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   47629篇
  免费   3535篇
  国内免费   1971篇
耳鼻咽喉   177篇
儿科学   830篇
妇产科学   490篇
基础医学   6848篇
口腔科学   507篇
临床医学   3715篇
内科学   13433篇
皮肤病学   637篇
神经病学   3160篇
特种医学   912篇
外国民族医学   2篇
外科学   3721篇
综合类   5240篇
现状与发展   5篇
预防医学   2836篇
眼科学   909篇
药学   6169篇
  6篇
中国医学   1530篇
肿瘤学   2008篇
  2023年   470篇
  2022年   911篇
  2021年   1181篇
  2020年   1164篇
  2019年   1828篇
  2018年   1801篇
  2017年   1619篇
  2016年   1593篇
  2015年   1754篇
  2014年   2871篇
  2013年   3320篇
  2012年   2621篇
  2011年   2909篇
  2010年   2192篇
  2009年   2120篇
  2008年   2108篇
  2007年   2316篇
  2006年   2042篇
  2005年   1793篇
  2004年   1575篇
  2003年   1454篇
  2002年   1227篇
  2001年   1101篇
  2000年   934篇
  1999年   848篇
  1998年   722篇
  1997年   775篇
  1996年   578篇
  1995年   580篇
  1994年   502篇
  1993年   380篇
  1992年   336篇
  1991年   262篇
  1990年   202篇
  1989年   181篇
  1988年   150篇
  1987年   131篇
  1985年   466篇
  1984年   566篇
  1983年   453篇
  1982年   418篇
  1981年   406篇
  1980年   363篇
  1979年   324篇
  1978年   276篇
  1977年   208篇
  1976年   247篇
  1975年   250篇
  1974年   196篇
  1973年   174篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
对HCV血清标记阳性的静脉内毒瘤者进行半年和15个月随访,并调查影响转归的部分因素。结果显示,静脉内毒瘾者抗-HCV自然转阴率分别为11.0/和33.3%。单因素和多因素分析均提示转阴率以婚姻状况良好的已婚者较离婚者高、人均年收入高者较低者高,说明婚姻状况和人们的经济水平对毒瘾者抗-HCV转阴有一定的影响。  相似文献   
102.
A 25-year-old female has had brown to erythematous telangiectatic patches and grouped papules on her face, neck, arm, and trunk since childhood following B.C.G. vaccination. Histopathologically, the lesions consisted of hyperkeratosis, slight acanthosis, tuberculoid granulomas with some Langerhans type giant cells in the mid-dermis. Although various forms of cutaneous tuberculosis after B.C.G. vaccination have been reported, it was difficult for us to assign the patient's skin lesion to any specific disease entity. Remission of her cutaneous lesions occurred clinically and histopathologically after treatment with isoniazid and rifampin.  相似文献   
103.
Behcet's disease (BD) is characterized by recurrent oral aphthae, skin lesions, eye lesions, and genital ulceration. To determine the pathogenesis of BD, we performed histological and immunohistochemical studies of these mucocutaneous lesions, an assay of neutrophil activity, and HLA typing. Dense dermal or subcutaneous infiltrations of polymorphonuclear cells (PMN) without leukocytoclastic vasculitis were found in 28 of 57 lesions. Immunohistochemically, deposits of C3 on the vessels were found in 12 of 31 lesions. Deposits of immunoglobulin were not found except for one of IgM. C3 deposits and PMN infiltrations were significantly related (p<0.05). PMN activity by polarization was enhanced; however, the results did not show a significant relationship with the PMN infiltrations or the C3 deposits. The incidence of HLA-B51 was significantly high in BD, but no significant relationship was found between HLA-B51 and the results of other examinations. These results suggest that the pathogenesis of BD lesions differs from that of collagen diseases and that C3 deposits on the vessels may play an important role in the development of mucocutaneous lesions where PMN have mainly infiltrated.  相似文献   
104.
Our new finding of de novo synthesis and secretion of C3 by both murine peritoneal macrophages and polymorphonuclear leukocytes (PMN) was confirmed by the incorporation of [35S]methionine into C3 molecules and their complete inhibition by cycloheximide. The methods of secretion of C3 from these two types of cells were compared by examining the C3 contents in their culture supernatants. Completely different modes of secretion were observed, i.e. although macrophages synthesize and secrete C3 constitutively, PMN has a mechanism to store the already synthesized C3 in the cell and secrete it in response to stimuli. Protein kinase C (PKC) activators, e.g. 12-O-tetradecanoyl-phorbol 13-acetate, dioctanoyl glycerol, and mezerein, as well as calcium ionophore A23187 stimulate the secretion of C3 from PMN. These results suggest the involvement of PKC and the calmodulin pathway. A very sensitive method for measuring C3 activity was developed which enabled us to show for the first time that C3 secreted by PMN had opsonizing activity and that particles cultured with PMN were phagocytosed effectively.  相似文献   
105.
