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   93846篇
  免费   9312篇
  国内免费   4731篇
耳鼻咽喉   2596篇
儿科学   386篇
妇产科学   1707篇
基础医学   10662篇
口腔科学   3400篇
临床医学   6709篇
内科学   11618篇
皮肤病学   1976篇
神经病学   218篇
特种医学   4291篇
外国民族医学   122篇
外科学   13762篇
综合类   16542篇
现状与发展   23篇
预防医学   2027篇
眼科学   396篇
药学   4624篇
  14篇
中国医学   1135篇
肿瘤学   25681篇
  2024年   105篇
  2023年   1277篇
  2022年   2002篇
  2021年   3642篇
  2020年   3152篇
  2019年   2997篇
  2018年   2865篇
  2017年   3275篇
  2016年   3701篇
  2015年   4227篇
  2014年   6217篇
  2013年   5459篇
  2012年   5652篇
  2011年   6124篇
  2010年   4988篇
  2009年   4925篇
  2008年   5119篇
  2007年   5427篇
  2006年   5071篇
  2005年   4529篇
  2004年   3577篇
  2003年   3139篇
  2002年   2680篇
  2001年   2580篇
  2000年   2187篇
  1999年   1754篇
  1998年   1596篇
  1997年   1430篇
  1996年   1258篇
  1995年   1068篇
  1994年   978篇
  1993年   679篇
  1992年   594篇
  1991年   517篇
  1990年   437篇
  1989年   380篇
  1988年   363篇
  1987年   291篇
  1986年   240篇
  1985年   260篇
  1984年   212篇
  1983年   151篇
  1982年   172篇
  1981年   147篇
  1980年   136篇
  1979年   109篇
  1978年   76篇
  1977年   53篇
  1976年   45篇
  1975年   11篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Sarcomatoid renal cell carcinomas (SRC) are rare neoplasms associated with a very poor prognosis. The aim of this study was to evaluate biomarker expression and clinical significance in this uncommon renal cancer. Cytokeratin, epithelial membrane antigen, vimentin, desmin, smooth muscle actin, CD34, S-100 protein, MIB 1, p53, Fas and Fas ligand immunohistochemical expression was investigated in seven renal cell carcinomas with sarcomatoid changes. No significant difference between sarcomatoid and nonsarcomatoid areas was observed with the different biomarkers, excepted for Fas ligand. Fas expression was diffuse in sarcomatoid and nonsarcomatoid areas. However, Fas ligand had a higher expression in sarcomatoid in comparison to nonsarcomatoid areas. Our results showed that Fas and Fas ligand are both expressed in renal cancer. We suggest that the aggressive behavior of sarcomatoid carcinoma may be related to a higher expression of Fas ligand by tumor sarcomatoid cells. These findings may indicate that Fas ligand is a possible therapeutic molecular target for treatment of SRC.  相似文献   
992.
We report on a case of invasive lobular carcinoma of the breast with a previously undescribed cytologic feature. Diff-Quik-stained cytologic preparations showed uniform single cells with prominent coarse cytoplasmic granules. Ultrastructurally, the granules showed features suggestive of autophagosomes and/or degenerative mitochondria. The cytologic differential diagnosis included granulocytic sarcoma, metastatic melanoma, extramedullary hematopoiesis, large granulocytic leukemia/lymphoma, and mast-cell tumor. Adjunctive studies were helpful in the diagnosis of carcinoma. Histologic study of the mastectomy specimen showed classic type of invasive lobular carcinoma.  相似文献   
993.
目的探讨非小细胞肺癌(non-sm all cell lung cancer,NSCLC))急慢性乏氧状况、乏氧与COX-2过度表达及与临床病理特征的关系。方法应用兔抗人H IF-1α、GLUT1抗体和鼠抗人COX-2抗体对手术切除的46例肺癌组织进行免疫组化染色,并与临床病理资料进行相关性分析。结果肺癌患者46例,其中ⅠA期12例,ⅠB期20例,Ⅱ期8例,ⅢA期6例。H IF-1α、GLUT1和COX-2的阳性表达率分别为58.70%(27/46)、39.11%(18/46)和67.39%(31/46)。COX-2表达与H IF-1α、GLUT1的表达相关(P<0.01)。GLUT1表达与肺癌患者淋巴结转移(P<0.05)、组织学类型(P<0.01)有关,而H IF-1α、COX-2表达与年龄、性别、分期、肿瘤大小、淋巴结转移、组织学类型和肿瘤分化程度均无相关性。结论NSCLC患者同时存在着急、慢性乏氧,而肿瘤转移主要与慢性乏氧有关。另外,乏氧可能参与了COX-2增强表达的机制。  相似文献   
994.
