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   16967篇
  免费   1358篇
  国内免费   286篇
耳鼻咽喉   31篇
儿科学   1651篇
妇产科学   1214篇
基础医学   1414篇
口腔科学   155篇
临床医学   1504篇
内科学   2049篇
皮肤病学   75篇
神经病学   904篇
特种医学   274篇
外科学   1162篇
综合类   1811篇
一般理论   1篇
预防医学   3634篇
眼科学   117篇
药学   1793篇
  6篇
中国医学   454篇
肿瘤学   362篇
  2023年   294篇
  2022年   355篇
  2021年   683篇
  2020年   578篇
  2019年   669篇
  2018年   581篇
  2017年   661篇
  2016年   622篇
  2015年   623篇
  2014年   1120篇
  2013年   1473篇
  2012年   987篇
  2011年   1098篇
  2010年   886篇
  2009年   806篇
  2008年   892篇
  2007年   804篇
  2006年   656篇
  2005年   616篇
  2004年   500篇
  2003年   451篇
  2002年   346篇
  2001年   303篇
  2000年   261篇
  1999年   202篇
  1998年   166篇
  1997年   137篇
  1996年   122篇
  1995年   123篇
  1994年   135篇
  1993年   107篇
  1992年   107篇
  1991年   93篇
  1990年   86篇
  1989年   62篇
  1988年   66篇
  1987年   62篇
  1986年   64篇
  1985年   120篇
  1984年   112篇
  1983年   85篇
  1982年   79篇
  1981年   66篇
  1980年   68篇
  1979年   60篇
  1978年   50篇
  1977年   28篇
  1976年   38篇
  1975年   21篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
BackgroundWhile studies have demonstrated favorable outcomes in utilization of primary total shoulder arthroplasty (TSA) for the treatment of glenohumeral osteoarthritis (OA), adverse events such as infections can still occur. Periprosthetic joint infections (PJIs) are associated with worse outcomes and patient morbidity. The purpose of this study was to: (1) compare patient demographics amongst TSA patients with and without PJIs following primary TSA; and (2) identify patient-related risk factors for PJIs following primary TSA.MethodsPatients undergoing primary TSA for the treatment of glenohumeral OA were identified using the Mariner administrative claims database by CPT code 23,472. Laterality modifiers were utilized to ensure PJIs were developing in the correct laterality as those patients undergoing primary TSA. Inclusion for the study group consisted of patients who developed PJIs within 2-years after the index procedure, whereas patients who did not develop PJIs served as the comparison cohort. Primary outcomes analyzed included patient demographics and patient-related risk factors for PJIs following primary TSA. A stepwise backwards elimination multivariate binomial logistic regression analyses was performed to determine the odds (OR) of PJIs in patients undergoing primary TSA. A P value less than .05 was considered statistically significant.ResultsThe query yielded 15,396 patients who underwent primary TSA for glenohumeral OA, of which 191 patients developed PJIs and 15,205 did not develop PJIs. The study found statistically significant differences amongst patients who did and did not develop PJIs following primary TSA with respect to age, sex, and presence of comorbid conditions. Risk factors associated with developing PJIs following primary TSA included: pathologic weight loss (OR: 2.06, P < .0001), obesity (OR: 1.56, P = .0001), male sex (OR: 1.52, P = .007), and peripheral vascular disease (OR: 1.46, P = .022).ConclusionAs the number of primary TSAs for the treatment of glenohumeral OA increase worldwide, identifying modifiable risk-factors to reduce the incidence of infection is critical. The study found various modifiable and non-modifiable risk factors associated with developing PJIs following primary TSA. This study is valuable to orthopedists in order to identify and risk-stratify patients with regard to PJI in the setting of primary TSA for OA.Level of EvidenceLevel III; Case-Control Study  相似文献   
3.
