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   21807篇
  免费   1750篇
  国内免费   522篇
耳鼻咽喉   1648篇
儿科学   383篇
妇产科学   289篇
基础医学   1384篇
口腔科学   657篇
临床医学   3435篇
内科学   2816篇
皮肤病学   253篇
神经病学   1672篇
特种医学   1815篇
外科学   1657篇
综合类   2761篇
现状与发展   2篇
一般理论   4篇
预防医学   1407篇
眼科学   1951篇
药学   1192篇
  11篇
中国医学   442篇
肿瘤学   300篇
  2024年   35篇
  2023年   356篇
  2022年   517篇
  2021年   1030篇
  2020年   980篇
  2019年   900篇
  2018年   886篇
  2017年   812篇
  2016年   974篇
  2015年   902篇
  2014年   1575篇
  2013年   1620篇
  2012年   1243篇
  2011年   1296篇
  2010年   1077篇
  2009年   1086篇
  2008年   1057篇
  2007年   1097篇
  2006年   1017篇
  2005年   790篇
  2004年   649篇
  2003年   557篇
  2002年   437篇
  2001年   388篇
  2000年   312篇
  1999年   282篇
  1998年   244篇
  1997年   198篇
  1996年   156篇
  1995年   151篇
  1994年   173篇
  1993年   115篇
  1992年   137篇
  1991年   91篇
  1990年   95篇
  1989年   89篇
  1988年   84篇
  1987年   65篇
  1986年   73篇
  1985年   101篇
  1984年   78篇
  1983年   53篇
  1982年   78篇
  1981年   51篇
  1980年   57篇
  1979年   32篇
  1978年   34篇
  1977年   13篇
  1976年   13篇
  1975年   11篇
排序方式: 共有10000条查询结果,搜索用时 530 毫秒
71.
1. The effects of acute bilateral superior cervical ganglionectomy on cerebral blood flow and metabolism were investigated in stroke-prone spontaneously hypertensive rats (SHRsp), before and during cerebral ischaemia. 2. The resting cerebral blood flow was comparable between the control and denervated animals. 3. There was no significant difference in cerebral blood flow or concentration of tissue energy metabolites (adenosine triphosphate [ATP], lactate and pyruvate) between the sham-operated control and denervated animals during ischaemia. 4. The results suggest that sympathetic innervation of cerebral vessels originating from superior cervical ganglia may not play a major role in the progression of cerebral ischaemia in SHRsp.  相似文献   
72.
The authors describe their preliminary experience with the use of superparamagnetic magnetic resonance (MR) imaging contrast media for suppression of signal from flowing blood. The goal of this work was to determine if a superparamagnetic contrast agent could successfully eliminate blood signal during cardiac-gated MR imaging, thereby eliminating or reducing flow artifacts associated with the complex and variable hemodynamics within the heart chambers. Imaging and data analysis were performed in 17 dogs subjected to experimental myocardial infarction as part of a parallel project. Six doses (0.2, 1, 2, 3.5, 4, 5, and 10 mg/kg) of AMI-25, an experimental contrast agent, were used in the study. Spin-echo imaging was performed immediately before and every 5 minutes (for an average of 25 minutes) after bolus injection of the contrast agent. Variations in the image signal-to-noise ratio relative to a baseline (before injection of contrast agent) image were assessed as a function of dose and time. Preliminary results suggest that a considerable reduction in blood flow artifacts and, hence, increases in image signal-tonoise ratio can be achieved at doses greater than or equal to 3.5 mg/kg, for approximately 20 minutes after injection. Doses equal to or less than 2 mg/kg and images obtained more than 20 minutes after injection (regardless of dose) did not reliably show hemodynamic artifact suppression.  相似文献   
73.
Purpose The goal of the study is to evaluate utility of contrast enhanced ultrasound (US) with carbon dioxide microbubbles in evaluation of hepatic lesions.Methods Twenty eight patients with single or multiple t hepatic lesions (11 hepatocellular carcinoma, 8 hemangiomas, 5 metastases, 1 adenoma, 1 focal nodular hyperplasia, 2 regenerative nodules) were examined. US exam was performed during intraarterial injection of 10 ml of CO2 through the same catheter employed for liver arteriography. The US exam was videotaped in its salient phases. Characteristics of enhancement were evaluated and correlated with histological findings or patient follow up.Results Sonographic angiography clearly demonstrated vascularization of the lesions. Hepatocellular carcinoma, hemangioma, metastases, focal nodular hyperplasia, and regenerative nodules had very characteristic patterns. The injection of CO2 allowed detection of small additional nodules.Conclusion Sonographic angiography can improve characterization and staging of hepatic tumors. Low cost and the simplicity of the technique should encourage further experimentation.  相似文献   
74.
Summary: We studied the effect of antiepileptic drugs (AEDs) on internal carotid artery (ICA) blood flow velocity, as an index of total cerebral blood flow (CBF). The subjects were 45 newly diagnosed children with febrile convulsion or epilepsy who were seizure-free for a period long enough not to affect the results. They had no neurologic deficit, received fixed monotherapy, and were examined by a noninvasive Doppler ultrasound method, in comparisonwith 13 age-matched normal volunteers with no AED. In 30 patients, the measurements were performed before and after AED administration [10 with phenobarbital (PB), 10 with carbamazepine (CBZ), and 10 with valproate (VPA)], and performed before and after AED discontinuation in the remaining 15 patients (all with PB). Normal volunteers underwent the two consecutive examinations with a mean interval equal to that of the entire patient group, and there was no difference in velocity values between the measurements. In patients receiving CBZ or VPA, a significant reduction was noted in blood flow velocity after drug administration. Although velocity values in the patients receiving PB did not change after drug administration, they were significantly increased after complete discontinuation. In the present study, a slight but significant reduction in CBF caused by AED administration at therapeutic doses in children was suggested.  相似文献   
75.
