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   6486篇
  免费   412篇
  国内免费   101篇
耳鼻咽喉   99篇
儿科学   165篇
妇产科学   235篇
基础医学   987篇
口腔科学   100篇
临床医学   776篇
内科学   1328篇
皮肤病学   109篇
神经病学   672篇
特种医学   428篇
外科学   826篇
综合类   83篇
一般理论   1篇
预防医学   294篇
眼科学   122篇
药学   354篇
中国医学   12篇
肿瘤学   408篇
  2022年   47篇
  2021年   91篇
  2020年   55篇
  2019年   85篇
  2018年   87篇
  2017年   68篇
  2016年   95篇
  2015年   136篇
  2014年   181篇
  2013年   246篇
  2012年   312篇
  2011年   311篇
  2010年   244篇
  2009年   189篇
  2008年   292篇
  2007年   353篇
  2006年   323篇
  2005年   301篇
  2004年   255篇
  2003年   242篇
  2002年   217篇
  2001年   244篇
  2000年   222篇
  1999年   176篇
  1998年   113篇
  1997年   82篇
  1996年   89篇
  1995年   83篇
  1994年   64篇
  1993年   87篇
  1992年   117篇
  1991年   126篇
  1990年   118篇
  1989年   122篇
  1988年   115篇
  1987年   93篇
  1986年   78篇
  1985年   85篇
  1984年   63篇
  1983年   42篇
  1982年   38篇
  1980年   34篇
  1979年   62篇
  1978年   34篇
  1977年   46篇
  1975年   33篇
  1974年   41篇
  1973年   43篇
  1972年   45篇
  1971年   36篇
排序方式: 共有6999条查询结果,搜索用时 0 毫秒
1.
2.
Ten years experience with acute peritoneal dialysis in 39 preterm-, newborn and small infants shows advantage and low risk of surgically implanted single dacron cuffed silicone catheters compared to trocar catheters.  相似文献   
3.
A rotating contact lens holder for the three-mirror Goldmann lens permits circular examination of the fundus or chamber angle without having to change the position of the fingers on the edge of the lens. The contact lens holder consists of an outer polygonal ring hold by the thumber and index finger. An inner rotating ring holds the contact lens. Continuous rotation of the contact lens is performed with the free middle Finger. This device permits circular examination of the retina without interruption of fixation. The instrument improves not only the speed but also the reliability of the examination.  相似文献   
4.
顺铂聚乳酸微球的药物释放特性及肝动脉栓塞研究   总被引:5,自引:0,他引:5  
对顺铂聚乳酸微球进行了体外药物释放和家犬肝动脉栓塞研究。该微球粒径范围为50~200μm,平均粒径为115.76±35.94μm,顺铂含量为37.16%(W/W);体外药物释放机制符合Higuchi方程;肝动脉栓塞后8h,肝组织顺铂浓度高达21.55±12.18μg/g,明显高于肝动脉灌注顺铂组:3.16±0.09μg/g(P<0.05);肝动脉栓塞组的顺铂血浓峰值、各取血点浓度及曲线下面积AUC皆低于肝动脉灌注顺铂组。可望达到提高栓塞部位的药物疗效,降低全身毒副反应的作用。  相似文献   
5.
Cerebral infarction is rare in premature newborns and is most commonly the result of arterial embolization from the placenta. A focal echodense area was identified on prenatal cranial ultrasonography (US) in a premature infant (34 weeks of gestation). After birth, cerebral infarction was confirmed by magnetic resonance imaging (MRI). The clinical findings, imaging findings and pathogenesis are discussed. New diagnostic methods such as MRI show to be a useful approach in the neonatal period facilitating recognition of cerebrovascular accidents also in low-birth-weight infants.  相似文献   
6.
