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   2374篇
  免费   252篇
  国内免费   3篇
耳鼻咽喉   30篇
儿科学   75篇
妇产科学   47篇
基础医学   333篇
口腔科学   21篇
临床医学   308篇
内科学   504篇
皮肤病学   64篇
神经病学   251篇
特种医学   37篇
外科学   206篇
综合类   31篇
一般理论   1篇
预防医学   335篇
眼科学   48篇
药学   139篇
中国医学   6篇
肿瘤学   193篇
  2024年   10篇
  2023年   66篇
  2022年   71篇
  2021年   116篇
  2020年   107篇
  2019年   130篇
  2018年   121篇
  2017年   93篇
  2016年   91篇
  2015年   82篇
  2014年   108篇
  2013年   141篇
  2012年   207篇
  2011年   209篇
  2010年   108篇
  2009年   117篇
  2008年   163篇
  2007年   138篇
  2006年   129篇
  2005年   99篇
  2004年   94篇
  2003年   79篇
  2002年   68篇
  2001年   15篇
  2000年   6篇
  1999年   10篇
  1998年   6篇
  1997年   6篇
  1996年   6篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   3篇
  1990年   5篇
  1989年   1篇
  1988年   3篇
  1987年   2篇
  1984年   1篇
  1983年   1篇
  1982年   3篇
  1979年   1篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
  1970年   1篇
  1969年   1篇
  1965年   1篇
  1828年   1篇
排序方式: 共有2629条查询结果,搜索用时 11 毫秒
11.
OBJECTIVE: Community-based lifestyle intervention may offer the best means of reducing the global epidemic of childhood obesity and its consequences, yet few successful interventions have been reported. The objective was to determine whether increasing extra-curricular levels of activity could reduce weight gain in children. METHODS: A controlled intervention study was conducted using standardised methods to assess outcomes. Two comparable relatively rural communities in Otago, New Zealand formed intervention and control settings. Height, weight, waist circumference and participation in physical activity (by accelerometry) were measured at baseline and at 1 year in 384 children aged 5 to 12 years representing the majority of children in this age group in intervention and control communities. Community Activity Co-ordinators were employed at each school in the intervention area. Their brief was to widen exposure to activity and engage children not interested in traditional sporting activities by encouraging lifestyle-based activities (e.g. walking) and non-traditional sports (e.g. golf and taekwondo) during extra-curricular time at school, after school and during vacations. Simple dietary advice was offered and the wider community was encouraged to participate. RESULTS: Average accelerometry counts at 1 year were 28% (95% CI: 11 to 47%) higher in intervention compared with control children after adjusting for age, sex, baseline values and school. Intervention children spent less time in sedentary activity (ratio 0.91, p = 0.007) and more time in moderate (1.07, p = 0.001) and moderate/vigorous (1.10, p = 0.01) activity. Adjusted mean BMI Z-score was lower in intervention relative to control children by -0.12 units (95% CI: -0.22 to -0.02). CONCLUSION:. An intervention designed to maximise opportunities for physical activity during extra-curricular time at school and during leisure time through the provision of community-based Activity Co-ordinators significantly increased participation in physical activity and slowed unhealthy weight gain in primary school-aged children.  相似文献   
12.
Background: Five of the most abundant human milk oligosaccharides (HMOs) in human milk are 2′-fucosyllactose (2′-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), 3′-sialyllactose (3′-SL) and 6′-sialyllactose (6′-SL). Methods: A randomized, double-blind, controlled parallel feeding trial evaluated growth in healthy term infants fed a control milk-based formula (CF; n = 129), experimental milk-based formula (EF; n = 130) containing five HMOs (5.75 g/L; 2′-FL, 3-FL, LNT, 3′-SL and 6′-SL) or human milk (HM; n = 104). Results: No significant differences (all p ≥ 0.337, protocol evaluable cohort) were observed among the three groups for weight gain per day from 14 to 119 days (D) of age, irrespective of COVID-19 or combined non-COVID-19 and COVID-19 periods. There were no differences (p ≥ 0.05) among the three groups for gains in weight and length from D14 to D119. Compared to the CF group, the EF group had more stools that were soft, frequent and yellow and were similar to the HM group. Serious and non-serious adverse events were not different among groups, but more CF-fed infants were seen by health care professionals for illness from study entry to D56 (p = 0.044) and D84 (p = 0.028) compared to EF-fed infants. Conclusions: The study demonstrated that the EF containing five HMOs supported normal growth, gastrointestinal (GI) tolerance and safe use in healthy term infants.  相似文献   
13.
