首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   118篇
  免费   5篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2016年   5篇
  2015年   7篇
  2014年   4篇
  2013年   3篇
  2012年   8篇
  2011年   7篇
  2010年   5篇
  2009年   7篇
  2008年   5篇
  2007年   2篇
  2006年   3篇
  2005年   1篇
  2004年   10篇
  2003年   5篇
  2002年   3篇
  2001年   6篇
  2000年   1篇
  1999年   5篇
  1998年   5篇
  1997年   2篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1990年   2篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1981年   1篇
  1977年   1篇
  1976年   1篇
  1970年   1篇
  1967年   1篇
排序方式: 共有123条查询结果,搜索用时 15 毫秒
11.
The relationship between dental morphology, sex, body length and age of small cetaceans can be used to determine ontogeny, sexual dimorphism and geographical variation. The objective of this study was to determine the relationship between dental morphology, sex, body size and age. A total of 91 specimens of P. blainvillei and 80 specimens of S. fluviatilis accidentally captured in fisheries or stranded in northern Rio de Janeiro (21 masculine37'-22 masculine25'S), from September 1988 to November 1996 were analysed. The teeth root diameter in P. blainvillei was significantly different between the sex; the values for females were larger than males. In neither species aid we observed significant in variations dimension and number of teeth, thickness of dentine and cemental layers and in the maximum width of cement as a function of body size. Age was related to increases in tooth length, root and cingulum diameters, and maximum width of cement in individuals of P. blainvillei, and tooth and crown lengths and maximum width of cement in individuals of S. fluviatilis. The observation of a linear growth between maximum width of cement and age in both species indicates that the equations obtained can be used to estimate relative age in P. blainvillei and S. fluviatilis in northern of Rio de Janeiro.  相似文献   
12.
The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press.  相似文献   
13.
Pneumocystis pneumonia (PcP) is a serious fungal infection among immunocompromised patients. In developed countries, the epidemiology and clinical spectrum of PcP have been clearly defined and well documented. However, in most developing countries, relatively little is known about the prevalence of pneumocystosis. Several articles covering African, Asian and American countries were reviewed in the present study. PcP was identified as a frequent opportunistic infection in AIDS patients from different geographic regions. A trend to an increasing rate of PcP was apparent in developing countries from 2002 to 2010.  相似文献   
14.
15.
White tip, caused by Phytophthora porri, is a devastating disease in the autumn and winter production of leek (Allium porrum) in Europe. This study investigated the disease cycle of P. porri in laboratory and field conditions. Oospores readily germinated in the presence of non‐sterile soil extract at any temperature between 4 and 22°C, with the formation of sporangia which released zoospores. The zoospores survived at least 7 weeks in water at a temperature range of 0 till 24°C. Microscopic examinations revealed that zoospores encysted and germinated on the leek leaf surface and hyphae entered the leaf directly through stomata or by penetrating via appressoria. Oospores were formed in the leaves within 6 days, while sporangia were not produced. By monitoring disease progress in fields with a different cropping history of leek, it could be deduced that P. porri survives in soil for up to 4 years. Disease progress during three consecutive years was correlated with average daily rainfall in the infection period. Disease incidence on leek was reduced when rain splash was excluded by growing the plants in an open hoop greenhouse. Based on these findings, we propose a disease cycle for P. porri in which oospores germinate in puddles, and zoospores reach the leaves by rain splash and survive in water in the leaf axils, from where they infect the plant by direct penetration or via stomata. When conditions become unfavourable, oospores are produced in the leaves which again reach the soil when leaves decay. Secondary spread of the disease by sporangia does not seem to be important.  相似文献   
16.