乳腺微浸润癌的临床病理学特征及生物学特性   总被引:1,自引:0,他引:1  
目的探讨乳腺微浸润癌(microinvasive carcinoma,MIC)的临床病理学特征及生物学特性和其病理诊断标准。方法回顾性研究40例MIC,按文献报道诊断标准分为两个亚型,并对病理学特征、分子生物学指标及预后进行比较。结果MIC占同期乳腺癌的1.5%,乳腺钼靶拍片85.0%的病例(34例/40例)显示不同程度的泥沙样钙化。粉刺型和高核分级的导管内癌更易形成间质浸润。淋巴结转移2.5%(1例/40例)。31例平均8个月随访显示无复发及转移。两亚型各指标比较结果差异均无显著性。结论MIC是一种少见、淋巴结转移率低、预后较好的恶性肿瘤。建议诊断标准:单个浸润灶时,最大径应〈2mm;出现几个浸润灶时,其中单个浸润灶的最大径应〈1mm,且几个浸润灶面积总和不应超过整个肿瘤组织面积的10%。  相似文献   
995.
目的筛选与涎腺腺样囊性癌转移相关的候选基因,并对其中的候选基因进行初步的验证。方法用限制片段差异显示PCR技术(restriction fragments differential display PCR, RFDD-PCR)建立涎腺腺样囊性癌高、低转移细胞株(ACC-M、ACC-2)的表达谱。对两个表达谱的片段进行比较,通过生物信息学的分析,初步筛选出候选基因。用半定量逆转录PCR技术对筛选出的基因进行初步验证。结果RFDD-PCR方法共获得5420个基因片段,其中包含12个基质金属蛋白酶(matrix metalloproteinase,MMP)基因。半定量逆转录PCR方法发现MMP2、MMP7、MMP9、MMP14、MMP15、MMP24在ACC-M和ACC-2中的表达存在明显差异。结论构建了ACC-M和ACC-2细胞株的表达谱,为寻找目的基因奠定了基础。发现MMP2、MMP7、MMP9和MMP15与涎腺腺样囊性癌的发生、发展、转移有关,不同肿瘤细胞的转移能力可能与不同的MMPs家族基因相关。  相似文献   
996.
AIMS: Three cases with features of so-called 'Warthin-like tumour' of the thyroid (WaLTT) are described, in order to evaluate its relationship with papillary carcinoma (PC). METHODS AND RESULTS: We performed an histological and immunohistochemical study with emphasis on RET/PTC expression. The most striking features are represented by marked lymphocytic infiltration in the stalks of papillae and by oxyphilic metaplasia of epithelium, resembling Warthin tumour of the salivary gland. In all cases, we found nuclear features reminiscent of PC. The neoplastic cells were strongly positive for Leu M1 and epithelial membrane antigen (EMA), less for thyroglobulin and negative for calcitonin. The lymphocytic infiltrate was composed of a mixed population of B and T-cells with sparse S100-positive Langerhans cells. An interesting finding was the strong positivity with the antibody against RET/PTC. CONCLUSION: All clinicopathological data along with the presence of the extensive lymphocytic infiltrate could imply a more favourable prognosis. The expression of RET/PTC fusion gene adds support to the hypothesis that this tumour is a variant of PC, probably related to the oncocytic variant of PC.  相似文献   
997.
