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   363765篇
  免费   33592篇
  国内免费   9918篇
耳鼻咽喉   4115篇
儿科学   7044篇
妇产科学   5284篇
基础医学   42611篇
口腔科学   10644篇
临床医学   29506篇
内科学   46075篇
皮肤病学   5032篇
神经病学   25339篇
特种医学   9335篇
外国民族医学   43篇
外科学   31638篇
综合类   51385篇
现状与发展   30篇
一般理论   24篇
预防医学   36591篇
眼科学   3543篇
药学   44124篇
  375篇
中国医学   33068篇
肿瘤学   21469篇
  2024年   1338篇
  2023年   6872篇
  2022年   14139篇
  2021年   17406篇
  2020年   15904篇
  2019年   17085篇
  2018年   15664篇
  2017年   14302篇
  2016年   13221篇
  2015年   13344篇
  2014年   23270篇
  2013年   24241篇
  2012年   21098篇
  2011年   23534篇
  2010年   18808篇
  2009年   17369篇
  2008年   16571篇
  2007年   15762篇
  2006年   13602篇
  2005年   11879篇
  2004年   10120篇
  2003年   8894篇
  2002年   6995篇
  2001年   5785篇
  2000年   5140篇
  1999年   4416篇
  1998年   3816篇
  1997年   3617篇
  1996年   3096篇
  1995年   2908篇
  1994年   2673篇
  1993年   2372篇
  1992年   1994篇
  1991年   1832篇
  1990年   1602篇
  1989年   1457篇
  1988年   1382篇
  1987年   1262篇
  1986年   1317篇
  1985年   2879篇
  1984年   3073篇
  1983年   2105篇
  1982年   2590篇
  1981年   1914篇
  1980年   1698篇
  1979年   1463篇
  1978年   1140篇
  1977年   870篇
  1976年   1043篇
  1975年   716篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
During an exposure monitoring study, 78 saw maintenance tradesmen were randomly assigned to be interviewed about their exposures using one of two questionnaire formats: open-ended and partly prompted questions about five categories of materials; and detailed prompting about 75 agents. The more open-ended questionnaire elicited fewer exposure responses overall, but more responses about agents not included on the detailed questionnaire. Composite materials and trade name products were more frequently cited as exposures than individual metals or compounds. Validity of responses was ascertained using air measurements (individual metals) or observations of the employees (composite materials). Sums of sensitivities and specificities were very low (near 1.0) for most of the metals for both types of questionnaire. For composite materials, validity improved substantially. Sensitivities with the partly prompted format (0.44–0.85) were always lower than with detailed prompting (0.80–1.00). Specificities were usually, but not always, higher with partial prompting (0.66–0.92) than with detailed prompting (0.18–0.86). Selection of questionnaire format for an epidemiologic study would depend on the likely prevalence of exposure in controls and the effects of trade-offs in sensitivity and specificity.  相似文献   
972.
本文对5105例乙肝三系统检测结果的32种组合形式出现率进行了统计分析,并引 入年龄因素分层分析。分析讨论了19岁以下、20~39岁、40~59岁及60岁以上四组受检者乙肝三系 统检测结果表现与分布的异同,并据此结合文献报道资料提出了预防处理意见。  相似文献   
973.
