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   10173篇
  免费   771篇
  国内免费   230篇
耳鼻咽喉   70篇
儿科学   169篇
妇产科学   242篇
基础医学   691篇
口腔科学   93篇
临床医学   1593篇
内科学   738篇
皮肤病学   50篇
神经病学   593篇
特种医学   159篇
外科学   998篇
综合类   2145篇
预防医学   1099篇
眼科学   70篇
药学   1477篇
  37篇
中国医学   673篇
肿瘤学   277篇
  2024年   44篇
  2023年   137篇
  2022年   287篇
  2021年   402篇
  2020年   495篇
  2019年   285篇
  2018年   251篇
  2017年   372篇
  2016年   398篇
  2015年   374篇
  2014年   776篇
  2013年   698篇
  2012年   881篇
  2011年   786篇
  2010年   656篇
  2009年   510篇
  2008年   450篇
  2007年   471篇
  2006年   426篇
  2005年   342篇
  2004年   263篇
  2003年   260篇
  2002年   220篇
  2001年   151篇
  2000年   122篇
  1999年   115篇
  1998年   86篇
  1997年   62篇
  1996年   68篇
  1995年   61篇
  1994年   68篇
  1993年   47篇
  1992年   39篇
  1991年   53篇
  1990年   46篇
  1989年   48篇
  1988年   45篇
  1987年   29篇
  1986年   48篇
  1985年   41篇
  1984年   43篇
  1983年   20篇
  1982年   23篇
  1981年   35篇
  1980年   19篇
  1979年   24篇
  1978年   17篇
  1977年   17篇
  1976年   25篇
  1973年   10篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
71.
In this study, the relationship between physiological arousal, as indexed by heart rate variability, was examined in boys with fragile X syndrome (FXS) and typically developing boys matched on chronological age. In addition, the relationship of heart activity to clinical and molecular factors in the group of boys with FXS was examined. Results suggest that boys with FXS have higher levels of heart activity during the passive phases, as reflected in shorter heart periods. This high level of heart activity appears to be due to increased sympathetic activity and reduced parasympathetic activity. Boys with FXS did not display the expected patterns of heart activity in response to phases of increasing challenge, and sympathetic and parasympathetic systems did not appear coordinated in these boys with FXS. Clinical factors may be related to neural regulation of heart activity while molecular factors do not appear to be.  相似文献   
72.
围产期母亲和胎儿心动周期信号分析   总被引:1,自引:2,他引:1  
同时分析围产期胎儿和孕妇心动周期信号的数字特征(混沌和谱特征)以评价自主神经系统功能。用可视化程序设计的方法实现提取和分析围产期母亲和胎儿心动周期信号。受试者取仰卧位,心电信号从置于腹壁下部耻骨联合导联获得。胎儿心电信号用小波分解进行信号预处理。采用本实验室已经完成开发的技术实现心动周期信号数字特征的分析。该系统可以评价胎儿和孕妇的自主神经系统功能,特别是分别定量评价交感和副交感神经系统功能;该系统还可用以预测胎儿窘迫。胎儿和其它年龄段的心动周期信号数字特征随年龄的变化提示了自主神经系统的发育、成熟和衰老的生理过程,基于这一点我们可以寻找抗衰老的方法;胎儿的心动周期信号数字特征介于新生儿和成人之间,提示胎儿的自主神经系统的调节可能受母体神经内分泌系统的影响。  相似文献   
73.
Summary The ultrastructure of neuroglial fatty metamorphosis (GFM) has been investigated in the telencephalic white matter of 12 premature and mature infants (gestational age 22–40 weeks; survival 0–96 days). GFM was found in all cases apart from a 22-week-old fetus, and involves predominantly astrocytic cells (68.8%), then glioblasts (43.5%), but only 7.4% of oligodendrocytes. GFM, therefore, seems to be independent of the myelination process and indicates the vulnerability of the immature neuroglial population in the metabolic and circulatory disorders of the perinatal period. Since GFM is found in almost all children dying within the early postnatal period, this subtle alteration reflects a special form of minimal brain damage. The relationship between GFM, astrocytic hypertrophy and periventricular leucomalacia and their role in the telencephalic leucoencephalopathy are discussed.
Zusammenfassung Die Gliazellverfettung im unreifen Großhirn-Marklager wurde bei 12 Kindern ultrastrukturell untersucht (Gestationsalter 22–40 Wochen; Überlebenszeit 0–96 Tage). Die fettige Metamorphose der Neuroglia (Virchow) fand sich in allen Fällen, ausgenommen den 22 Wochen alten Feten, und betrifft vorwiegend junge Astrozyten (68,8%), ferner zu 43,5% unreife Vorstufen, jedoch nur zu 7.4% die (z.Z. der Geburt erst in Erscheinung tretende) Oligodendroglia. Die Fett-Metamorphose der unreifen Glia stellt einen sensiblen Indikator für metabolisch-zirkulatorische Störungen der Perinatalperiode dar und erfolgt unabhängig von dem Prozeß der Markscheidenbildung. Zusammen mit einer oft auffälligen Astroglia-Proliferation ist die intracytoplasmatische Akkumulation nicht membrangebundener Lipide Ausdruck einer temporären Differenzierungsstörung der unreifen Neuroglia. Die resultierende Reifungsdissoziation mit Unterdrückung der oligodendrozytären Zellinie führt zur retardierten Markscheidenbildung und dem Bild der telencephalen Leucoencephalopathie.
