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   3226358篇
  免费   251034篇
  国内免费   7569篇
耳鼻咽喉   45469篇
儿科学   101496篇
妇产科学   86693篇
基础医学   460663篇
口腔科学   92478篇
临床医学   303050篇
内科学   621174篇
皮肤病学   64951篇
神经病学   271019篇
特种医学   125154篇
外国民族医学   1128篇
外科学   471982篇
综合类   76387篇
现状与发展   2篇
一般理论   1361篇
预防医学   269476篇
眼科学   74989篇
药学   240873篇
  10篇
中国医学   6508篇
肿瘤学   170098篇
  2018年   34768篇
  2017年   26571篇
  2016年   29071篇
  2015年   33096篇
  2014年   47026篇
  2013年   72367篇
  2012年   98226篇
  2011年   103926篇
  2010年   60968篇
  2009年   57625篇
  2008年   97444篇
  2007年   103591篇
  2006年   104433篇
  2005年   101433篇
  2004年   97142篇
  2003年   93427篇
  2002年   91599篇
  2001年   144601篇
  2000年   149462篇
  1999年   126435篇
  1998年   37239篇
  1997年   33787篇
  1996年   33220篇
  1995年   32102篇
  1994年   30138篇
  1993年   28218篇
  1992年   102226篇
  1991年   99308篇
  1990年   96198篇
  1989年   92258篇
  1988年   85730篇
  1987年   84299篇
  1986年   80192篇
  1985年   76635篇
  1984年   58253篇
  1983年   49715篇
  1982年   30261篇
  1981年   26934篇
  1979年   54331篇
  1978年   38436篇
  1977年   32134篇
  1976年   30613篇
  1975年   32085篇
  1974年   39423篇
  1973年   37948篇
  1972年   35356篇
  1971年   32798篇
  1970年   30681篇
  1969年   28388篇
  1968年   26267篇
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
941.
942.
943.
944.
945.
The contributors propose a selective photometric technique for detection of sodium and potassium cyanides in different washings, sewage, overalls extraction. The technique was based on the formation of a polymetyne dye, and barbituric acid and pyridine reactions. It proved efficient in detecting the cyanides within 0.01-0.054 mg/dm3, 1-100 mg/l, 0.08-1.24 mg/dm3 with deviations not exceeding 23%. Duration of the test was limited to 25-30 min.  相似文献   
946.
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   
947.
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   
948.
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   
949.
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   
950.
Access to care     
J La Puma 《JAMA》1991,266(20):2832-2833
  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