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   22493篇
  免费   1861篇
  国内免费   596篇
耳鼻咽喉   1511篇
儿科学   752篇
妇产科学   154篇
基础医学   3486篇
口腔科学   539篇
临床医学   2274篇
内科学   4442篇
皮肤病学   80篇
神经病学   3854篇
特种医学   309篇
外科学   930篇
综合类   2721篇
现状与发展   1篇
预防医学   1040篇
眼科学   167篇
药学   1113篇
  6篇
中国医学   1056篇
肿瘤学   515篇
  2024年   71篇
  2023年   475篇
  2022年   750篇
  2021年   1239篇
  2020年   1254篇
  2019年   948篇
  2018年   903篇
  2017年   973篇
  2016年   900篇
  2015年   817篇
  2014年   1395篇
  2013年   1519篇
  2012年   1141篇
  2011年   1289篇
  2010年   1110篇
  2009年   1160篇
  2008年   1184篇
  2007年   1081篇
  2006年   890篇
  2005年   771篇
  2004年   621篇
  2003年   554篇
  2002年   481篇
  2001年   391篇
  2000年   352篇
  1999年   322篇
  1998年   290篇
  1997年   193篇
  1996年   146篇
  1995年   188篇
  1994年   134篇
  1993年   148篇
  1992年   139篇
  1991年   69篇
  1990年   71篇
  1989年   68篇
  1988年   66篇
  1987年   59篇
  1986年   60篇
  1985年   95篇
  1984年   94篇
  1983年   72篇
  1982年   87篇
  1981年   64篇
  1980年   79篇
  1979年   57篇
  1978年   50篇
  1977年   29篇
  1976年   23篇
  1975年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
张庆文 《上海医药》2012,(23):45-48
阿扎胞苷是一种新型表观遗传学抗肿瘤药,是目前唯一被临床证明可延长高风险骨髓增生异常综合征患者总生存期的抗肿瘤药。  相似文献   
92.
93.
宋超  王彦霞 《光明中医》2016,(10):1362-1363
目的探讨肺栓塞中医证型分析结果与西医分类关联。方法本次选取肺栓塞患者80例,均为我院呼吸内科2013年5月—2015年5月收治,依据西医分类划为3个组别,即A组:急性广泛型30例;B组:急性亚广泛型40例;C组:伴肺动脉高压型10例。并行中医辨证分型,分析与西医分类间的相关性。结果 80例中,气虚水停型6例,占7.5%;气虚血瘀型28例,占35%;痰浊阻肺型20例,占25%;阳气暴脱型26例,占30%。阳气暴脱型血糖高于其他证型,脉压低于其他证型(P0.05),其他组间比较无差异(P0.05)。气虚血瘀型C组占86.7%,痰浊阻肺B组占50%;阳气暴脱A组占72%,与同证型其他比较均有统计学差异(P0.05)。结论临床显性肺栓塞中,阳气暴脱、痰浊阻肺、气虚血瘀为主要证型,气虚血瘀型多见于慢性肺栓塞,痰浊阻肺型以急性亚广泛性肺栓塞为主,阳气暴脱型以急性广泛性肺栓塞为主,分析证型,可对肺栓塞的病程急缓、程度间接反映。  相似文献   
94.
ContextThe sleep-promoting activity of Nelumbo nucifera Gaertn. (Nymphaeaceae) alkaloids in leaves or seeds are well known. However, the sleep-promoting activity of the lotus rhizome (LE), which is used mainly as food, has not yet been evaluated.ObjectiveWe investigated the sleep-promoting activity of LE water extract.Materials and methodsInstitute of Cancer Research (ICR) mice (n = 8) were subject to a pentobarbital-induced sleep test to assess changes in sleep latency and duration following the administration of LE (80–150 mg/kg). In addition, electroencephalography analysis was performed to determine the sleep quality after LE treatment as well as the sleep recovery effect of LE using a caffeine-induced insomnia SD rat model. Real-time PCR and western blot analysis were performed to investigate the expression of neurotransmitter receptors, and the GABAA receptor antagonists were used for receptor binding analysis.ResultsAn oral administration of 150 mg/kg LE significantly increased sleep duration by 24% compared to the control. Furthermore, LE increased nonrapid eye movement (NREM) sleep by increasing theta and delta powers. In the insomnia model, LE increased sleep time by increasing NREM sleep. Moreover, treatment with picrotoxin and flumazenil decreased the sleep time by 33% and 23%, respectively, indicating an involvement of the GABAA receptor in the sleep-enhancing activity of LE. The expression of GABAA receptors and the concentration of GABA in the brain were increased by LE.Discussion and conclusionsThe results suggest that the sleep-promoting activity of LE was via the GABAA receptor. Collectively, these data show that LE may promote sleep.  相似文献   
95.
