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   2794篇
  免费   254篇
  国内免费   252篇
耳鼻咽喉   28篇
儿科学   23篇
妇产科学   19篇
基础医学   333篇
口腔科学   20篇
临床医学   345篇
内科学   418篇
皮肤病学   16篇
神经病学   132篇
特种医学   111篇
外国民族医学   1篇
外科学   324篇
综合类   564篇
一般理论   1篇
预防医学   185篇
眼科学   37篇
药学   332篇
  1篇
中国医学   144篇
肿瘤学   266篇
  2024年   14篇
  2023年   32篇
  2022年   116篇
  2021年   120篇
  2020年   89篇
  2019年   79篇
  2018年   80篇
  2017年   92篇
  2016年   79篇
  2015年   101篇
  2014年   138篇
  2013年   127篇
  2012年   156篇
  2011年   184篇
  2010年   127篇
  2009年   100篇
  2008年   94篇
  2007年   126篇
  2006年   117篇
  2005年   115篇
  2004年   149篇
  2003年   241篇
  2002年   205篇
  2001年   156篇
  2000年   90篇
  1999年   71篇
  1998年   44篇
  1997年   35篇
  1996年   32篇
  1995年   37篇
  1994年   29篇
  1993年   15篇
  1992年   15篇
  1991年   12篇
  1990年   20篇
  1989年   15篇
  1988年   10篇
  1987年   12篇
  1986年   8篇
  1985年   6篇
  1984年   5篇
  1983年   4篇
  1982年   1篇
  1979年   2篇
排序方式: 共有3300条查询结果,搜索用时 13 毫秒
101.
微载体培养MEK和Vero细胞试制甲肝灭活疫苗   总被引:2,自引:0,他引:2  
目的探索微载体培养细胞大量制备甲肝病毒抗原及其灭活疫苗的可行性。方法使用 Cytodex- 1培养恒河猴胚肾细胞和 Vero细胞制备 HAV ,经过初步纯化、甲醛灭活、吸附佐剂 ,制成甲肝灭活疫苗 ,免疫昆明种小白鼠 ,测定免疫原性。结果 HAV X株和 W株抗原滴度分别为 1∶ 2 5 6、1∶ 12 8,感染滴度 (log TCID5 0 / m l)分别为 8.5 0、8.17,与静止培养获得的滴度相当。小鼠抗 HAV抗体第 45 d达到峰值 ,滴度分别为 1∶ (96 .0± 78.4)、1∶ (12 8.0± 70 .1)。结论实验性甲肝灭活疫苗具有良好的免疫原性 ,应用微载体培养细胞制备甲肝灭活疫苗是可行的。  相似文献   
102.
PurposeTo evaluate the prognosis of nasopharyngeal carcinoma (NPC) patients who developed bone-only metastasis after primary treatment and the stratification of these patients into different risk groups based on independent prognostic factors.ResultsThe median follow-up time was 15.5 months (range, 2–67 months) for the whole cohort. The median overall metastatic survival (OMS) time and the 2-year estimate OMS rate were 26.5 months and 52%, respectively. Multivariate analysis indicated that patients with short metastases-free interval, multiple bone metastases sites, high serum lactic dehydrogenase levels, and treated with radiotherapy or chemotherapy alone had significantly worse outcomes. Patients were stratified into three different risk groups based on the number of adverse factors present. The OMS curves of the three groups were all significantly different (p<0.001).ConclusionSeverl prognostic factors were found to be associated with worse outcomes. According to the number of adverse factors present, bone-only metastasis patients can be stratified into three risk groups with significantly different prognoses. Such grouping may help in improving the design of clinical trials and in guiding individualized treatment for NPC patients with bone-only metastasis.  相似文献   
103.
Syndecan-1 (CD138), a heparan sulfate proteoglycan, acts as a co-receptor for growth factors and chemokines and is a molecular marker associated with the epithelial–mesenchymal transition during development and carcinogenesis. In this study, we generated two specific mouse anti-human CD138 monoclonal antibodies (mAbs, clone ID: 480CT5.4.3, 587CT7.3.6.5) using hybridoma technology and identified their immunological characteristics. After hybridoma sequencing, the single-chain variable fragments (ScFvs) cloned from two hybridoma cells were combined with anti-CD3 OKT-3 ScFv to generate two recombinant bispecific antibodies (h-STL002, m-STL002) against CD138 and CD3 molecules, respectively. The bispecific antibodies were able to specifically target CD138?+?multiple myeloma (MM) cells and CD3?+?T cells, and showed the potent cytotoxicity against MM RPMI-8226 cell line through T cell activation. However, these bispecific antibodies without T cells did not cause toxic side effect on MM cells. Overall, the two hybridoma clones and their bispecific formats have great potential to promote diagnosis and immunotherapy of plasma cell malignancy.  相似文献   
104.