本文采用热变性温度法和液相复性速率法对—轻型特征及血清学反应相似米克戴德军团菌(Lm)的菌株进行了测定,结果表明该菌与标准Lm(C DC株)的DNA G Cmol%相差3.45%,与标准Lm(C DC株)的DNA同源性达81.99%,根据伯杰细菌鉴定手册(1984),可判定该菌株与标准Lm(C DC株)为遗传型一致的类群,即从遗传学角度证明该菌为Lm。  相似文献   
106.
对血清抗-HCV阳性的65名个体供血者进行血清HCV-RNA检测,并作HCV基因分型,结果发现其中60例为HCV-RNA阳性,且均为HCV-Ⅱ型,提示本组个体供血者中以HCV-Ⅱ型为感染优势株。通过对HCV5'-非编码区基因PCR为基础的核酸内切酶分型法和HCV核心区基因PCR直接分型法的比较发现,前者在敏感性及经济、简便等方面优于后者。  相似文献   
107.
中国人不同C4基因型时血中C4浓度的定量检测   总被引:1,自引:0,他引:1  
吴锋  姜晓丹 《免疫学杂志》1992,8(4):256-259
用神经氨酸酶及羧肽酶B处理血浆,依次经C4高压琼脂糖电泳、免疫固定、薄层激光扫描等步骤,并结合血浆免疫火箭电泳定量法对我国武汉地区随机人群的血浆C4总量及C4两种同种型,主要别型,单、双QO,重复座位等时的血浆C4含量进行了检测与分析。结果发现:遗传因素明显影响血浆C4水平,因而在群体中表现宽广的C4浓度范围,特别在有C4QO与C4重复基因座位时差异特别明显。这一研究提示,不同的C4基因型,循环C4含量表现明显差异。临床上检测C4含量时应该考虑患者的C4基因型别。  相似文献   
108.
丙型肝炎患者外周血单核细胞中丙型肝炎病毒复制的研究   总被引:2,自引:0,他引:2  
9例临床诊断为丙型肝炎患者,研究其外周血单核细胞中HCVRNA的存在及复制。9例患者血清标本抗-HCV及HCVRNA均为阳性,采用高敏感的逆转录一套式PCR法测定其外周血单核细胞中HCV正、负链RNA,结果9例患者外周血单核细胞中7例HCV正链RNA阳性,3例HCV负链RNA阳性,证实部分丙肝患者外周血单核细胞中存在HCV的复制,表明肝细胞并非为HCV感染与复制的唯一场所。  相似文献   
109.
Nerve biopsy findings in Niemann-Pick type II (NPC)   总被引:1,自引:0,他引:1  
The severe infantile form of Niemann-Pick disease type II was diagnosed in a 4-year-old girl and confirmed by demonstrating in cultured skin fibroblasts a deficiency of low-density lipoprotein-stimulated cholesterol ester synthesis of < 5% of normal. Electrodiagnostic studies revealed changes of a predominantly demyelinating motor and sensory polyneuropathy. Light microscope and ultrastructural examination of a peroneal nerve biopsy showed unique changes. Compacted myelin sheaths were disproportionately thin with marked globular irregularities in single teased nerve fibres and evidence of chronic demyelination. The majority of axons were preserved but axonal spheroids and cytoskeletal abnormalities akin to neuroaxonal dystrophy were noted. Membrane-bound multilobulated lysosomal inclusions of floccular and electron-dense material were present in Schwann cells (SC), endoneurial fibroblasts, macrophages, pericytes and endothelial cells. SC of myelinated fibres were stuffed with whorls of concentric osmiophilic membranous profiles and electron-lucent material. The findings are diagnostic and differ from those of classical Niemann-Pick disease.  相似文献   
110.
本文报道2,5-二硝基苯酚在0.5mol/L氢氧化钠介质中及在40℃恒温水浴中加热15min的条件下与维生素C作用生成红色还原产物,其最大吸收波长位于500nm。维生素C浓度介于0.03~0.1mg/ml之间服从比耳定律,其mol吸光系数为3.2×10~3L·mol~(-1)·cm~(-1),Sandell灵敏度为0.055μg/cm~2。红色还原产物的色泽可稳定24h。本法曾用于药物片剂中维生素C含量的测定获得满意结果。  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