Study ObjectivesSleep abnormalities emerge early in dementia and may accelerate cognitive decline. Their accurate characterization may facilitate earlier clinical identification of dementia and allow for assessment of sleep intervention efficacy. This scoping review determines how sleep is currently measured and reported in Mild Cognitive Impairment (MCI) and early dementia, as a basis for future core outcome alignment.MethodsThis review follows the PRISMA Guidelines for Scoping Reviews. CINAHL, Embase, Medline, Psychinfo, and British Nursing Index databases were searched from inception—March 12, 2021. Included studies had participants diagnosed with MCI and early dementia and reported on sleep as a key objective/ outcome measure.ResultsNineteen thousand five hundred and ninety-six titles were returned following duplicate removal with 188 studies [N] included in final analysis. Sleep data was reported on 17 139 unique, diagnostically diverse participants (n). “Unspecified MCI” was the most common diagnosis amongst patients with MCI (n = 5003, 60.6%). Despite technological advances, sleep was measured most commonly by validated questionnaires (n = 12 586, N = 131). Fewer participants underwent polysomnography (PSG) (n = 3492, N = 88) and actigraphy (n = 3359, N = 38) with little adoption of non-PSG electroencephalograms (EEG) (n = 74, N = 3). Sleep outcome parameters were reported heterogeneously. 62/165 (37.6%) were described only once in the literature (33/60 (60%) in interventional studies). There was underrepresentation of circadian (n = 725, N = 25) and micro-architectural (n = 360, N = 12) sleep parameters.ConclusionsAlongside under-researched areas, there is a need for more detailed diagnostic characterization. Due to outcome heterogeneity, we advocate for international consensus on core sleep outcome parameters to support causal inference and comparison of therapeutic sleep interventions.  相似文献   
96.
Background and PurposeThe relationship between napping and cognition remains controversial. This study aimed to investigate the association between napping and cognition according to sleep debt in the Korean adult population.MethodsA population-based nationwide cross-sectional survey was conducted in 2018. A two-stage stratified random sample of Koreans aged ≥19 years was selected and evaluated using questionnaires by trained interviewers. Cognitive function was assessed using the Mail-In Cognitive Function Screening Instrument (MCFSI). Sleep habits on weekdays and weekends, napping, and subjective sleep requirements were assessed using the questionnaires. Accumulated sleep debt was calculated by subtracting the weekly average sleep duration from subjective sleep requirements. Sleep quality, daytime sleepiness, insomnia, depression, demographics, and comorbidities were assessed. Participants were grouped into those with sleep debt ≤60 min and those with sleep debt >60 min. Multiple linear regression was used to estimate the independent association between the factors and cognition.ResultsIn total, 2,501 participants were included in the analysis. Naps were reported in 726 (29.0%) participants (nappers). The mean MCFSI score was higher in nappers (3.4±3.6) than in non-nappers (2.3±3.0) (p<0.001). Multiple linear regression controlling for age, alcohol, smoking, depression, insomnia, daytime sleepiness, sleep quality, and education revealed that 30 to 60 min of napping was associated with worse cognitive function in participants with sleep debts ≤60 min, while >60 min of napping was associated with better cognitive function in participants with sleep debts >60 min.ConclusionsIn general, naps are associated with worse cognitive function in the Korean adult population. However, for those with sleep debt of >60 min, naps for >60 min were associated with better cognitive function.  相似文献   
97.
