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   28607篇
  免费   2890篇
  国内免费   2434篇
耳鼻咽喉   331篇
儿科学   242篇
妇产科学   341篇
基础医学   3611篇
口腔科学   327篇
临床医学   3977篇
内科学   4123篇
皮肤病学   274篇
神经病学   1622篇
特种医学   1169篇
外国民族医学   15篇
外科学   2775篇
综合类   4898篇
现状与发展   7篇
一般理论   1篇
预防医学   1894篇
眼科学   774篇
药学   3245篇
  41篇
中国医学   1936篇
肿瘤学   2328篇
  2024年   104篇
  2023年   516篇
  2022年   1255篇
  2021年   1573篇
  2020年   1230篇
  2019年   975篇
  2018年   999篇
  2017年   1007篇
  2016年   940篇
  2015年   1451篇
  2014年   1748篇
  2013年   1475篇
  2012年   2063篇
  2011年   2505篇
  2010年   1565篇
  2009年   1268篇
  2008年   1549篇
  2007年   1463篇
  2006年   1497篇
  2005年   1504篇
  2004年   941篇
  2003年   953篇
  2002年   758篇
  2001年   668篇
  2000年   665篇
  1999年   640篇
  1998年   383篇
  1997年   404篇
  1996年   304篇
  1995年   305篇
  1994年   240篇
  1993年   141篇
  1992年   163篇
  1991年   119篇
  1990年   121篇
  1989年   102篇
  1988年   93篇
  1987年   80篇
  1986年   66篇
  1985年   43篇
  1984年   13篇
  1983年   13篇
  1982年   10篇
  1981年   9篇
  1980年   2篇
  1979年   6篇
  1976年   1篇
  1932年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
通过三年资料实证医院检验科常规项目全成本   总被引:2,自引:0,他引:2  
目的弄清医院常规检验项目的实际成本,为医院及卫生主管部门进行科学管理和政府物价部门制订科学合理的收费价格体系提供科学依据。方法对某二级甲等医院检验科3年中所开展的全部7大类16个项目组169个检验项目的成本按耗材、设备折旧、劳务费、房屋折旧、业务费与后勤管理费共5大类进行实证分析。结果该科的成本构成比是:耗材成本34.1%、设备折旧24.3%、劳务费30.0%、房屋折旧4.0%、业务费与后勤管理费7.6%;检验项目的每项次平均成本为7.17元;成本最低的两类检验项目是生化及定性免疫,其项次成本分别为3.18元和4.25元;最高的则为微生物和血库,项次成本分别为48.63元和35.21元;项次成本过百元的有7项,多为输血项目;5至10倍于平均成本的28项,2至5倍于全科平均成本的22项,其余112项介于全科平均成本上下。结论实证研究是准确掌握检验项目成本的有效方法。  相似文献   
23.
PURPOSES: Inhibition of cerulenin on the endogenous fatty acid synthetic activities of oral squamous cell carcinoma (OSCC) and normal oral mucosa was assayed. METHODS: Squamous cell carcinoma and normal oral mucosa were collected fresh from surgical specimens. The collected tissues were minced in RPMI 1640 and divided into 3 groups: cerulenin treated, dimethylsulfoxide treated, and control. The tissues were incubated in [1(2)-(14)C]acetic acid, sodium salt for the last 2.5 hours of the treatment at 37 degrees C in 5% CO(2). After labeling, total lipids were extracted and counted for (14)C by scintillation counting. RESULTS: Endogenous fatty acid synthetic activities of oral squamous cell caranoma in the cerulenin-treated group decreased by 19% at 1 hour, 64% at 2 hours, and 87% at 4 hours; remained nearly unchanged in the dimethylsulfoxide-treated group; and increased slightly in the control group. The oral mucosa tissues were only mildly affected by cerulenin in fatty acid synthesis. CONCLUSIONS: Cerulenin significantly inhibits fatty acid synthetic activity in squamous cell carcinoma and only mildly affected the oral mucosa, indicating that the fatty acid synthetic pathway may be exploited as a target for developing anticancer drugs.  相似文献   
24.
目的探讨高频超声引导定位穿刺前臂浅静脉的应用价值。方法对40例常规浅静脉穿刺失败,采用高频探头在同一体表区域寻找并标记浅静脉走行及深度,确认进针方向后再次静脉穿刺,必要时采用实时引导。结果11例经高频超声标记、29例经高频超声实时引导静脉穿刺均一次成功。结论高频超声引导下静脉穿刺的成功率高,无并发症,是一种简便有效的方法,值得在临床推广应用。  相似文献   
25.
