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   15784篇
  免费   1525篇
  国内免费   249篇
耳鼻咽喉   115篇
儿科学   1124篇
妇产科学   962篇
基础医学   1484篇
口腔科学   373篇
临床医学   1518篇
内科学   1812篇
皮肤病学   220篇
神经病学   1387篇
特种医学   433篇
外国民族医学   2篇
外科学   1146篇
综合类   1702篇
一般理论   2篇
预防医学   2349篇
眼科学   663篇
药学   1041篇
  23篇
中国医学   394篇
肿瘤学   808篇
  2024年   25篇
  2023年   243篇
  2022年   426篇
  2021年   667篇
  2020年   651篇
  2019年   636篇
  2018年   559篇
  2017年   672篇
  2016年   666篇
  2015年   605篇
  2014年   1048篇
  2013年   1286篇
  2012年   877篇
  2011年   954篇
  2010年   797篇
  2009年   716篇
  2008年   695篇
  2007年   696篇
  2006年   655篇
  2005年   589篇
  2004年   447篇
  2003年   360篇
  2002年   351篇
  2001年   297篇
  2000年   232篇
  1999年   210篇
  1998年   179篇
  1997年   184篇
  1996年   169篇
  1995年   140篇
  1994年   162篇
  1993年   132篇
  1992年   134篇
  1991年   115篇
  1990年   103篇
  1989年   104篇
  1988年   89篇
  1987年   70篇
  1986年   68篇
  1985年   99篇
  1984年   79篇
  1983年   37篇
  1982年   49篇
  1981年   42篇
  1980年   61篇
  1979年   33篇
  1978年   29篇
  1977年   23篇
  1976年   23篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This article reports findings from a longitudinal survey of very elderly people living at home in London. The research aimed to identify social, psychological and physical characteristics associated with positive ageing and successful survival in the community in later life and its converse—negative ageing—as well as the associated policy implications. Associations with psychiatric morbidity, measured using the General Health Questionnaire, among sample members without cognitive impairment between the baseline interviews in 1987 and at follow-up, two and a half years later in 1990, are reported. Twenty-five per cent of survivors scored over the threshold of the GHQ in 1987 and 30% scored over the threshold in 1990. Half of those with a score over the threshold in 1990 also scored over the threshold in 1987. Hierarchical regression (using residualized change analysis) was used to estimate the effects of the independent variables on changes in psychiatric morbidity. The most significant predictor of psychiatric morbidity (GHQ score) in 1990 was baseline GHQ score, followed by health and functional status scores. Health and functional status were also the strongest predictors of baseline (1987) GHQ scores. The uniqueness of the study lies in the collection of follow-up data on a sample of very elderly people, given that most surveys are corss-sectional and contain too few people aged 85+ to merit separate analysis. It contributes to the small body of literature on outcome of depression. The lack of consistent associations with recovery from psychiatric morbidity in the literature enhances the importance of studies aiming to identify factors associated with different outcomes.  相似文献   
52.
From September 1984 to December 1989, 38 patients of pediatric age with localized bone sarcomas received intraoperative radiotherapy (IORT) as part of a multidisci plinary treatment program. The age ranged from 6 to 21 years. The tumor histologies were 22 osteosarcomas and 16 Ewing's sarcomas. Thirty-four had initial primary disease (90%) and 4 were treated for local recurrence (10%). IORT was used on 32 untreated patients and in 6 previously treated with external beam radiotherapy (EBR). The IORT field included the surgically exposed tumor bed area. Single radiation doses ranging from 10 to 20 Gy were delivered, using 6–20 MeV electron beams. The median follow-up time for the entire group is 25 months (2–65+ months). The projected 5-year disease-free and overall survival rates are 65% and 69%, respectively. One patient developed a local recurrence in each histological group: one chondroblastic osteosarcoma and one cervical Ewing's sarcoma. Six patients died from metastatic progression: 3 initially recurrent tumors and three primary disease cases. Severe neuropathy and soft tissue necrosis were seen in some patients as IORT related complications. IORT is a feasible technique to be integrated in multidisciplinary programs that may promote local control in pediatric and adolescent patients with bone sarcomas. Peripheral nerves are dose-limiting tissue structures for IORT.  相似文献   
53.
Object: Diesel soot has been recognized as probably carcinogenic to humans. Elemental carbon (also called black carbon) in soot is considered at the moment as the most significant surrogate to be measured for assessing the exposure to this pollutant. Its analysis is done by combustion in an oven and determination of the CO2 formed, after elimination of the organic fraction of the soot by heating and/or by solvent extraction. The analysis allows determination of both fractions of the soot: “elemental carbon” (EC) and organic carbon␣(OC). The sum of EC and OC is called TC (total carbon). Method: An informal European coordination group organized two round robin tests on filter samples collected from diluted diesel emissions. The first round (RRT1) was performed on 13 different samples analyzed by ten laboratories. The range of loading was 2.5 to 150 μg/cm2 of EC. No evaluation of the precision within laboratories could be made since each laboratory gave only one result per sample. Therefore a second round (RRT2) was organized with two samples and a blank filter sent in several portions to 11 laboratories. It should be stressed that each laboratory used its own method and that no standardization was planned at this stage. Results: Results of RRT1 showed that the coefficient of variation between laboratories decreased with higher loading and was around 10% to 15% for EC above about 20 μg/cm2. Dispersion of the results varied and it appeared that the way OC is removed from the soot is probably the most important factor of influence. The correlation between the laboratories was good as a whole but some systematic differences could be detected. Besides the different techniques to remove the organic carbon, the pretreatment of the filter by HCl (either as a vapor or as a solution) to remove the inorganic carbonates (potential interference sources), is probably also a significant factor of influence in the dispersion of the results between laboratories. It is not yet clear from these results whether the “environmental” laboratories give different results from the “occupational” laboratories, but it is clear that their objectives differ since for the “environmentalists”, EC is not a specific marker of diesel immissions, in contrast to the “occupationalists”. Conclusion: It can be concluded that, although significant differences exist between laboratories they can be attributed mainly to the narrow distribution of the results within a single laboratory, and that the overall agreement of the results for EC and TC is fairly good. These results obtained with pure diesel engine emissions, should be complemented by field samples, but they have already achieved relevant findings in the performance of the procedures used to assess exposure to diesel soot. Received: 30 December 1996 / Accepted: 21 February 1997  相似文献   
54.
