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1.
1. Semi-arid rangeland productivity is limited by precipitation, and yet droughts are projected to increase in frequency and duration with unknown impacts on insect populations. As some katydids prolong diapause and remain in an egg bank as a blastoderm for multiple growing seasons, is it possible that drought could prolong diapause and promote outbreaks by synchronising embryonic development and hatching of Mormon crickets, Anabrus simplex, after moisture is restored? 2. In this study, a high-elevation Wyoming population (WY) was compared with a mid-elevation Idaho (ID) and a low-elevation Oregon population (OR). It was predicted that eggs from the drier ID and OR habitats would be more tolerant of desiccation. Developmental state and water loss of eggs were measured after drought treatments, and when moisture was restored. 3. The two drier treatments had significantly more WY eggs prolonging diapause until after drought ended compared with the two wetter treatments. Whether WY eggs developed in the second or subsequent warm periods was independent of drought treatments. Significantly fewer OR embryos developed in the driest treatment compared with the others, whereas almost all ID eggs developed irrespective of the drought treatment. 4. In conclusion, Mormon crickets can delay embryonic development to improve drought tolerance. Although drought did not synchronise development and hatching, diapause plasticity allowed insects to cope and await more favourable conditions. 5. Unexpectedly, eggs from WY (the highest, wettest site) were more tolerant, because postponing development resulted in less water loss than in developed embryos. OR egg loss was also reduced by prolonging diapause, relative to ID, which developed in even the driest conditions.  相似文献   
2.
The latest emergence of influenza A (H1N1) virus outbreak demonstrated how swiftly a new strain of flu can evolve and spread around the globe. The A/H1N1 flu has been spreading at unprecedented speed, and further spread within the countries being affected and to other adjacent or far way countries is considered inevitable due to the rapid emigration of infected individuals across the world. In this bioinformation, we discuss the mechanism of evolution of a new HxNy strain and the essential criteria for potentially breaking the outbreak of these extremely harmful and rapidly evolving viral strains in the near future by taking the recent H1N1 pandemic as a classical paradigm.  相似文献   
3.
Models for integrated pest control and their biological implications   总被引:2,自引:0,他引:2  
Successful integrated pest management (IPM) control programmes depend on many factors which include host-parasitoid ratios, starting densities, timings of parasitoid releases, dosages and timings of insecticide applications and levels of host-feeding and parasitism. Mathematical models can help us to clarify and predict the effects of such factors on the stability of host-parasitoid systems, which we illustrate here by extending the classical continuous and discrete host-parasitoid models to include an IPM control programme. The results indicate that one of three control methods can maintain the host level below the economic threshold (ET) in relation to different ET levels, initial densities of host and parasitoid populations and host-parasitoid ratios. The effects of host intrinsic growth rate and parasitoid searching efficiency on host mean outbreak period can be calculated numerically from the models presented. The instantaneous pest killing rate of an insecticide application is also estimated from the models. The results imply that the modelling methods described can help in the design of appropriate control strategies and assist management decision-making. The results also indicate that a high initial density of parasitoids (such as in inundative releases) and high parasitoid inter-generational survival rates will lead to more frequent host outbreaks and, therefore, greater economic damage. The biological implications of this counter intuitive result are discussed.  相似文献   
4.
Three isolates of Histoplasma capsulatum were identified from mice lung, liver, and spleen inoculated with soil samples of the X hotel's ornamental potted plants that had been fertilized with organic material known as compost. The presence of H. capsulatum in the original compost was detected using the dot-enzyme-linked immunosorbent assay. Nested-PCR, using a specific protein Hcp100 coding gene sequence, confirmed the fungal identification associated with an unusual histoplasmosis outbreak in Acapulco. Although, diversity between the H. capsulatum isolate from the hotel and some clinical isolates from Guerrero (positive controls) was observed using random amplification of polymorphic DNA based-PCR, sequence analyses of H-anti and ole fragment genes revealed a high homology (92-99%) between them.  相似文献   
5.
The Red locust (Nomadacris septemfasciata Serville) is commonly found in southern Africa and the Indian Ocean islands. In Madagascar until 1998, only infested crop fields were controlled. However, since 1998 the Red locust has caused considerable crop damage in northern Madagascar, where gregarious individuals were identified for the first time in Madagascar in 2002. In this study, an accurate history of the outbreaks which occurred between 1998 and 2004 is drawn up on the basis of field surveys and anecdotal data. A total area of more than 60,000 ha was infested between 2001 and 2003, at the peak of the outbreak. With these results, we can make out a first biogeographical synthesis for this locust.  相似文献   
6.