Corrosion of medical implants is a possible failure mode via induced local inflammatory effects, systemic deposition and corrosion related mechanical failure. Cyclic potentiodynamic polarisation (CPP) testing was utilized to evaluate the effect of increased porosity (60% and 80%) and decreased wall thickness in gyroid lattice structures on the electrochemical behaviour of LPBF Ti6Al4V structures. The use of CPP allowed for the landmarks of breakdown potential, resting potential and vertex potential to be analysed, as well as facilitating the construction of Tafel plots and qualitative Goldberg analysis. The results indicated that 60% gyroid samples were most susceptible to the onset of pitting corrosion when compared to 80% gyroid and solid samples. This was shown through decreased breakdown and vertex potentials and were found to correlate to increased lattice surface area to void volume ratio. Tafel plots indicated that despite the earlier onset of pitting corrosion, both gyroid test groups displayed lower rates of corrosion per year, indicating a lower severity of corrosion. This study highlighted inherent tradeoffs between lattice optimisation and corrosion behaviour with a potential parabolic link between void volume, surface area and corrosion being identified. This potential link is supported by 60% gyroid samples having the lowest breakdown potentials, but investigation into other porosity ranges is suggested to support the hypothesis. All 3D printed materials studied here showed breakdown potentials higher than ASTM F2129′s suggestion of 800 mV for evaluation within the physiological environment, indicating that under static conditions pitting and crevice corrosion should not initiate within the body.  相似文献   
14.
BACKGROUND: Preterm birth (PTB) is the major determinant of perinatal morbidity and mortality. Infection is implicated in a large proportion of preterm deliveries, but there is no consensus regarding the efficacy of antibiotic prophylaxis for women at risk. AIM: To determine whether antibiotic treatment reduces the risk of preterm delivery in asymptomatic pregnant women at risk of PTB. METHOD: Relevant publications were identified via electronic searches of MEDLINE (1966 to August 2005), The Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Central Register of Controlled Trials (the Cochrane Library, Issue 3, 2005) and PubMed using multiple search terms related to PTB and antibiotics. Publications were limited to randomised controlled trials comparing antibiotics with placebo given to asymptomatic non-labouring women. A random effect model was used, and combined risk ratios calculated for the various risk groups. Associations between treatment effect and the rate of PTB were analysed by meta-regression. RESULTS: Seventeen trials were included, 12 identifying women at risk by abnormal vaginal flora, three on women at high risk from a previous PTB and two recruiting women based on positive fetal fibronectin status. There was no significant association between antibiotic treatment and reduction in PTB irrespective of criteria used to assess risk, the antimicrobial agent administered, or gestational age at time of treatment (overall combined random effect for delivery at less than 37 weeks RR 1.03 (95% CI 0.86-1.24)). CONCLUSIONS: Treating women at risk of PTB with antibiotics does not reduce the risk of subsequent PTB.  相似文献   
15.
16.
Context/Objective: Provisions of the Affordable Care Act (ACA) potentially increase insurance options for Veterans with disabilities. We examined Veterans with spinal cord injuries and disorders (SCI/D) to assess whether the ACA was associated with changes in healthcare utilization from Department of Veterans Affairs (VA) healthcare facilities.Design: Using national VA data, we investigated impacts on VA healthcare utilization pre- (2012/13) and post-ACA (2014/15) implementation with negative binomial regression models.Setting: VA healthcare facilities.Participants: 8,591 VA users with SCI/D. Veterans with acute myelitis, Guillain-Barré syndrome, multiple sclerosis, or amyotrophic lateral sclerosis were excluded as were patients who died during the study period.Interventions: We assessed VA healthcare utilization before and after ACA implementation.Outcome Measures: Total numbers of VA visits for SCI/D care, diagnostic care, primary care, specialty care, and mental health care, and VA admissions.Results: The number of VA admissions was 7% higher in the post than pre-ACA implementation period (P < 0.01). The number of VA visits post-implementation increased for SCI/D care (8%; P < 0.01) and specialty care (12%; P < 0.001). Conversely, the number of mental health visits was 17% lower in the post-ACA period (P < 0.001). Veterans with SCI/D who live <5 miles from their nearest VA facility received VA care more frequently than those ≥40 miles from VA (P < 0.001).Conclusion: Counter to expectations, results suggest that Veterans with SCI/D sought more frequent VA care after ACA implementation, indicating Veterans with SCI/D continue to utilize the lifelong, comprehensive care provided at VA.  相似文献   
17.
18.
OBJECTIVE: Defects in glycosylation of alpha-dystroglycan are associated with several forms of muscular dystrophy, often characterized by congenital onset and severe structural brain involvement, collectively known as dystroglycanopathies. Six causative genes have been identified in these disorders including fukutin. Mutations in fukutin cause Fukuyama congenital muscular dystrophy. This is the second most common form of muscular dystrophy in Japan and is invariably associated with mental retardation and structural brain defects. The aim of this study was to determine the genetic defect in two white families with a dystroglycanopathy. METHODS: The six genes responsible for dystroglycanopathies were studied in three children with a severe reduction of alpha-dystroglycan in skeletal muscle. RESULTS: We identified pathogenic fukutin mutations in these two families. Affected children had normal intelligence and brain structure and shared a limb girdle muscular dystrophy (LGMD) phenotype, had marked elevation of serum creatine kinase, and were all ambulant with remarkable steroid responsiveness. INTERPRETATION: Our data suggest that fukutin mutations occur outside Japan and can be associated with much milder phenotypes than Fukuyama congenital muscular dystrophy. These findings significantly expand the spectrum of phenotypes associated with fukutin mutations to include this novel form of limb girdle muscular dystrophy that we propose to name LGMD2L.  相似文献   
19.
20.
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