全文获取类型
收费全文 | 187篇 |
免费 | 9篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 21篇 |
2011年 | 17篇 |
2010年 | 4篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 20篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1983年 | 1篇 |
1964年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 15 毫秒
101.
Multiple origins of dendroid shrubs in the eastern Mediterranean Euphorbia hierosolymitana group (Euphorbiaceae) with description of a new species,Euphorbia lemesiana,from Cyprus
下载免费PDF全文
![点击此处可从《Botanical journal of the Linnean Society. Linnean Society of London》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ralf Hand Georgios N. Hadjikyriakou Charalambos S. Christodoulou Boo Frajman 《Botanical journal of the Linnean Society. Linnean Society of London》2015,179(2):295-307
The leafy spurges, Euphorbia subgenus Esula, have one of their diversity centres in the Mediterranean, which is considered to be one of the 25 biodiversity hot‐spots. The eastern Mediterranean, in particular, is characterized by its high species richness and is therefore considered to be a cradle for lineage diversification. However, the area remains neglected in phylogenetic studies. Using nuclear ribosomal internal transcribed spacer (ITS) and plastid trnT‐trnF sequences, we explored the phylogenetic relationships in the predominantly eastern Mediterranean E. hierosolymitana group, which is characterized by a woody habit. The widespread shrublets E. acanthothamnos, E. glabriflora and E. spinosa, which are similar in habit, are not most closely related, the last two forming a sister clade to other taxa. From the E. acanthothamnos alliance, dendroid shrubs evolved at least two, but possibly four, times, giving rise to widespread E. bivonae and E. hierosolymitana, the Cretan endemic E. sultan‐hassei and the here newly described and genetically most divergent E . lemesiana , endemic to Cyprus. We provide a taxonomic treatment and morphological comparison with the similar, but not most closely related, E. hierosolymitana. Our study underlines the phytogeographical peculiarity of Cyprus and contributes to our current knowledge on the diversification patterns in the eastern Mediterranean. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 295–307. 相似文献
102.
Helen Ayles Albertus Schaap Amos Nota Charalambos Sismanidis Ruth Tembwe Petra De Haas Monde Muyoyeta Nulda Beyers Peter Godfrey-Faussett for the ZAMSTAR Study Team 《PloS one》2009,4(5)
Background
The Stop TB Partnership target for tuberculosis is to have reduced the prevalence of tuberculosis by 50% comparing 2015 to 1990. This target is challenging as few prevalence surveys have been conducted, especially in high burden tuberculosis and HIV countries. Current tuberculosis control strategies in high HIV prevalent settings are therefore based on limited epidemiological evidence and more evidence is needed from community-based surveys to inform improved policy formulation.Methods and Findings
8044 adults were sampled from 2 sub-districts (wards) in Lusaka province, Zambia. Questionnaires were used to screen for symptoms, respiratory samples were obtained for culture and oral secretions collected for HIV testing. 79 individuals were found to have Mycobacterium tuberculosis in their sputum, giving an adjusted overall prevalence of tuberculosis of 870/100,000 (95% CI 570–1160/100,000). The adjusted overall prevalence of HIV was 28.61% (95% CI 26.04–31.19). HIV- infection was significantly associated with prevalent tuberculosis (Adj OR 2.3, 95% CI 1.42–3.74) and the population attributable fraction of HIV for prevalent tuberculosis was 36%. Symptoms such as prolonged cough (adj OR 12.72, 95% CI 7.05–22.94) and fever (Adj OR 2.04, 95%CI 1.23–3.39), were associated with prevalent tuberculosis, but 8 (10%) individuals with prevalent tuberculosis denied having any symptoms at all and only 34 (43%) would have been classified as a TB suspect by current guidelines.Conclusions
Undiagnosed tuberculosis is a challenge for tuberculosis control and new approaches are needed if we are to reach international targets. Epidemiological studies can inform screening algorithms for both detection and prevention of active tuberculosis. 相似文献103.
