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   57258篇
  免费   5434篇
  国内免费   4669篇
耳鼻咽喉   557篇
儿科学   517篇
妇产科学   532篇
基础医学   6600篇
口腔科学   839篇
临床医学   7952篇
内科学   8198篇
皮肤病学   470篇
神经病学   3033篇
特种医学   2189篇
外国民族医学   45篇
外科学   5508篇
综合类   10368篇
现状与发展   8篇
一般理论   5篇
预防医学   3882篇
眼科学   1433篇
药学   6379篇
  66篇
中国医学   3693篇
肿瘤学   5087篇
  2024年   198篇
  2023年   943篇
  2022年   2437篇
  2021年   2920篇
  2020年   2283篇
  2019年   1980篇
  2018年   2077篇
  2017年   1817篇
  2016年   1770篇
  2015年   2757篇
  2014年   3196篇
  2013年   2713篇
  2012年   4134篇
  2011年   4419篇
  2010年   2842篇
  2009年   2146篇
  2008年   2817篇
  2007年   2914篇
  2006年   2933篇
  2005年   2734篇
  2004年   2083篇
  2003年   2298篇
  2002年   2019篇
  2001年   1760篇
  2000年   1509篇
  1999年   1417篇
  1998年   1025篇
  1997年   935篇
  1996年   677篇
  1995年   699篇
  1994年   604篇
  1993年   300篇
  1992年   401篇
  1991年   336篇
  1990年   265篇
  1989年   265篇
  1988年   193篇
  1987年   154篇
  1986年   128篇
  1985年   97篇
  1984年   45篇
  1983年   36篇
  1982年   25篇
  1981年   25篇
  1980年   19篇
  1979年   12篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
目的 :研究孕激素受体拮抗剂米索前列醇对妊娠晚期引产的效果。方法 :采用双盲对照法 ,选择晚期妊娠无米索前列醇禁忌证 6 0例为研究组 ,采用阴道给药总量 1 0 0mg ;另选择有关参数相同的 6 0例 ,应用催产素 ,两组观察相关指标体系进行比较。结果 :引产效果 ,分娩时间 ,宫颈评分等指标研究组均优于对照组。结论 :米索前列醇用于晚期妊娠引产效果优 ,安全  相似文献   
102.
The geographic range of Zika virus (ZIKV) has expanded from Asia to the Americas, leading to the 2015–2016 pandemic with enhanced neurovirulence. At present, ZIKV is continuously circulating in many Southeast Asian countries. Unfortunately, the persistent evolution of ZIKV in Southeast Asia and its influence on the biological characteristics of the virus remain incompletely understood. In this study, the in vitro and in vivo properties of a new ZIKV isolate obtained from Cambodia in 2019 (CAM/2019) were characterized and compared with those of the Cambodian strain (CAM/2010). Compared with CAM/2010, the CAM/2019 virus showed similar plaque morphology and growth curves in cell cultures and induced comparable viremia and organ viral loads profiles in both BALB/c and A129 (IFNAR1−/−) mice upon intraperitoneal (i.p.) inoculation. Remarkably, the CAM/2019 virus exhibited enhanced neurovirulence in neonatal mice compared with CAM/2010, with a 74-fold reduction in the 50% lethal dose (LD50). Consistently, CAM/2019 produced higher viral loads in the brains of BALB/c neonatal mice than CAM/2010 did. Sequence alignment showed that the CAM/2019 virus has acquired 12 amino acid substitutions, several of which were found to be associated with neurovirulence. In particular, the CAM/2019 virus shared an A1204T substitution in NS2A with the Thai isolate SI-BKK02 that was isolated from a microcephaly case. Taken together, our results indicate that a ZIKV strain isolated with specific mutations has emerged in Cambodia, highlighting the need for extensive molecular and disease surveillance in Cambodia and other Asian countries.  相似文献   
103.
探讨药物致肾损伤早期诊断方法。用酶法测定碱性磷酸酶(ALP)。速率法测γ-谷氨酰转肽酶(GGT),N-乙酰-β-D氨基葡萄糖苷酶(NAG)、β-半乳糖苷酶(Gal)及肌肝(UCr),磺柳酸法测尿蛋白(Pro)。结果:尿酶升高均早于尿蛋白的出现,特别是NAG于用药后第3天即有显著升高,Gal则在用药后3d内持续升高,尿酶,特别是NAG是药物引起肾损伤早期诊断指标。  相似文献   
104.
目的:综述P^27的研究进展。方法:光盘检索有关献,归纳综合整理。结果:P^27是细胞周期的相关蛋白,P^27白过度表达可抑制细胞周期的进程,阻断细胞生长于G1期。结论:P^27是细胞周期中重要的负性调控控因子,是一种新的侯选的肿瘤抑制基因。  相似文献   
105.