Activities of the xenobiotic metabolizing enzymes were measured in the liver, kidney, duodenum and lung microsomes and cytosol fractions of Wistar rats after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent bacterial mutagen in chlorinated drinking water. MX was administered by gavage at the dose level of 30 mg/kg for 18 weeks (low dose), or at the dose level which was raised gradually from 45 mg/kg for 7 weeks via 60 mg/kg for 2 weeks to a clearly toxic dose of 75 mg/kg for 5 weeks (high dose). Microsomal and cytosolic preparations were made and the activities of 7-ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-dealkylase (PROD), NADPH-cytochrome-c-reductase, UDP-glucuronosyltransferase (UDPGT) and glutathione-S-transferase (GST) were measured. Kidneys were affected most. A dose-dependent decrease was observed in EROD (90% in males, 80% in females at the high dose) and in PROD (58% in females, at the high dose) in kidneys. An increase was, however, detected in kidney NADPH-cytochrome-c-reductase (66% in females at high dose), UDPGT (89% in males and 97% in females at high dose) and GST activities (56% in males and 50% in females at high dose). MX caused only a few changes in the enzyme activities of the liver. The EROD activity was decreased 25% to 37%, both in the livers of males and females, but the total content of P450s was not altered. Hepatic GST activity was elevated in females in a dose-dependent manner (31% and 44%). GST activity was elevated in duodenum in females (59%) at the high dose. There were no marked changes in the enzyme activities in the lungs. MX was a weak inhibitor of EROD activity both in the liver and kidney microsomes in vitro, decreasing the EROD activity by 53% and 43%, respectively at the concentration of 0.9 mM. The results indicate that MX decreases the activity of phase I metabolism enzymes, but induces phase II conjugation enzyme activities, particularly in kidneys in vivo. It is possible that these changes contribute to metabolism of MX in kidneys and renders them susceptible to MX in the course of repeated exposure.  相似文献   
974.
975.
We report on a family with ataxia type 6 (SCA6) showing peculiar oculomotor symptoms. The proband presented with periodic alternating nystagmus (PAN), and her 2 brothers had rebound nystagmus and gaze-evoked nystagmus. They carried the identical mutation (the number of expanded CAG repeat, 24) in the CACNA1A gene. The intrafamilial variability of oculomotor symptoms may be ascribed to factors other than CAG repeat expansion size in SCA6.  相似文献   
976.
977.
口溃液主要成分为三氯化铁。本品经对208例复发性口腔溃疡患者的临床疗效观察,总有效率为97.1%,并具有显效迅速,作用持久、涂抹方便等优点。  相似文献   
978.
新安药店始于宋,成于明,至清末一度达到鼎盛。较有代表的宋有“陆氏保和堂”,明有“徐保元堂”、“正田药店”、“胞与堂”等,清有“胡庆余堂”、“胡咸春”、“种德堂”等。这些药店明多为医家兼营,清多为徽商经营。新安药店作为集医疗、生产、经营一体的传统手工业,至今不少成为著名药厂,如“武汉健民制药厂”、“胡庆余堂”等。其在生产、经营、管理上积累了许多经验,同时在方剂学以及药物炮炙、贮藏、采集、加工、成方制作等方面皆有不少成就。  相似文献   
979.
Perceptions of family cohesion and hierarchy structures were assessed by theFamily System Test (FAST), a clinically-derived figure placement technique. Parents (N=140) and their preadolescent offspring (N=70) completed typical and conflict representations in individual as well as group settings. Typical representations were characterized by balanced family structures (i.e. cohesive and moderately hierarchical) and those displaying conflict situations showed predominantly unbalanced patterns. FAST portrayals were related to respondent (mother vs. father vs. child). Fathers represented typical family relations as balanced more often than mothers. Regarding conflict representations, children were more likely than fathers to portray the family as unbalanced. However, analyses of representations of the same family (i.e. intra-family comparisons) indicated that all respondents differed in their perceptions and, that fathers' typical portrayals showed most often the same structure as those done by the family members as a group.  相似文献   
980.
对病理学确诊的25例病毒性心肌炎(VMC)和10例扩张型心肌病(DCM)患者心内膜心肌活检标本,运用ABC技术,进行了免疫球蛋白IgG、IgM、IgA和补体C3的检测。结果:20例VMC和9例DCM的标本中,发现了IgG和IgM的沉积,主要分布于心肌肌膜和毛细血管内皮,IgG的肌膜沉积与同步做的病理切片中观察到的心肌细胞坏死和炎性细胞浸润有病理形态学联系。两组患者中均未发现IgA和C3沉积。结果显示,IgG是参与VMC和DCM心肌损伤的主要免疫球蛋白,心肌病变与抗体诱导的免疫反应有关。  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