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   67篇
  免费   1篇
  68篇
  2023年   3篇
  2022年   2篇
  2021年   8篇
  2020年   2篇
  2019年   1篇
  2018年   4篇
  2017年   2篇
  2016年   1篇
  2015年   3篇
  2014年   1篇
  2013年   2篇
  2012年   6篇
  2011年   4篇
  2010年   1篇
  2009年   5篇
  2008年   2篇
  2007年   3篇
  2006年   2篇
  2005年   5篇
  2004年   3篇
  2003年   4篇
  2002年   2篇
  1993年   1篇
  1985年   1篇
排序方式: 共有68条查询结果,搜索用时 0 毫秒
51.

Introduction

Understanding the context where adolescents’ physical activity (PA) takes place could impact a more targeted approach to implement PA promotion and interventions in Africa. However, standardized data on adolescents’ PA behaviour is lacking in Nigeria. We described PA patterns in the various domains (home, school, transport, leisure-time) and intensity categories (light-intensity PA, moderate- to vigorous- intensity physical activity [MVPA] and total PA), and their associations with sociodemographic factors and socioeconomic status (SES) among secondary school adolescents in Nigeria.

Methods

A cross-sectional survey was conducted in a representative sample of 1006 secondary school adolescents (12–18 years, 50.4% girls) in Maiduguri, Nigeria. Self-reported PA was assessed with an adapted version of the Activity Questionnaire for Adolescents and Young Adults. Outcomes were weekly minutes (min/wk) of PA spent in the various domains and intensity categories. Multivariate ANOVA was used to examine associations of PA scores (domains and intensity levels) with adolescents’ sociodemographic characteristics and SES, and track differences in PA scores between subgroups.

Results

The total sample reported most PA at school (1525 min/wk), the least during active transportation (210 min/wk), and only 37% engaged in 60 min of MVPA daily. Boys reported significantly more leisure-time PA (P<0.001), active transportation (P<0.001), MVPA (P = 0.023) and total PA (P = 0.003) than girls, while girls reported more school-based PA (P = 0.009), home-based PA (P<0.001) and light-intensity PA (P<0.001) than boys. Moderate-intensity PA (P = 0.024) and total PA (P = 0.049) were significantly higher in younger age group than in older group. Household car ownership was associated with less active transportation (P = 0.009), less moderate-intensity PA (P = 0.048) and with more leisure-time PA (P = 0.013). High parental SES was associated with more leisure-time PA (P = 0.002), more MVPA (P = 0.047) and less active transportation (P<0.001). Adolescents of various weight status differed significantly in their leisure-time PA (P<0.001), moderate-intensity PA (P = 0.011) and total PA (P = 0.033).

