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   2180412篇
  免费   149895篇
  国内免费   3202篇
耳鼻咽喉   31181篇
儿科学   71478篇
妇产科学   61990篇
基础医学   313501篇
口腔科学   61323篇
临床医学   189038篇
内科学   419122篇
皮肤病学   47232篇
神经病学   167666篇
特种医学   85963篇
外国民族医学   564篇
外科学   334624篇
综合类   45128篇
现状与发展   2篇
一般理论   544篇
预防医学   156220篇
眼科学   49882篇
药学   170180篇
  8篇
中国医学   4901篇
肿瘤学   122962篇
  2018年   21344篇
  2016年   18533篇
  2015年   21048篇
  2014年   28799篇
  2013年   43166篇
  2012年   59207篇
  2011年   63170篇
  2010年   37357篇
  2009年   35070篇
  2008年   60173篇
  2007年   64879篇
  2006年   65888篇
  2005年   63815篇
  2004年   61298篇
  2003年   59358篇
  2002年   57942篇
  2001年   107109篇
  2000年   109940篇
  1999年   92496篇
  1998年   24726篇
  1997年   21964篇
  1996年   22091篇
  1995年   20869篇
  1994年   19403篇
  1993年   18100篇
  1992年   72327篇
  1991年   70395篇
  1990年   69431篇
  1989年   67136篇
  1988年   61754篇
  1987年   60348篇
  1986年   57314篇
  1985年   54265篇
  1984年   39996篇
  1983年   34333篇
  1982年   19685篇
  1981年   17382篇
  1979年   36999篇
  1978年   25494篇
  1977年   22383篇
  1976年   20370篇
  1975年   22735篇
  1974年   26632篇
  1973年   25738篇
  1972年   24580篇
  1971年   22943篇
  1970年   21201篇
  1969年   20544篇
  1968年   18837篇
  1967年   16685篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
32.
33.
Abstract

Objective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.

Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.

Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.

Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings.  相似文献   
34.
35.
36.
37.
38.
39.
Esophageal adenocarcinoma is the fastest rising cancer in the United States. It develops from long‐standing gastroesophageal reflux disease which affects >20% of the general population. It carries a very poor prognosis with 5‐year survival <20%. The disease is known to sequentially progress from reflux esophagitis to a metaplastic precursor, Barrett''s esophagus and then onto dysplasia and esophageal adenocarcinoma. However, only few patients with reflux develop Barrett''s esophagus and only a minority of these turn malignant. The reason for this heterogeneity in clinical progression is unknown. To improve patient management, molecular changes which facilitate disease progression must be identified. Animal models can provide a comprehensive functional and anatomic platform for such a study. Rats and mice have been the most widely studied but disease homology with humans has been questioned. No animal model naturally simulates the inflammation to adenocarcinoma progression as in humans, with all models requiring surgical bypass or destruction of existing antireflux mechanisms. Valuable properties of individual models could be utilized to holistically evaluate disease progression. In this review paper, we critically examined the current animal models of Barrett''s esophagus, their differences and homologies with human disease and how they have shaped our current understanding of Barrett''s carcinogenesis.  相似文献   
40.
Delayed contrast enhancement after injection of a gadolinium-chelate (Gd-chelate) is a reference imaging method to detect myocardial tissue changes. Its localization within the thickness of the myocardial wall allows differentiating various pathological processes such as myocardial infarction (MI), inflammatory myocarditis, and cardiomyopathies. The aim of the study was first to characterize benign myocarditis using quantitative delayed-enhancement imaging and then to investigate whether the measure of the extracellular volume fraction (ECV) can be used to discriminate between MI and myocarditis.In 6 patients with acute benign myocarditis (32.2 ± 13.8 year-old, subepicardial late gadolinium enhancement [LGE]) and 18 patients with MI (52.3 ± 10.9 year-old, subendocardial/transmural LGE), myocardial T1 was determined using the Modified Look-Locker Imaging (MOLLI) sequence at 3 Tesla before and after Gd-chelate injection. T1 values were compared in LGE and normal regions of the myocardium. The myocardial T1 values were normalized to the T1 of blood, and the ECV was calculated from T1 values of myocardium and blood pre- and post-Gd injection.In both myocarditis and MI, the T1 was lower in LGE regions than in normal regions of the left ventricle. T1 of LGE areas was significantly higher in myocarditis than in MI (446.8 ± 45.8 vs 360.5 ± 66.9 ms, P = 0.003) and ECV was lower in myocarditis than in MI (34.5 ± 3.3 vs 53.8 ± 13.0 %, P = 0.004).Both inflammatory process and chronic fibrosis induce LGE (subepicardial in myocarditis and subendocardial in MI). The present study demonstrates that the determination of T1 and ECV is able to differentiate the 2 histological patterns.Further investigation will indicate whether the severity of ECV changes might help refine the predictive risk of LGE in myocarditis.  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