全文获取类型
收费全文 | 3012篇 |
免费 | 311篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 37篇 |
儿科学 | 106篇 |
妇产科学 | 85篇 |
基础医学 | 339篇 |
口腔科学 | 51篇 |
临床医学 | 324篇 |
内科学 | 715篇 |
皮肤病学 | 23篇 |
神经病学 | 505篇 |
特种医学 | 41篇 |
外科学 | 186篇 |
综合类 | 210篇 |
预防医学 | 297篇 |
眼科学 | 54篇 |
药学 | 237篇 |
6篇 | |
中国医学 | 57篇 |
肿瘤学 | 89篇 |
出版年
2024年 | 13篇 |
2023年 | 92篇 |
2022年 | 111篇 |
2021年 | 185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 | 33篇 |
1996年 | 32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 | 28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3362条查询结果,搜索用时 218 毫秒
1.
2.
《Sleep medicine》2020
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
3.
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
4.
5.
6.
《Sleep medicine》2020
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
7.
Summary Methods in current practice for ascertaining time of death are largely based on the cooling of the body after death and are
somewhat unreliable. A theoretica relationship is known to exist between the decline in the properties defining nerve conduction
and time after death caused by the gradual cessation of metabolic activity in nerves. A number of such properties were measured
in rats during life and after death. In most cases the relationship was found to be inconsistent. The chronaxie of the strength
duration curve for the sciatic nerve was, however, found to increase consistently and reproducibly in a linear fashion over
the first 90 min after death to a plateau value which was maintained beyond 135 min. These findings are discussed as the possible
basis of a forensic method of determining the duration of the “post mortem interval” within the first few hours after death.
相似文献
8.
Do weekly and fast-rotating shiftwork schedules differentially affect duration and quality of sleep?
F. M. Fischer Antonio Castro Bruni Adelaide Berwerth Claudia Roberta Castro Moreno Rosaneli Lima Fernandez Claudia Riviello 《International archives of occupational and environmental health》1997,69(5):354-360
Characteristics of shiftwork schedules can have distinct impacts on workers’ sleep. This report presents comparisons of the
effects of two different shiftwork schedules on duration and quality of the main sleep episodes in comparable worker populations
at two different petrochemical plants. No significant differences were found for sleep duration in comparing the two plants.
However, within each plant’s shift cycles, morning and night shifts showed shorter sleep durations than all other workdays
and days off. Quality of sleep was perceived as lowest for night shifts of both plant schedules, and of lesser quality for
weekly than for fast-rotating shifts. These results support recommendations for reducing the number of consecutive nights
of shiftwork. However, before recommending any optimal shift schedule, interactions of sleep duration and quality with shift
schedules need much further evaluation.
Received: 18 December 1995/Accepted: 18 July 1996 相似文献
9.
Christina A. Burbeck 《Vision research》1992,32(12):2295-2302
Previous research has shown that separation discrimination thresholds are independent of the internal spatial scale (local spatial frequency) of the targets whose separation is being judged. The experiments reported here tested the generality of this conclusion for separation discrimination of targets that were embedded in an array of identical objects, where crowding could enhance the importance of the scale at which the individual target locations are encoded. No effect of the local spatial scale of the targets was found under these conditions. 相似文献
10.
The Na+–Ca2+ exchange (NCX) system plays a pivotal role in regulating intracellular Ca2+ concentration in cardiomyocytes, neuronal cells, kidney and a variety of other cells. It performs a particularly important function in regulating cardiac contractility and electrical activity. One of the leading NCX inhibitors is KB‐R9743 (KBR) that appears to exhibit selectivity for Ca2+‐influx‐mode NCX activity (reverse mode of NCX). In this article we reviewed pharmacology of KBR and provide a brief summary of studies with other NCX inhibitors, such as SEA0400 (SEA) and SN‐6 (SN). Potential clinical usefulness of KBR and other NCX inhibitors is still controversial but the reviewed findings may be helpful in designing more selective and clinically useful NCX inhibitors for the treatment of cardiac, neuronal and kidney diseases. 相似文献