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   34623篇
  免费   2396篇
  国内免费   1432篇
耳鼻咽喉   197篇
儿科学   262篇
妇产科学   54篇
基础医学   1839篇
口腔科学   57篇
临床医学   4738篇
内科学   13472篇
皮肤病学   59篇
神经病学   389篇
特种医学   1621篇
外科学   1637篇
综合类   7575篇
现状与发展   1篇
预防医学   925篇
眼科学   41篇
药学   3785篇
  26篇
中国医学   1709篇
肿瘤学   64篇
  2024年   42篇
  2023年   394篇
  2022年   652篇
  2021年   1224篇
  2020年   1153篇
  2019年   979篇
  2018年   948篇
  2017年   834篇
  2016年   905篇
  2015年   970篇
  2014年   2049篇
  2013年   2250篇
  2012年   1702篇
  2011年   1994篇
  2010年   1689篇
  2009年   1573篇
  2008年   1704篇
  2007年   1827篇
  2006年   1760篇
  2005年   1499篇
  2004年   1307篇
  2003年   1191篇
  2002年   1031篇
  2001年   1104篇
  2000年   911篇
  1999年   829篇
  1998年   736篇
  1997年   687篇
  1996年   552篇
  1995年   490篇
  1994年   469篇
  1993年   371篇
  1992年   311篇
  1991年   301篇
  1990年   249篇
  1989年   202篇
  1988年   205篇
  1987年   191篇
  1986年   157篇
  1985年   200篇
  1984年   173篇
  1983年   104篇
  1982年   116篇
  1981年   93篇
  1980年   71篇
  1979年   60篇
  1978年   50篇
  1977年   43篇
  1976年   35篇
  1975年   20篇
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
61.
用~3H-亮氨酸参入法与放射免疫分析法分别测定大鼠心肌蛋白质合成速度与心脏组织中神经肽Y(NPY)含量。结果显示NPY能显著促进心肌蛋白质合成,其最大效应较去甲肾上腺素(NE)大35%,所需浓度是NE的1/100。心肌梗塞后非梗塞区组织内NPY的含量在2天时无显著改变,15天时则降低71%,提示2~15天期间该区域NPY释放增加,此为非梗塞区心肌肥大的机制之一  相似文献   
62.
A two and half year old male child was seen with systemic hypertension, left ventricular dysfunction, mitral regurgitation and congestive cardiac failure. Examination revealed adenoid hypertrophy. He was also suffering from obstructive sleep apnea. He was being treated with anti-hypertensive and anti-failure drugs. Adenoidectomy was performed following which obstructive sleep apnea symptoms disappeared and his cardiac status improved markedly. Subsequently he was weaned off anti-hypertensive and anti-failure therapy.  相似文献   
63.
AIMS: To assess the association between abnormal stress myocardial perfusion imaging (MPI) and cardiac events (CE) in asymptomatic patients with diabetes and with > or = 1 additional risk factor. Predictors of abnormal stress MPI were also evaluated. METHODS: Four hundred and forty-seven consecutive patients who underwent stress MPI were prospectively followed for 2.1 [0.5-4.1] years for the subsequent occurrence of hard CE (myocardial infarction and sudden or coronary death) and soft CE (unstable angina and ischaemic heart failure requiring hospitalization). Re-vascularization procedures performed as a result of the screening protocol were not included in the analysis. RESULTS: Follow-up was successful in 419 of 447 patients (94%), of whom 71 had abnormal MPI at baseline. Medical therapy was intensified in all subjects and especially in those with abnormal MPI. Twenty-three patients with abnormal MPI underwent a re-vascularization procedure. CEs occurred in 14 patients, including six of 71 patients (8.5%) with abnormal MPI and eight of 348 patients (2.3%) with normal MPI (P < 0.005). Only two patients developed a hard CE and 12 a soft CE. In multivariate analysis, abnormal MPI was the strongest predictor for CEs [odds ratio (OR) (95% CI) = 5.6 (1.7-18.5)]. Low-density lipoprotein cholesterol > or = 3.35 mmol/l [OR (95% CI) = 7.3; 1.5-34.7] and age > median [OR (95% CI) = 6.0 (1.2-28.6)] were additional independent predictors for CE. The independent predictors for abnormal MPI were male gender, plasma triglycerides > or = 1.70 mmol/l, creatinine clearance < 60 ml/min and HbA1c > 8%, with male gender the strongest [OR (95% CI) = 4.0 (1.8-8.8)]. CONCLUSIONS: Asymptomatic patients with diabetes in this study had a very low hard cardiac event rate over an intermediate period. This could be explained by the effects of intervention or by the low event rate in the background population. Randomized studies of cardiac heart disease screening are required in asymptomatic subjects with diabetes to determine the effectiveness of this intervention.  相似文献   
64.
Background Oxidative stress and increased inflammation have been reported to be increased in subjects with diabetes and to be involved in the pathogenesis of cardiovascular complications after myocardial infarction (MI). It is well recognized that red wine has antioxidant and anti‐inflammatory activities. We examined the effects of moderate red wine intake on echocardiographic parameters of functional cardiac outcome in addition to inflammatory cytokines and nitrotyrosine (oxidative stress marker), in subjects with diabetes after a first uncomplicated MI. Methods One hundred and fifteen subjects with diabetes who had sustained a first non‐fatal MI were randomized to receive a moderate daily amount of red wine (intervention group) or not (control group). Echocardiographic parameters of ventricular dys‐synchrony, circulating levels of nitrotyrosine, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐18 (IL‐18) and C‐reactive protein (CRP) were investigated at baseline and 12 months after randomization. Results After 1 year of diet intervention, concentrations of nitrotyrosine (P < 0.01), CRP (P < 0.01), TNF‐α (P < 0.01), IL‐6 (P < 0.01) and IL‐18 (P < 0.01) were increased in the control group compared with the intervention group. In addition, myocardial performance index (P < 0.02) was higher, and transmitral Doppler flow (P < 0.05), pulmonary venous flow analysis (P < 0.02) and ejection fraction (P < 0.05) were lower in the control group, indicating ventricular dys‐synchrony. The concentrations of nitrotyrosine, CRP, TNF‐α and IL‐6 were related to echocardiographic parameters of ventricular dys‐synchrony. Conclusions In subjects with diabetes, red wine consumption, taken with meals, significantly reduces oxidative stress and pro‐inflammatory cytokines as well as improving cardiac function after MI. Moderate red wine intake with meals may have a beneficial effect in the prevention of cardiovascular complications after MI in subjects with diabetes.  相似文献   
65.
