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   10062篇
  免费   890篇
  国内免费   263篇
耳鼻咽喉   1554篇
儿科学   175篇
妇产科学   45篇
基础医学   883篇
口腔科学   1080篇
临床医学   1105篇
内科学   1730篇
皮肤病学   56篇
神经病学   789篇
特种医学   505篇
外国民族医学   1篇
外科学   952篇
综合类   1291篇
预防医学   106篇
眼科学   176篇
药学   341篇
  7篇
中国医学   105篇
肿瘤学   314篇
  2024年   9篇
  2023年   145篇
  2022年   175篇
  2021年   364篇
  2020年   339篇
  2019年   349篇
  2018年   334篇
  2017年   359篇
  2016年   395篇
  2015年   380篇
  2014年   625篇
  2013年   606篇
  2012年   544篇
  2011年   603篇
  2010年   465篇
  2009年   475篇
  2008年   494篇
  2007年   530篇
  2006年   469篇
  2005年   436篇
  2004年   381篇
  2003年   302篇
  2002年   245篇
  2001年   230篇
  2000年   212篇
  1999年   186篇
  1998年   176篇
  1997年   154篇
  1996年   114篇
  1995年   121篇
  1994年   102篇
  1993年   99篇
  1992年   87篇
  1991年   75篇
  1990年   67篇
  1989年   77篇
  1988年   66篇
  1987年   59篇
  1986年   56篇
  1985年   60篇
  1984年   47篇
  1983年   39篇
  1982年   44篇
  1981年   35篇
  1980年   25篇
  1979年   19篇
  1978年   10篇
  1977年   12篇
  1976年   7篇
  1972年   5篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
101.
目的:探讨心肌梗死(心梗)患者窦性心律震荡检测的临床意义。方法:测定24小时动态心电监测的170例心梗患者和116例正常人室性早搏(室早)后的震荡初始(TO)和震荡斜率(TS)值及平均值,并进行对比分析。结果:心梗患者室早后的TO值明显高于对照组、鸭值明显低于对照组(P〈0.05和P〈0.01),TO和/或TS异常组死亡率明显高于TO和鸭均正常组(P〈0.001)。结论:心梗后患者窦性心律震荡现象减弱或消失时,其猝死的发生率增高,及时检测心梗患者室早后的TO和TS值,对发生猝死的高危患者的检出、危险度分层以及对其进行干预治疗都有重要的临床意义。  相似文献   
102.
We report two cases of acquired toxoplasmic lymphadenitis, one with toxoplasmic cysts and the organisms of Toxoplasma gondii and the other with the organisms only. These cysts and organisms were observed in paraffin-embedded sections, touch smears and ultrathin sections for electron microscopy. Touch smears were especially valuable for the quick and accurate diagnosis of toxoplasmic lymphadenitis. We also studied immature sinus histiocytosis (ISH) in these cases. The predominant cells of ISH were confirmed to be B lymphocytes immunohistochemically, the majority being positive for polyclonal surface IgM. ISH was observed in the perifollicular and paracortical areas surrounding post-capillary venules (PCV), whereas the sinuses were only partially involved.  相似文献   
103.
目的:报道1例偶然发现的右侧永久性三叉动脉形态、特点,并进行文献复习。方法:利用显微解剖对此例永久性三叉动脉的起源、走行、分支、分布、与后循环连接关系、以及相关动脉解剖特点等进行了研究。结果:此例永久性三叉动脉与脑膜垂体干共干起源于颈内动脉海绵窦段,于展神经外侧进入后颅窝,分支与基底动脉和小脑上动脉吻合,其终末支之一延续为同侧的小脑下后动脉,此动脉与三叉神经关系密切,分支分布于脑干和小脑。结论:永久性三叉动脉与后循环关系复杂,广泛参与正常脑组织供血。  相似文献   
104.
The urethral duct and vagina are formed from the urogenital sinus (UGS) during the early neonatal period in mice. Neonatal estrogen exposure results in hypospadias, or the malpositioning of vaginal and urethral openings, with wide cleft clitoris. We sought to characterize diethylstilbestrol (DES) influence on UGS morphogenesis and hypospadias formation. Newborn (day 0) and 1–4‐day‐old female mice (ICR/Jcl) were given (s.c.) oil or 3.0 μg DES. Animals were killed 24 hr later; then hypospadias formation and epithelial apoptosis and proliferation within the developing UGS were assessed. DES did not alter normal UGS morphogenesis by day 1, in comparison with controls. However, hypospadias formation was observed in DES‐treated mice by day 3. In these mice, the distal dorsal urethral duct appeared to fuse with and open into the lower vaginal solid cord region. Further, DES treatment produced a gradual significant increase in dorsal urethral epithelial apoptosis (P < 0.05) just prior to and during fusion and hypospadias formation. DES‐induced urethral epithelial and sinus cord proliferation appeared significantly increased (P < 0.05) and unchanged, respectively, just prior to fusion. By day 5, DES‐treated mice exhibited wide cleft clitoris. In addition, if DES was given on day 3 or 5, a gradual, distinct caudal shift in the vaginal‐urethral junction was observed compared to mice treated on days 0–2. Although hypospadias was not induced when neonates were given DES on day 7, these mice continued to display early vaginal opening. Dose‐response analysis indicated that 0.03 μg DES for 5 days is the lowest known critical dose for hypospadias induction. We have shown for the first time that DES‐induced hypospadias onset may primarily be the result of changes in developing dorsal urethral epithelial cell apoptotic and proliferative activity, and that the location of DES‐induced hypospadias formation is dependent on age at time of exposure. Anat Rec 266:43–50, 2002. © 2002 Wiley‐Liss, Inc.  相似文献   
105.
