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   1696121篇
  免费   123356篇
  国内免费   3784篇
耳鼻咽喉   21739篇
儿科学   55643篇
妇产科学   46173篇
基础医学   241292篇
口腔科学   48784篇
临床医学   151333篇
内科学   333623篇
皮肤病学   38659篇
神经病学   131157篇
特种医学   63881篇
外国民族医学   242篇
外科学   257290篇
综合类   38949篇
现状与发展   4篇
一般理论   531篇
预防医学   124286篇
眼科学   40214篇
药学   123636篇
  7篇
中国医学   4475篇
肿瘤学   101343篇
  2021年   12810篇
  2019年   13550篇
  2018年   19981篇
  2017年   15240篇
  2016年   16642篇
  2015年   18982篇
  2014年   26234篇
  2013年   37967篇
  2012年   52764篇
  2011年   55465篇
  2010年   32796篇
  2009年   30717篇
  2008年   51548篇
  2007年   54821篇
  2006年   55280篇
  2005年   52563篇
  2004年   50755篇
  2003年   48163篇
  2002年   46384篇
  2001年   91787篇
  2000年   93611篇
  1999年   76961篇
  1998年   19718篇
  1997年   17268篇
  1996年   17392篇
  1995年   16742篇
  1994年   15291篇
  1993年   14071篇
  1992年   57382篇
  1991年   55271篇
  1990年   52970篇
  1989年   50748篇
  1988年   46131篇
  1987年   44938篇
  1986年   42226篇
  1985年   39988篇
  1984年   29350篇
  1983年   24908篇
  1982年   13898篇
  1979年   25531篇
  1978年   17576篇
  1977年   14907篇
  1976年   13874篇
  1975年   14563篇
  1974年   17630篇
  1973年   16945篇
  1972年   15673篇
  1971年   14454篇
  1970年   13432篇
  1969年   12517篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Analytical epidemiology techniques were used to study the malignant neoplasms prevalence in the population of Magnitogorsk (400,000), and among the workers engaged in the Magnitogorsk metallurgical plant (64,000 workers). Revealed was that the malignant neoplasms related morbidity rate was 1.6 higher in men and 3.2 higher in women among the plant workers as compared with the city population in general. The cancer risk factors were predominantly occupational ones, e. i. the major industrial carcinogens--benzopyrene in tars and carbon-black; benzol, chromium and nickel in the dust; the carcinogenesis modifying substances--nitrogen oxide, sulfur dioxide, phenols, iron oxides, lead and its non-organic compounds, high temperatures. The data received can be used in further studies and elaboration of primary preventive measures.  相似文献   
995.
Results are presented from approximately 9000 Rn measurements made in New York state, North Carolina, and South Carolina. The estimated statewide geometric mean concentrations were 28.1 Bq m-3 and 55.8 Bq m-3 for basements in New York state, 27.5 Bq m-3 for living rooms and 108.9 Bq m-3 for basements in North Carolina, and 25.0 Bq m-3 for living rooms in South Carolina.  相似文献   
996.
Three groups of weanling female mice were fed one of two iron-deficient diets (5 and 12 mg Fe/kg diet) or a normal diet (30 mg Fe/kg diet) for 6 wk. A control pair-fed group was included. Seven mice received the 5 mg Fe/kg diet for 6 wk, then were rehabilitated using the 30 mg Fe/kg diet for 10 d. Mice fed the 5 mg Fe/kg diet were moderately iron-deficient, as shown by indices of iron status. No significant differences were observed in thymus weight or in the proportion and number of thymocyte subsets in thymuses of anemic, moderately iron-deficient and control mice. Thymus weight was decreased in pair-fed mice. No significant difference was found in lymph node subsets. In the spleen of anemic mice, the proportions and total number of Thy-1+ splenocytes, CD4-8+ and CD4+8- cells were very low compared with control (P less than 0.01) and iron-deficient (P less than 0.02) mice. The decrease was not only observed for the percentage of subsets but also for the absolute number of cell subtypes per spleen. Thy-1+ splenocyte subpopulations were normalized after rehabilitation. These quantitative modifications could explain alterations in the blastogenic response of splenic lymphocytes described by other authors.  相似文献   
997.
Serum lipoproteins, body composition, and adipose cholesterol contents of six obese women were studied during and after major weight loss by very-low-calorie diets (VLCDs). Subjects started at 168 +/- 11% of ideal body weight, lost 30.3 +/- 3.7 kg in 5-7 mo, followed by 2+ mo in weight maintenance. Serum cholesterol fell from a prediet (baseline) value of 5.49 +/- 0.32 to 3.62 +/- 0.31 mmol/L (P less than 0.01) after 1-2 mo of VLCDs (nadir), after which it rose to 5.95 +/- 0.36 mmol/L (peak, P less than 0.01 compared with nadir and baseline) as weight loss continued. With weight maintenance, serum cholesterol fell to 4.92 +/- 0.34 mmol/L (P less than 0.05 compared with peak). Adipose cholesterol content did not change in peripheral (arm and leg) biopsy sites but rose significantly in abdominal adipose tissue with weight loss. We conclude that major weight loss was associated with a late rise in serum cholesterol, possibly from mobilization of adipose cholesterol stores, which resolved when weight loss ceased.  相似文献   
998.
Quantitative studies of morbidity, food intake, and somatic growth were done prospectively during 14 mo for 70 children aged 5-18 mo in two Bangladeshi villages. When random-effect regression models were used, monthly changes in weight were inversely related to proportions of days in the month with fever and diarrhea and positively related to energy intake per kilogram body weight. Interestingly, weight changes did not vary with age in this interval. Estimates indicate that increasing energy intakes to the recommended World Health Organization level would have a significantly greater effect on weight gain than would the elimination of diarrhea and fever. With energy at recommended intake and diarrhea and fever prevalence as found in US children, weight gain is predicted to be near that of the international reference population. Therefore, interventions aimed at improving dietary intake may be as important as infection-control programs for improving growth of children in poor developing nations.  相似文献   
999.
We examined seven 1-d diet records kept during 1 y by 272 men and women instructed to follow a lipid-lowering diet while participating in a clinical trial of pravastatin, a new 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor. The mean percentage of calories from total fat and saturated, unsaturated, and monounsaturated fatty acids was similar throughout the year even though the patients knew they were taking an effective lipid-lowering agent. However, the diets of greater than 40% of women included less than two-thirds of the recommended dietary allowance (RDA) of folic acid, vitamins B-6 and D, and calcium and zinc; in men, folic acid and zinc intakes were low. We conclude that patients comply with lipid-lowering diets even when they know that they are receiving an effective serum lipid-lowering agent. However, for both men and women special attention should be given to the intake of several nutrients.  相似文献   
1000.
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   
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