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   2958466篇
  免费   233228篇
  国内免费   6002篇
耳鼻咽喉   42723篇
儿科学   91655篇
妇产科学   80909篇
基础医学   416613篇
口腔科学   84598篇
临床医学   266121篇
内科学   580469篇
皮肤病学   60764篇
神经病学   246496篇
特种医学   119044篇
外国民族医学   1129篇
外科学   452512篇
综合类   68701篇
现状与发展   1篇
一般理论   1175篇
预防医学   235183篇
眼科学   69576篇
药学   219164篇
  5篇
中国医学   5555篇
肿瘤学   155303篇
  2018年   30127篇
  2016年   25807篇
  2015年   29320篇
  2014年   42348篇
  2013年   64785篇
  2012年   85838篇
  2011年   90600篇
  2010年   54227篇
  2009年   52188篇
  2008年   86317篇
  2007年   91538篇
  2006年   92492篇
  2005年   90258篇
  2004年   86743篇
  2003年   83854篇
  2002年   82689篇
  2001年   135473篇
  2000年   139767篇
  1999年   118559篇
  1998年   34535篇
  1997年   31449篇
  1996年   31211篇
  1995年   29979篇
  1994年   28133篇
  1993年   26306篇
  1992年   95110篇
  1991年   91769篇
  1990年   88783篇
  1989年   85635篇
  1988年   79685篇
  1987年   78439篇
  1986年   74634篇
  1985年   71182篇
  1984年   53888篇
  1983年   46014篇
  1982年   28250篇
  1981年   25035篇
  1980年   23589篇
  1979年   50547篇
  1978年   35540篇
  1977年   30135篇
  1976年   28270篇
  1975年   29998篇
  1974年   36685篇
  1973年   34892篇
  1972年   32811篇
  1971年   30310篇
  1970年   28657篇
  1969年   26729篇
  1968年   24653篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
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   
992.
Reference data for obesity   总被引:1,自引:0,他引:1  
  相似文献   
993.
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   
994.
995.
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   
996.
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   
997.
Access to care     
J La Puma 《JAMA》1991,266(20):2832-2833
  相似文献   
998.
Exposure of young children to group day-care settings increases the risk of illness and may result in higher use of medical care. These observations raise concerns that the use of such settings for early intervention programs for low-birth-weight infants may increase the already high burden of medical care costs incurred by these children and their families. To address the question of medical care use associated with center-based care, we examined the hospital-based and ambulatory care reported for participants of the Infant Health and Development Program. This project is a multisite randomized trial of an early intervention program for preterm low-birth-weight infants with an intervention including 2 years of center-based care. The Intervention group did not differ in hospital-based care and averaged only two more physicians' visits over the 3-year observation period than the comparison group. We conclude that early intervention programs involving high-quality group care are not accompanied by substantial increases in health care use.  相似文献   
999.
J Winkler  M Neuman-Levin  G Boner 《JAMA》1991,265(5):631-632
A 37-year-old woman patient, known to have poorly controlled arterial hypertension that was diagnosed following a cerebrovascular accident at the age of 15 years, was referred to our outpatient clinic for investigation in 1987. An intrarenal arteriovenous fistula was diagnosed by selective renal angiography. Embolization of the fistula was performed using four 15-mm/5-cm coils, which induced thrombosis and obstructed the fistula. The vascularization of the affected kidney improved immediately. During the following 4 months, the antihypertensive treatment was stopped gradually, and the patient remained normotensive. This is an unusual case of a large intrarenal arteriovenous fistula, whose etiology was not clear, that was successfully treated by percutaneous embolization.  相似文献   
1000.
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