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   15329篇
  免费   1605篇
  国内免费   15篇
耳鼻咽喉   103篇
儿科学   582篇
妇产科学   467篇
基础医学   2167篇
口腔科学   259篇
临床医学   1866篇
内科学   2819篇
皮肤病学   195篇
神经病学   1206篇
特种医学   524篇
外科学   2245篇
综合类   274篇
一般理论   12篇
预防医学   1705篇
眼科学   301篇
药学   1358篇
中国医学   15篇
肿瘤学   851篇
  2021年   213篇
  2019年   218篇
  2018年   266篇
  2017年   204篇
  2016年   185篇
  2015年   229篇
  2014年   304篇
  2013年   483篇
  2012年   723篇
  2011年   718篇
  2010年   455篇
  2009年   342篇
  2008年   652篇
  2007年   686篇
  2006年   671篇
  2005年   699篇
  2004年   670篇
  2003年   677篇
  2002年   581篇
  2001年   539篇
  2000年   529篇
  1999年   454篇
  1998年   183篇
  1997年   130篇
  1996年   137篇
  1995年   123篇
  1994年   137篇
  1993年   128篇
  1992年   341篇
  1991年   354篇
  1990年   321篇
  1989年   302篇
  1988年   329篇
  1987年   319篇
  1986年   280篇
  1985年   277篇
  1984年   245篇
  1983年   206篇
  1982年   136篇
  1981年   120篇
  1980年   113篇
  1979年   191篇
  1978年   115篇
  1977年   112篇
  1976年   137篇
  1974年   151篇
  1973年   143篇
  1972年   126篇
  1971年   126篇
  1970年   141篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Mercury and selenium act as mutual antagonists in mature birds, but their toxicity is additive or synergistic in avian embryos and immature birds. Twenty eggs and livers from 18 mature and 9 immature common loon carcasses found in Minnesota were collected. Livers and eggs were analyzed for mercury and selenium by atomic emission and atomic absorption spectroscopy. Liver mercury concentrations were significantly higher in mature loons compared to those of immature loons and eggs. Liver selenium concentrations were significantly higher in mature loons than those of immature loons, and selenium concentrations in immature loon livers were significantly higher than levels in eggs. There was a significant positive correlation between mercury and selenium in loon livers. There was a negative correlation between mercury and selenium in eggs. Received: 2 February 2001/Accepted: 28 May 2001  相似文献   
34.
Conchotome and needle percutaneous biopsy of skeletal muscle.   总被引:5,自引:0,他引:5       下载免费PDF全文
Percutaneous muscle biopsy is an important and acceptable technique in the study of conditions involving human skeletal muscle. A review of 436 conchotome and needle muscle biopsies obtained over 18 months in this centre is presented.  相似文献   
35.
36.
Studies in animals have suggested that the products of the irradiation of tryptophan in the presence of riboflavin may play a role in the development of hepatic dysfunction during parenteral nutrition. In this paper we describe the formation of an adduct between tryptophan and riboflavin obtained as a consequence of an anaerobic irradiation of these compounds. Through the use of molecular sieves and of an ion-exchange resin it was possible to separate the photo-adduct from the dimer riboflavin and other reaction products. The various fractions were characterized on the basis of their absorption and emission spectra. Also used were measures of anisotropy of fluorescence emission in order to characterize the derived adduct.  相似文献   
37.
A series of studies designed to define the requirement of normal infants for sulfur-containing amino acids (methionine, cystine) was conducted with formulas providing 3.0, 2.8, 2.6, 2.2 or 1.8 g of isolated soy protein per 100 kcal. The formulas were fed with or without a methionine supplement. Adequacy of the diet was determined by measurement of growth, serum chemical indices and nitrogen balance. Nitrogen balance demonstrated a beneficial effect of methionine supplementation only at the lowest protein concentration (1.8 g/100 kcal). However, measurement of weight gain and/or serum concentrations of urea nitrogen and albumin clearly showed a beneficial effect of methionine supplementation at protein concentrations of 2.2 and 2.6 g/100 kcal. Intakes of sulfur-containing amino acids of 435 and 495 mumol/100 kcal therefore appear inadequate. At higher intakes of protein (2.8 and 3.0 g/100 kcal) there was no beneficial effect of methionine supplementation. Possible exceptions were male infants provided with 3.0 g protein per 100 kcal, in whom weight gain between 8 and 56 d of age was significantly (P less than 0.05) greater with than without a methionine supplement. Based on intakes of sulfur-containing amino acids from the formula providing 2.8 g of isolated soy protein per 100 kcal without methionine supplementation, we conclude that for male infants older than 56 d the requirement for sulfur-containing amino acids is no more than 588 mumol/100 kcal when intake of methionine is 264 mumol/100 kcal. However, it seems possible that such intake fails to meet the requirement in male infants less than 56 d of age. For female infants, regardless of age, 533 mumol/100 of sulfur-containing amino acids per 100 kcal meet the requirement when intake of methionine is 239 mumol/100 kcal.  相似文献   
38.
Valves in the subclavian and internal jugular veins were studied in 100 autopsy cases (52 men and 48 women; range, 18 to 91 years old; mean, 67 years). In 87 cases, valves were present in all 4 veins, and in 13 cases, valves anatomically were absent from 16 veins, 9 of which were the left internal jugular vein. The average distance from the valve to the junction with the innominate vein was 1.7 cm for the subclavian vein and 0.3 cm for the internal jugular vein. Cuspid height averaged 0.9 cm. Valves were bicuspid in 347 (90%) and unicuspid in 39 (10%); unicuspid valves were more common in the internal jugular vein than in the subclavian vein. Catheter-induced trauma was observed in 4 cases and implied in 4 more. These findings may have important implications concerning the failure, in some cases, of closed-chest cardiac resuscitation to maintain forward blood flow at adequate pressure.  相似文献   
39.
Traditionally, neuropsychological deficits due to Sickle Cell Disease (SCD) have been understudied in adults. We have begun to suspect, however, that symptomatic and asymptomatic Cerebrovascular Events (CVE) may account for an alarming number of deficits in this population. In the current brief review, we critically evaluated the pediatric and adult literatures on the neurocognitive effects of SCD. We highlighted the studies that have been published on this topic and posit that early detection of CVE via neurocognitive testing, neuropsychiatric evaluations, and neuroimaging may significantly reduce adult cognitive and functional morbidities.  相似文献   
40.
Throughout history, the heart has been associated not only with its life-sustaining function but also with its close ties to the human emotions. In this literature and internet review, we attempt to gather and organize information from both of these perspectives as they relate to the heart in the following 11 categories: (1) fun facts, (2) medical photography, (3) history, (4) languages (etymology), (5) nonmedical English expressions, (6) death, (7) the arts, (8) movie titles, (9) song titles, (10) Shakespeare, and (11) the Bible. Part 1 (previously published) covered the first five topics, and Part 2 will cover the last six topics. These data may be useful to those who are engaged in teaching about the cardiovascular system.  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