Bone marrow stromal cells (MSCs) increase vascular endothelial growth factor (VEGF) expression and promote angiogenesis after stroke. Angiopoietin-1 (Ang1) and its receptor Tie2 mediate vascular integrity and angiogenesis as does VEGF and its receptors. In this study, we tested whether MSC treatment of stroke increases Ang1/Tie2 expression, and whether Ang1/Tie2 with VEGF/ vascular endothelial growth factor receptor 2 (VEGFR2) (Flk1), in combination, induced by MSCs enhances angiogenesis and vascular integrity. Male Wistar rats were subjected to middle cerebral artery occlusion (MCAo) and treated with or without MSCs. Marrow stromal cell treatment significantly decreased blood-brain barrier (BBB) leakage and increased Ang1, Tie2, and occludin (a tight junction protein) expression in the ischemic border compared with MCAo control. To further test the mechanisms of MSC-induced angiogenesis and vascular stabilization, cocultures of MSCs with mouse brain endothelial cells (MBECs) or astrocytes were performed. Supernatant derived from MSCs cocultured with MBECs significantly increased MBEC expression of Ang1/Tie2 and Flk1 compared with MBEC alone. Marrow stromal cells cocultured with astrocytes also significantly increased astrocyte VEGF and Ang1/Tie2 expression compared with astrocyte culture alone. Conditioned media from MSCs alone, and media from cocultures of MSCs with astrocytes or MBECs, all significantly increased capillary tube-like formation of MBEC compared with control Dulbecco's modified Eagle's medium media. Inhibition of Flk1 and/or Ang1 significantly decreased MSC-induced MBEC tube formation. Knockdown of Tie2 expression in MBECs significantly inhibited MSC-induced tube formation. Our data indicate MSC treatment of stroke promotes angiogenesis and vascular stabilization, which is at least partially mediated by VEGF/Flk1 and Ang1/Tie2.  相似文献   
26.
Glial glutamate transporter-1 (GLT-1) plays an essential role in removing glutamate from the extracellular space and maintaining the glutamate below neurotoxic level in the brain. To explore whether GLT-1 plays a role in the acquisition of brain ischemic tolerance (BIT) induced by cerebral ischemic preconditioning (CIP), the present study was undertaken to observe in vivo changes in the expression of GLT-1 and glial fibrillary acidic protein (GFAP) in the CA1 hippocampus during the induction of BIT, and the effect of dihydrokainate (DHK), an inhibitor of GLT-1, on the acquisition of BIT in rats. Immunohistochemistry for GFAP showed that the processes of astrocytes were prolonged after a CIP 2 days before the lethal ischemic insult, which could protect pyramidal neurons in the CA1 hippocampus against delayed neuronal death induced normally by lethal ischemic insult. The prolonged processes extended into the area between the pyramidal neurons and tightly surrounded them. These changes made the pyramidal layer look like a 'shape grid'. Simultaneously, the prolonged and extended processes showed a great deal of GLT-1. Western blotting analysis showed significant upregulation of GLT-1 expression after the CIP, especially when it was administered 2 days before the subsequent lethal ischemic insult. Neuropathological evaluation by thionin staining showed that DHK dose-dependently blocked the protective role of CIP against delayed neuronal death induced normally by lethal brain ischemia. It might be concluded that the surrounding of pyramidal neurons by astrocytes and upregulation of GLT-1 induced by CIP played an important role in the acquisition of the BIT induced by CIP.  相似文献   
27.
应用气相色谱法鉴别海南省大劣按蚊   总被引:4,自引:0,他引:4  
大劣按蚊是海南省疟疾的主要传播媒介。本文应用气相色谱法,分析海南省不同地区、不同季节大劣按蚊的皮质烃类。经统计学分析,它们的成分无显著性差异。应用聚类分析法,它们的距离系数很接近。提示海南省的大劣按蚊很可能是同一种。  相似文献   
28.
扩散法被动式甲醛个体监测器(Ⅱ型)的研制   总被引:1,自引:0,他引:1  
介绍了一种基于气体分子扩散原理的被动式甲醛个体采样器,它是在Ⅰ型采样器的基础上完成的。采用甘油(20%)/偏重亚硫酸钠(0.25%)浸渍的定量滤纸(φ42mm)作为吸收层,空气中甲醛扩散到吸收层上,形成稳定的化合物。采样一定时间后,取出吸收层,洗脱后,用AHMT化学比色法测定所采集到的甲醛。这种采样器的平均采样速率为83ml/min,标准偏差为7.2ml/min,与有动力吸收管采样的方法相比较,总不确定度小于±25%。  相似文献   
29.
目的:分析立体定向X-刀放射治疗颅内肿瘤后的近期疗效,并进行阶段性工作总结。材料和方法:53例不同类型脑瘤患者,以CT、MR、DSA图像资料作为定位依据,用德国Brain LAB治疗计划系统设计三维优化方案,西门子MD-2型直线加速器旋转照射。结果:53例患者经X-刀治疗后,近期均取得了满意效果,诸如以卡氏评分法评价,临床症状有所改善;以CT增强扫描复查观察,肿瘤大小趋于缩小或消失。结论:立体定向放射治疗后的追踪观察表明,只要严格掌握适应症,精确定位,精确计划,精心治疗,X-刀是一种安全、有效、无痛苦的治疗脑肿瘤的方法。它可起到改善临床症状,提高患者生活质量,延长生存期限的作用。  相似文献   
30.
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