determine whether the alewife controls the abundance of two invasive, predatory cladocerans, Bythotrephes longimanus and Cercopagis pengoi .
2. Bosminidae was the most abundant prey taxon and Chydoridae, Leptodora , Chironomidae and Bythotrephes were the least abundant. Neither Bythotrephes nor Cercopagis were important prey for small alewives (≤100 mm). Bythotrephes was eaten by over 50% of large alewives (>100 mm) and accounted for 10–27% of the diet weight. Cercopagis was eaten by about 30% of the large alewives but only accounted 1% of the diet weight.
3. Food weight in stomachs was highest early in the night for small alewives and lowest at night for large alewives. Chironomidae and large Chydoridae were the preferred prey of small alewives. Bythotrephes and large Chydoridae were the preferred prey for large alewives.
4. Food requirements of alewife were much less than production for most prey taxa, although the consumption of Bythotrephes greatly exceeded production on both dates. Alewives consumed only 3% of Cercopagis production. High selectivity and food requirements of alewife for Bythotrephes , and low selectivity and food requirements for Cercopagis , probably explain the difference in abundance between these two invasive cladocerans at our nearshore site in Lake Michigan. 相似文献
2. Bosminidae was the most abundant prey taxon and Chydoridae, Leptodora , Chironomidae and Bythotrephes were the least abundant. Neither Bythotrephes nor Cercopagis were important prey for small alewives (≤100 mm). Bythotrephes was eaten by over 50% of large alewives (>100 mm) and accounted for 10–27% of the diet weight. Cercopagis was eaten by about 30% of the large alewives but only accounted 1% of the diet weight.
3. Food weight in stomachs was highest early in the night for small alewives and lowest at night for large alewives. Chironomidae and large Chydoridae were the preferred prey of small alewives. Bythotrephes and large Chydoridae were the preferred prey for large alewives.
4. Food requirements of alewife were much less than production for most prey taxa, although the consumption of Bythotrephes greatly exceeded production on both dates. Alewives consumed only 3% of Cercopagis production. High selectivity and food requirements of alewife for Bythotrephes , and low selectivity and food requirements for Cercopagis , probably explain the difference in abundance between these two invasive cladocerans at our nearshore site in Lake Michigan. 相似文献
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CAROLE TOÏGO SABRINA SERVANTY JEAN-MICHEL GAILLARD SERGE BRANDT ERIC BAUBET 《The Journal of wildlife management》2008,72(7):1532-1539
Abstract We assessed age-specific natural mortality (i.e., excluding hunting mortality) and hunting mortality of 1,175 male and 1,076 female wild boar (Sus scrofa) from Chǎteauvillain-Arc en Barrois (eastern France), using a 22-year dataset (1982–2004) and mark-recapture-recovery methods. Overall yearly mortality was >50% for all sex and age-classes. Low survival was mostly due to high hunting mortality; a wild boar had a >40% of chance of being harvested annually, and this risk was as high as 70% for adult males. Natural mortality rates of wild boar were similar for males and females (approx. 0.15). These rates were comparable to rates typical of male ungulates but high for female ungulates. Wild boar survival did not vary across sex and age-classes. Despite high hunting mortality, we did not detect evidence of compensatory mortality. Whereas natural mortality for males was constant over time, female mortality varied annually, independent of fluctuations in mast availability. Female wild boar survival patterns differed from those reported in other ungulates, with high and variable natural mortality. In other ungulates, natural mortality is typically low and stable across a wide range of environmental conditions. These differences may partly reflect high litter sizes for wild boar, which carries high energetic costs. High hunting mortality may induce a high investment of females in reproduction early in life, at the detriment to survival. Despite high hunting mortality, the study population increased. Effective population control of wild boar should target a high harvest rate of piglets and reproductive females. 相似文献
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JOSEPH M. MACEDONIA YONI BRANDT DAVID L. CLARK 《Biological journal of the Linnean Society. Linnean Society of London》2002,77(1):67-85
The common collared lizard (Crotaphytus collaris) exhibits considerable geographical colour variation, particularly among males. Populations of this diurnal saxicolous iguanian inhabit patches of rocky habitat throughout the species’ broad distribution in North America and are anticipated to experience local differences in selective pressures that influence colouration. Specifically, while social interactions might favour conspicuous colouration, crypsis may be advantageous in interactions with visually orienting predator and prey species. To address the local relationship between lizard and substrate colouration we compared the reflectance spectra of two geographically distant and phenotypically divergent populations of collared lizards with the rocky substrates they inhabit. Our northern study population (C. c. auriceps in eastern Utah) occurs on red rocks, where males exhibit boldly coloured turquoise bodies and bright yellow heads. In contrast, our southern study population (C. c. fuscus in southern New Mexico) lives on grey and tan rocks, and males in this location exhibit subdued brown and tan dorsal colours. Spectral comparisons revealed that males in the northern population contrasted strongly with their local rocks, whereas males in the southern population matched their rock colours with reasonably good fidelity. This relationship held under a variety of lighting conditions. Females in both populations were less conspicuously coloured than males, although northern females contrasted more with their rocks than did southern females. In addition, sexual dichromatism was pronounced in the northern population but minimal in the southern population. Finally, sexual size and weight dimorphism was strong in the southern population while being virtually absent in the northern population. A comparison of the local predator and prey assemblages suggests that the conspicuous and sexually dichromatic colouration of the northern population may have evolved in response to reduced pressure from visually orienting predators as well as reduced dependence on saurian prey. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77 , 67–85 相似文献
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