目的:构建最近克隆的人era基因的定点突变体。方法:利用数据库对era的结构特点进行分析,在此基础上用改良的重叠延伸法分别构建人EraN端和C端的定点突变体。结果:获得了分别针对人EraN端TGP结合结构域(位于29-36氨基酸残基)和C端具有RNA结合活性的 KH结构域(位于297-340氨基酸残基)的定点突变体。结论:人era定点突变体的构建为进一步的功能研究奠定了基础。  相似文献   
105.
凋亡肿瘤细胞负载的树突状细胞对抗原特异性CTL的激活   总被引:4,自引:0,他引:4  
为探讨凋亡Daudi细胞负载的树突状细胞 (DC )激发诱导肿瘤抗原特异性CTL及其生物学特性 ,采用常规方法从人外周血单个核细胞 (PBMC )诱导DC ,激发型CD40mAb联合 50Gyγ射线辐照诱导Daudi凋亡后负载DC ,然后与自体T细胞共育 ,并联合IL 2激发诱导肿瘤特异性CTL ;采用免疫荧光标记和流式细胞仪测定分析膜分子的表达 ;ELISA检测细胞因子的产生 ;Dextran FITC内吞实验分析DC的抗原摄取能力 ;3H掺入试验和51 Cr释放试验分别测定CTL的增殖和细胞毒效应。结果 :(1 )细胞因子序贯体外诱导 7d的DC ,对Dextran吞噬能力最强 ;(2 )CD40mAb诱导联合γ射线辐照 ,能有效介导Daudi细胞的凋亡 ;(3 )抗原负载联合CD40mAb激发可使DC上调表达CD1a、CD80、CD86和HLA DR ,并能促进IL 1 2的分泌 ;(4)凋亡Daudi负载后的DC在激发型CD40mAb作用下 ,能激发和扩增对Daudi细胞具有高效和特异杀伤作用的细胞毒性T细胞。因而认为凋亡肿瘤细胞负载联合CD40mAb刺激的DC可有效激活和扩增肿瘤特异性CTL。  相似文献   
106.
神经营养素-4在成年猴脑的分布   总被引:2,自引:0,他引:2  
目的 :为探讨神经营养素 4(Neurotrophin 4,NT 4)在成年灵长类动物猴脑的分布及功能提供有用的形态学依据。方法 :免疫组织化学SP法。结果 :NT 4 IR(Neurotrophin 4immunoreactive)分布于大脑皮层Ⅲ Ⅴ层的部分神经元胞体及突起以及白质内少量的神经胶质细胞 ;小脑皮质及白质内的部分神经元 ;海马CA1、CA2 、CA3区的部分神经元 ;此外豆状核、尾状核、脑桥核、前庭神经核、薄、契束核、副神经核等可见散在阳性反应细胞及交织成网的纤维。结论 :NT 4 IR广泛地分布于猴脑的多种组织和细胞 ,提示其功能可能涉及不同类型的神经元及可能的非神经元  相似文献   
107.
The etiological role of human papillomavirus (HPV) in cervical cancer has been well established. However, it is inconclusive whether HPV plays the same role in esophageal carcinogenesis. In this study, we detected HPV infection in 145 frozen esophageal tissues, including 30 normal epithelium (ENOR), 37 dysplasia (DYS) and 78 invasive squamous cell carcinoma (ESCC), and in 143 frozen cervical tissues composed of 30 normal epithelium (CNOR), 38 intraepithelial neoplasia (CIN) and 75 invasive squamous cell carcinoma (CSCC). The patients and symptom-free subjects enrolled in this study were from a high-incidence area for both ESCC and CSCC, Linzhou City, Northern China, from 2007 to 2009. The HPV infection analysis was conducted by using an HPV GenoArray Test Kit. We found that the high-risk HPV types accounted for more than 90 % of the HPV-positive lesions of esophagus and cervix tissues. The prevalence of high-risk HPV types increased significantly during the progression of both esophageal and cervical carcinogenesis (positive rate in esophageal tissues: 33 % ENOR, 70 % in DYS and 69 % in ESCC; positive rate in cervical tissues: 27 % in CNOR, 82 % in CIN and 88 % in CSCC; P < 0.001, respectively). Infection with the high-risk HPV types increased the risk for both DYS and ESCC by 4-fold (DYS vs. ENOR: OR = 4.73, 95 %CI = 1.68-13.32; ESCC vs. ENOR: OR = 4.50, 95 %CI = 1.83-11.05) and increased the risk for both CIN and CSCC by 12-fold and 20-fold (CIN vs. CNOR: OR = 12.18, 95 %CI = 3.85-38.55; CSCC vs. CNOR: OR = 20.17, 95 %CI = 6.93-58.65), respectively. The prevalence of high-risk types in ESCC patients was lower than that in CSCC patients (P = 0.005) and was significantly associated with the degree of ESCC tumor infiltration (P = 0.001). HPV 16 was the most prevalent subtype in both esophageal and cervical tissues. Single HPV infection increased significantly along with the progression of ESCC and maintained a high level in cervical tissues, regardless of whether they were CNOR or CSCC tissues. Our results showed that infection with HPV, especially the high-risk types, was positively associated with both esophageal and cervical cancers, suggesting that HPV also plays a role in the etiology of ESCC in the high-incidence area.  相似文献   
108.