Background
Normal aging significantly influences motor and cognitive performance. Little is known about age-related changes in action simulation. Here, we investigated the influence of aging on implicit motor imagery.Methodology/Principal Findings
Twenty young (mean age: 23.9±2.8 years) and nineteen elderly (mean age: 78.3±4.5 years) subjects, all right-handed, were required to determine the laterality of hands presented in various positions. To do so, they mentally rotated their hands to match them with the hand-stimuli. We showed that: (1) elderly subjects were affected in their ability to implicitly simulate movements of the upper limbs, especially those requiring the largest amplitude of displacement and/or with strong biomechanical constraints; (2) this decline was greater for movements of the non-dominant arm than of the dominant arm.Conclusions/Significance
These results extend recent findings showing age-related alterations of the explicit side of motor imagery. They suggest that a general decline in action simulation occurs with normal aging, in particular for the non-dominant side of the body. 相似文献104.
Background
Several molecular and cellular processes in the vertebrate brain exhibit differences between males and females, leading to sexual dimorphism in the formation of neural circuits and brain organization. While studies on large-scale brain networks provide ample evidence for both structural and functional sex differences, smaller-scale local networks have remained largely unexplored. In the current study, we investigate sexual dimorphism in cortical dynamics by means of spontaneous Up/Down states, a type of network activity that is exhibited during slow-wave sleep, quiet wakefulness, and anesthesia and is thought to represent the default activity of the cortex.Methods
Up state activity was monitored by local field potential recordings in coronal brain slices of male and female mice across three ages with distinct secretion profiles of sex hormones: (i) pre-puberty (17–21 days old), (ii) 3–9 adult (months old), and (iii) old (19–24 months old).Results
Female mice of all ages exhibited longer and more frequent Up states compared to aged-matched male mice. Power spectrum analysis revealed sex differences in the relative power of Up state events, with female mice showing reduced power in the delta range (1–4 Hz) and increased power in the theta range (4–8 Hz) compared to male mice. No sex differences were found in the characteristics of Up state peak voltage and latency.Conclusions
The present study revealed for the first time sex differences in intracortical network activity, using an ex vivo paradigm of spontaneously occurring Up/Down states. We report significant sex differences in Up state properties that are already present in pre-puberty animals and are maintained through adulthood and old age.105.
106.
Arvanitis Nikolaos Kotzamanidis Charalambos Z. Skaracis George N. Karagouni Amalia D. 《World journal of microbiology & biotechnology》2004,20(3):291-296
The antimicrobial activities of five commercial disinfectants containing quaternary ammonium compound-isopropanol (D1), sodium
methyl dithiocarbamate (D2), sodium thiocarbamate (D3), sodium dimethyl dithiocarbamate (D4) and formaldehyde (D5) were studied
against three main saccharolytic indigenous isolates (Bacillus cereus, Lactobacillus plantarum and Leuconostoc mesenteroides) from a beet sugar extraction line. Preliminary studies suggested that although all the disinfectants were effective against
those isolates, the high economic cost in combination with large amounts of the disinfectants D2, D3 and D4 weaken their possibility
for industrial use. Therefore, the minimum inhibitory concentration (MIC) of the other two examined disinfectants D1 and D5
was determined and survivor curves were obtained, for a period of 7 days. Bacterial counts against time (h) suggested that
D1 was more effective than D5 against the microbial population. In particular, D1 was bacteriolytic above 7 mg/l for B. cereus and bactericidal above 80 mg/l for Lc. mesenteroides and above 100 mg/l for L. plantarum. The disinfectant D5 was bacteriolytic above 25 mg/l for B. cereus and bactericidal above 500 mg/l for Lc. mesenteroides and L. plantarum. Taking into consideration both features, i.e. high concentration and very low cost, the use of D5 (formaldehyde) appeared
more suitable to the concerned beet sugar processor.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
107.
