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   1970747篇
  免费   150310篇
  国内免费   3545篇
耳鼻咽喉   29002篇
儿科学   62575篇
妇产科学   58140篇
基础医学   286799篇
口腔科学   56575篇
临床医学   170071篇
内科学   380494篇
皮肤病学   40459篇
神经病学   156124篇
特种医学   77618篇
外国民族医学   524篇
外科学   306549篇
综合类   47121篇
现状与发展   3篇
一般理论   540篇
预防医学   148685篇
眼科学   46231篇
药学   149877篇
  1篇
中国医学   3769篇
肿瘤学   103445篇
  2018年   17903篇
  2015年   17974篇
  2014年   25168篇
  2013年   38493篇
  2012年   52507篇
  2011年   55886篇
  2010年   32818篇
  2009年   30928篇
  2008年   53706篇
  2007年   58377篇
  2006年   58627篇
  2005年   57819篇
  2004年   55975篇
  2003年   54181篇
  2002年   52896篇
  2001年   85044篇
  2000年   87269篇
  1999年   74235篇
  1998年   21757篇
  1997年   19703篇
  1996年   19754篇
  1995年   18685篇
  1994年   17799篇
  1993年   16517篇
  1992年   61368篇
  1991年   60437篇
  1990年   59486篇
  1989年   57757篇
  1988年   53900篇
  1987年   52998篇
  1986年   50598篇
  1985年   48557篇
  1984年   36892篇
  1983年   31923篇
  1982年   19504篇
  1981年   17577篇
  1980年   16358篇
  1979年   35985篇
  1978年   25610篇
  1977年   21829篇
  1976年   20470篇
  1975年   22320篇
  1974年   26933篇
  1973年   26030篇
  1972年   24715篇
  1971年   22927篇
  1970年   21614篇
  1969年   20887篇
  1968年   19358篇
  1967年   17361篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Porocarcinoma is an unusual, locally aggressive and potentially fatal neoplasm. Several cutaneous malignancies have been described in association with porocarcinoma, including squamous cell carcinoma, basal cell carcinoma and tricholemmal carcinoma. Previous reports have indicated that the occurrence of malignant tumours in combination with porocarcinoma is extremely rare, in particular with regard to Bowen disease (BD). We report an uncommon case of porocarcinoma occurring synchronously in a single BD lesion in a 63‐year‐old woman with multiple BD lesions. The clinical and histological findings confirmed this diagnosis.  相似文献   
72.
73.
74.
75.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
76.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
77.
78.
A 17‐year‐old boy presented with recurring severe dermatitis of the face of 5‐months duration that resembled impetigo. He had been treated with several courses of antibiotics without improvement. Biopsy showed changes consistent with allergic contact dermatitis and patch testing later revealed sensitization to benzoyl peroxide, which the patient had been using for the treatment of acne vulgaris.  相似文献   
79.
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   
80.
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