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   2957篇
  免费   312篇
  国内免费   37篇
耳鼻咽喉   37篇
儿科学   104篇
妇产科学   85篇
基础医学   337篇
口腔科学   51篇
临床医学   321篇
内科学   702篇
皮肤病学   23篇
神经病学   494篇
特种医学   41篇
外科学   183篇
综合类   208篇
预防医学   281篇
眼科学   54篇
药学   235篇
  6篇
中国医学   56篇
肿瘤学   88篇
  2024年   8篇
  2023年   92篇
  2022年   82篇
  2021年   170篇
  2020年   188篇
  2019年   119篇
  2018年   125篇
  2017年   141篇
  2016年   122篇
  2015年   99篇
  2014年   206篇
  2013年   210篇
  2012年   110篇
  2011年   134篇
  2010年   135篇
  2009年   123篇
  2008年   137篇
  2007年   109篇
  2006年   124篇
  2005年   91篇
  2004年   74篇
  2003年   66篇
  2002年   74篇
  2001年   51篇
  2000年   41篇
  1999年   49篇
  1998年   31篇
  1997年   29篇
  1996年   30篇
  1995年   22篇
  1994年   22篇
  1993年   20篇
  1992年   33篇
  1991年   21篇
  1990年   17篇
  1989年   18篇
  1988年   16篇
  1987年   14篇
  1986年   14篇
  1985年   27篇
  1984年   26篇
  1983年   10篇
  1982年   16篇
  1981年   13篇
  1980年   12篇
  1979年   7篇
  1978年   4篇
  1977年   5篇
  1975年   5篇
  1974年   5篇
排序方式: 共有3306条查询结果,搜索用时 78 毫秒
11.
ObjectivesTo explore the relationships among potentially modifiable factors related to childbirth and effective breastfeeding initiation at approximately 36 hours after birth and duration and exclusivity at hospital discharge, 2 weeks, 2 months, and 6 months after birth in primiparous women and to explore whether modifiable and nonmodifiable secondary factors and covariates influenced the relationships among factors related to childbirth and these breastfeeding outcomes.DesignA prospective, longitudinal, cohort study.SettingThe postpartum units of two general hospitals in eastern Canada.ParticipantsNinety-seven mother–infant dyads.MethodsWe recorded demographic, childbirth, obstetric history, and breastfeeding data through chart review. A breastfeeding observation was completed at approximately 36 hours after birth by unit nurses. Participants maintained breastfeeding logs in hospital and for 6 months after birth and completed three self-report questionnaires before discharge. We analyzed outcomes using backward stepwise linear and logistic regression.ResultsOne childbirth factor, labor induced with oxytocin, was negatively associated with effective initiation of breastfeeding, and none was related to breastfeeding duration and exclusivity at any time point. Maternal weight; professional support; and newborn’s gestational age at birth, 5-minute Apgar score, weight loss, LATCH score, and active feeds (newborn actively suckled at the breast) were significantly associated with breastfeeding outcomes.ConclusionInduction of labor with oxytocin should be used judiciously; when used, nurses must be hypervigilant to assess the mother–infant dyad for breastfeeding issues and to intervene to prevent or remediate them.  相似文献   
12.
