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   102篇
  免费   15篇
  2021年   2篇
  2020年   1篇
  2019年   5篇
  2017年   2篇
  2016年   1篇
  2015年   3篇
  2014年   5篇
  2013年   10篇
  2012年   5篇
  2011年   5篇
  2010年   3篇
  2008年   4篇
  2007年   3篇
  2006年   3篇
  2005年   4篇
  2004年   3篇
  2003年   7篇
  2002年   5篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   2篇
  1994年   2篇
  1991年   2篇
  1989年   2篇
  1988年   3篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1976年   3篇
  1974年   1篇
  1973年   3篇
  1972年   1篇
  1971年   3篇
  1970年   1篇
  1966年   1篇
  1965年   1篇
  1956年   1篇
  1954年   1篇
  1950年   1篇
排序方式: 共有117条查询结果,搜索用时 109 毫秒
61.
Objective: This study examines whether obese individuals have a greater rate of nursing care facility admission than normal weight individuals. Research Methods and Procedures: Data from the National Health and Nutrition Examination Survey Epidemiological Follow‐up Survey were analyzed. Cox proportional hazards models were used to examine the relationship between baseline weight status and subsequent time to first nursing home admission while adjusting for sex, age, race, marital status, height, presence of children, smoking status, education, region, urban residence, income, and physical activity. Results: Of 5960 adults 45 to 74 years old, 989 individuals were admitted to a nursing care facility over the subsequent 20 years. Body mass index (BMI) was studied using five categories: < 18.5, 18.5 to <25, 25.0 to <30, 30.0 to <35, ≥35 kg/m2. The effects of BMI differed by race: compared with those with a BMI of 18.5 to < 25 kg/m2, adults with a BMI ≥30 kg/m2 or a BMI <18.5 kg/m2 had a greater rate of nursing home admission in whites, whereas no relationship was found in blacks. The inclusion of time to death with nursing home admission as a joint outcome yielded similar results. Discussion: The large increase in the prevalence of obesity coupled with the rapid expansion of the number of older Americans will likely increase the demand for nursing facility use. More research is needed to understand differences in factors related to nursing home admission among ethnic groups.  相似文献   
62.
63.
Actual working hours of employees vary widely, especially in the transportation industry. We developed a tool, the RAS (Representation and Analysis Software), to ease the assessment of such irregular hours and the transfer of existing knowledge of proper schedule design to the problem of irregular hours. This article discusses several critical design questions that were addressed during software development in order for it to assess irregular work patterns, including the (1) importance, in spite of a lack of established definitions, of basic concepts like, e.g., night shift, (2) difficulty of modeling and adapting existing knowledge on proper design, and (3) large number of analytical methods and additional data beyond company schedule that are necessary to meet the needs of various research groups. This article describes how the RAS addresses these three issues by illustrating its application to the work schedule of a train driver involved in the Hinton train disaster.  相似文献   
64.

Objective

The association between monetary value of the diet (MVD, $/day) with dietary quality was examined using a large sample of urban US adults, differentially by socio-demographic factors.

Methods

This was a cross-sectional study of 2,111 participants, aged 30–64y, using data from the Healthy Aging in Neighborhoods of Diversity across the Life Span Study. Dietary quality indices included Healthy Eating Index–2010 (HEI–2010) and Mean Adequacy Ratio (MAR), (two 24-hr recalls). A national food price database was used to estimate MVD. Multiple linear/logistic regression analyses were conducted stratifying separately by sex, race and poverty status.

Results

Women had significantly higher HEI-2010 scores than men (43.35 vs 41.57 out of 100, respectively), whereas MAR scores were higher for men (76.8 vs 69.9, out of 100), reflecting energy intake gender differentials. Importantly, a $3/day higher MVD (IQR: $3.70/d (Q1) to $6.62/d (Q4)) was associated with a 4.98±0.35 higher total HEI-2010 and a 3.88±0.37 higher MAR score, after energy-adjustment and control for key confounders. For HEI-2010 and MAR, stronger associations were observed among participants above poverty and among women, whilethe MVD vs. HEI-2010 association was additionally stronger among Whites. Sex and poverty status differentials were observed for many MAR and some HEI-2010 components.

Conclusions

Despite positive associations between measures of dietary quality and MVD, particularly above poverty and among women, approaching compliance with the Dietary Guidelines (80 or more for HEI-2010) requires a substantially higher MVD. Thus, nutrition education may further improve people’s decision-making regarding food venues and dietary choices.  相似文献   
65.