Conclusions

The patterns and levels of physical activity among adolescents in Nigeria vary according to the adolescents’ age, gender, weight status and SES. These findings have important public health implications for identifying subgroups of Nigerian adolescents that should be targeted for effective physical activity promoting interventions.  相似文献   
52.
Summary Sawdust fromCanarium schweinfurthii (Engl.), a common source of timber in the rainforest zone of Nigeria was subjected to various treatments to improve the nutrient content and aid the decomposition of the otherwise highly-lignified material. The treatments were then either incorporated into the soil or added to the soil surface as a mulch in both greenhouse and field studies. The greenhouse studies involved two six-week sowings in the same soil while the field study involved 3 season sowings (2 rainly, one dry season) using maize (Zea mays L.var. Western yellow) as a test crop.Results indicated that in the greenhouse, incorporation of untreated sawdust led to significant reductions in maize growth, dry matter yield and uptake of N and other nutrients. While the incorporated inorganically amended sawdust treatment produced significantly higher dry matter yield, that produced by the surface-applied organically amended treatment was significantly higher than the incorporated treatment. Except for untreated sawdust, the incorporation of organically and inorganically amended sawdust increased the contents insoil of N, available P, and exchangeable K.  相似文献   
53.
Oxidative stress and inflammation mostly contribute to aging and age-related conditions including skin aging. The potential of natural products in the form of naturally-derived cosmetics, cosmeceuticals, and nutricosmetics have, however, not been fully harnessed. This review, thus, critically analyzes the potential roles of natural products in inflammation-related skin aging diseases due to the increasing consumers’ concerns and demands for efficacious, safe, natural, sustainable, and religiously permitted alternatives to synthetic products. The information and data were collated from various resources and literature databases such as PubMed, Science Direct, Wiley, Springer, Taylor and Francis, Scopus, Inflibnet, Google, and Google Scholar using relevant keywords and Medical Subject Headings (MeSH). The role of green extraction solvents as promising alternatives is also elucidated. The potential enhancements of the bioavailability, stability, solubility and controlled release profile of the bioactives using different delivery systems are also presented. The current potential global market value, motivators, drivers, trends, challenges, halal, and other regulatory certifications for cosmeceuticals and nutricosmetics are equally discussed. The adoption of the suggested extractions and delivery systems would enhance the stability, bioavailability, and target delivery of the bioactives.  相似文献   
54.
Cellulases are important in the hydrolysis of lignocellulosic materials and thereby contribute to biomass conversion into fuels and chemicals. A cellulase-producing bacterium was isolated from decayed plant leaf litter in soil of a botanical garden. Based on morphological, biochemical and 16S rRNA gene sequencing, it was identified as Enterobacter cloacae IP8, with gene bank accession number NR118568.1. The bacterial cellulase was purified in a three-step procedure using lyophilization, ion exchange chromatography (QAE Sephadex A-50) and gel filtration (Biogel P-100). Two isoforms of the enzyme were purified 1.21 and 1.23 folds, respectively, with yields of 30 and 29% for isoforms A and B, respectively. Apparent molecular weights of 36.61?±?1.40 and 14.1?±?0.10?kDa were obtained for isoforms A and B, respectively, using gel filtration chromatography. Kinetic parameters Km and Vmax were 0.13?±?0.04?mg/ml and 3.84?±?0.05?U/ml/min, respectively, for isoform A and 0.58?±?0.06?mg/ml and 13.8?±?0.10?U/ml/min, respectively, for isoform B. Optimum pH (7.0) and temperature (60?°C) of cellulase activity were determined for both isoforms A and B. Na+ and Ca2+ enhanced the activities of both isoforms. Mg2+ inhibited the enzyme activity at concentrations 4–15?mM but, while it stimulated the activity of isoform A at concentrations 15–200?mM, it inhibited that of isoform B at same concentration range. The strong inhibition of the enzyme by ethylenediaminetetraacetic acid (EDTA) confirmed the enzyme as a metalloenzyme. These results reveal the purified cellulase from E. cloacae IP8 as a thermostable, acidic to neutral metalloenzyme, suggesting that it has good potential for biotechnological applications.  相似文献   
55.

Objective

This study assessed the diagnostic performance and prognostic properties of C-reactive protein (CRP), copeptin and cortisol in individuals with sickle cell anaemia (SCA).

Design

Prospective case-control study

Methods

Sixty consecutive SCA subjects (18–40 years) comprising 30 subjects in the steady state and 30 subjects in vaso-occlusive crisis (VOC) were recruited into this study. Thirty (30) apparently healthy individuals with HbAA genotype served as controls. ELISA was used for the determination of serum levels of copeptin, CRP and cortisol. Data obtained were statistically analyzed using the Student’s t-test and Mann Whitney U as appropriate and P<0.05 was considered significant.

Results

SCA subjects in VOC had significantly lower copeptin level and significantly higher CRP level compared with controls. However, serum levels of copeptin, cortisol and CRP were significantly higher in SCA subjects in VOC compared with SCA subjects in steady state. Furthermore, CRP had the widest Area under the ROC curve (AUROC) than copeptin and cortisol. No significant difference was observed in the levels of copeptin, CRP and cortisol when SCA subjects in VOC who were hospitalized for less ≤5 days were compared with subjects who had longer stays.