ObjectiveTo investigate the prevalence and main factors associated with short and long sleep duration and excessive daytime sleepiness in Brazilian adolescents.MethodsThis was a cross-sectional study of 11.525 students of both genders, aged 14–17 years, from the public high-school system. Sleep duration was assessed by self-report and <8 h of sleep per day was considered short sleep and >10 h, long sleep. Socio-demographic and behavioral factors were investigated through a purpose-built questionnaire and daytime somnolence was assessed by the Epworth sleepiness scale (ESS).ResultsThe overall prevalence of short and long sleep was 54.7% and 3.3%, respectively. Frequency of short sleep was lowest in the afternoon shift (38.2%) and highest in the morning shift (62.9%) and full-day students (70.0%). Insufficient sleep was more frequent in working (63.0%) than non-working adolescents (53.1%; p = 0.001) and among those who used their cell phone before bedtime (56.3%) compared to non-users (49.7%, p = 0.001). On average, ESS score was higher in subjects with short and long sleep (respectively, 9.7 ± 4.4 and 10.0 ± 4.5) compared to those with normal sleep duration (8.9 ± 4.2; p = 0.001).ConclusionInsufficient sleep and excessive daytime sleepiness are very common among urban high-school Brazilian adolescents. Full day and morning school shifts are associated with short sleep and daytime somnolence, suggesting later start times may have a role in reducing sleep loss in these subjects. Older age, work activity, and cell phone use before bedtime, are also risk factors for of short sleep in adolescents. Although less common, long sleep can also be associated with excessive daytime sleepiness.  相似文献   
13.
BackgroundTo date, no previous studies have evaluated the relationship between sleep duration and quality of life (QOL) or depression in the general population after controlling for daytime sleepiness and sleep disturbances.MethodsA web-based cross-sectional survey was conducted with 8698 subjects aged 20–69 years. We examined the relationships between weekday sleep duration and daytime sleepiness, sleep disturbance, QOL and depression, using the Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index (without the item for sleep duration), 8-item Short Form and Center for Epidemiological Studies Depression Scale (CES-D).ResultsDaytime sleepiness tended to increase in proportion to shorter weekday sleep durations. Sleep disturbances, physical and mental QOL, and CES-D scores were worse in both the shorter and longer sleep groups compared with the group with 7–8 h of sleep. Hierarchical logistic regression analyses revealed that short sleep duration but not long sleep duration was significantly associated with reduction of both physical and mental QOL, even after controlling for the presence of daytime sleepiness and sleep disturbance. Both short and long sleep duration were independently and significantly correlated with depression after controlling for daytime sleepiness; however, there was no statistically significant association after adjusting for the effects of sleep disturbance.ConclusionsThe results suggested adverse effects of short sleep but not long sleep on both physical and mental QOL. In addition, the negative impact of specific types of sleep disturbance on depression may be greater than the impact of shortening of sleep duration.  相似文献   
14.
ObjectivesTo examine the cross-sectional relationship between sleep duration and 11 chronic diseases (risk of obesity, depression, diabetes, asthma, COPD, arthritis, kidney, CHD, stroke, and cancer [excluding skin cancer]) by using data from Behavioral Risk Factor Surveillance System.MethodsUsing data from the 2013, 2014 and 2016 Behavioral Risk Factor Surveillance System, a total sample consisted of 1,191,768 participants. Logistic regression models were constructed to calculate OR and 95% confidence intervals (CI) for the association between sleep duration and 11 chronic diseases. In addition, we also conducted subgroup analysis based on age and gender.ResultsIn multi-adjusted model, the positive association between extremely short or long sleep duration and risk of chronic diseases was significant (P < 0.05) with the exception of skin cancer (P = 0.14 and P = 0.43). There are stronger association between extremely short or long sleep duration and obesity, diabetes, asthma, chronic obstructive pulmonary disease, arthritis, kidney, coronary heart disease, stroke, and cancer in women and aged 18–64 years old.ConclusionsOur results indicated a higher risk of common chronic diseases due to short or long sleep duration in women and aged 18–64 years. Further studies are needed to demonstrate these association.  相似文献   
15.
