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   487篇
  免费   32篇
  2023年   3篇
  2022年   11篇
  2021年   14篇
  2020年   10篇
  2019年   13篇
  2018年   10篇
  2017年   13篇
  2016年   15篇
  2015年   28篇
  2014年   30篇
  2013年   40篇
  2012年   44篇
  2011年   49篇
  2010年   31篇
  2009年   27篇
  2008年   24篇
  2007年   23篇
  2006年   18篇
  2005年   18篇
  2004年   8篇
  2003年   19篇
  2002年   14篇
  2001年   5篇
  2000年   13篇
  1999年   2篇
  1998年   5篇
  1997年   1篇
  1996年   5篇
  1995年   2篇
  1993年   5篇
  1991年   2篇
  1990年   1篇
  1988年   2篇
  1986年   6篇
  1984年   2篇
  1978年   1篇
  1975年   1篇
  1972年   1篇
  1968年   1篇
  1943年   2篇
排序方式: 共有519条查询结果,搜索用时 31 毫秒
461.
Spermatogenesis is a tightly regulated, selenium-dependent process. Nutritional deficiencies, including Se, have been associated with decreased fertility. During Se depletion, testes preferentially retain Se while other tissues are depleted. This study was aimed at evaluating the effect of Se source (inorganic or organic yeast derived) on testes weight, Se content, and gene expression. At 17 weeks of age, roosters were randomly assigned to one of three treatments: basal diet (control), basal diet?+?0.3 mg organic Se/kg organic yeast-derived Se (YS; Sel-Plex®, Alltech Inc.), or basal diet?+?0.3 mg inorganic Se /kg inorganic Se as sodium selenite (SS). At 40 weeks of age, seven roosters from each treatment were euthanized and testes removed. Testes weight did not differ between treatments, but Se content was greater (P?≤?0.01) in YS than SS and control. Testicular differential gene expression profiling was accomplished using the Affymetrix Genechip® chicken genome array. Ingenuity® pathway analysis revealed that Se supplementation, regardless of source, results in the up-regulation of genes governing cell structure/morphology. The enrichment of such pathways was greater with YS than SS. These expression patterns suggest that aside from playing a role in antioxidant defense, Se, especially in the organic YS form, is useful for maintaining testicular cell structure.  相似文献   
462.
463.
464.

Objective

To evaluate effectiveness, safety and cost-effectiveness of Computerised Clinical Decision Support (CCDS) for paramedics attending older people who fall.

Design

Cluster trial randomised by paramedic; modelling.

Setting

13 ambulance stations in two UK emergency ambulance services.

Participants

42 of 409 eligible paramedics, who attended 779 older patients for a reported fall.

Interventions

Intervention paramedics received CCDS on Tablet computers to guide patient care. Control paramedics provided care as usual. One service had already installed electronic data capture.

Main Outcome Measures

Effectiveness: patients referred to falls service, patient reported quality of life and satisfaction, processes of care.

Safety

Further emergency contacts or death within one month.

Cost-Effectiveness

Costs and quality of life. We used findings from published Community Falls Prevention Trial to model cost-effectiveness.

Results

17 intervention paramedics used CCDS for 54 (12.4%) of 436 participants. They referred 42 (9.6%) to falls services, compared with 17 (5.0%) of 343 participants seen by 19 control paramedics [Odds ratio (OR) 2.04, 95% CI 1.12 to 3.72]. No adverse events were related to the intervention. Non-significant differences between groups included: subsequent emergency contacts (34.6% versus 29.1%; OR 1.27, 95% CI 0.93 to 1.72); quality of life (mean SF12 differences: MCS −0.74, 95% CI −2.83 to +1.28; PCS −0.13, 95% CI −1.65 to +1.39) and non-conveyance (42.0% versus 36.7%; OR 1.13, 95% CI 0.84 to 1.52). However ambulance job cycle time was 8.9 minutes longer for intervention patients (95% CI 2.3 to 15.3). Average net cost of implementing CCDS was £208 per patient with existing electronic data capture, and £308 without. Modelling estimated cost per quality-adjusted life-year at £15,000 with existing electronic data capture; and £22,200 without.

Conclusions

Intervention paramedics referred twice as many participants to falls services with no difference in safety. CCDS is potentially cost-effective, especially with existing electronic data capture.

Trial Registration

ISRCTN Register ISRCTN10538608   相似文献   
465.
The chemical composition of rehabilitated Bauxite Residue Disposal Areas (BRDA) remains the primary indicator of rehabilitation success, with little consideration of microbial community development. We investigated links between the chemical and microbial components of rehabilitated residue at the Aughinish Alumina BRDA (Ireland). Rehabilitated was compared to unamended residue and to an analogy reference soil from unmanaged grassland within the refinery boundary. Bauxite residue comprised of areas with 1, 11, and 12 years following rehabilitation establishment, and gypsum applied at 45 and 90 t/ha. The unamended residue was typical of bauxite residues with high pH (10), sodicity (exchangeable sodium percentage [ESP]‐79), exchangeable sodium (19 cmol/kg), salinity (electrical conductivity [EC] 2.6 mS/cm), and low/negligible nutrient content, microbial biomass (71 µg‐C/g), and fungal phospholipid fatty acid (PLF). Microbial biomass increased 10‐fold with only 1 year of rehabilitation. Gypsum application rate had no effect on microbial biomass. Phospholipid fatty acid analysis (PLFA) demonstrated the emergence of distinct microbial community dependent on rehabilitation time and gypsum application rates. Changes of PLFA profiles were correlated (multiple regressions analysis) to shifts in residue chemical properties (sodicity, organic C, total C, total N, salinity, Mg). An increase of the arbuscular mycorrhizal fungi fatty acid (16:1ω5) with reducing pH has implications on rehabilitation practices. The microbial characteristics of the rehabilitated residue were approaching that of a soil from an unmanaged reference site adjacent to the working site. Gypsum affected PLFA properties, and thereby application has implications for rehabilitation success. For successful ecosystem reconstruction, it is critical that rehabilitation practices consider microbial development.  相似文献   
466.