Background  

Recently, a Risk Assessment methodology was applied to animal welfare issues in a report of the European Food Safety Authority (EFSA) on intensively housed calves.  相似文献   
66.
67.
The R-spondin protein family   总被引:1,自引:0,他引:1  
The four vertebrate R-spondin proteins are secreted agonists of the canonical Wnt/β-catenin signaling pathway. These proteins are approximately 35 kDa, and are characterized by two amino-terminal furin-like repeats, which are necessary and sufficient for Wnt signal potentiation, and a thrombospondin domain situated more towards the carboxyl terminus that can bind matrix glycosaminoglycans and/or proteoglycans. Although R-spondins are unable to initiate Wnt signaling, they can potently enhance responses to low-dose Wnt proteins. In humans, rare disruptions of the gene encoding R-spondin1 cause a syndrome of XX sex reversal (phenotypic male), palmoplantar keratosis (a thickening of the palms and soles caused by excess keratin formation) and predisposition to squamous cell carcinoma of the skin. Mutations in the gene encoding R-spondin4 cause anonychia (absence or hypoplasia of nails on fingers and toes). Recently, leucine-rich repeat-containing G-protein-coupled receptor (Lgr)4, Lgr5 and Lgr6, three closely related orphans of the leucine-rich repeat family of G-protein-coupled receptors, have been identified as receptors for R-spondins. Lgr5 and Lgr6 are markers for adult stem cells. Because R-spondins are potent stimulators of adult stem cell proliferation in vivo and in vitro, these findings might guide the therapeutic use of R-spondins in regenerative medicine.  相似文献   
68.
Duffey KJ  Popkin BM 《PLoS medicine》2011,8(6):e1001050

Background

Competing theories attempt to explain changes in total energy (TE) intake; however, a rigorous, comprehensive examination of these explanations has not been undertaken. Our objective was to examine the relative contribution of energy density (ED), portion size (PS), and the number of eating/drinking occasions (EOs) to changes in daily TE.

Methods and Findings

Using cross-sectional nationally representative data from the Nationwide Food Consumption Survey (1977–78), Continuing Survey of Food Intakes of Individuals (1989–91), and National Health and Nutrition Examination Surveys (1994–98 and 2003–06) for adults (aged ≥19 y), we mathematically decompose TE (kcal/d) to understand the relative contributions of each component—PS (grams/EO), ED (kcal/g/EO) and EO(number)—to changes in TE over time. There was an increase in TE intake (+570 kcal/d) and the number of daily EOs (+1.1) between 1977–78 and 2003–06. The average PS increased between 1977–78 and 1994–98, then dropped slightly between 1994–98 and 2003–06, while the average ED remained steady between 1977–78 and 1989–91, then declined slightly between 1989–91 and 1994–98. Estimates from the decomposition statistical models suggest that between 1977–78 and 1989–91, annualized changes in PS contributed nearly 15 kcal/d/y to increases in TE, while changes in EO accounted for just 4 kcal/d/y. Between 1994–98 and 2003–06 changes in EO accounted for 39 kcal/d/y of increase and changes in PS accounted for 1 kcal/d/y of decline in the annualized change in TE.

Conclusions

While all three components have contributed to some extent to 30-y changes in TE, changes in EO and PS have accounted for most of the change. These findings suggest a new focus for efforts to reduce energy imbalances in US adults. Please see later in the article for the Editors'' Summary  相似文献   
69.

Background

BRCA protein interacts with at least 13 different proteins that have been implicated with cancer susceptibility and loss of BRCA function is correlated to sensitivity to DNA crosslinking agents in preclinical models.

Results

BRCA2 methylation frequency was 44%, p53 Pro22 allele frequency was 32% and heterozygous frequency of Arg/Pro72 genotype was 60% which could be associated as risk factor for metastasis (p = 0.046 OR = 4.190). Regarding to polymorphism of codon 249 the frequency of Arg249 allele presented 82% which was considered not statistically significant.

Conclusions

There was not statistical significance to BRCA2 promoter methylation with any parameters chosen. However, our findings suggest that patients who present heterozygous genotype at codon 72 of p53 gene may have a major susceptibility to any type of metastasis and this could serve as potential auxiliary biomarker for poor prognosis.  相似文献   
70.
The possible role of glycosphingolipids as adhesion receptors for the human gastric pathogen Helicobacter pylori was examined by use of radiolabeled bacteria, or protein extracts from the bacterial cell surface, in the thin-layer chromatogram binding assay. Of several binding specificities found, the binding to lactosylceramide is described in detail here, the others being reported elsewhere. By autoradiography a preferential binding to lactosylceramide having sphingosine/phytosphingosine and 2-D hydroxy fatty acids was detected, whereas lactosylceramide having sphingosine and nonhydroxy fatty acids was consistently nonbinding. A selective binding of H. pylori to lactosylceramide with phytosphingosine and 2-D hydroxy fatty acid was obtained when the different lactosylceramide species were incorporated into liposomes, but only in the presence of cholesterol, suggesting that this selectivity may be present also in vivo . Importantly, lactosylceramide with sphingosine and hydroxy fatty acids does not bind in this assay. Furthermore, a lactosylceramide-based binding pattern obtained for different trisaccharide glycosphingolipids is consistent with the assumption that this selectivity is due to binding of a conformation of lactosylceramide in which the oxygen of the 2-D fatty acid hydroxyl group forms a hydrogen bond with the Glc hydroxy methyl group, yielding an epitope presentation different from other possible conformers. An alternative conformation that may come into consideration corresponds to the crystal structure found for cerebroside, in which the fatty acid hydroxyl group is free to interact directly with the adhesin. By isolating glycosphingolipids from epithelial cells of human stomach from seven individuals, a binding of H.pylori to the diglycosylceramide region of the non-acid fraction could be demonstrated in one of these cases. Mass spectrometry showed that the binding-active sample contained diglycosylceramides with phytosphingosine and 2-D hydroxy fatty acids with 16-24 carbon atoms in agreement with the results related above.   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