ObjectiveThis systematic review and meta-analysis evaluated the influence of sleep duration or impairment (poor sleep quality, snoring, and obstructive sleep apnea [OSA]) on gestational diabetes mellitus (GDM) risk.MethodsPubMed, Embase, EBSCO, and WOS databases were searched up to March 4th, 2019. Cohort studies were included and relative risk (RR) with 95% confidence interval (CI) were used as the measure of effects. Heterogeneity was assessed by the Chi-squared and I2 tests. Subgroup analyses, sensitivity analysis, and dose-response analysis were performed. The overall quality of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.ResultsA total of 16 studies with 2,551,017 pregnant women and 142,103 GDM cases were included in this study. Both short and long sleep duration were associated with increased risk of GDM. There was a U-shaped relationship between sleep duration and GDM risk (P-nonlinearity < 0.001), and pregnant women with 8 h of sleep presented lower GDM risk. Poor sleep quality, snoring and OSA also increased the subsequent risk of GDM.ConclusionsPregnant women should be made aware of the benefits of proper sleep, and those with poor sleep quality, snoring, and OSA should be screened for GDM.  相似文献   
16.
ObjectivesPrior evidence suggests that sleep duration and sleep difficulties may be associated with cognitive function in old age, but little is known about the sleep–cognition association in late mid-life. Our aim was to examine the associations of accelerometer-based sleep duration as well as subjective sleep difficulties with different domains of cognitive function among aging workers.MethodsThe study population consisted of 289 participants (mean age 62.4 years, SD 1.02; 83% women) from the Finnish Retirement and Aging Study (FIREA). Sleep difficulties were measured using Jenkins Sleep Problem Scale (difficulties falling asleep, difficulties maintaining sleep, waking up too early in the morning, and nonrestorative sleep). Sleep duration was measured with wrist-worn accelerometer and self-report, and participants were divided into short (<7 h/night), mid-range (7–9 h/night) and long (≥9 h/night) sleepers. Participants underwent extensive cognitive testing covering three domains: (1) memory, (2) executive function, and (3) attention and information processing.ResultsGreater difficulties in waking up too early in the morning were associated with poorer executive function measured with Spatial Working Memory (SWM) test (p = 0.005). Additionally, nonrestorative sleep was associated with poorer executive function measured with Trail Making Test, B–A, (p = 0.036) and borderline significantly with lower SWM (p = 0.056). Compared to mid-range sleepers, long sleepers tended to have poorer cognitive function (all memory function tests and SWM), but the associations were not statistically significant due to small number of long sleepers.ConclusionsSubjective sleep difficulties may be linked to poorer executive function in a relatively healthy population of older workers in their 60 s. Thus, promoting good sleep quality may translate into better cognitive health in late mid-life.  相似文献   
17.
18.
19.
《The Journal of arthroplasty》2022,37(12):2387-2393
BackgroundOperative time is related to complications in primary total hip arthroplasty (THA). This study compared operative time in direct anterior (DA) and posterior approach THA and whether differences were related to increased hospital readmissions within 90 days of discharge.MethodsProspectively documented data on 3,152 consecutively performed THAs by 16 surgeons at a large Midwestern United States academic healthcare system were retrospectively reviewed. All surgeons were beyond their learning curve. Cases characterized by factors extending operative time were excluded. A total of 1,235 analysis cases were performed with the DA approach and 1,608 with the posterior approach. DA patients had lower mean body mass index (P < .001), were more likely to be classified as American Society of Anesthesiologists Physical Status 1 or 2 (P < .001), and more likely to have surgery in an ambulatory setting (P < .001).ResultsTime under anesthesia was significantly longer for DA procedures by 19 to 27 minutes in hospital and ambulatory settings, respectively (P < .001). Increasing body mass index had a greater impact on anesthesia time for DA patients (P = .020). There were no differences in nontraumatic readmissions within 90 days of surgery based on surgical approach (P ≥ .480); however, significantly more DA patients classified as ASA-PS 3 or 4 were readmitted compared to those classified as ASA-PS 1 or 2 (P < .001), a difference not observed for posterior approach patients.ConclusionAnesthesia time is a modifiable risk factor for patient safety and an important factor in healthcare resource utilization. Consideration of ways to reduce DA operative times is encouraged.  相似文献   
20.
《Clinical neurophysiology》2020,131(11):2641-2650
ObjectiveTo assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN).MethodsWe performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position.ResultsAll MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers.ConclusionsExcitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers.SignificanceExcitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.  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