The dissection of the circadian clock into its molecular components represents the most striking and well-studied example of a gene regulatory network underlying a complex behavioural trait. By contrast, the evolutionary analysis of the clock has developed more slowly. Here we review studies that have surveyed intraspecific clock gene variation over large geographical areas and have discovered latitudinal clines in gene frequencies. Such spatial patterns traditionally suggest that natural selection shapes genetic variation, but it is equally possible that population history, or a mixture of demography and selection, could contribute to the clines. We discuss how population genetics, together with functional assays, can illuminate these possible cases of natural selection in Drosophila clock genes. 相似文献
108.
Sofia M Billinis C Psychas V Birtsas P Sofianidis G Leontides L Knowles N Spyrou V 《Journal of wildlife diseases》2008,44(4):864-870
In 2002, postweaning multisystemic wasting syndrome (PMWS) was diagnosed in a European female wild boar (Sus scrofa), based on the detection of porcine circovirus 2 (PCV2) DNA in various organs, including the uterus, and on histopathologic lesions. This is the first detection of PCV2 DNA in the uterus of a wild boar. Three years later (2005), a wild boar < 6-8 mo of age was found moribund. It presented wasting and dyspnea and finally died. PCV2 DNA was detected in tissue samples, and histopathologic lesions consistent with PMWS were observed. Both wild boars were from neighboring hunting areas in central Greece. Two PCV2 strains from the wild boars were genetically characterized and compared to other reported PCV2 sequences from wild boars and domestic pigs. The PCV-2 sequences from the wild boars in this study were closely related to each other and were grouped with two isolates from wild boars from Hungary. The phylogenetic analysis revealed that the virus might be transmitted between hunting areas. In addition, PCV2 may spread from domestic pigs to wild boars and vice versa. 相似文献
109.
Androniki Nirgianaki Gina K. Banks Donald R. Frohlich Zoe Veneti Henk R. Braig Thomas A. Miller Ian D. Bedford Peter G. Markham Charalambos Savakis Kostas Bourtzis 《Current microbiology》2003,47(2):0093-0101
We report the first systematic survey for the presence of Wolbachia endosymbionts in aphids and whiteflies, particularly different populations and biotypes of Bemisia tabaci. Additional agriculturally important species included were predator species, leafhoppers, and lepidopterans. We used a polymerase chain reaction (PCR)-based detection assay with ribosomal 16S rDNA and Wolbachia cell surface protein (wsp) gene primers. Wolbachia were detected in a number of whitefly populations and species, whitefly predators, and one leafhopper species; however, none of the aphid species tested were found infected. Single, double, and triple infections were detected in some of the B. tabaci populations. PCR and phylogenetic analysis of wsp gene sequences indicated that all Wolbachia strains found belong to group B. Topologies of the optimal tree derived by maximum likelihood (ML) and a ML tree in which Wolbachia sequences from B. tabaci are constrained to be monophyletic are significantly different. Our results indicate that there have been at least four independent Wolbachia infection events in B. tabaci. The importance of the presence of Wolbachia infections in B. tabaci is discussed. RID= ID= <E5>Correspondence to: </E5>K. Bourtzis; <E5>email:</E5> kbourtz@cc.uoi.gr Received: 9 September 2002 / Accepted: 25 September 2002 相似文献
110.
Circadian rhythm entrainment in flies and mammals 总被引:1,自引:0,他引:1
Circadian rhythms are a fundamental adaptation of living cells to the daily and seasonal fluctuation in light and temperature. Circadian oscillations persist in constant conditions; however, they are also phase-adjusted (entrained) by day-night cycles. It is this entrainability that provides for the proper phasing of the program, to the sequence of external changes that it has evolved to exploit. Synchronization of circadian oscillators with the outside world is achieved because light, temperature, or other external temporal cues, have acute effects on the levels of one or more of the clock's components. The consequences are ripples through the interconnected molecular loops, leading to a stable phase realignment of the endogenous rhythm generator and the external conditions. This review summarized the evolving knowledge of the different types, modes, and molecular processes of entrainment in flies and mammals. 相似文献