B超测量皮脂厚度的临床应用   总被引:1,自引:0,他引:1  
目的 :采用B型超声诊断仪进行皮脂厚度测量 ,探讨B超与皮皱厚度卡尺测定结果的相关性。 方法 :选取健康成人 2 19例 ,非疾病死亡 10h之内尸体 11例。用B型超声诊断仪和皮皱厚度卡尺分别测量皮脂厚度。 结果 :B超与皮皱厚度卡尺测量值比较 ,二者差异不显著 (P >0 .0 5 )。 结论 :B型超声诊断仪用于临床评价皮脂厚度是可行的  相似文献   
76.
All-Union Surgical Research Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Malinovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 12, pp. 653–657, December, 1991.  相似文献   
77.
扩大经蝶入路进入海绵窦内侧腔的应用显微解剖   总被引:1,自引:0,他引:1  
目的为临床开展扩大经蝶入路进入海绵窦内侧腔手术提供解剖学依据。方法用50例成人头颅标本.在显微镜下对蝶窦外侧壁、蝶鞍、海绵窦及周围结构进行解剖学观察并测量。模拟扩大经蝶入路磨除海绵窦腹侧骨质,切开海绵窦内侧壁,显露海绵窦内侧腔。结果颈内动脉(ICA)明显隆起于蝶窦侧壁的占58%,蝶窦内隆起呈管型占3%。鞍底硬膜分为2层,海绵窦内侧壁的上部南垂体硬膜构成,无骨性结构支撑;下部由骨周硬膜构成,有蝶窦侧壁骨质支撑。两侧海绵窦内侧壁的距离为(14.8±2.7)mm。海绵窦内侧腔位于C4段ICA与垂体之间,腔内为丰富的静脉丛,最宽可达7mm,但常因ICA扭曲而闭塞。无颅神经穿越海绵窦内侧腔,ICA是扩大经蝶入路探查海绵窦遇到的第一个主要结构。结论扩大经蝶入路进入海绵窦内侧腔是安全可行的。  相似文献   
78.
The media and obesity   总被引:2,自引:1,他引:1  
T. Boyce 《Obesity reviews》2007,8(S1):201-205
  相似文献   
79.
高血压患者左室舒张功能与左室肥厚的关系及随龄改变   总被引:1,自引:0,他引:1  
为探讨原发性高血压 (以下简称高血压 )患者的左室舒张功能和左室肥厚的关系及其随龄改变 ,抽取 1995年 2月至 2 0 0 2年 7月间门诊高血压患者 4 81例为高血压组 ,以同期体检健康者 2 54 3例为对照组 ,年龄 10~ 80岁 ,并将原发性高血压患者分为 3级 ,每级中按性别分 2组。采用惠普 2 50 0彩色多普勒超声诊断系统检测 2组的室间隔厚度、左室后壁厚度、E/A等指标。使用SPSS软件进行统计学处理分析。结果 :高血压和正常对照组相比E/A显著下降 ,室间隔和左室后壁显著增厚 (P <0 .0 1)。 2个组的E/A均随年龄下降 ,而室间隔厚度随年龄增厚 ,且室间隔厚度和E/A呈显著负偏相关 (P <0 .0 1)。在高血压分级组中 ,Ⅰ~Ⅲ级高血压组中男性的室间隔厚度均厚于女性 (均P <0 .0 1) ,Ⅰ、Ⅱ级高血压组中男性的左室后壁厚度厚于女性 (P <0 .0 5,P <0 .0 1) ,Ⅰ级高血压组中女性的E/A低于男性 (P <0 .0 5)。提示 :左室舒张功能随着年龄的增加而降低 ,而且和高血压左室肥厚呈负偏相关关系 ,性别对其也有一定的影响  相似文献   
80.
Background/purpose: The localized or generalized skin thickness detected on mammography may reflect an underlying pathology of breast or a systemic disease involving the skin. The aim of this report is to describe the range of normal breast skin thickness in women using a film-screen mammographic technique.
Methods: Measurement of the mammographic skin thickness over different parts of the breast was performed in 144 women who had normal findings in a combined mammographic and ultrasonographic examination. Patients were grouped as premenopause, postmenopause and surgical menopause who were under continuous oestrogen treatment. The skin thickness in four regions (superior, inferior, medial, lateral) of both breasts was compared, and their relations with age, breast size, menopausal and hormonal status were investigated. The interobserver reliability was tested in a small subgroup of patients.
Results: Interobserver agreement was good for all measurements. The range of normal breast skin thickness was between 0.50 and 3.10 mm. There were no differences in skin thickness between the corresponding regions of the breasts, with significant differences between the regions in the same breast. While breast size increased with age, skin thickness decreased in all regions.
Conclusion: The breast size, age, regional variations and hormonal status of the patients should be considered when defining the normal range of skin thickness in mammographic examinations. We assume that upper limit of mammographic skin thickness should be set as 3.0 mm, regardless of the focal spot size and film-focus distance.  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