全文获取类型
收费全文 | 93篇 |
免费 | 7篇 |
专业分类
100篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 0 毫秒
11.
12.
Scandura Massimo Iacolina Laura Capitani Claudia Gazzola Andrea Mattioli Luca Apollonio Marco 《European Journal of Wildlife Research》2011,57(4):949-958
We investigated local gene flow in a high-density wolf (Canis lupus) population of the Italian Apennines, where no effective barrier to wolf dispersal was present. From 1998 to 2004 we examined
wolf carcasses and non-invasively collected samples, focusing on three mountain districts, separated by two valleys, where
wolf packs showed high spatial stability. Using nine autosomal microsatellites we successfully genotyped 177 samples, achieving
the identification of 74 wolves. Genetic relatedness steeply decreased with increasing distance between sampling areas, thus
suggesting that short-distance interpack migration is infrequent in this population. In addition, no individual from a central
pack under intensive monitoring was sampled in the range of the surrounding packs over a 4-year period. The limited short-distance
gene flow resulted in a cryptic genetic structure, which was revealed by Bayesian analysis. A different genetic cluster was
found in each of the three mountain areas, and a small proportion of first-generation immigrants was detected. Overall, the
present study suggests that local genetic differentiation in Italian wolves might arise from high spatial stability of packs
and can be favoured by a combination of long-range dispersal, the attitude to mate between unrelated individuals and a high
young mortality rate. 相似文献
13.
We studied different genetic models and evaluation systems to select against a genetic disease with additive, recessive or polygenic inheritance in genetic conservation schemes. When using optimum contribution selection with a restriction on the rate of inbreeding (ΔF) to select against a disease allele, selection directly on DNA-genotypes is, as expected, the most efficient strategy. Selection for BLUP or segregation analysis breeding value estimates both need 1–2 generations more to halve the frequency of the disease allele, while these methods do not require knowledge of the disease mutation at the DNA level. BLUP and segregation analysis methods were equally efficient when selecting against a disease with single gene or complex polygene inheritance, i.e. knowledge about the mode of inheritance of the disease was not needed for efficient selection against the disease. Smaller schemes or schemes with a more stringent restriction on ΔF needed more generations to halve the frequency of the disease alleles or the fraction of diseased animals. Optimum contribution selection maintained ΔF at its predefined level, even when selection of females was at random. It is argued that in the investigated small conservation schemes with selection against a genetic defect, control of ΔF is very important. 相似文献
14.
Marine primary productivity studies pursued in the Canadian Arctic in 1961–1963, using standard techniques (oxygen and carbon-14)
of the time, showed that maximum production developed rapidly in July at 5-m depth under very low light intensities and under
intact but melting sea ice. The time of maximum production was correlated with depths of snow in spring. Low production levels
were found in August in those years and estimated in 1956. Nitrate exhaustion occurred before maximum production and was followed
by rapid sinking of chlorophyll and productivity and reduction of assimilation numbers. Gross production values greatly exceeded
net production values in 1961–1963, and gross production in 2 years was about double that of a third year, which may be due
to different initial conditions of nutrient concentrations in the euphotic zone. Interannual variability in primary production
may be the result of changes in water masses in the surface layer, as driven by atmospheric pressure patterns. 相似文献
15.
Stefano Grignolio Francesca Brivio Nicoletta Sica Marco Apollonio 《Ethology : formerly Zeitschrift fur Tierpsychologie》2019,125(9):603-612
Predators may influence their prey populations not only through direct lethal effects, but also by causing behavioural changes. The natural expansion of the wolf (Canis lupus) into the Alps provided the rare opportunity to monitor the responses of a prey species to the return of a large predator. Density effects have rarely been considered in the study of antipredator strategies. We examined the effects of wolf recolonisation and density modifications on group size and use of safe areas by Alpine ibex (Capra ibex) in Gran Paradiso National Park (Italy), where no large terrestrial predator has been present for about a century. We documented that, in a few years, the variation in the factors affecting the landscape of fear caused significant modifications in ibex behavioural patterns that could not be accounted for by density changes only. Male groups decreased in size and moved closer to safer areas. The distance of female groups from refuge sites, instead, was not affected, and their propensity to live in groups was scarcely modified. Behavioural modifications likely caused a reduction in nutrient intake in adult male ibex, as they necessarily used lower‐quality feeding patches. Our results showed that male and female ibex, which are characterised by a strong dimorphism, adopted different strategies to solve the conflicting demands of foraging efficiently and avoiding predators. 相似文献
16.
17.