论网络化时代电视教材的重要性   总被引:7,自引:3,他引:4  
针对教学实践中重视计算机辅助教学忽视电视教材的倾向,本文通过对网络时代中电视教材的作用和地位的分析,阐述了加强计算机辅助教学的必要性和加强电视教材制作及应用的重要性以及二者间的关系。  相似文献   
55.
56.
Summary The protein binding of furosemide was investigated in plasma from 22 old and 11 young subjects by equilibrium dialysis. The unbound fraction of furosemide was 3.16% in plasma from the elderly and 1.71% in plasma from the young. A significant correlation was found between the unbound fraction of furosemide and the plasma concentration of albumin. The average number of binding sites was 3.8 (elderly) and 2.7 (young) 10–6 mol/g albumin. The average association constant (K) was 4.3 (elderly) and 4.2 (young) 105 M–1. By increasing the concentration of furosemide up to 200 µg/ml buffer the unbound fraction of the drug rose to 5.2% (elderly) and 3.5% (young).  相似文献   
57.
苗宗华  蒋艳池 《现代医学》1989,17(3):132-133
调查了1280例银屑病患者的初发年龄,平均初发年龄27.23岁,男性29.25岁,女性23.46岁。初发年龄大多在15~39岁组,占72.96%,最高峰在20~24岁组,占19.53%。初发年龄大小与病情轻重无明显关系,而与病程长短有明显关系,即初发年龄越小者,其病程一般较长。  相似文献   
58.
The assumed advantages of the so-called leg-lifting technique over the back-lifting technique are still the subject of much debate. The present study was aimed at studying the consequences of performing both lifting techniques on net lumbar moments and spinal shrinkage. Furthermore, the relation between age and spinal shrinkage was studied. Five subjects approximately 40 years old and six subjects 20 years old performed six 5-min bouts of repetitive lifting using each technique on a separate day. Net lumbar moments were calculated using a two-dimensional dynamic linked segment model. Spinal shrinkage was measured at T12 and at the head after each bout of lifting and every 5 min during 1 h preceding the lifting bouts. The peak moments were marginally but significantly higher in the leg-lift. No differences in mean moments and shrinkage between lifting techniques were found. The shrinkage after the back-lift was more pronounced in the older subjects and a similar tendency was found after the leg-lift. The creep rate, i.e. the rate at which the shrinkage approaches its equilibrium was higher in the older subjects. No clear relations of anthropometrical variables and net moments with shrinkage was found. The common advice of using a leg-lift rather than a back-lift was not supported by the present study. Both the mechanical load on the low back (net moments) and the resulting shrinkage show considerable interindividual variation, the causes of which need further elucidation.

The leg-lifting technique is still widely advocated, thought its merits from a biomechanical point of view have been questioned. In this study spinal shrinkage and lumbar moments calculated by means of a dynamic linked segment model are used to compare the leg-lift to the more commonly used back-lift.  相似文献   

59.
育龄妇女、孕妇及乳母碘营养状况调查   总被引:1,自引:0,他引:1  
目的 了解缺碘地区食用合格碘盐的育龄妇女和孕妇及乳母碘营养状况。方法 对病区育龄妇女和孕妇及乳母进行观察。采用酸消化砷铈接触法及全定量直接滴定法分别检测尿碘,乳碘和盐碘含量。结果 育龄妇女和孕妇及乳母尿碘含量分别为219.37μg/L,203.98μg/L,178.55μg/L,尿碘值小于100μg/L占24.14%,三组人群尿碘水平依次降低,但差异未显示统计学意义;乳碘值为122.72μg/L,小于100μg/L达33.93%,提示应关注特需人群的碘营养问题。结论 应开展对育龄妇女和孕妇及乳母的尿碘监测。以指导合理补碘,防止胎儿和婴幼儿碘营养不良的发生。  相似文献   
60.
某医科大学中老年教职工健康状况分析   总被引:6,自引:0,他引:6  
对1004名50岁以上中老年教职工进行健康检查。结果:健康者仅占11.25%,而88.75%的中老年教职工至少患有1例次疾病,最多患有5例次疾病,总例次患病率为186.95%,男女例次患病率分别为187.24%和186.62%,男女间无差异。前5位疾病的顺位是:心血管疾病、呼吸系疾病、脑血管疾病、消化系统病、泌尿生殖疾病。  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