BackgroundProsthetic choice for mitral valve replacement is generally driven by patient age and patient and surgeon preference, and current guidelines do not discriminate between different etiologies of mitral valve disease. Our objective was to assess and compare short- and long-term outcomes after mitral valve replacement among patients with biological or mechanical prostheses in the setting of severe ischemic mitral regurgitation.MethodsBetween 2000 and 2016, 424 patients underwent mitral valve replacement for severe ischemic mitral regurgitation at our institution, using biological prosthesis in 188 (44%) and mechanical prosthesis in 236 (56%). A 1:1 propensity score match (n = 126 per group) and inverse probability of treatment weighting were used to compare groups. Short-term outcomes included in-hospital mortality and other cardiovascular adverse events. Long-term outcomes included survival and hospital readmission for cardiovascular causes, stroke, and major bleeding.ResultsIn-hospital mortality and early postoperative adverse events were similar between groups in the propensity score match and inverse probability of treatment weighting cohorts. Overall long-term survival was similar at 5 and 9 years, but mechanical prosthesis recipients were more frequently readmitted to hospital for cardiovascular causes, including stroke and non-neurological bleeding in propensity score matching and inverse probability of treatment weighting analyses (all P values < .004). Type of prosthesis did not independently influence all-cause mortality (hazard ratio, 1.01; 95% confidence interval, 0.71-1.43; P = .959), but placement of a mechanical prosthesis was associated with increased risk of readmission for cardiovascular events (hazard ratio, 1.65; 95% confidence interval, 1.17-2.32; P = .004) among matched patients.ConclusionsThe type of prosthesis has no influence on long-term survival among patients with severe ischemic mitral regurgitation undergoing mitral valve replacement. There may be an increased risk of neurologic events and serious bleeding associated with mechanical prostheses.  相似文献   
4.
ObjectiveThis study aimed to systematically review the current literature on the economic costs of micro preemie as well as evidence on the cost-effectiveness of interventions to improve outcomes for micro preemie babies with a birth weight of ≤500 g.MethodWe searched MEDLINE, CINAHL, Scopus, ECONLIT, Business Source Premier and Cochrane Library for studies reporting costs of micro preemie from January 2000. Costs were inflated to 2019 United States dollars (US$). All full-text articles were assessed for eligibility and a quality assessment of included articles was conducted using the Drummond and the Larg and Moss checklists.ResultsThe search identified three studies that met the inclusion criteria; two cost-of-illness studies and one cost-effectiveness study. Across studies, the mean healthcare spending per micro preemie survivor (in 2019 US$) ranged from US$61,310 (birth admission) to US$263,958 (inpatient and outpatient for the first six months of life). One modelling study reported exclusive human milk diet for micro preemies at birth was more cost-effective compared to the standard approach with cow milk diet from the third-party payer and societal perspectives.ConclusionDespite significant advances in perinatal care and expanded access to life-saving equipment to improve survival outcomes of micro preemie, there remains a paucity of research on economic costs associated with these babies. No study has utilised quality-adjusted life-years as an outcome measure. Given the chronic conditions and long-term neurologic disability associated with micro preemie survivors, an estimate of the lifetime cost to the individual, healthcare providers and society would provide a benchmark of the potential cost-savings that could accrue from cost-effective interventions to improve the survival rate of micro preemies.  相似文献   
5.
Child benefits are typically paid from birth. This paper asks whether starting universal child benefits in pregnancy leads to improvements in infant health. Leveraging administrative birth registry and hospital microdata from England and Wales, I study the effects of the Health in Pregnancy Grant, a universal conditional cash transfer equivalent to three months of child benefit (190 GBP) as a lump sum to pregnant mothers from 2009 to 2011. I exploit quasi-experimental variation in eligibility with a regression discontinuity design in the date of birth of the baby. I find that the policy increased birth weight by 8–12 grams on average, reduced low birth weight (<2500 g) by 3-6 percent and decreased prematurity by 9–11 percent. Younger mothers, particularly those living in deprived areas, benefit the most. I present evidence that the mechanisms are unlikely to be antenatal care, nutrition or smoking, with reductions in stress remaining a possible explanation.  相似文献   
6.
The present study investigated whether associations between greenness and birth outcomes can be detected in children belonging to a Swedish birth cohort (BAMSE). Normalized difference vegetation index (NDVI) within a 500 m buffer zone around maternal address was used as estimate of greenness. Ordinary least squares and quantile regression models were performed to investigate associations between neighbourhood NDVI and birthweight (n = 2619), birth length (n = 2490) and head circumference (n = 2243). Logistic regression analyses were used to detect the association between NDVI and odds of being born as “small-” or “large-for-gestational-age”. There were no clear associations between NDVI and birth weight in the total sample. However, in a suburban sub-sample, increased NDVI levels were significantly associated with elevated birthweight of small new-borns (β2nd percentile = 276 g, 95% CI 61 to 492, p = 0.012), and significantly reduced the odds ratio (OR) for children being born as small-for-gestational-age (OR = 0.31 95% CI 0.1 to 1, p = 0.049). No significant associations were found between NDVI and birth length or head circumference. In conclusion, neighbourhood greenness appears not to be associated with birthweight as such, but rather decrease the odds of being born underweight, in particular in suburban areas.  相似文献   
7.