Roberta Lecis Olivia Dondina Valerio Orioli Daniela Biosa Antonio Canu Giulia Fabbri Laura Iacolina Antonio Cossu Luciano Bani Marco Apollonio Massimo Scandura 《Ecology and evolution》2022,12(4)
Patterns of genetic differentiation within and among animal populations might vary due to the simple effect of distance or landscape features hindering gene flow. An assessment of how landscape connectivity affects gene flow can help guide management, especially in fragmented landscapes. Our objective was to analyze population genetic structure and landscape genetics of the native wild boar (Sus scrofa meridionalis) population inhabiting the island of Sardinia (Italy), and test for the existence of Isolation‐by‐Distance (IBD), Isolation‐by‐Barrier (IBB), and Isolation‐by‐Resistance (IBR). A total of 393 Sardinian wild boar samples were analyzed using a set of 16 microsatellite loci. Signals of genetic introgression from introduced non‐native wild boars or from domestic pigs were revealed by a Bayesian cluster analysis including 250 reference individuals belonging to European wild populations and domestic breeds. After removal of introgressed individuals, genetic structure in the population was investigated by different statistical approaches, supporting a partition into five discrete subpopulations, corresponding to five geographic areas on the island: north‐west (NW), central west (CW), south‐west (SW), north‐central east (NCE), and south‐east (SE). To test the IBD, IBB, and IBR hypotheses, we optimized resistance surfaces using genetic algorithms and linear mixed‐effects models with a maximum likelihood population effects parameterization. Landscape genetics analyses revealed that genetic discontinuities between subpopulations can be explained by landscape elements, suggesting that main roads, urban settings, and intensively cultivated areas are hampering gene flow (and thus individual movements) within the Sardinian wild boar population. Our results reveal how human‐transformed landscapes can affect genetic connectivity even in a large‐sized and highly mobile mammal such as the wild boar, and provide crucial information to manage the spread of pathogens, including the African Swine Fever virus, endemic in Sardinia. 相似文献
18.
F. Suchentrunk H. Ben Slimen C. Stamatis H. Sert M. Scandura M. Apollonio Z. Mamuris 《Human Evolution》2006,21(2):151-165
Although only of medium size, and thus of little nutritional value compared to big game such as mammoths and ungulates, hares (Lepus spp.) probably have always been a food source for humans, as documented in archaeological finds. Nowadays, hares, particularly such species as the brown hare (L. europaeus), are among the most important game species in many European countries. For hunting, perhaps religious reasons, and in connection with certain myths, hares have been and are still being intentionally translocated. Ancient translocations by humans can be inferred from the presence of hares on islands that had no mainland connections, at least during the Pleistocene, the major evolutionary period of the genus Lepus. We review some of the literature on anthropogenic translocations of hares. We focus on three examples [the brown hare (L. europaeus), the Corsican hare (L. corsicanus), and the Sardinian hare (L. capensis)], where some molecular data could be used to trace the translocation routes and possible origins of introduced hare populations. Certain molecular marker systems, such as sequences of the hypervariable part I (HV-1) of the mitochondrial control region, show high variability in hare species and are thus promising for tracing both recent and ancient origins of translocated hares. Some other molecular marker systems as well as caveats connected with the use of such marker systems in the genus Lepus are also discussed. 相似文献
19.
Modeling electromagnetic fields detectability in a HH-like neuronal system: stochastic resonance and window behavior 总被引:1,自引:0,他引:1
Noise has already been shown to play a constructive role in neuronal processing and reliability, according to stochastic resonance
(SR). Here another issue is addressed, concerning noise role in the detectability of an exogenous signal, here representing
an electromagnetic (EM) field. A Hodgkin–Huxley like neuronal model describing a myelinated nerve fiber is proposed and validated,
excited with a suprathreshold stimulation. EM field is introduced as an additive voltage input and its detectability in neuronal
response is evaluated in terms of the output signal-to-noise ratio. Noise intensities maximizing spiking activity coherence
with the exogenous EM signal are clearly shown, indicating a stochastic resonant behavior, strictly connected to the model
frequency sensitivity. In this study SR exhibits a window of occurrence in the values of field frequency and intensity, which
is a kind of effect long reported in bioelectromagnetic experimental studies. The spatial distribution of the modeled structure
also allows to investigate possible effects on action potentials saltatory propagation, which results to be reliable and robust
over the presence of an exogenous EM field and biological noise. The proposed approach can be seen as assessing biophysical
bases of medical applications funded on electric and magnetic stimulation where the role of noise as a cooperative factor
has recently gained growing attention.
This work investigates the role of noise as a cooperative factor for the detection of an exogenous electromagnetic field in
a compartimental model of a myelinated nerve fiber. The occurrence of stochastic resonance is discussed in relation to neuronal
frequency sensitivity. 相似文献
20.
Job B Bernheim A Beau-Faller M Camilleri-Broët S Girard P Hofman P Mazières J Toujani S Lacroix L Laffaire J Dessen P Fouret P;LG Investigators 《PloS one》2010,5(12):e15145