全文获取类型
收费全文 | 68篇 |
免费 | 3篇 |
专业分类
71篇 |
出版年
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 2篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1955年 | 4篇 |
1954年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 0 毫秒
1.
2.
BRUNO STUDER FRANCO WIDMER JÜRG ENKERLI ROLAND K
LLIKER 《Molecular ecology resources》2006,6(4):1108-1110
Twelve microsatellite markers were isolated from Lolium multiflorum. Allelic variability and cross‐species amplification were assessed on 16 individuals of each of the three grassland species L. multiflorum, Lolium perenne and Festuca pratensis. Cross‐species amplification success was 100% for L. perenne and 83% for F. pratensis. The number of alleles detected ranged from one to 14 with an average of 3.4. While three microsatellite loci were polymorphic in all three species, one marker produced species‐specific alleles in all three species. These microsatellite markers provide a valuable tool for population genetic studies within and among species of the Festuca–Lolium complex. 相似文献
3.
MASSIMILIANO BABBUCCI LORENZO ZANE FRANCO ANDALORO TOMASO PATARNELLO 《Molecular ecology resources》2006,6(4):1126-1128
The Mediterranean yellowtail Seriola dumerilii (Risso, 1810) is a semi‐pelagic fish economically important to fisheries and aquaculture. We developed nine microsatellite primer pairs for this species. Microsatellites were isolated from a partial genomic library enriched for an AC motif. The developed loci proved to be polymorphic showing three to 11 alleles per locus. They can be employed for population studies as well as for parentage assessment. Cross‐species amplification was successfully tested in Seriola fasciata and Seriola rivoliana. 相似文献
4.
Impacts of climate warming and habitat loss on extinctions at species' low-latitude range boundaries 总被引:3,自引:0,他引:3
ALDINA M. A. FRANCO JANE K. HILL CLAUDIA KITSCHKE YVONNE C. COLLINGHAM† DAVID B. ROY‡ RICHARD FOX§ BRIAN HUNTLEY† CHRIS D. THOMAS 《Global Change Biology》2006,12(8):1545-1553
Polewards expansions of species' distributions have been attributed to climate warming, but evidence for climate‐driven local extinctions at warm (low latitude/elevation) boundaries is equivocal. We surveyed the four species of butterflies that reach their southern limits in Britain. We visited 421 sites where the species had been recorded previously to determine whether recent extinctions were primarily due to climate or habitat changes. Coenonympha tullia had become extinct at 52% of study sites and all losses were associated with habitat degradation. Aricia artaxerxes was extinct from 50% of sites, with approximately one‐third to half of extinctions associated with climate‐related factors and the remainder with habitat loss. For Erebia aethiops (extinct from 24% of sites), approximately a quarter of the extinctions were associated with habitat and three‐quarters with climate. For Erebia epiphron, extinctions (37% of sites) were attributed mainly to climate with almost no habitat effects. For the three species affected by climate, range boundaries retracted 70–100 km northwards (A. artaxerxes, E. aethiops) and 130–150 m uphill (E. epiphron) in the sample of sites analysed. These shifts are consistent with estimated latitudinal and elevational temperature shifts of 88 km northwards and 98 m uphill over the 19‐year study period. These results suggest that the southern/warm range margins of some species are as sensitive to climate change as are northern/cool margins. Our data indicate that climate warming has been of comparable importance to habitat loss in driving local extinctions of northern species over the past few decades; future climate warming is likely to jeopardize the long‐term survival of many northern and mountain species. 相似文献
5.
Spatial and temporal variation in prey abundance have been shown to impact the time of breeding and breeding success of birds. Understanding the ecological requirements of preferred prey can help develop management measures to improve food supply for target species. For the colonial Lesser Kestrel Falco naumanni, mole crickets Gryllotalpa spp. are one of the most important prey items during the mate‐feeding period. Lesser Kestrel colonies with higher mole cricket consumption had earlier egg‐laying dates, suggesting that differences between individuals in the time of breeding could be caused by differences in the diet. Moreover, the mean number of mole crickets in pellets was significantly correlated with clutch size (in one of the studied years) and egg volume. Thus, the impact of environmental variables and land use on mole crickets is likely to be relevant to Lesser Kestrel conservation. Weekly consumption of mole crickets was higher following an increase in either precipitation or minimum temperature values. Furthermore, mole cricket consumption was higher in colonies surrounded by higher quality soils and in wetter areas and years. Predicted probability of mole cricket occurrence in surveyed watercourse margins suggested a positive relationship between soil penetrability and mole cricket occurrence. Among variables that might be the target of management, the presence of riparian vegetation positively influenced the occurrence of mole crickets, whilst tillage and sowing of streambeds were revealed as the most important threats. We suggest that the maintenance of native vegetation in the margins of watercourses could improve soil resilience to erosion, increase water retention, soil penetrability and fertility, and provide a food supply and shelter for mole crickets. Overall, the implementation of such recommendations is likely to benefit other farmland species known to consume mole crickets, including several endangered species. 相似文献
6.
