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   323514篇
  免费   29659篇
  国内免费   22792篇
耳鼻咽喉   2995篇
儿科学   3421篇
妇产科学   4926篇
基础医学   39885篇
口腔科学   5490篇
临床医学   45246篇
内科学   49700篇
皮肤病学   3082篇
神经病学   18342篇
特种医学   11978篇
外国民族医学   213篇
外科学   33208篇
综合类   49835篇
现状与发展   76篇
一般理论   20篇
预防医学   19615篇
眼科学   9565篇
药学   32767篇
  335篇
中国医学   17401篇
肿瘤学   27865篇
  2024年   995篇
  2023年   5000篇
  2022年   13027篇
  2021年   16301篇
  2020年   12032篇
  2019年   10827篇
  2018年   11411篇
  2017年   9915篇
  2016年   9358篇
  2015年   14352篇
  2014年   17800篇
  2013年   15339篇
  2012年   22801篇
  2011年   25805篇
  2010年   15904篇
  2009年   12248篇
  2008年   17015篇
  2007年   17014篇
  2006年   17049篇
  2005年   16776篇
  2004年   10663篇
  2003年   9757篇
  2002年   8439篇
  2001年   7465篇
  2000年   8280篇
  1999年   9019篇
  1998年   5476篇
  1997年   5501篇
  1996年   4332篇
  1995年   3923篇
  1994年   3214篇
  1993年   2097篇
  1992年   2827篇
  1991年   2415篇
  1990年   2117篇
  1989年   1861篇
  1988年   1563篇
  1987年   1352篇
  1986年   1107篇
  1985年   912篇
  1984年   526篇
  1983年   373篇
  1982年   242篇
  1981年   238篇
  1980年   188篇
  1979年   221篇
  1978年   82篇
  1977年   89篇
  1974年   102篇
  1973年   83篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
分析了经病理证实的40例胃占位病变的X线及超声资料,旨在探讨超声及其与X线结合在胃占位病变中的价值。结果提示,超声和X线各有优缺点,二者结合使用,可互相取长补短,对提高胃占位病变的诊断质量,帮助临床制定合理的治疗方案有肯定价值。  相似文献   
992.
Computer algorithms to design bolus for electron beam radiotherapy treatment planning were investigated. Because of the significant electron multiple scatter, there is no unique solution to the problem of bolus design. However, using a sequence of operators, a bolus can be designed that attempts to meet three important criteria: adequate dose delivery to the target volume, avoidance of critical structures, and dose homogeneity within the target volume. Initial calculation of bolus shape was based upon creation operators forcing either the physical or the effective depths of the distal surface of the target volume to a specified value. Modification operators were then applied to the bolus to alter the shape to better meet the design criteria. Because the operators each address a single dosimetric issue, they can often adversely affect some other attribute of the dose distribution. In addition, an extension operator is used to design the bolus thickness outside the target volume. Application of these operators is therefore carried out in certain sequences and each may be used more than once in the design of a particular bolus. The effects of these operators on both the bolus and the resulting dose distribution are investigated for test geometries and patient geometries in the nose, parotid, and paraspinal region.  相似文献   
993.
本文对云南老山前、后方医院环境及战伤感染标本中绿脓杆菌(简称PA)进行调查,对所分离的333株PA进行血清学分型及药物敏感性测定。结果可看出除炸伤时创口易被泥土中PA污染外,前、后方医院环境也是感染源之一。提示各级医疗单位在战伤救治中对PA的监控十分重要。本文结果直接有益于前、后方医院对战创伤PA的防治。  相似文献   
994.
运用巢式聚合酶链反应(PCR)等方法检测了5例丙型肝炎病毒核糖核酸(HCV—RNA)阳性患者的肝癌、癌旁组织和周围血清中HCV—RNA正链和负链,其中男4例,女1例。结果,正链检测:血清及癌旁组织全部阳性,癌组织中3例阳性。负链检测:血清中均阴性,癌组织3例阳性,癌旁组织5例均阳性。本组5例患者肝脏HCV—RNA负链阳性,推测HCV以HCV—RNA负链作为模板在感染的肝脏组织中复制,HCV持续存在于肝脏组织中对肝癌的发生起了一定的作用。  相似文献   
995.
为探察人左心室壁心外膜区微血管的三维空间构型和形态计量学指标。本研究应用微血管腐蚀铸型/扫描电子显微镜技术和酶组化(碱性磷酸酶反应)染色方法,观察10例心脏标本,得出心外膜区的毛细血管直径为7.2±1.9μm(±S.D),微血管密度是3484.44/mm~2。获得左心室壁心外膜区从微动脉-动脉端毛细血管-毛细血管网-静脉端毛细血管-“萝卜根样”微静脉这个微循环单位的三维空间构型资料。  相似文献   
996.
997.
本文对12例体表恶性肿瘤病人采用放射治疗与微波加热治疗并用的方法取得了较好的效果,总有效率100%。  相似文献   
998.
Yao nationality is one of the minority nationalities living mainly in South China (Guangxi Province). The purpose of this study was to provide data of MHC classI and GLO in Chinese Yao nationality and the different genetic background of Yao and Han nationality, the latter representing the major nationality in China. The genetic polymorphism of MHC classI and GLO in Chinese Yao nationality was determined. Previously the Japanese were considered to have the lowest C*2C frequencies (0.9386), but now we ascertained that the Yao have the lowest C2*C frequencies (0.9336). The data concerning gene frequencies of Yao are presented. They were also compared with the available data of Han.  相似文献   
999.
Three representative types of houses in Beijing were selected and, in each type, smoking and nonsmoking households were compared, IP, RP, and CO concentrations in the living room and kitchen were monitored during each season, and the level of COHb in the heads of the households were measured. The study showed that indoor air pollution was rather severe, especially during winter, when particulate concentrations markedly exceeded the standard and CO concentration was as high as 47 ppm. Indoor air pollution was closely related to the type of house, particularly to the mode of heating. In houses, of the same type, pollution improved greatly after central heating facilities were installed. Analysis of 30 elements revealed that pollution was typically caused by coal burning, aggravated by dusty wind, but high indoor Pb levels were probably due to the use of LPG for cooking. In our study the effect of cigarette smoking was sometimes masked by the severe indoor pollution.  相似文献   
1000.
The hepatocarcinogen aflatoxin B1 is converted to reactive metabolites that bind covalently to cellular macromolecules. These metabolites may also react with glutathione, resulting in the formation of glutathione conjugates and detoxication of the reactive metabolite. When rats were pretreated with ethanol by gastric intubation at a dose of 100 mmol/kg, 6 hr (the time of maximal GSH depletion) before the administration of aflatoxin B1, the covalent binding of 8,9-epoxide-aflatoxin B1 to DNA in vivo was increased by 47% and the hepatotoxicity was also potentiated. However, the covalent binding was not increased by pretreatment with ethanol 18 hr (time with approximately normal GSH levels) before administration of the toxin, and no potentiation of hepatotoxicity was observed. Pretreatment with a non-toxic dose of ethanol had no effects on the activity of glutathione S-transferase and glutathione peroxidase. These results suggest that the depletion of GSH and the increased formation of DNA-adduct from the liver constitute an important mechanism for the potentiation of aflatoxin B1-induced hepatotoxicity by ethanol.  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