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   188篇
  免费   7篇
  195篇
  2023年   1篇
  2022年   2篇
  2021年   4篇
  2020年   1篇
  2018年   4篇
  2017年   4篇
  2016年   5篇
  2015年   11篇
  2014年   15篇
  2013年   15篇
  2012年   24篇
  2011年   14篇
  2010年   6篇
  2009年   7篇
  2008年   18篇
  2007年   12篇
  2006年   8篇
  2005年   5篇
  2004年   9篇
  2003年   4篇
  2002年   7篇
  2001年   3篇
  1999年   1篇
  1998年   2篇
  1995年   1篇
  1994年   4篇
  1992年   3篇
  1991年   3篇
  1990年   1篇
  1970年   1篇
排序方式: 共有195条查询结果,搜索用时 15 毫秒
91.

Background

Studies from the UK and North America have reported vitamin C deficiency in around 1 in 5 men and 1 in 9 women in low income groups. There are few data on vitamin C deficiency in resource poor countries.

Objectives

To investigate the prevalence of vitamin C deficiency in India.

Design

We carried out a population-based cross-sectional survey in two areas of north and south India. Randomly sampled clusters were enumerated to identify people aged 60 and over. Participants (75% response rate) were interviewed for tobacco, alcohol, cooking fuel use, 24 hour diet recall and underwent anthropometry and blood collection. Vitamin C was measured using an enzyme-based assay in plasma stabilized with metaphosphoric acid. We categorised vitamin C status as deficient (<11 µmol/L), sub-optimal (11–28 µmol/L) and adequate (>28 µmol/L). We investigated factors associated with vitamin C deficiency using multivariable Poisson regression.

Results

The age, sex and season standardized prevalence of vitamin C deficiency was 73.9% (95% confidence Interval, CI 70.4,77.5) in 2668 people in north India and 45.7% (95% CI 42.5,48.9) in 2970 from south India. Only 10.8% in the north and 25.9% in the south met the criteria for adequate levels. Vitamin C deficiency varied by season, and was more prevalent in men, with increasing age, users of tobacco and biomass fuels, in those with anthropometric indicators of poor nutrition and with lower intakes of dietary vitamin C.