BackgroundPrenatal exposure to perfluoroalkyl substances (PFASs) has been associated with impaired immune and respiratory health during childhood but the evidence is inconsistent and limited for lung function. We studied the association between prenatal PFASs exposure and immune and respiratory health, including lung function, up to age 7 years in the Spanish INMA birth cohort study.MethodsWe assessed four PFASs in maternal plasma samples collected during the 1st trimester of pregnancy (years: 2003–2008): perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorononanoate (PFNA). Mothers reported the occurrence (yes/no) of lower respiratory tract infections, wheezing, asthma, and eczema in the previous 12 months at 1.5 and 4 years of the child (n = 1188) and at 7 years (n = 1071). At ages 4 (n = 503) and 7 (n = 992) years lung function was assessed using spirometry tests.ResultsThe most abundant PFASs were PFOS and PFOA (geometric means: 5.80 and 2.31 ng/mL, respectively). The relative risk of asthma during childhood per each doubling in PFNA concentration was 0.74 (95 CI%: 0.57, 0.96). The relative risk of eczema during childhood per every doubling in PFOS concentration was 0.86 (95 CI%: 0.75, 0.98). Higher PFOA concentrations were associated with lower forced vital capacity and lower forced expiratory volume in 1 s z-scores at 4 years [β (95 CI %): −0.17 (−0.34, −0.01) and −0.13 (−0.29, 0.03), respectively], but not at 7 years.ConclusionThis longitudinal study suggests that different PFASs may affect the developing immune and respiratory systems differently. Prenatal exposure to PFNA and PFOS may be associated with reduced risk of respiratory and immune outcomes, particularly asthma and eczema whereas exposure to PFOA may be associated with reduced lung function in young children. These mixed results need to be replicated in follow-up studies at later ages.  相似文献   
8.
Randomized controlled trials, being published in English and investigating the associations of at least 4 weeks intervention of citrus and/or its extracts on weight loss among adults, were searched from PubMed, Web of Science, Scopus, and Cochrane by June 2019 to conduct a meta‐analysis. Thirteen articles, including 921 participants, were selected and evaluated by modified Jadad scale. Pooled results by the random‐effects model showed that citrus and/or its extracts administration significantly reduced 1.280 kg body weight (95% CI: ?1.818 to ?0.741, p = 0.000, I2 = 81.4%), 0.322 kg/m2 BMI (95% CI: ?0.599 to ?0.046, p = 0.022, I2 = 87.0%), 2.185 cm WC (95% CI: ?3.804 to ?0.566, p = 0.008, I2 = 98.3%), and 2.137 cm HC (95% CI: ?3.775 to ?0.500, p = 0.011, I2 = 96.2%), respectively, but no significantly decreased effects on WHR and body fat were observed. Subgroup analysis deduced the different effects of study location, intervention duration on body weight associated indices. No publication bias was observed. Our meta‐analysis supported the beneficial effects of citrus and/or its extracts supplement on body weight control, and future well‐designed studies are required to firmly establish the clinical efficacy of citrus and/or its extracts intervention on body weight.  相似文献   
9.
目的:研究苓桂术甘汤中多糖的结构,包括单糖组成以及官能团检测,并对其抗氧化能力进行评估,为体外生物测定法运用于苓桂术甘汤的质量评价提供基础。方法:利用高效凝胶色谱对全方多糖分子量进行研究;进一步采用气相色谱-质谱(GC-MS)柱前衍生化法及红外光谱扫描分析全方多糖结构组成;采用1,1-二苯基-2-三硝基苯肼(DPPH)及羟基自由基测定全方粗多糖及精多糖的抗氧化能力。结果:全方多糖由单一峰组成,且相对分子质量为3 689 Da,主要由阿拉伯糖、甘露糖、葡萄糖、半乳糖、果糖组成,摩尔比为6. 85∶1. 00∶109. 21∶1. 04∶21. 82,其中葡萄糖和果糖为主要组成成分;红外结果显示聚糖结构中存在吡喃糖及糖醛酸,并且糖苷键存在2种立体异构(α-糖苷键及β-糖苷键);抗氧化研究发现全方多糖有一定清除DPPH自由基及羟基自由基的能力,粗多糖的活性优于精多糖。进一步采用LC-Q-TOF-MS对粗多糖中的其他成分进行定性分析,提示这与甘草中五环三萜类成分的吸附有关。结论:苓桂术甘汤中多糖及五环三萜类物质均是苓桂术甘汤抗氧化作用的物质基础,利用体外生物测定法测定抗氧化活性可作为全面控制苓桂术甘汤质量的评价指标。  相似文献   
10.
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