Summary 819 salivary gland tumors in surgical pathology files over a 25-year period were reviewed. Among 117 adenoid cystic carcinomas, 86 were located in minor salivary glands and were selected for a clinico-pathological analysis. Complementary histoenzymological investigations and electron microscopic study were performed on specimens from 7 and 13 patients respectively.Adenoid cystic carcinoma occured in older patients (mean age of 54 years) than the other salivary neoplasms. The sex ratio was 1/1. The tumor was located more often in the palate and, to a lesser degree in the buccal floor, tongue or gums.Histologically, epithelial nests contained characteristic cyst-like spaces (cylinders) and 3 varieties of such cylinders were described (mucoid, mucohyalin and hyalin). According to the predominant pattern, 3 types of tumors were shown: basaloïd, cribriform and trabecular. A comparison between histological results and clinical behaviour, available in 67 patients, demonstrated positive correlations. The basaloïd form had always a poor prognosis (numerous early recurrences and metastases, frequent lethal evolution). The cribriform type had an intermediate prognosis, better than basaloïd type and less good than trabecular group (100% of patients still alive at 8 years).Histoenzymological studies revealed high level of acid phosphatase, alkaline phosphatase and leucine aminopeptidase activities round cylindromatous cavities. On the other hand, high oxidative enzyme activities were evenly distributed in all cell types.Ultrastructural findings emphasized the immature characters of epithelial tumor cells. These cells contained numerous ribosomes, but few other organelles. Some more differentiated glandular or epidermoid cells were scattered in neoplastic islands. Rare myoepithelial cells lay in periphery of lobules. Cylinder-like spaces were filled with replicated basal lamellae, mucopolysaccharidic granules and fibrillar structures (microfibrils and periodic collagen fibrils).In the light of these results the histogenesis of this neoplasm was discussed. Like the pleomorphic adenoma, adenoid cystic carcinoma was thought to arise from intercalated ducts. Unable to acquire any high degree of differentiation, this blastomatous tumor had a cellular component almost similar to that shown in intermediate stage of salivary gland embryogenesis.The authors wish to thank M.A. Leost and M. Tacnet for their technical assistance  相似文献   
998.
CCR7 chemokine-receptor expression on tumour cells of gastric carcinoma has been associated with lymph-node metastasis and is thought to play an important role in metastasis. However, so far it is unknown whether CCR7 is newly up-regulated on gastric carcinoma or already expressed in non-neoplastic gastric epithelium. Therefore, epithelial CCR7 expression was investigated in the process of gastric carcinogenesis: non-inflamed mucosa --Helicobacter pylori gastritis -- intestinal metaplasia/dysplasia -- gastric carcinoma. CCR7 was expressed by gastric epithelium in non-inflamed gastric mucosa (n = 5), H. pylori gastritis (n = 17), intestinal metaplasia (n = 10), dysplasia (n = 3) and on tumour cells in 20 of 24 patients with gastric carcinoma (13/14 intestinal-type; 7/10 diffuse-type) as tested by immunohistochemistry. As CCR7 expression by gastric epithelium was significantly stronger in H. pylori gastritis than in non-infected mucosa, the influence of H. pylori on CCR7 receptor expression of gastric epithelial cells was investigated by fluorescence activated cell sorter analysis. H. pylori strains up-regulated the CCR7 chemokine-receptor in CCR7-positive cell lines. No difference in CCR7 up-regulation between cag(+) and cag(-)H. pylori strains was found. Epithelial CCR7 up-regulation by H. pylori may alter the metastatic fate of gastric carcinoma. Additionally, CCR7 expression not only on gastric carcinoma, but also on non-neoplastic gastric epithelium, suggests a novel biological function.  相似文献   
999.
乙酰紫草素注射液对小鼠Lewis肺癌生长抑制的研究   总被引:3,自引:1,他引:3  
目的:探讨乙酰紫草素注射液对小鼠Lewis肺癌的生长抑制作用。方法:建立C57BL/6小鼠lewis肺癌模型进行体内抗瘤实验并计算抑瘤率。结果:乙酰紫草素注射液高中低剂量组的抑瘤率分别为55.49%,45.25%和28.09%。结论:乙酰紫草素注射液能明显抑制小鼠Lewis肺癌的生长。  相似文献   
1000.
原发性食管小细胞癌16例临床分析   总被引:1,自引:0,他引:1  
目的探讨原发性食管小细胞癌的临床特点、治疗及预后。方法回顾分析16例原发性食管小细胞癌患者的临床资料。结果1年总生存率为56.2%,2年总生存率25.0%,3年总生存率12.5%。中位生存期15.7个月。结论对于原发性食管小细胞癌应采用以化疗占主要地位的综合治疗,局限期以手术联合化疗,广泛期以放疗联合化疗为宜。  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