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   2389217篇
  免费   190252篇
  国内免费   9782篇
耳鼻咽喉   30647篇
儿科学   78191篇
妇产科学   65444篇
基础医学   339475篇
口腔科学   65911篇
临床医学   225354篇
内科学   474365篇
皮肤病学   52828篇
神经病学   198508篇
特种医学   92313篇
外国民族医学   622篇
外科学   352298篇
综合类   55307篇
现状与发展   3篇
一般理论   838篇
预防医学   200619篇
眼科学   51838篇
药学   172165篇
  11篇
中国医学   4914篇
肿瘤学   127600篇
  2018年   26435篇
  2017年   20379篇
  2016年   23273篇
  2015年   26341篇
  2014年   36568篇
  2013年   55984篇
  2012年   72213篇
  2011年   77252篇
  2010年   46555篇
  2009年   44271篇
  2008年   71237篇
  2007年   75561篇
  2006年   76843篇
  2005年   74263篇
  2004年   70800篇
  2003年   68139篇
  2002年   65353篇
  2001年   109609篇
  2000年   112701篇
  1999年   94596篇
  1998年   28205篇
  1997年   25354篇
  1996年   25948篇
  1995年   25545篇
  1994年   23928篇
  1993年   22428篇
  1992年   77370篇
  1991年   75531篇
  1990年   72885篇
  1989年   69262篇
  1988年   64375篇
  1987年   63099篇
  1986年   59938篇
  1985年   57609篇
  1984年   43902篇
  1983年   37022篇
  1982年   22913篇
  1981年   20465篇
  1980年   19157篇
  1979年   39711篇
  1978年   28770篇
  1977年   23898篇
  1976年   22736篇
  1975年   23472篇
  1974年   28125篇
  1973年   27179篇
  1972年   25118篇
  1971年   23275篇
  1970年   21394篇
  1969年   19812篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
N-3 fatty acid deficiency is described in a 7-year-old girl who had been fed solely by gastric tube from the age of 3 years. She had received the same nutrient during the last 22 months, supplying 16.2% of calories from linoleate and 0.07% from alpha-linolenate. She weighed 9.5 kg at the age of 3, and 10.3 kg at the start of the study, the weight being constant the last 15 months. She was now supplemented daily with 1.2 ml of a linseed- and cod liver-oil mixture (5:1, v/v), thereby increasing her alpha-linolenate intake to 0.71% and total N-3 fatty acids to 0.74% of total energy. Two months later, her rate of weight gain was 0.43 kg/month. After 5 months, the fatty acid supplement was changed to 7.5 ml of cod liver oil daily, thereby changing alpha-linolenate and total N-3 acid intake to 0.10% and 1.3% of total energy, respectively. Her rate of weight gain now increased to 0.64 kg/month, and her length increased from 117 to 122 cm in 5 months. The results indicate that the optimal dietary requirement for N-3 fatty acids in this child is higher than 0.74%, and extrapolation estimated the optimal requirement to be 1.1%-1.2% of total calories. The results suggest that N-3 fatty acids are required for normal growth in man.  相似文献   
992.
993.
Certain groups of patients requiring enteral nutritional support are at increased risk of regurgitation and pulmonary aspiration of feed. Positioning of enteral feeding tubes distal to the pylorus has been advocated as a method of reducing such complications. Various techniques have been suggested to achieve postpyloric siting. Reports have indicated that lengthening the tube or altering the distal end tip configuration, by varying the tip profile or by the addition of a weight, may facilitate spontaneous transpyloric passage of the tube. This prospective controlled clinical study using three new polyurethane tubes demonstrates that the frequency of spontaneous transpyloric passage of the tube is not affected by tip profile or by the addition of a weight. Indeed, with all three tube designs only about one-third had passed spontaneously through the pylorus at 24 hr. Once through the pylorus the unweighted tube stayed in position significantly longer than the weighted tubes (p less than 0.005). We suggest that in those patients requiring post-pyloric feeding, endoscopic or fluoroscopic techniques should be used to position the tubes at the time of insertion, and that an unweighted tube should be used to prolong tube usage.  相似文献   
994.
995.
A cross-sectional, longitudinal study was undertaken on a group of acute non-A, non-B hepatitis patients, as well as on a control group of hepatitis B patients, in order to assess both the prevalence of the most important factors favoring infection, and the relevance of these factors in promoting evolution towards chronic liver disease. Exposures to unknown risk factors were present in 47.4% of acute non-A, non-B infections, followed by blood transfusions (17.9%), sporadic exposures (17.9%) and drug addiction (16.6%). Unknown as well as sporadic exposures showed a greater prevalence in control population if compared to non-A, non-B cases, while drug addiction was equally represented in the two groups, and blood transfusion nearly absent from control group. The risk of evolution to chronic liver disease was about 13 times greater in non-A, non-B group than in controls, with the greatest risk for drug addicts and the lowest for patients with unknown exposures. Among patients with known exposures, the lowest risk of chronic hepatitis was observed in post-transfusion and in sporadic cases, while the greatest was observed in drug addicts.Corresponding author.  相似文献   
996.
997.
998.
The number and complexity of available tests and therapies is expanding and financial resources are shrinking. Clinicians must now consider how to give the best care while limiting health expenses. Decision analysis is a tool used to guide clinicians in the practice of medicine, and to supplement and enhance intuitive decision making based on clinical experience.  相似文献   
999.
The pilot study for a sentinel health events surveillance system for deaths among persons under age 45 with diabetes was conducted in six states in 1984 and 1985. Two hundred and thirty-three events were identified. Information from death certificates, physicians, and families revealed that 22% died from acute complications of diabetes and 53% from chronic complications. Blood pressure measurement and urinalysis testing had been performed in the last year for almost all of the decedents, but other preventive practices were reported less frequently. Hypertension was present in 57% and of those, was not controlled in 73%. Forty-four percent were cigarette smokers at the time of death. Agreement between physicians and families was generally higher for clinical conditions than for care practices. This surveillance system appears to yield information about the health care of persons with diabetes not readily available from other sources, although modifications may be necessary before implementation.  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