陶伟  韩卉  邓雪飞  陈方宏  庞刚  刘斌  赵红 《解剖学杂志》2007,30(3):347-350,F0003
目的:通过对上矢状窦(SSS)旁大脑桥静脉的显微解剖、影像学观察及其对照研究,为各种纵裂间手术入路中桥静脉的保护提供基础。方法:分别对30例(60侧)上矢状窦和颈内静脉内灌注蓝色乳胶的成人头颅湿标本、40侧DSA静脉相和16侧CTV进行显微解剖和影像学观察。结果:上矢状窦前部和后部分别有一缺乏桥静脉注入段,显微解剖、DSA和CTV观察上矢状窦旁桥静脉的数量分别为11.2支、8.9支和7.0支,DSA和CTV观察发现桥静脉注入上矢状窦处常显示不清。结论:熟悉和比较上矢状窦旁桥静脉的解剖学和影像学特征有利于各种纵裂间手术入路和手术过程中桥静脉的保护。  相似文献   
106.
The root mean square successive difference (RMSSD) in heart period series is a time domain measure of heart period variability. The RMSSD is sensitive to high-frequency heart period fluctuations in the respiratory frequency range and has been used as an index of vagal cardiac control. By transfer function simulations, the RMSSD statistic is shown to represent a high-pass filter that effectively captures respiratory sinus arrhythmia but also passes lower frequency fluctuations that can include sympathetic influences. These simulations, together with analysis of actual heart period series, reveal that the RMSSD is biased by basal heart period. Although between-subjects levels of RMSSD covary highly with spectral estimates of high-frequency variability, within-subject RMSSD change scores account for only 50-60% of the variance in spectral estimates. The present findings raise caveats in the applications and interpretation of the RMSSD statistic.  相似文献   
107.
额窦筛窦向眶顶气化的应用解剖   总被引:1,自引:0,他引:1  
目的:观察额窦、筛窦气房向眶顶气化情况。方法:对60具成人尸体头部标本额窦、筛窦向眶顶气化进行解剖观察,并结合全部标本的鼻窦冠状位CT扫描了解气化情况。结果:120侧标本气化眶顶骨板的有36.7%(44侧),其中气化整个眶顶者36.4%(16侧),气化部分眶顶者63.6%(28侧),气化眶顶的前颅底骨质内侧缘及外侧缘骨壁厚度分别为(0.3±0.1)mm(0.1-0.4mm)和(0.2±0.1)mm(0.1-0.3mm),无气化的前颅底骨质骨壁厚度为(0.9±0.3)mm(0.4-1.8 mm);CT扫描显示额窦、筛窦向眶顶气化结果与解剖观察一致。结论:了解额窦、筛窦气房向眶顶气化情况对预防鼻微创手术颅内及眶内并发症有重要的临床意义。  相似文献   
108.
上颌窦窦口的形态观察及其临床意义   总被引:1,自引:0,他引:1  
目的:为了指导鼻内窥镜下功能性上颌窦手术。方法:对60个头部标本(男34,女26)120侧进行了上颌窦口及其毗邻结构的观察测量。结果:上颌窦鼻通道的鼻开口口径为平均3.8mm,上颌窦通道长度为5.6mm,鼻内开口到前鼻棘连线与鼻底平面夹角为45.2°,前鼻棘至鼻内开口的距离为37.0mm,下鼻甲前端至鼻内开口距离为19.5mm,中鼻甲前端至鼻内开口距离为14.6mm。结论:上颌窦窦口为管状通道,该处的病变可以导致窦腔炎症,可以进行内窥镜下窦口扩大术,术中应避免损伤眼眶及鼻泪管。  相似文献   
109.
The aim of the study was to test the hypothesis that baroreceptor unloading increases jejunal fluid absorption rate via an α2-adrenergic effect on electrogenic active transport. In 13 chloralose-anaesthetized cats, the carotid sinus baroreceptors were isolated and perfused with arterial blood, and we studied the effects of a graded decrease in carotid sinus pressure on intestinal vascular resistance, net fluid absorption rate and the potential difference between the intestinal lumen and the peritoneal cavity (PD). Experiments were performed in seven control animals and in six animals pretreated with yohimbine, an α2-adrenergic antagonist, at a dose of 0.1 mg kg-I i.v. Yohimbine per se had no significant effects on systemic arterial pressure, intestinal vascular resistance, net fluid absorption rate or PD. In the control animals, baroreceptor unloading induced an increase in systemic arterial pressure, intestinal vascular resistance and net fluid absorption rate, and a decrease in the PD. Yohimbine pretreatment did not significantly affect the systemic blood pressure response to baroreceptor unloading, but abolished the effect on intestinal vascular resistance and PD. After yohimbine treatment, decreases in carotid sinus pressure still enhanced net fluid absorption rate, but this response was observed in a higher range of carotid sinus pressures than in control animals. We conclude that (1) a major component of the increase in jejunal absorption rate during baroreceptor unloading is due to a non-electrogenic mechanism, which may be either active or passive; (2) this component of the response is not blocked by yohimbine at a dose sufficient for an effect on presynaptic α2-receptors; (3) the absorptive response to baroreceptor unloading is not a phenomenon secondary to the concomitant jejunal vasoconstriction.  相似文献   
110.
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   
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