PURPOSE: To investigate whether balloon angioplasty of the superficial femoral artery (SFA) increases serum levels of C5a and whether C5a predicts risk of restenosis. METHODS: C5a antigen was measured at baseline and 8 hours after intervention in 131 consecutive patients (76 women; median age 72 years) with intermittent claudication who underwent successful primary SFA balloon angioplasty. Patients were followed for a median 10 months [interquartile range (IQR) 6 to 14] for the occurrence of >50% restenosis by duplex ultrasound. RESULTS: Median C5a levels increased significantly from 39.7 ng/mL (IQR 27.8 to 55.0) at baseline to 53.8 ng/mL (IQR 35.6 to 85.1, p<0.001) 8 hours post intervention. During the follow-up period, 70 (53%) patients developed restenosis. Increasing levels of C5a (quartiles) at baseline were significantly associated with an increased risk for restenosis (p=0.0092). Adjusted hazard ratios (95% confidence intervals) for restenosis with increasing quartiles of baseline serum C5a levels were 1.24 (0.60 to 2.58), 1.93 (0.95 to 3.93), and 2.08 (1.02 to 4.21), respectively, compared to the lowest quartile. This effect was independent of nonspecific inflammation as reflected by plasma levels of C-reactive protein. CONCLUSION: Inflammatory mechanisms play a major role in the development of restenosis after angioplasty. The complement component C5a exerts strong chemotactic and proinflammatory effects. Enhanced complement activation prior to PTA, as measured by higher levels of C5a, was significantly associated with restenosis after SFA balloon angioplasty. Pathways of complement inhibition thus may be worth investigating with respect to improving patency rates.  相似文献   
7.
One method used to control costs in community cardiovascular disease surveillance is to limit the number of electrocardiograms (ECGs) used to validate acute myocardial infarction (AMI). The Minnesota Heart Survey investigated the impact of decreasing the maximum number of ECGs analyzed on classification of ECG pattern and final AMI diagnosis (definite, probable, none). A 50% sample of all 1980 acute CHD hospital discharge records (ICD-9 code 410 or 411) from 30 of 31 Twin Cities hospitals were abstracted. Comparing results using all available ECGs in the record (maximum of 12) with those obtained using up to 4 ECGs showed little differences in the ECG classification or final AMI diagnosis.  相似文献   
8.
Although intellectual impairment is common in patients with myotonic dystrophy, this aspect of the disease has received relatively little research attention. We examined 41 patients with myotonic dystrophy using objective neuropsychological procedures and magnetic resonance imaging. Ten patients (24%) had severe and generalized intellectual dysfunction, while lesser or no cognitive impairment characterized the remaining patients. Degree of intellectual impairment was not related to neuromuscular status or sex. Patients with severe intellectual disturbance had significantly earlier onset of both myotonia and weakness and were more likely to inherit the disease from their mother. Magnetic resonance imaging findings indicated that while degree of cerebral atrophy was not related to severity of intellectual impairment, skull thickness, focal white matter lesions, and anterior temporal lobe abnormalities were significantly more common in patients with severely disturbed intellect. This study reports a number of previously unreported cerebral magnetic resonance imaging findings associated with intellectual impairment in myotonic dystrophy, but the etiology of these changes awaits neuropathologic examination.  相似文献   
9.
In a newly developed dual-source computed tomography system (DSCT) the relation of heart rate and image quality and the possible advantages of the system’s superior temporal resolution in the evaluation of left ventricular parameters as compared to results of cardiac magnetic resonance imaging (MRI) were assessed. Coronary CT angiography was performed using a DSCT (Somatom Defintion, Siemens Medical Solutions, Forchheim, Germany) in 21 patients (mean age 62±8; 15 male, 6 female). Image quality of the coronary arteries, the heart valves, and the left ventricular myocardium was assessed using a three-point grading scale. Ten of these patients also underwent cardiac MRI for the assessment of left ventricular function, using a SSFP (steady-state free precession) sequence. Left ventricular ejection fractions (LV-EF), the end-systolic volumes (ESV), and the end-diastolic volumes (EDV) were measured employing MRI and DSCT datasets. The image quality ratings for the coronary arteries at the optimal reconstruction interval were diagnostic even in patients with high heart rates (1.42±0.49). Analysis of global LV function using DSCT quantified from CTA datasets showed a good correlation with results of cardiac MRI [EF: r=0.75 (p=0.01); ESV: r=0.72 (p=0.19); EDV: r=0.71 (p=0.02)]. The dual-source CT system offers robust image quality of the coronary arteries, independent of the heart rate, and provides combined diagnostic imaging of coronary arteries, the heart valves, the myocardium, and the global left ventricular function.  相似文献   
10.
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