T. Rozkos, A. Ryska, J. Cap, F. Sobande and J. Laco
Cellular cohesiveness in benign and malignant thyroid follicular tumours varies significantly, but the difference is not useful in diagnosis of individual cases Introduction: The aim of our study was to search for new, readily available and statistically reliable cytological markers for differentiating benign and malignant follicular thyroid neoplasms pre‐operatively. Methods: Cohesiveness of tumour cells in cytology slides from a series of 58 follicular tumours diagnosed between 1998 and 2004 inclusive was studied, including 48 follicular adenomas, and eight minimally invasive and two widely invasive follicular carcinomas. Photomicrographs of the cytology slides were taken and the digital images were analysed using computer image analysis software. We evaluated the relative proportions of cells arranged in groups of various sizes. The cohesiveness of the cells in cytological smears was then correlated with the immunohistochemical expression of E‐cadherin in corresponding histological slides. Results: Cases from 15 men (26%) and 43 women (74%) with a mean age of 50 years (range, 19–79) were analysed. In follicular adenomas and carcinomas, respectively, isolated cells were seen in 16.8% and 24.7% (P = 0.028), groups of two to five cells in 9.7% and 11.5% (P = 0.145) and groups of more than five cells in 73.5% and 63.8% (P = 0.041). The mean cell count in groups with more than five cells was 46.5 and 27.0 in adenomas and carcinomas, respectively (P < 0.001). Cell cohesiveness, either as percentage of cells in groups of more than five (R2 = 0.026) or as mean cell count per group of more than five (R2 = 0.005), was not found to be dependent on the expression of E‐cadherin. Using a threshold of 13% isolated tumour cells in cytological smears, follicular adenomas and carcinomas could be distinguished with 90% sensitivity and 41% specificity. Conclusions: Although we demonstrated a statistically significant difference in cell cohesion between follicular adenomas and carcinomas, these could not be distinguished in the clinical setting by evaluation of the percentage of isolated cells in cytological smears because the specificity was too low. The absence of correlation of cellular cohesiveness with E‐cadherin expression indicates that other factors are probably responsible for the loss of cohesiveness observed in follicular thyroid malignancy.  相似文献   
17.
Aiming to provide a tentative framework for the study of the neural correlates of aesthetic preference, we review three recent neuroimaging studies carried out with the purpose of locating brain activity associated with decisions about the beauty of visual stimuli (Cela-Conde et al., 2004; Kawabata and Zeki, 2004; Vartanian and Goel, 2004). We find that the results of the three studies are not in line with previous neuropsychological data. Moreover, there are no coincidences among their results. However, when they are mapped on to Chatterjee's (2003) neuropsychological model of aesthetic preference it becomes clear that neuroimaging data are not contradictory, but complementary, and their interpretation is enriched. The results of these studies suggest that affective processes have an important role in aesthetic preference, and that they are integrated with cognitive processes to reach a decision regarding the beauty of visual stimuli. Future studies must aim to clarify whether certain methodological procedures are better suited to study any of the particular cognitive operations involved in aesthetic preference, and ascertain the extent to which the proposed framework is compatible with the aesthetic appreciation of musical stimuli.  相似文献   
18.
19.
The phylogenetic relationships among 11 species of the Cervidae family were inferred from an analysis of male vocalizations. Eighteen characters, including call types (e.g. antipredator barks, mating loudcalls) and acoustic characteristics (call composition, fundamental frequency and formant frequencies), were used for phylogeny inference. The resulting topology and the phylogenetic consistency of behavioral characters were compared with those of current molecular phylogenies of Cervidae and with separate and simultaneous parsimony analyses of molecular and behavioral data. Our results indicate that male vocalizations constitute plausible phylogenetic characters in this taxon. Evolutionary scenarios for the vocal characters are discussed in relation with associated behaviors.  相似文献   
20.
Dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) are considered the most important arthropod-borne viral diseases in terms of morbidity and mortality. The emergency and severity of dengue (Den) infections increase the necessity of an early, quick and effective dengue laboratory diagnostic. Viral isolation is considered a gold standard for diagnosis of dengue infection using monoclonal antibodies (mAbs) as a tool for determining serotype specificity. Alternatives have been used to improve sensitivity and time to dengue diagnosis. Based on the early expression of dengue C protein in the life cycle, we focused our study on the application of an anti-dengue 2 virus capsid protein mAb in dengue diagnosis. The kinetic expression of dengue-2 capsid in mosquito cells and its immuno-localization in experimentally infected suckling albin Swiss (OF-1) mice brain tissues was established. The results demonstrate the possible utility of this mAb in early dengue diagnosis versus traditional isolation. In addition, a preliminary study of an enzyme immunoassay method using 8H8 mAb for specific detection of dengue C protein antigen was performed, making possible recombinant C protein quantification. The results suggest that detection of dengue capsid protein could be useful in the diagnosis of early dengue infection.Key words: monoclonal antibodies, capsid protein, dengue virus, diagnosis, immunoassays  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号