Aims

Oxidative stress is involved in the pathophysiology of diabetic nephropathy. Manganese superoxide dismutase (SOD2) catalyses the dismutation of superoxide, regulates the metabolism of reactive oxygen species in the mitochondria and is highly expressed in the kidney. Plasma concentration of advanced oxidation protein products (AOPP), a marker of oxidative stress, was found to be increased in patients with kidney disease. We investigated associations of SOD2 allelic variations, plasma SOD activity and AOPP concentration with diabetic nephropathy in type 1 diabetic subjects.

Methods

Eight SNPs in the SOD2 region were analysed in 1285 Caucasian subjects with type 1 diabetes from the SURGENE prospective study (n = 340; 10-year follow-up), GENESIS (n = 501) and GENEDIAB (n = 444) cross-sectional studies. Baseline plasma concentration of AOPP and SOD activity were measured in GENEDIAB participants. Hazard ratio (HR) and odds ratio (OR) were determined for incidence and prevalence of nephropathy. Analyses were adjusted or stratified by retinopathy stages.

Results

In the SURGENE cohort, the T-allele of rs4880 (V16A) was associated with the incidence of renal events (new cases, or the progression to a more severe stage of nephropathy; HR 1.99, 95% CI 1.24–3.12, p = 0.004) and with the decline in estimated glomerular filtration rate (eGFR) during follow-up. Similar associations were observed for rs2758329 and rs8031. Associations were replicated in GENESIS/GENEDIAB cohorts, in the subset of participants without proliferative retinopathy, and were confirmed by haplotype analyses. Risk allele and haplotype were also associated with higher plasma AOPP concentration and lower SOD activity.

Conclusions

SOD2 allelic variations were associated with the incidence and the progression of diabetic nephropathy, with a faster decline in eGFR and with plasma AOPP concentration and SOD activity in subjects with type 1 diabetes. These results are consistent with a role for SOD2 in the protection against oxidative stress and kidney disease in type 1 diabetes.  相似文献   
467.

Background and Objectives

Blood-brain barrier (BBB) dysfunction is an integral feature of neurological disorders and involves the action of multiple proinflammatory cytokines on the microvascular endothelial cells lining cerebral capillaries. There is still however, considerable ambiguity throughout the scientific literature regarding the mechanistic role(s) of cytokines in this context, thereby warranting a comprehensive in vitro investigation into how different cytokines may cause dysregulation of adherens and tight junctions leading to BBB permeabilization.

Methods

The present study employs human brain microvascular endothelial cells (HBMvECs) to compare/contrast the effects of TNF-α and IL-6 on BBB characteristics ranging from the expression of interendothelial junction proteins (VE-cadherin, occludin and claudin-5) to endothelial monolayer permeability. The contribution of cytokine-induced NADPH oxidase activation to altered barrier phenotype was also investigated.

Results

In response to treatment with either TNF-α or IL-6 (0–100 ng/ml, 0–24 hrs), our studies consistently demonstrated significant dose- and time-dependent decreases in the expression of all interendothelial junction proteins examined, in parallel with dose- and time-dependent increases in ROS generation and HBMvEC permeability. Increased expression and co-association of gp91 and p47, pivotal NADPH oxidase subunits, was also observed in response to either cytokine. Finally, cytokine-dependent effects on junctional protein expression, ROS generation and endothelial permeability could all be attenuated to a comparable extent using a range of antioxidant strategies, which included ROS depleting agents (superoxide dismutase, catalase, N-acetylcysteine, apocynin) and targeted NADPH oxidase blockade (gp91 and p47 siRNA, NSC23766).

Conclusion

A timely and wide-ranging investigation comparing the permeabilizing actions of TNF-α and IL-6 in HBMvECs is presented, in which we demonstrate how either cytokine can similarly downregulate the expression of interendothelial adherens and tight junction proteins leading to elevation of paracellular permeability. The cytokine-dependent activation of NADPH oxidase leading to ROS generation was also confirmed to be responsible in-part for these events.  相似文献   
468.
469.
470.

Background  

Adherence to therapies is a primary determinant of treatment success, yet the World Health Organisation estimate that only 50% of patients who suffer from chronic diseases adhere to treatment recommendations. In a previous project, we found that 30% of stroke patients reported sub-optimal medication adherence, and this was associated with younger age, greater cognitive impairment, lower perceptions of medication benefits and higher specific concerns about medication. We now wish to pilot a brief intervention aimed at (a) helping patients establish a better medication-taking routine, and (b) eliciting and modifying any erroneous beliefs regarding their medication and their stroke.  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