为了探讨戊肝流行20年后再爆发的特点,对2001年喀什地区莎车县某乡戊型肝炎的流行和临床特点进行了调查,并对病后半年的部分病例用ELISA方法检测戊肝抗体水平。结果发生在1981~1983年大流行时散发病的疫区,间隔20年后再次局部爆发戊肝,乡总患病率0.64%(167/25979),分布在相邻六个自然村,每村平均患病人数为28人。饮用水为手压井(地下水),全年以8~12月为一高峰,均为维族农民,男98人,女69人,最大年龄54岁,最小年龄12岁,中位年龄28.9岁。临床表现符合急性黄疸型肝炎,病情轻,无重症和死亡病例。抽查病例中病后半年抗-HEVIgG阳性率68%,IgM阳性率16%,双阳性12%。首发病例传染源尚不清楚,可排除水源和食物污染,流行和临床特征符合戊肝,应探讨HEV的变异和人群抗体及保护力的持续时间。  相似文献   
7.
Ebolavirus can cause a highly fatal and panic-generating human disease which may jump from bats to other mammals and human. High viral loads in body fluids allow efficient transmission by contact. Lack of effective antivirals, vaccines and public health infrastructures in parts of Africa make it difficult to health workers to contain the outbreak.  相似文献   
8.
In infectious disease epidemiology, statistical methods are an indispensable component for the automated detection of outbreaks in routinely collected surveillance data. So far, methodology in this area has been largely of frequentist nature and has increasingly been taking inspiration from statistical process control. The present work is concerned with strengthening Bayesian thinking in this field. We extend the widely used approach of Farrington et al. and Heisterkamp et al. to a modern Bayesian framework within a time series decomposition context. This approach facilitates a direct calculation of the decision‐making threshold while taking all sources of uncertainty in both prediction and estimation into account. More importantly, with the methodology it is now also possible to integrate covariate processes, e.g. weather influence, into the outbreak detection. Model inference is performed using fast and efficient integrated nested Laplace approximations, enabling the use of this method in routine surveillance at public health institutions. Performance of the algorithm was investigated by comparing simulations with existing methods as well as by analysing the time series of notified campylobacteriosis cases in Germany for the years 2002–2011, which include absolute humidity as a covariate process. Altogether, a flexible and modern surveillance algorithm is presented with an implementation available through the R package ‘surveillance’.  相似文献   
9.
We describe an outbreak of rabies in a pack of African wild dogs (Lycaon pictus) in the Limpopo-Lipadi Private Game and Wilderness Reserve in the Tuli region of south-eastern Botswana. We define the pack’s behavioural response to the disease, clinical signs, and management interventions undertaken and make recommendations to mitigate against future disease outbreaks of this nature. The outbreak, which occurred in late 2014 and early 2015, resulted in the death or disappearance of 29 individuals out of a pack of 35 wild dogs. The disruption to the social structure within the pack, the behaviour of the animals and clinical signs were similar to that documented during previous rabies outbreaks amongst African wild dogs in Southern and East Africa in recent years. Management interventions taken during the outbreak were aimed at preventing extirpation of the pack and reducing the risk of further disease spread to other mammals in the reserve.  相似文献   
10.
The drive to understand the invasion, spread and fade out of infectious disease in structured populations has produced a variety of mathematical models for pathogen dynamics in metapopulations. Very rarely are these models fully coupled, by which we mean that the spread of an infection within a subpopulation affects the transmission between subpopulations and vice versa. It is also rare that these models are accessible to biologists, in the sense that all parameters have a clear biological meaning and the biological assumptions are explained. Here we present an accessible model that is fully coupled without being an individual-based model. We use the model to show that the duration of an epidemic has a highly non-linear relationship with the movement rate between subpopulations, with a peak in epidemic duration appearing at small movement rates and a global maximum at large movement rates. Intuitively, the first peak is due to asynchrony in the dynamics of infection between subpopulations; we confirm this intuition and also show the peak coincides with successful invasion of the infection into most subpopulations. The global maximum at relatively large movement rates occurs because then the infectious agent perceives the metapopulation as if it is a single well-mixed population wherein the effective population size is greater than the critical community size.  相似文献   
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