Francisella tularensis is a facultative intracellular, Gram-negative pathogen and the causative agent of tularemia. We previously identified TolC as a virulence factor of the F. tularensis live vaccine strain (LVS) and demonstrated that a ΔtolC mutant exhibits increased cytotoxicity toward host cells and elicits increased proinflammatory responses compared to those of the wild-type (WT) strain. TolC is the outer membrane channel component used by the type I secretion pathway to export toxins and other bacterial virulence factors. Here, we show that the LVS delays activation of the intrinsic apoptotic pathway in a TolC-dependent manner, both during infection of primary macrophages and during organ colonization in mice. The TolC-dependent delay in host cell death is required for F. tularensis to preserve its intracellular replicative niche. We demonstrate that TolC-mediated inhibition of apoptosis is an active process and not due to defects in the structural integrity of the ΔtolC mutant. These findings support a model wherein the immunomodulatory capacity of F. tularensis relies, at least in part, on TolC-secreted effectors. Finally, mice vaccinated with the ΔtolC LVS are protected from lethal challenge and clear challenge doses faster than WT-vaccinated mice, demonstrating that the altered host responses to primary infection with the ΔtolC mutant led to altered adaptive immune responses. Taken together, our data demonstrate that TolC is required for temporal modulation of host cell death during infection by F. tularensis and highlight how shifts in the magnitude and timing of host innate immune responses may lead to dramatic changes in the outcome of infection.  相似文献   
109.
目的:观察自然夜间多导睡眠图(PSG)对酒依赖(CA)的辅助诊断价值。方法:应用日本Nihon Kohden公司的Neurofax-1518K多导睡眠生理仪,采用眼电图和下颌肌电图及脑电图技术,对25例经戒断后的酒依赖患者和23名正常对照者进行PSG整夜监测。结果:与健康男性组比较,酒依赖组睡眠潜伏期延长(NC组18.7±8.9分,CA组31.5±14.3分,P〈0.01),Ⅰ期睡眠增加(NC组9.1±1.8%,CA组19.9±7.4%,P〈0.05),睡眠效率降低’(NC组95.1±7.8%,CA组81.5±11.3%,P〈0.01),快速眼动潜伏期前移(NC组89.4±13.1分,CA组74.9±21.4分,P〈0.05)。结论:长期滥用酒精会引起睡眠生理障碍,而睡眠障碍又会加重酒依赖躯体功能的变化。  相似文献   
110.
背景:目前国内外对全酸蚀、自酸蚀及自黏结树脂黏结剂对纤维桩的冠向微渗漏及黏结强度影响的研究仍存在差异。 目的:评价全酸蚀、自酸蚀及自黏结3种树脂黏结剂对纤维桩黏固后冠向微渗漏及黏结强度影响。 方法:将32颗人离体上前牙随机分成5组,其中3组为实验组,2组为对照组。实验组离体牙经根管预备后,选用全酸蚀、自酸蚀及自黏结3种树脂黏结剂分别黏结直径为1.4 mm的玻璃纤维桩。体视显微镜下观察试件各剖面的微渗漏情况,再将实验组试件沿垂直牙长轴方向切成厚度为2 mm的薄片,万能材料测试机进行微推出实验,并观察试件断裂方式。阳性对照组不进行根管预备,根部涂布指甲油,冠部直接暴露于染色剂中;阴性对照组不进行根管预备,树脂覆盖根管口,将牙体整体涂布指甲油后黏蜡包埋至截面下1 mm。 结果与结论:各种树脂黏结剂均存在微渗漏现象,其中全酸蚀树脂黏结剂的微渗漏程度最轻,自酸蚀树脂黏结剂的微渗漏程度最重。3种树脂黏结剂间的微渗漏程度差异有显著性意义(P < 0.05)。黏结剂间的黏结强度由高到低分别为全酸蚀树脂黏结剂、自酸蚀树脂黏结剂、自黏结树脂黏结剂,3种黏结剂的黏结强度差异有显著性意义(P < 0.05)。试件的主要断裂方式为黏结剂/纤维桩间断裂及混合破坏。说明全酸蚀树脂黏结剂与牙本质结合紧密,与自酸蚀树脂黏结剂、自黏结树脂黏结剂比较在微渗漏程度及黏结性能方面显示出优越性。  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