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   2452篇
  免费   412篇
  国内免费   39篇
耳鼻咽喉   16篇
儿科学   132篇
妇产科学   23篇
基础医学   194篇
口腔科学   29篇
临床医学   359篇
内科学   691篇
皮肤病学   153篇
神经病学   199篇
特种医学   295篇
外科学   356篇
综合类   55篇
预防医学   215篇
眼科学   25篇
药学   82篇
中国医学   1篇
肿瘤学   78篇
  2023年   56篇
  2022年   18篇
  2021年   39篇
  2020年   102篇
  2019年   29篇
  2018年   106篇
  2017年   78篇
  2016年   76篇
  2015年   71篇
  2014年   108篇
  2013年   134篇
  2012年   74篇
  2011年   63篇
  2010年   94篇
  2009年   121篇
  2008年   69篇
  2007年   68篇
  2006年   73篇
  2005年   57篇
  2004年   51篇
  2003年   58篇
  2002年   45篇
  2001年   58篇
  2000年   49篇
  1999年   59篇
  1998年   92篇
  1997年   103篇
  1996年   86篇
  1995年   82篇
  1994年   61篇
  1993年   65篇
  1992年   55篇
  1991年   36篇
  1990年   55篇
  1989年   66篇
  1988年   54篇
  1987年   48篇
  1986年   39篇
  1985年   45篇
  1984年   31篇
  1983年   13篇
  1982年   21篇
  1981年   18篇
  1980年   18篇
  1979年   23篇
  1978年   12篇
  1977年   10篇
  1976年   16篇
  1975年   9篇
  1971年   9篇
排序方式: 共有2903条查询结果,搜索用时 15 毫秒
41.
Background: Small cell carcinomas of pulmonary or extrapulmonary origin are neuroendocrine tumors classically associated with ectopic hormone production, particularly ACTH secretion resulting in Cushing's syndrome. However, ectopic Cushing's syndrome has not previously been reported in the setting of small cell carcinoma of the vagina. Methods: A primary vaginal tumor with hepatic metastases was evaluated with light microscopy. Serum cortisol and plasma ACTH levels were evaluated by radioimmunoassay and immunoradiometric assay, respectively, during a standard high-dose (8 mg) overnight dexamethasone suppression test. Results: Vaginal small cell carcinoma with hepatic metastases was demonstrated. Electrolyte abnormalities, elevated cortisol and ACTH levels, and failure to suppress ACTH secretion during high-dose dexamethasone administration confirmed the diagnosis of ectopic ACTH syndrome. Conclusions: This case report establishes a clinical association between vaginal small cell carcinoma and ectopic Cushing's syndrome, confirming the neuroendocrine potential of this malignancy and features common to small cell neoplasms originating in other sites.  相似文献   
42.
Increased placental apoptosis in intrauterine growth restriction   总被引:2,自引:0,他引:2  
OBJECTIVES: Our purpose was to investigate a possible role for apoptosis in the pathophysiologic mechanisms of intrauterine growth restriction. STUDY DESIGN: Placental samples were obtained from 43 uncomplicated third-trimester pregnancies and from 26 pregnancies complicated by intrauterine growth restriction. The definition used to identify cases of intrauterine growth restriction depended on three criteria: clinical evidence of suboptimal growth, ultrasonographic evidence of deviation from an appropriate growth percentile, and individualized birth weight ratios <10th percentile. Light microscopy was used to quantify the incidence of apoptosis. Electron microscopy and TUNEL (terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling) staining were used to confirm the occurrence of apoptosis. RESULTS: Quantification of apoptosis (medians and interquartile ranges) resulted in the following values: normal third trimester (n = 43) 0.14% of cells (0.08% to 0.20%) and intrauterine growth restriction third trimester (n  = 26) 0.24% of cells (0.16% to 0.29%). The incidence of apoptosis was significantly higher in placentas from pregnancies with intrauterine growth restriction compared with normal third-trimester placentas (p < 0.01, Mann Whitney U test). CONCLUSIONS: These results suggest that apoptosis may play a role in the pathophysiologic mechanisms of intrauterine growth restriction.(Am J Obstet Gynecol 1997;177:401)  相似文献   
43.
44.
食品中明矾含量的快速测定方法   总被引:1,自引:0,他引:1  
梁伟  戴京晶  刘奋  林奕芝  莫浩联 《职业与健康》2006,22(14):1068-1069
目的建立一种能简单快速检测食品中明矾含量的方法。方法采用特征离子鉴别方法定性,用Na2EDTA络合滴定方法定量。结果该方法回收率在99.0%~102.8%之间,RSD在0.91%~1.38%之间。结论方法操作简单,准确性好,适合于大批量样本检测。  相似文献   
45.
46.
47.
Intermittent dysfunction of mechanical mitral valve prosthesis is an uncommon condition. It carries serious clinical implications if unrecognized. Here, we present a case of a 28‐year‐old female with a history of rheumatic multivalvular disease, for which she had undergone double valve replacement and tricuspid annuloplasty. Six months later, she presented with heart failure. Clinical examination revealed intermittent loss of closing clicks followed by a pansystolic murmur at the apex, suggestive of mitral prosthetic valve dysfunction. We highlight the echocardiographic findings of paroxysmal mitral valvular regurgitation secondary to prosthetic valve malfunction secondary to prosthetic valve thrombosis.  相似文献   
48.
Retroaortic course of coronary artery is a relative contraindication for device closure of an atrial septal defect. In this brief report, we demonstrate, for the first time, inferior aortic recess mimicking retroaortic left circumflex coronary artery in a patient with atrial septal defect. This distinction is important to avoid spurious diagnosis of anomalous coronary artery denying patient a chance of nonsurgical closure of atrial septal defect.  相似文献   
49.
Sinus of Valsalva aneurysm is a rare congenital cardiac abnormality and is usually diagnosed when it ruptures. An asymptomatic 55‐year‐old male of unruptured sinus of Valsalva aneurysm of noncoronary cusp was on medical follow‐up. At 2‐year follow‐up, there was thrombus formation in the aneurysm, mimicking right atrium tumor on 2D transthoracic echocardiography. Cardiac computed tomography showed filling defect in the aneurysm suggestive of thrombus. Considering the high risk of systemic emboli surgery was performed, and aneurysm was repaired with Dacron patch.  相似文献   
50.
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