Conclusion

It could be concluded that C-reactive protein has a superior diagnostic performance for vaso-occlusive crisis in individuals with sickle cell anaemia and that C-reactive protein, cortisol and copeptin are not good prognostic markers in SCA subjects in vaso-occlusive crisis.  相似文献   
56.
Bacterial strains were isolated from cassava-derived food products and, for the first time, from cassava by-products, with a focus on gari, a flour-like product, and the effluents from the production processes for gari and fufu (a dough also made from cassava flour). A total of 47 strains were isolated, all of which were tested to determine their resistance to acidic pH and to bile salt environments. Four of the 47 isolates tested positive in both environments, and these four isolates also showed antibacterial behaviour towards both Gram-positive and Gram-negative microbial pathogens (i.e. Methicillin-resistance Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Salmonella enteritidis, Escherichia coli, Escherichia coli (O157), Yersinia enterocolitica). In most cases, the antibacterial activity was related to bacteriocin production. Molecular identification analysis (16S rDNA and randomly amplified polymorphic DNA-PCR) revealed that the four isolates were different strains of the same species, Lactobacillus fermentum. These results demonstrate that bacteria isolated from cassava-derived food items and cassava by-products have interesting properties and could potentially be used as probiotics.  相似文献   
57.

Background  

Gene-set analysis evaluates the expression of biological pathways, or a priori defined gene sets, rather than that of individual genes, in association with a binary phenotype, and is of great biologic interest in many DNA microarray studies. Gene Set Enrichment Analysis (GSEA) has been applied widely as a tool for gene-set analyses. We describe here some critical problems with GSEA and propose an alternative method by extending the individual-gene analysis method, Significance Analysis of Microarray (SAM), to gene-set analyses (SAM-GS).  相似文献   
58.
Pathway analysis of microarray data evaluates gene expression profiles of a priori defined biological pathways in association with a phenotype of interest. We propose a unified pathway-analysis method that can be used for diverse phenotypes including binary, multiclass, continuous, count, rate, and censored survival phenotypes. The proposed method also allows covariate adjustments and correlation in the phenotype variable that is encountered in longitudinal, cluster-sampled, and paired designs. These are accomplished by combining the regression-based test statistic for each individual gene in a pathway of interest into a pathway-level test statistic. Applications of the proposed method are illustrated with two real pathway-analysis examples: one evaluating relapse-associated gene expression involving a matched-pair binary phenotype in children with acute lymphoblastic leukemia; and the other investigating gene expression in breast cancer tissues in relation to patients' survival (a censored survival phenotype). Implementations for various phenotypes are available in R. Additionally, an Excel Add-in for a user-friendly interface is currently being developed.  相似文献   
59.
Adio AM  König WA 《Phytochemistry》2005,66(5):599-609
The essential oil of the liverwort Plagiochila asplenioides from two different locations in Northern Germany were investigated by chromatographic and spectroscopic methods. Seven compounds were isolated by preparative gas chromatography (GC) and their structures investigated by mass spectrometry (MS), NMR techniques and chemical correlations in combination with enantioselective GC. In addition to known constituents, aromadendra-1(10),3-diene, two aromatic sesquiterpene hydrocarbons, bisabola-1,3,5,7(14)-tetraene and bisabola-1,3,5,7-tetraene, three sesquiterpene ethers, muurolan-4,7-peroxide, plagiochilines W and X, in addition to ent-4-epi-maaliol, could be identified as natural compounds for the first time.  相似文献   
60.
The peptides DRPVPY and MDWNMHAA, which were identified as mimics of the cell-surface polysaccharides of Streptococcus Group A and Shigella flexneri Y, respectively, were used in this study to develop experimental vaccines directed against these two bacteria. Both oligopeptides were synthesized employing the Fmoc solid-phase strategy and linked via the amino end to a bifunctional linker, diethylsquarate. These adducts were then conjugated to the two carrier proteins, bovine serum albumin (BSA) and tetanus toxoid (TT) to yield the peptide conjugate vaccines. The average level of incorporation of DRPVPY and MDWNMHAA on TT was 65% and 75%, respectively, whereas that of both peptide haptens on BSA was 100%. A polysaccharide conjugate against S. flexneri Y, which comprises about 10 tetrasaccharide repeating units, was also prepared based on reductive amination at the reducing end with 1,3-diaminopropane, followed by coupling of the aminated polysaccharide to diethylsquarate, and subsequent coupling of the adduct to TT. An average incorporation of 73% of polysaccharide haptens was achieved. The glycoconjugate and the oligopeptide conjugates were shown to bind effectively to the respective monoclonal antibodies directed against the cell-surface polysaccharides.  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