Conclusions

In poor communities, such as in our study, consideration needs to be given to measures to improve the consumption of vitamin C rich foods and to discourage the use of tobacco.  相似文献   
92.
Acinetobacter baumannii and Pseudomonas aeruginosa are pathogens capable of colonizing the same infection sites and employing N-acyl homoserine lactone (AHL) based quorum-sensing systems to co-ordinate biofilm formation. Hence, the effect of P. aeruginosa AHLs on biofilm formation by A. baumannii and vice versa were investigated using the biofilm impaired quorum sensing mutants, A. baumannii M2 (abaI::Km) and P. aeruginosa PAO-JP2. Complementing the mutants with heterologous, extracted and pure AHLs increased biofilm mass significantly. The surface area coverage and biovolume also increased significantly as observed by confocal scanning laser microscopy which corroborated scanning electron microscope analysis. Autoinducer synthase gene promoters of A. baumannii, P( abaI)-lacZ, and P. aeruginosa, P( lasI)-lacZ, were induced (p?相似文献   
93.
The weeble mutant mouse has a frame shift mutation in inositol polyphosphate 4-phosphatase type I (Inpp4a). The phenotype is characterized by an early onset cerebellar ataxia and neurodegeneration, especially apparent in the Purkinje cells. Purkinje cell loss is a common pathological finding in many human and mouse ataxic disorders. Here we show that in the Inpp4awbl mutant, Purkinje cells are lost in a specific temporal and spatial pattern. Loss occurs early in postnatal development; however, prior to the appearance of climbing fibers in the developing molecular layer, the mutant has a normal complement of Purkinje cells and they are properly positioned. Degeneration and reactive gliosis are present at postnatal day 5 and progress rapidly in a defined pattern of patches; however, Inpp4a is expressed uniformly across Purkinje cells. In late stage mutants, patches of surviving Purkinje cells appear remarkably normal with the exception that the climbing fibers have been excessively eliminated. Surviving Purkinje cells express Eaat4, a glutamate transporter that is differentially expressed in subsets of Purkinje cells during development and into adult stages. Prior to Purkinje cell loss, reactive gliosis and dendritic atrophy can be seen in Eaat4 negative stripes. Our data suggest that Purkinje cell loss in the Inpp4awbl mutant is due to glutamate excitotoxicity initiated by the climbing fiber, and that Eaat4 may exert a protective effect.  相似文献   
94.
Attempts were made to purify and study the kinetics of extracellular phospholipase A of Salmonella newport (6,8, eb; 1,2). The enzyme was purified by salt precipitation followed by gel filtration, using different grades of Sephadex. The enzymically active purified preparation was found to be a protein, having molar mass ranging between 43 and 67 kDa. The enzyme had a pH optimum at 7.5, giving 18.2 micrograms of lysophosphatidylcholine per mg protein. Its activity was enhanced by all metal ions except potassium, by solvents and surfactants except sodium dodecyl sulfate. It hydrolyzed the membrane phospholipids of red blood cells and was inhibitory to the growth of other microorganisms.  相似文献   
95.
Pre-eclampsia, a life-threatening disease during pregnancy, is a leading cause of global maternal mortality. Although there is substantial evidence of a genetic background, the complexity of the processes involved and nature of the maternal-fetal phenomenon do not make the search for the causative genes easy. Recent retrospective studies on the subject suggest the heritable allelic variations, particularly the utero-placental renin-angiotensin system with defective placental vascular development, could become the cornerstone for the genetics of pre-eclampsia and hence might well be associated with such defective development. Moreover, the role of immune mechanisms (immune maladaptation) deserves not to be ignored. Large-scale studies entailing genomewide scanning, sib-pair linkage analysis, and family-based association studies with appropriate power to detect genes with a lower relative risk are necessary to understand the puzzle of the disease. Moreover, recently, the importance of epigenetic features and the effect of imprinted genes related to trophoblast growth as well as fetal development on hypertension in pregnancy have been highlighted. All these possibilities are intuitively attractive and are supported by some circumstantial evidence. Although the consistent tenor of a series of papers instill some confidence, we need meticulously designed larger-scale investigations including large numbers of affected women and their babies to provide the analytic stringency essential to study the polygenic multifactorial basis of pre-eclampsia.  相似文献   
96.
The retinal degeneration 7 (rd7) mouse, lacking expression of the Nr2e3 gene, exhibits retinal dysplasia and a slow, progressive degeneration due to an abnormal production of blue opsin-expressing cone cells. In this study we evaluated three strains of mice to identify alleles that would slow or ameliorate the retinal degeneration observed in Nr2e3 rd7/rd7 mice. Our studies reveal that genetic background greatly influences the expression of the Nr2e3 rd7/rd7 phenotype and that the inbred mouse strains CAST/EiJ, AKR/J, and NOD.NON-H2 nb1 carry alleles that confer resistance to Nr2e3 rd7/rd7 -induced retinal degeneration. B6.Cg-Nr2e3 rd7/rd7 mice were outcrossed to each strain and the F1 progeny were intercrossed to produce F2 mice. In each intercross, 20–24% of the total F2 progeny were homozygous for the Nr2e3 rd7/rd7 mutation in a mixed genetic background; approximately 28–48% of the Nr2e3 rd7/rd7 homozygotes were suppressed for the degenerative retina phenotype in a mixed genetic background. The suppressed mice had no retinal spots and normal retinal morphology with a normal complement of blue opsin-expressing cone cells. An initial genome scan revealed a significant association of the suppressed phenotype with loci on chromosomes 8 and 19 with the CAST/EiJ background, two marginal loci on chromosomes 7 and 11 with the AKR/J background, and no significant QTL with the NOD.NON-H2 nb1 background. We did not observe any significant epistatic effects in this study. Our results suggest that there are several genes that are likely to act in the same or parallel pathway as NR2E3 that can rescue the Nr2e3 rd7/rd7 phenotype and may serve as potential therapeutic targets. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
97.
Protozoan parasites in the order Kinetoplastida cause severe disease primarily in tropical and subtropical areas. Vaccines to control these diseases have shown some promise, but none are in active clinical use. Drug treatments are available for all of the acute infections, but the emergence of resistance and an unresponsive chronic phase are current problems. Rapid advances in genomic technology open the possibility of discovering new genes that can contribute to vaccine initiatives or serve as targets for development of new drugs. The DNA microarray is a genomic technology, which is being applied to new gene discovery in kinetoplastid parasites. Both cDNA and genomic microarrays for Leishmania major have identified a number of new genes that are expressed in a stage-specific fashion and preliminary results from a L. donovani genomic microarray also demonstrated new gene discovery. A microarray of Trypanosoma brucei genomic fragments identified new genes whose expression differs between the insect borne stage and the human infectious stage of the parasite. The next few years, building on this foundational work, should witness the most exciting stage as microarrays are applied to questions such as the basis of drug resistance, post kala azar dermal leishmaniasis, the regulation of differentiation to infectious stages, linking coordinately regulated pathways of genes and development of genetically defined parasites that may have potential as live attenuated vaccines.  相似文献   
98.
Obesity, a global problem, is a multifactorial disorder. The factors are environmental, metabolic and genetic and their interaction with each other regulates the body weight. Imbalance in either of the factors may be responsible for weight gain. With advancement of research techniques in the last decade, genetic studies have been undertaken for several different causative mutations involving obesity loci on different chromosomes. Monogenic and polygenic obesity has been observed however, polygenic forms are more common. So far more than 200 genes in mouse and more than 100 genes in humans have been identified which result in phenotypes that affect body weight regulation. In spite of this knowledge, the field of obesity has still not been explored extensively. There remain a lot of lacuna regarding causes and treatment of obesity. Challenges are still there to identify the exact cause of weight gain and the use of current knowledge for development of anti-obesity drugs targeted for body weight regulation. In this review, we have explained neuropathophysiologic regulation of feeding behaviour and some aspects of obesity-genetics especially with single nucleotide polymorphism of selected candidate genes and their functional aspects mainly in monogenic obesity.  相似文献   
99.

Background

This paper describes the rationale, design, and methodology of the Ecological Study of Sexual Behaviors and HIV/STI among African American Men Who Have Sex with Men (MSM) in the Southeastern United States (U.S.; known locally simply as the MARI Study).

Methods

Participants are African American MSM aged 18 years and older residing in the deep South.

Results

Between 2013 and 2015, 800 African American MSM recruited from two study sites (Jackson, MS and Atlanta, GA) will undergo a 1.5-hour examination to obtain anthropometric and blood pressure measures as well as to undergo testing for sexually transmitted infections (STI), including HIV. Intrapersonal, interpersonal, and environmental factors are assessed by audio computer-assisted self-interview survey. Primary outcomes include sexual risk behaviors (e.g., condomless anal sex) and prevalent STIs (HIV, syphilis, gonorrhea, and Chlamydia).

Conclusion

The MARI Study will typify the HIV environmental ''riskscape'' and provide empirical evidence into novel ecological correlates of HIV risk among African American MSM in the deep South, a population most heavily impacted by HIV. The study''s anticipated findings will be of interest to a broad audience and lead to more informed prevention efforts, including effective policies and interventions, that achieve the goals of the updated 2020 U.S. National HIV/AIDS Strategy.  相似文献   
100.
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