The poly(l -lactic acid) (PLLA)/carbon nanomaterials composite foams with hierarchical surface microstructural and internal conductive pathways are successfully prepared by a simple crystallization-assisted rapid phase separation (CARPS). The dimension and morphology of carbon nanomaterials can induce different crystallization forms to construct the hierarchical surface microstructure, and they are distributed on the phase interface of solvent and non-solvent to form conductive pathways. It is found that the heterogeneous nucleation of nanomaterials promotes a significant increase in crystallinity, and a stacked granular structure formed on the surface promotes the increase of the water contact angle to 148.7°. Foams with interconnecting pore structures contribute to the formation of 85.3% porosity and 12.33 g g−1 oil absorption. Carbon nanomaterials are distributed on the pore walls of the porous foam, which converts the foam from an insulating material to a conducting polymer. Furthermore, the uniform distribution of nanomaterials significantly affects the thermal stability of the PLLA. In belief, the multifunctional biodegradable foam, prepared by a CARPS method, makes it promising for industrial production and has potential applications in electrical conductivity, oil-water separation, and many other fields.  相似文献   
106.
Purification of thrombospondin from human platelets   总被引:1,自引:0,他引:1  
Summary Thrombospondins are a rapidly growing family of adhesive proteins that have diverse activities to modulate cellular growth, motility, and gene expression. Thrombospondin-1 (TSP) was the first identified member of this family and is the major form of thrombospondin in human platelets. A method is described to prepare TSP from human platelets in biologically active form with minimal degradation or contamination with other platelet proteins.  相似文献   
107.
The push-pull technique was used to investigate the release of the excitatory amino acid glutamate in the posterior hypothalamic area of the conscious rat. The hypothalamus was superfused through the pushpull cannula with artificial cerebrospinal fluid (CSF), and the superfusate was collected in time periods of 10 min when ionic conditions in the CSF were changed, or in short periods of 3 min when blood pressure changes were evoked. The mean glutamate release rate was 2.8 + 0.7 pmol/min. Depolarization by hypothalamic superfusion with CSF containing 50 mM K+ enhanced the release of glutamate in the presence of Ca2+. The K+-induced release was attenuated by 40% when the hypothalamus was superfused with Ca2+-free CSF. Replacement of Ca2+ by Mg2+ abolished the K+-induced release of glutamate. Hypovolaemia elicited by haemorrhage enhanced the release rate of glutamate. Similarly, a hypotension elicited by i.v. injection of chlorisondamine (3 mg/kg) led to a pronounced and permanent enhancement in glutamate release. The effects of hypovolaemia and chlorisondamine on glutamate release were abolished in aortic denervated rats, indicating that this response is due to a decrease of impulse generation in baroreceptors. A hypovolaemia elicited by blood infusion did not affect the release of glutamate. Similarly, a pronounced pressor response to phenylephrine (15 /kg per minute) infused intravenously for 9 min was ineffective.The results show that the K+-induced release of glutamate in the hypothalamus is dependent on the presence of Ca2+. The increase in glutamate release rate by hypovolaemia or chlorisondamine suggests that the glutamatergic neurons in the posterior hypothalamic area respond to unloading of aortic baroreceptors and possess a counteracting, hypertensive function.  相似文献   
108.
目的 探讨上海市≥50岁人群维生素D水平与握力的关系。方法 数据来源于WHO全球老龄化与成人健康研究我国上海市2018-2019年数据,采用logistic回归模型分析维生素D水平与握力的关系,进一步按照性别、年龄及乳制品摄入情况进行分层;采用限制性立方样条曲线绘制维生素D水平与低握力的剂量-反应曲线。结果 共4 391人纳入研究,其中男性2 054人(46.8%);年龄(67.02±8.81)岁;低握力1 421人(32.4%);维生素D不足及缺乏分别为1 533人(34.9%)和401人(9.1%)。在调整相关混杂因素后,logistic回归分析结果显示,维生素D缺乏的人群发生低握力的风险更高(OR=1.41,95%CI:1.09~1.83);在男性中,调整相关混杂因素后,维生素D缺乏与低握力发生风险呈显著正相关(OR=1.67,95%CI:1.12~2.50),而女性中两者之间无关联(OR=1.30,95%CI:0.97~1.74);在60~69岁及≥80岁年龄组中,调整相关混杂因素后,维生素D缺乏与低握力发生风险呈显著正相关(OR=1.57,95%CI:1.05~2.35;OR=2.40,95%CI:1.08~5.31),在乳制品摄入<250 ml/d的人群中,调整相关混杂因素后,二者之间呈显著正相关(OR=1.57,95%CI:1.17~2.09),而在乳制品摄入≥250 ml/d的人群中无明显关联。限制性立方条样图显示,低握力的发生风险可能随维生素D含量的上升而降低,但差异无统计学意义(P>0.05)。结论 维生素D水平与握力存在一定的关系,维生素D缺乏人群出现低握力的风险更高。  相似文献   
109.
对原发性肝癌(PHC)81例;良性肝病58例;转移性肝癌11例;正常对照20例,进行血清标志物甲胎蛋白(AFP)、AFP异质体、5′-核苷酸磷酸二酯酶同工酶(5′-NPD)、唾液酸(SA)联合检测。结果显示四项标志物的组合能提高对PHC的诊断率(93.83%),同时还可用于小肝癌的诊断及PHC疗效观察及估计预后。  相似文献   
110.
以对氨基苯磺酸修饰聚乙二醇端头,制备兼具刚性与极性端头的聚合物,考察其制备LB膜与自组装膜的条件,用原子力/摩擦力显微镜表征自组装膜的表面形貌,对其微摩擦性能进行初步的探讨。  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