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   718954篇
  免费   49642篇
  国内免费   1725篇
耳鼻咽喉   9336篇
儿科学   23690篇
妇产科学   17792篇
基础医学   111915篇
口腔科学   20229篇
临床医学   65057篇
内科学   137061篇
皮肤病学   16410篇
神经病学   50282篇
特种医学   26170篇
外国民族医学   78篇
外科学   105803篇
综合类   15901篇
现状与发展   2篇
一般理论   162篇
预防医学   52408篇
眼科学   16788篇
药学   54976篇
  9篇
中国医学   2700篇
肿瘤学   43552篇
  2021年   5864篇
  2019年   5784篇
  2018年   8376篇
  2017年   6476篇
  2016年   7176篇
  2015年   8021篇
  2014年   10821篇
  2013年   16032篇
  2012年   21430篇
  2011年   22506篇
  2010年   13321篇
  2009年   12349篇
  2008年   20673篇
  2007年   22227篇
  2006年   22516篇
  2005年   21098篇
  2004年   20567篇
  2003年   19499篇
  2002年   18982篇
  2001年   36730篇
  2000年   37348篇
  1999年   30733篇
  1998年   7987篇
  1997年   6753篇
  1996年   7066篇
  1995年   6714篇
  1994年   6144篇
  1992年   23100篇
  1991年   23033篇
  1990年   22400篇
  1989年   22177篇
  1988年   20114篇
  1987年   19488篇
  1986年   18530篇
  1985年   17351篇
  1984年   12732篇
  1983年   10760篇
  1982年   5933篇
  1979年   11530篇
  1978年   8135篇
  1977年   6843篇
  1976年   6601篇
  1975年   7274篇
  1974年   8505篇
  1973年   8149篇
  1972年   7664篇
  1971年   7134篇
  1970年   6885篇
  1969年   6313篇
  1968年   5786篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A case of seminoma in a monorchid adult guinea fowl (Numida meleagris) is described. Grossly, a right enlarged testis, which was soft in consistency, and white to pale in colour with few spots of haemorrhages was observed. Histologically, the testicle revealed diffusely spread sheets of tumour cells. The cells were large pleomorphic with eccentrically placed hyperchromic nuclei. Mitotic figures were evident. A scanty fibrous stroma, containing lymphocytes and histiocytes, separating the groups of tumour cells, along with few areas of haemorrhages were observed. Occurrence of seminoma in guinea fowl is unusual and hence reported.  相似文献   
102.
103.
Vitiligo and psoriasis are both common skin disorders. However, psoriasis strictly confined to pre-existing vitiligo areas is rare and suggests a causal relationship. We report here on two patients with a strict anatomical colocalization of vitiligo and psoriasis. The histopathological examinations showed typical changes for both diseases together with a dense infiltrate of CD4+ and CD8+ T cells. By immunohistochemistry, intracytoplasmatic granzyme B and tumour necrosis factor alpha (TNF-alpha) were detected within the T-cell population, suggesting the functional activity of these cells and the creation of a local T helper 1 (Th1)-cytokine milieu. Additionally, in one patient we could identify anti-melanocytic T cells by tetramer staining and enzyme-linked immunospot (ELISPOT) analysis. These skin-infiltrating lymphocytes might trigger, by the local production of Th-1 cytokines such as TNF-alpha and interferon-gamma (IFN-gamma), the eruption of psoriatic plaques in patients with a genetic predisposition for psoriasis.  相似文献   
104.
肾细胞癌罕见于儿童,通常在儿童晚期被发现。本文报道1例10岁女孩的特殊肾细胞癌。其影像学表现容易导致误诊,但在既往文献中未见报道。因先天性巨输尿管而导致肾皮质变薄,因此当原发性泌尿道上皮疾病(肿瘤或炎性)首次被发现时,肿瘤完全长入排泄腔(临近的输尿管)。萎缩的肾皮质  相似文献   
105.
