全文获取类型
收费全文 | 144篇 |
免费 | 3篇 |
出版年
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 1篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1971年 | 2篇 |
1960年 | 2篇 |
1959年 | 4篇 |
1958年 | 5篇 |
1957年 | 16篇 |
1956年 | 9篇 |
1955年 | 4篇 |
1954年 | 6篇 |
1953年 | 4篇 |
1952年 | 19篇 |
1951年 | 9篇 |
1950年 | 11篇 |
1949年 | 1篇 |
1948年 | 3篇 |
排序方式: 共有147条查询结果,搜索用时 78 毫秒
1.
FRAUKE M. MUENZEL MATTHIAS SANETRA WALTER SALZBURGER AXEL MEYER 《Molecular ecology resources》2007,7(6):1048-1050
Eleven microsatellites were isolated from the vairone Leuciscus souffia (Risso 1826), an endangered fish that inhabits river systems in and around the Alps in Europe. The level of genetic diversity was assessed in 29 individuals of the subspecies L. s. souffia, and their variability was further estimated in seven individuals of a different subspecies, L. s. muticellus. Eight of these microsatellite loci were also applied to seven closely related cyprinid species. Availability of the reported microsatellite loci will facilitate the investigation of population genetic structure of these species with applications for the development of conservation strategies and phylogeographical approaches. 相似文献
2.
EXCESS fat deposition after castration is thought to be a response to hyperinsulinism induced by an increased level of adrenal glucocorticoids1. Two mutant alleles, lethal yellow (Ay) and viable yellow (Avy), at the agouti locus in the mouse induce excess fat deposition; the Ay allele has also been found to induce insulin resistance2. Katsh3 concluded that in adrenalectomized KL strain mice a considerable portion of the high insulin tolerance depended on normal adrenal function. In the inbred YS/Wf and VY/Wf strains, both yellow pheno-types modulate serum insulin concentration4. Castration of inbred YS strain males causes a large decrease in serum insulin4, suggesting a possible relationship1 to the concentration of adrenal glucocorticoids. Growth of allogeneic tumour cells has different effects on the serum insulin concentrations of YS and VY strain mice4. 相似文献
3.
4.
Ecological and evolutionary consequences of the trophic polymorphism in Cichlasoma citrinellum (Pisces: Cichlidae) 总被引:1,自引:0,他引:1
The neotropical cichlid fish Cichlasoma citrinellum is polymorphic in the structure of its pharyngeal jaw apparatus and external morphology. The pharyngeal jaws are either gracile and bear slender, pointed teeth (papilliform) or robust with strong, rounded teeth (molariform). Molariform morphs have a ‘benthic’, and papilliform morphs a ‘limnetic’ body form. Furthermore, this species is also polychromatic, with yellow and black morphs. The molariform morphology of the pharyngeal jaw apparatus adapts the fish for cracking and feeding on snails. Based on analysis of stomach contents, 94% of the molariform morph ate snails whereas only 19%, of the papilliform morph did so. This result suggests that the morphs occupy different ecological niches. The morphology of the pharyngeal jaw apparatus does not correlate significantly with sex, but it does with body colouration (P<0.005). Cichlasoma citrinellum mate assortatively with their own colour; therefore a mating preference for colour may lead to genetic isolation of trophic morphs. The frequency of the molariform morph differs strikingly among populations of five Nicaraguan lakes and its abundance is correlated with the abundance of snails, the fishes' principal prey item. Among populations the frequency of molariform morphs decreases in the dry season. Morphology possibly changes reversibly within particular individuals between seasons. These results suggest that phenotypic plasticity and polymorphisms may be an adaptive characteristic of cichlid fishes. Patterns of intraspecific morphological variation match patterns of interspecific morphological diversification which suggests that universal developmental mechanisms canalize the possible expressions of morphology. The ability to respond morphologically to environmental shifts, in conjunction with genetically determined trophic polymorphisms and sexual selection via mate choice, could be the basis for speciation through intermediate stages of polymorphism of the impressive adaptive radiation of cichlid fishes. 相似文献
5.
6.
7.
8.
9.
10.