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   3231176篇
  免费   257521篇
  国内免费   6659篇
耳鼻咽喉   45959篇
儿科学   102114篇
妇产科学   89149篇
基础医学   452680篇
口腔科学   92450篇
临床医学   295435篇
内科学   631574篇
皮肤病学   69021篇
神经病学   271764篇
特种医学   126911篇
外国民族医学   1186篇
外科学   484702篇
综合类   78356篇
现状与发展   4篇
一般理论   1332篇
预防医学   262410篇
眼科学   76480篇
药学   236428篇
  5篇
中国医学   6554篇
肿瘤学   170842篇
  2018年   34556篇
  2017年   26521篇
  2016年   29459篇
  2015年   33292篇
  2014年   47937篇
  2013年   72590篇
  2012年   97930篇
  2011年   103516篇
  2010年   61069篇
  2009年   58442篇
  2008年   97278篇
  2007年   103259篇
  2006年   104287篇
  2005年   101470篇
  2004年   97346篇
  2003年   93646篇
  2002年   91641篇
  2001年   150832篇
  2000年   155550篇
  1999年   130992篇
  1998年   38392篇
  1997年   34790篇
  1996年   34450篇
  1995年   33032篇
  1994年   30726篇
  1993年   28792篇
  1992年   103535篇
  1991年   99536篇
  1990年   95865篇
  1989年   92160篇
  1988年   85473篇
  1987年   84071篇
  1986年   79250篇
  1985年   75721篇
  1984年   57797篇
  1983年   49245篇
  1982年   30168篇
  1981年   26834篇
  1979年   53484篇
  1978年   37748篇
  1977年   31653篇
  1976年   29755篇
  1975年   31000篇
  1974年   38124篇
  1973年   36431篇
  1972年   34180篇
  1971年   31435篇
  1970年   29733篇
  1969年   27663篇
  1968年   25612篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
942.
943.
The efficiency of the Racal Airstream helmet respirator in improving peak expiratory flow rates (PEFR) and symptoms (dyspnea, wheezing, and cough) in aluminum potroom workers with respiratory complaints was assessed in 19 workers. Peak expiratory flow readings and symptom recording from a 2-week working period with use of the respirator were compared with a period when the 3M 9906 disposable mask was used. The study was designed as a randomized, parallel, cross-over study with five or six daily measurements of PEFR and daily symptom recording. A significant number of workers (15) had a higher mean peak flow in the helmet period than in the nonhelmet period (p less than 0.01); symptoms did not improve significantly in the helmet period. Objective evidence of respiratory protection was observed for the group of workers as a whole, but the effect on symptoms as well as individual effect on peak flow was minor in the majority of the workers.  相似文献   
944.
Reference data for obesity   总被引:1,自引:0,他引:1  
  相似文献   
945.
This study estimated the effects of changing multiple levels and combinations of nutrition information format, load, expression, and order on consumers' perceptions of label usefulness in purchase decisions using adaptive conjoint analysis. A shopping mall intercept survey, which was administered by a marketing research firm, assessed consumer preferences for 12 label alternatives produced on Campbell's soup cans to portray nutrition information realistically; 252 of 258 respondents completed the computer interactive interview. Consumers significantly preferred the bar graph format to the bar graph/nutrient density and traditional label formats. Consumers considered the bar graph/nutrient density format to be as useful as the traditional label format. There was a highly significant difference among the three levels of information load; the most information load was preferred regardless of nutrient importance. Consumers significantly preferred nutrition information stated in absolute numbers and percentages vs in absolute numbers only in traditional, or in percentages only expressions. There was a significant difference between consumer preferences for the two types of information order. The findings indicate that consumers clearly preferred the nutrition label that displayed all nutrient values using a bar graph format, offered the most information load, and expressed nutrient values using both absolute numbers and percentages. Consumers also preferred nutrition information rearranged in an order that grouped nutrients that should be consumed in adequate amounts on the top, calories in the middle, and nutrients that should be consumed in lesser amounts on the bottom of the label.  相似文献   
946.
DNR in the operating room. Not really a paradox   总被引:1,自引:0,他引:1  
S J Youngner  H F Cascorbi  J M Shuck 《JAMA》1991,266(17):2433-2434
  相似文献   
947.
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts.  相似文献   
948.
Access to care     
J La Puma 《JAMA》1991,266(20):2832-2833
  相似文献   
949.
950.
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