  相似文献   
74.
Publication Guidelines for Heart Rate Studies in Man   总被引:1,自引:0,他引:1  
Publication guidelines are provided for the collection, quantification, and analysis of heart rate data.  相似文献   
75.
A survey is presented of techniques which transform heart-rate variability data into a signal that is both visually informative and accessible for analysis. The Instantaneous Heart-Rate (IHR) signal is introduced, i.e. the signal having the value of the heart rate (inverse interbeat interval) during the interval concerned. The IHR signal differs from the standard Delayed Heart-Rate (DHR) signal, which is always one beat late. The relationship is discussed between the different representation methods and the Integral Pulse Frequency Modulation (IPFM) model, the latter being a physiologically plausible model for the transformation of a continuous input signal (e.g., nervous influence on the cardiac pacemaker) into a series of events (heartbeats). It is shown that when the IHR signal is used as input of the IPFM model, the event series from which the signal was derived appears at the output. Hence, if the IPFM model is accepted as a model of the pacemaker, the IHR signal may be considered as an approximation of the neural (sympathetic and parasympathetic) influence on the pacemaker. In addition we show that the appearance of the IHR signal is less affected by trigger errors or extrasystoles than the standard DHR signal. It is concluded that the most attractive time-domain representation of physiological event series consists of the IHR signal, because this signal, being conceptually and computationally simple, is consistent with the IPFM model.  相似文献   
76.
Previous studies demonstrated distinct cardiovascular patterns associated with threat and challenge appraisals for groups of participants. We extend these results by assessing whether appraisals continue to be associated with these cardiovascular response patterns within an individual as appraisals change. Participants completed four verbal mental arithmetic tasks for which they made appraisals before and after each task. Cardiac reactivity and total peripheral resistance (TPR) were calculated for the first and last minutes of each task, and the number of responses and percent correct were measured for each task. In line with our prediction, pretask appraisals were related to some task-related cardiac responses across the four tasks. In addition, task-related cardiovascular reactivity and behaviors both influenced appraisals following the task. Our findings suggest that an idiographic analysis of appraisals, cardiovascular physiology, and task-related behaviors provides a richer understanding of the appraisal process and reveals sex differences deserving further assessment.  相似文献   
77.
Heart rate reactivity to mental stress is substantially blunted early after heart transplantation, suggesting that the loss of neural modulation limits the cardiovascular response to mental stress. We tested whether reactivity to mental stress recovers during the first year after heart transplantation. Hemodynamic and respiratory responses to mental arithmetic challenge were studied in 20 heart transplant recipients 3, 6, and 12 months after surgery. A normal comparison group was studied at equivalent intervals. Heart rate reactivity to mental arithmetic was significantly reduced in the cardiac transplant group compared to the normal subjects. This effect persisted up to 1 year after transplantation. Heart period variability in the heart transplant recipients was minimal in all three-test sessions. The findings suggest that no functional reinnervation or other compensatory adaptation occurs up to 1 year after heart transplantation.  相似文献   
78.
背景:近年来,随着全膝关节置换技术提升、手术时间缩短、术中及术后止血药的应用,其总失血量不断减少,术后引流量也逐渐减少,术后快速康复理论应运而生,引流管放置也再次成为骨科医生所热议的问题,越来越多的医生认为可以常规取消放置引流,引流似乎已可有可无。目的:旨在复习既往文献,对全膝关节置换后引流放置的相关问题归纳总结,提供围术期引流管理的相关经验。方法:检索中国知网、万方、维普、中国生物医学文献数据库等中文数据库,以及PubMed、The Cochrane Library、WebofScience、EMBASE、OVID等外文数据库,以"引流,膝关节置换术"及"totalknee arthroplasty,drainage"为检索词,检索自建库始至2020年2月为止所有与主题相关的文献,总结归纳全膝关节置换后不放置引流管围术期各方面需综合考虑的要素。结果与结论:①引流管的放置问题关乎全膝关节置换手术的最终结果,与术后出血、血肿、血栓、感染等并发症的发生关系密切;②目前全膝关节置换术后不推荐常规放置引流,但不意味着不需要管理,其实际上对临床医护在围术期各方面的管理提出更高的要求,包括但不限于术前适应证选择、手术操作、止血带使用、术中及术后药物使用、物理疗法的使用等。  相似文献   
79.
80.
目的探讨住院精神分裂症患者恢复期的心理卫生状况及心理护理干预效果。方法将76例处于恢复期的住院精神分裂症患者随机分为两组,封其中的38例追行心理谩理干预(干预组),并与对照组(未干预组)退行比较。采用SCL-90(症状自评量表)于干预前和干预后4周末造行量表抨定。枯果住院精神分裂症患者恢复期的主要心理闪题为抑郁、焦虑、人际关系、强迫、敌对、偏执等。干预组在干预后4周末SLC-90的焦虑、抑郁、人际关系3个因子分与干预前相比有非常显着性差异(P〈0.01)。强迫、敌对、偏执3个因子分有显着性差异(P〈0.05)。其他各项因子分差异无显着性(P〉0.05);而对照组各因子分干预前后相比无显着性差异(P〉0.05)。干预后两组在SCL-90的焦虑、抑郁、人际关系、强迫、敌对、偏执等6个因子分比较有显着性差异(P〈0.05)。结论心理护理干预能明显改善住院精神分裂症患者恢复期的心理卫生状况,促进病人的康复。  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