Background: Retinal pigment epithelium (RPE)lesions are predictive congenital phenotypic markersfor familial adenomatous polyposis (FAP). Thisprospective screening study aims at assessing theincidence and significance of these lesions in FAPpatients and their family members.Methods: Sixty-two members from three familiesincluding five patients with the diagnosis of FAP havebeen ophthalmologically surveyed. All RPE lesions weredocumented with fundus photography and fluoresceinangiography was performed in 13 subjects.Sigmoidoscopy and/or radiological examination wereperformed annually in 9 family members with typicalRPE lesions during 4 years to allow early diagnosis ofFAP.Results: Typical RPE lesions were present infive FAP patients and 15 family members.Telangiectatic dilatations in the retinal peripherywith small dot-like hemorrhages were detected in 6subjects from 3 families These lesions wereparticularly evident on fluorescein angiography.Annual colon analysis showed polyps in 3 out of 9subjects who were positive for RPE lesions.Conclusion: RPE lesions are valuable as aclinical marker in predicting FAP. The co-existingperipheral vascular alterations which have not beenreported before, are probably related to FAP.  相似文献   
66.

Background  

Experimental studies have shown that positron emission tomography (PET) with 13N-labeled ammonia provides accurate quantification of regional myocardial blood flow (MBF) under rest and stress conditions. To establish the clinical utility of this method, the interobserver variability and the temporal variability of serial measurements of blood flow and coronary flow reserve (CFR) must be known. This study investigated the interobserver and temporal reproducibility of 13N-labeled PET for measurement of MBF and CFR.  相似文献   
67.
目的:探索地奥心血康(DAXXK)对急性心肌梗死(AMI)的疗效。方法:AMI病人89例,采用随机单盲法分为2组,DAXXK胶囊组45例,男性36例,女性9例,年龄59±s8a.采用DAXXK200mg,po,tid,共4wk。地尔硫组44例,男性34例,女性10例,年龄58±7a.采用盐酸地尔硫30mg,po,tid,共4wk。结果:DAXXK组治疗后心绞痛发作频率须静脉滴注硝酸甘油的量及镇痛药需用次数均显著低于对照组;心功能(SV,CO,LVEF,STI)改善亦显著优于对照组;心肌酶(GOT,CK,CK-MB,LDH)峰值,住院期间心力衰竭及心律失常发生率亦均显著低于对照组。结论:DAXXK是防治AMI有较好疗效的纯中药制剂。  相似文献   
68.
目的:比较二维超声心动图(2DE)和心电图(ECG)对心肌梗塞(MI)定位诊断的异同、优劣。方法:对59例 MI 患者进行了2DE 和 ECG 检查。在2DE 上将左室分为16个节段而分别确定与 ECG 各导联的对应关系,分别计数2DE 上室壁运动异常(WMA)节段数和 ECG 上有异常 Q 波导联所对应节段数,对比分析两种方法检查结果的一致性。结果:2DE 和 ECG 分别检出338和311个节段阳性,两种方法阳性一致率57.9%,两种方法阳性一致率在各壁的高低依次为下壁、前壁、后壁、前间隔、侧壁;两种方法检测结果的差别有显著性(P<0.05);两种方法检测结果的相关系数 r=0.595(P=0.0000)。结论:两种方法的检查结果有较好的一致性,2DE 优于 ECG。  相似文献   
69.
The peak endocardial acceleration (PEA, unit g) shows a near correlation with myocardial contractility during the isometric systolic contraction of the heart (dP/dtmax), with sympathetic activity and, thus, with physiological heart rate modulation. The (Biomechanical Endocardial Sorin Transducer (BEST) sensor is incorporated in the tip of a pacing lead and measures PEA directly near the myocardium. In an international study, the lead was implanted with the dual chamber pacemaker Living-1 (Sorin) in 105 patients. The behavior of the PEA signal was tested under conditions of physical and mental stress and during daily life activities by 24-hour recordings of PEA (PEA Holter) at 1 to 2 months and approximately 1 year after implantation. Implantation of the BEST lead was performed without complications in all patients. The sensor functioned properly in the short- and long-term in 98% of patients. Although PEA values differed from patient to patient, the values closely reflected the variations in sympathetic activity due to physical and mental stress in each patient. During exercise and during daily life activities a close correlation between PEA and heart rate was observed among patients with normal sinus rhythm. Peak endocardial acceleration allows a nearly physiological control of the pacing rate.  相似文献   
70.
急性心肌梗塞患者溶栓治疗后内皮素水平变化的观察   总被引:1,自引:0,他引:1  
目的:探讨急性心肌梗塞患者溶栓治疗后内皮素变化规律,以及溶栓后冠状动脉(冠脉)再通与未通者ET变化的异同。方法:应用放免技术和酶法分别测定了AMI常规治疗组(21例)和溶栓组(19例)患者梗塞后ET和肌酸激酶同功酶(CK-MB)的动态变化。  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