Current evidence on the effects of continuous positive airway pressure (CPAP) on cardiac mechanics in patients with obstructive sleep apnea (OSA) is based on a few single studies. The authors investigated this topic through a meta‐analysis of speckle tracking echocardiography (STE) studies that provided data on left ventricular (LV) and right ventricular (RV) mechanics as assessed by global longitudinal strain (GLS). The PubMed, OVID‐MEDLINE, and Cochrane library databases were systematically analyzed to search English‐language review papers published from inception to January 31, 2022. Studies were identified by crossing the following terms: “obstructive sleep apnea”, “sleep quality”, “sleep disordered breathing”, “continuous positive airway pressure therapy”, “noninvasive ventilation”, “left ventricular hypertrophy”, “systolic dysfunction”, “global longitudinal strain”, “left ventricular mechanics”, “right ventricular mechanics”, “echocardiography” and “STE echocardiography”. The meta‐analysis, including a total of 337 patients with OSA from nine studies (follow‐up 2–24 months) showed a significant GLS improvement in both LV and RV after CPAP, standard mean difference (SMD) being 0.51±0.08, CI:0.36–0.66, p = .0001 and 0.28±0.07, CI:0.15–0.42, p = .0001), respectively. Corresponding SMD values for LV ejection fraction (LVEF) and tricuspid annular plane systolic excursion (TAPSE) were 0.20±0.06, CI:0.08–0.33, p = .001 and 0.08±0.06, CI: ‐0.04/0.20, p = .21. Our meta‐analysis suggests that: I) CPAP treatment exerts beneficial effects on biventricular function in patients with OSA; II) the assessment of cardiac mechanics by STE should be routinely recommended for monitoring cardiac function in this setting, due to limitations of conventional echocardiography in evaluating biventricular performance.  相似文献   
98.
ObjectivesObstructive sleep apnea (OSA) is a common condition closely related to obesity, insulin resistance, dyslipidemia, and cardiovascular disease. The aim of this study was to explore the possible relationship between OSA and proprotein convertase subtilisin/kexin type 9 (PCSK9).MethodsFull-night polysomnography was performed on 150 participants who were divided into three groups: controls, OSA patients on statin therapy, and OSA patients not on statin therapy. Biochemical markers, plasma low-density lipoprotein (LDL) and high-density lipoprotein (HDL) subclasses, and PCSK9 were determined.ResultsPCSK9 was highest in OSA patients on statins compared to the control group and to OSA patients not on statins (p = 0.036 and p = 0.039, respectively), after adjustment for body mass index (BMI). LDL diameter was greater in OSA patients not on statins compared to OSA patients on statins (p = 0.032). PCSK9 was highest in the group of patients with all three risk factors (diagnosed OSA, statins, BMI ≥25 kg/m<sup>2</sup>) compared to groups with no, one, and two risk factors (p = 0.031, p = 0.001, and p = 0.029, respectively). Presence of OSA, statin therapy, and BMI ≥25 kg/m<sup>2</sup> when combined were independently associated with higher levels of PCSK9 when adjusted for antihypertensive therapy, small dense LDL, and HDL 3c subclass (odds ratio = 2.849; interquartile range [1.026–7.912], p = 0.044).ConclusionStatin therapy was closely related to PCSK9. OSA along with obesity and statin use induces elevation of PCSK9.  相似文献   
99.
阻塞性睡眠呼吸暂停低通气综合征是心血管疾病的独立危险因素,严重影响患者的生命质量和生存时间,也是可以改变的心血管疾病危险因素之一。动脉粥样硬化是造成心血管疾病的病理基础,而大量研究发现阻塞性睡眠呼吸暂停低通气综合征与亚临床动脉粥样硬化相关,综述阻塞性睡眠呼吸暂停低通气综合征与亚临床动脉粥样硬化的研究进展,并梳理其中发病机制,为阻塞性睡眠呼吸暂停低通气综合征患者动脉粥样硬化的预防和早期干预提供依据。  相似文献   
100.
After experiences are encoded, post‐encoding reactivations during sleep have been proposed to mediate long‐term memory consolidation. Spindle–slow oscillation coupling during NREM sleep is a candidate mechanism through which a hippocampal‐cortical dialogue may strengthen a newly formed memory engram. Here, we investigated the role of fast spindle‐ and slow spindle–slow oscillation coupling in the consolidation of spatial memory in humans with a virtual watermaze task involving allocentric and egocentric learning strategies. Furthermore, we analyzed how resting‐state functional connectivity evolved across learning, consolidation, and retrieval of this task using a data‐driven approach. Our results show task‐related connectivity changes in the executive control network, the default mode network, and the hippocampal network at post‐task rest. The hippocampal network could further be divided into two subnetworks of which only one showed modulation by sleep. Decreased functional connectivity in this subnetwork was associated with higher spindle–slow oscillation coupling power, which was also related to better memory performance at test. Overall, this study contributes to a more holistic understanding of the functional resting‐state networks and the mechanisms during sleep associated to spatial memory consolidation.  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