Bone stock preservation is crucial when performing total hip replacement in young patients. The aim is to save good bone stock for a possible revision procedure. Furthermore, there is an increasing demand from young and active patients to receive a new joint which allows a normal or nearly normal life style. With this in mind, we began, in 1993, to develop a new femoral implant. The purpose of this ultra-short stem was a physiologic strain distribution on the proximal femur with a proximal load transfer from the implant to the femoral bone. Main features were an almost complete absence of the diaphyseal portion of the stem, a well defined lateral flare with load transfer on the lateral column of the femur, and a very high femoral neck cut. These innovations resulted in a conservative implant on both the bone stock and the soft tissues. This implant, in the first years, was recommended only for young and active patients. Over the last thirteen years, this project has undergone several modifications but the basic principles of the implant have remained the same. In the present review, we present the rationale, the surgical technique and the clinical and experimental results so far obtained with this implant.  相似文献   
106.
Sugar and tooth decays are bound closely. The mechanisms of destruction of the tooth from the glycolyse are known. The role played by the food in the development of the caries is unique. Foods sweetened of all ways, rich in sucrose are responsible of the intervening of the carious lesions. The transformation of the fermentable sugars in lactic with the absence of hygiene and the action conjugated of the bacteria leads to tooth decays in temporary and permanent denture that evolve very quickly in the absence of treatment. Reasons for which the authors put in evidence in this survey, the influence of the food sweetened on the teeth at the children while showing the cases of caries and its complications due to the excessive consumption of fermentable hydrates of carbon.  相似文献   
107.
BACKGROUND: Previous research has demonstrated that academic and neuropsychological functions are compromised in pediatric bipolar disorder (PBD). Investigation of the degree to which neuropsychological deficits might contribute to those academic problems is needed to aid in the recognition and intervention for school achievement difficulties in PBD. METHODS: A sample of 55 children and adolescents with PBD with and without attention-deficit/hyperactivity disorder (ADHD) (PBD group, n = 28; PBD+ADHD group, n = 27) were tested with a computerized neurocognitive battery and standardized neuropsychological tests. Age range of subjects was 7-17 years, with the mean age of 11.97 (3.18) years. Parents completed a structured questionnaire on school and academic functioning. RESULTS: Logistic regression analyses indicated that executive function, attention, working memory, and verbal memory scores were poorer in those with a history of reading/writing difficulties. A separate logistic regression analysis found that attentional dysfunction predicted math difficulties. These relationships between neuropsychological function and academic difficulties were not different in those with PBD+ADHD than in those with PBD alone. CONCLUSIONS: In PBD neuropsychological deficits in the areas of attention, working memory, and organization/problem solving skills all contribute to academic difficulties. Early identification and intervention for these difficulties might help prevent lower academic achievement in PBD.  相似文献   
108.
109.
110.
Background The objective was to measure the plasma concentrations of thymulin and nerve growth factor (NGF) in a group of patients with primary open angle glaucoma (POAG) and compare them with age- and sex-matched normal controls.Methods Twenty-eight patients newly diagnosed with POAG who were not undergoing treatment were compared with the same number of age- and sex-matched healthy controls. Blood samples were drawn into heparinized tubes and plasma samples were collected for the determination of the concentrations of thymulin and NGF, using specific enzyme-linked immunosorbent assay (ELISA). The Student’s t test was used to perform the necessary statistical analysis of the results.Results Seventeen women and 11 men were enrolled in each of the two groups (study and control), with a mean age of 63.7 (SD 10.3) years in the former and 63.3 (SD 9.6) years in the latter. There was a highly significant (p<0.001) elevation in the thymulin levels in POAG patients compared with the control group. However, no significant difference was observed when comparing the plasma NGF levels.Conclusion This is the first report to measure plasma thymulin levels in glaucoma patients. The significant results point the possible role of this immunomodulator in the pathogenesis of primary open angle glaucoma. The potential role of NGF seems to be less likely. These findings warrant further investigation.  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