FRANCO E. CHIARINI GLORIA E. BARBOZA 《Botanical journal of the Linnean Society. Linnean Society of London》2008,156(3):467-478
Sixteen species of Jaborosa (Solanaceae), including eight endemic to Argentina, were studied karyologically. The numbers n = 12 and/or 2n = 24 were found in all species, the majority of the cases being new reports. Mitotic chromosomes were small- to medium-sized, the average length varying from 2.95 to 4.93 µm. All species had one to three chromosome pairs with satellites. The karyotypes, obtained for 13 species, were slightly asymmetrical: A 1 ranged from 0.228 to 0.483, A 2 ranged from 0.095 to 0.182, and Paszko's asymmetry index ranged from 0.84 to 3.47. In all species, metacentric chromosomes were the most common, followed by submetacentrics, but subtelocentrics were rare. Morphological similarities and sectional arrangements were not reflected in either a principal components analysis plot or asymmetry index plot, but the species could be singled out by their karyotype formulae and the different karyotype parameters taken. In Jaborosa , a notably diversified genus, exo-morphological evolution has taken place, together with evident chromosome rearrangements, whose disposition is different and not as clear as in related genera. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 467–478. 相似文献
7.
JÜRG ENKERLI ROLAND K
LLIKER SIEGFRIED KELLER FRANCO WIDMER 《Molecular ecology resources》2005,5(2):384-386
Fourteen polymorphic microsatellite markers were isolated from the entomopathogenic fungus, Metarhizium anisopliae, based on enriched genomic libraries. In order to assess allelic variability, the microsatellite loci were analysed in a collection of 34 isolates sampled from across Switzerland. The number of detected alleles in 14 loci ranged from two to eight and expected heterozygosity from 0.265 to 0.808. Because of the high expected heterozygosity, the 14 microsatellite loci are very useful for ecological studies and analysis of population diversity, and to identifying, monitoring, and tracking M. anisopliae strains applied as biological control agents. 相似文献
8.
LUCAS C. R. SILVA † LEONEL STERNBERG‡ MUNDAYATAN HARIDASAN§ WILLIAM A. HOFFMANN¶ FERNANDO MIRALLES-WILHELM AUGUSTO C. FRANCO 《Global Change Biology》2008,14(9):2108-2118
Upland tropical forests have expanded and contracted in response to past climates, but it is not clear whether similar dynamics were exhibited by gallery (riparian) forests within savanna biomes. Because such forests generally have access to ample water, their extent may be buffered against changing climates. We tested the long‐term stability of gallery forest boundaries by characterizing the border between gallery forests and savannas and tracing the presence of gallery forest through isotopic analysis of organic carbon in the soil profile. We measured leaf area index, grass vs. shrub or tree coverage, the organic carbon, phosphorus, nitrogen and calcium concentrations in soils and the carbon isotope ratios of soil organic matter in two transitions spanning gallery forests and savanna in a Cerrado ecosystem. Gallery forests without grasses typically show a greater leaf area index in contrast to savannas, which show dense grass coverage. Soils of gallery forests have significantly greater concentrations of organic carbon, phosphorus, nitrogen and calcium than those of savannas. Soil organic carbon of savannas is significantly more enriched in 13C compared with that of gallery forests. This difference in enrichment is in part caused by the presence of C4 grasses in savanna ecosystem and its absence in gallery forests. Using the 13C abundance as a signature for savanna and gallery forest ecosystems in 1 m soil cores, we show that the borders of gallery forests have expanded into the savanna and that this process initiated at least 3000–4000 bp based on 14C analysis. Gallery forests, however, may be still expanding as we found more recent transitions according to 14C activity measurements. We discuss the possible mechanisms of gallery forest expansion and the means by which nutrients required for the expansion of gallery forest might accumulate. 相似文献
9.
FEDERICO BRILLI PAOLO CICCIOLI MASSIMILIANO FRATTONI MARCO PRESTININZI ANTONIO FRANCO SPANEDDA & FRANCESCO LORETO 《Plant, cell & environment》2009,32(5):542-552
Chrysomela populi beetles feed on poplar leaves and extensively damage plantations. We investigated whether olfactory cues orientate landing and feeding. Young, unexpanded leaves of hybrid poplar emit constitutively a blend of monoterpenes, primarily ( E )- β -ocimene and linalool. This blend attracts inexperienced adults of C. populi that were not previously fed with poplar leaves. In mature leaves constitutively emitting isoprene, insect attack induces biosynthesis and emission of the same blend of monoterpenes, but in larger amount than in young leaves. The olfactometric test indicates that inexperienced beetles are more attracted by adult than by young attacked leaves, suggesting that attraction by induced monoterpenes is dose dependent. The blend does not attract adults that previously fed on poplar leaves. Insect-induced emission of monoterpenes peaks 4 d after the attack, and is also detected in non-attacked leaves. Induced monoterpene emission is associated in mature leaves with a larger decrease of isoprene emission. The reduction of isoprene emission is faster than photosynthesis reduction in attacked leaves, and also occurs in non-attacked leaves. Insect-induced monoterpenes are quickly and completely labelled by 13 C. It is speculated that photosynthetic carbon preferentially allocated to constitutive isoprene in healthy leaves is in part diverted to induced monoterpenes after the insect attack. 相似文献