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   4326450篇
  免费   354282篇
  国内免费   15381篇
耳鼻咽喉   61589篇
儿科学   134364篇
妇产科学   112729篇
基础医学   660946篇
口腔科学   119875篇
临床医学   393849篇
内科学   783903篇
皮肤病学   103920篇
神经病学   370214篇
特种医学   172104篇
外国民族医学   922篇
外科学   657716篇
综合类   127121篇
现状与发展   23篇
一般理论   2629篇
预防医学   367956篇
眼科学   101530篇
药学   305777篇
  25篇
中国医学   11421篇
肿瘤学   207500篇
  2021年   55964篇
  2020年   35666篇
  2019年   58884篇
  2018年   73665篇
  2017年   56240篇
  2016年   62576篇
  2015年   75844篇
  2014年   110639篇
  2013年   176140篇
  2012年   120254篇
  2011年   123738篇
  2010年   123724篇
  2009年   126698篇
  2008年   110621篇
  2007年   117762篇
  2006年   127056篇
  2005年   122217篇
  2004年   123096篇
  2003年   113687篇
  2002年   104186篇
  2001年   155351篇
  2000年   151620篇
  1999年   140458篇
  1998年   71626篇
  1997年   68001篇
  1996年   65876篇
  1995年   61690篇
  1994年   55790篇
  1993年   51806篇
  1992年   104404篇
  1991年   99743篇
  1990年   94812篇
  1989年   92431篇
  1988年   85989篇
  1987年   84494篇
  1986年   80110篇
  1985年   78599篇
  1984年   66485篇
  1983年   59319篇
  1982年   48382篇
  1981年   45087篇
  1980年   42359篇
  1979年   58324篇
  1978年   47381篇
  1977年   41886篇
  1976年   38960篇
  1975年   38142篇
  1974年   42814篇
  1973年   40882篇
  1972年   38397篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Measurements were made of glutathione (GSH) levels, catalase activity and the oxidant sensitivity of the erythrocytes from the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula). The oxidant sensitivity was tested by treating the haemolysates with either 0.55 him H2O2 or 1.4mm NaNO2. The erythrocytes of the koala had greater levels of GSH and catalase and yet were found to be more susceptible to oxidation induced by both these oxidants.  相似文献   
992.
Parker  Lisa S. 《JAMA》1998,280(20):1798-1799
  相似文献   
993.
Study Objective . To characterize cytochrome P450 (CYP) 3A4 activity in premenopausal and postmenopausal women by evaluating the urinary 6-β-hydroxycortisokcortisol ratio. Design . Prospective study. Subjects . Thirteen premenopausal and 13 postmenopausal women who were healthy and not receiving drugs known to affect CYP3A4 activity. Interventions . Beginning on day 2 of menses, premenopausal women collected first morning urine samples every other day for a complete menstrual cycle. Postmenopausal women collected first morning urine every other day for 28 days. Measurements and Main Results . Mean weekly 6-β-hydroxycortisol:cortisol ratios did not differ during the phase (week) of the menstrual cycle. Daily ratios did not differ in postmenopausal women. No difference between premenopausal and postmenopausal women was found on comparing overall median ratios. Conclusion . Cytochrome P450 3A4 activity as measured by 6-β-hydroxy cortisol:cortisol ratio did not differ by week of menstrual cycle, suggesting no menstrual cycle-related changes. Menopause does not appear to be associated with differences in CYP3A4 activity, compared with premenopause.  相似文献   
994.
We prospectively enrolled 160 consecutive patients with inversion trauma of the ankle in a diagnostic protocol that included physical examination within 2 days and at 5 days after trauma, arthrography, stress radiography, and ultrasonography. 135 patients had pathological lateral ligament laxity on the later physical examination or lateral ligament rupture diagnosed on arthrography and they were operated on. 122 of these patients had ligament ruptures.

At clinical follow-up after a minimum of half a year, all of the patients who were not operated on had stable joints without signs of previous ligament ruptures.

Delayed physical examination at 5 days after the injury led to the highest overall sensitivity (96%) and specificity (84%) for the detection of a ligament rupture. Additional diagnostic procedures, at a considerable cost, yielded little additional information.  相似文献   
995.
为了了解常用化妆品对皮肤的损伤情况,作者研究了87例化妆品皮肤损伤的临床特点,并对致病化妆品种类进行了分析。认为染发、洗发、祛斑霜类化妆品易引起急性损伤,但病程短,病因明确,易于诊断。而各种营养霜、护肤霜膏类化妆品多次涂搽后才缓慢致病,病程长,影响因素多,临床诊断需结合化妆品斑贴试验综合考虑  相似文献   
996.
Aim : The study was designed to determine the effect of computerized nutrition information on consumer food choice in two workplace restaurants, one in which customers had to pay for their lunch and the other providing a free lunch. Methods : Customers entering the restaurants were asked to make selections from the menu on a computer screen. The energy, saturated fatty acids, non-milk extrinsic sugars and non-starch polysaccharide content of the meal selected was displayed graphically in proportion to the dietary reference values. They were given the opportunity to change their selected meal and the composition of all meals was recorded. Results : The nutritional composition of the first meal provoked 16% of customers to make a second selection. The proportion of energy in the first selection had been 31% higher for saturated fatty acids and 23% higher for non-milk extrinsic sugars than the first selection made by people who were satisfied with their first choice. In their second attempt they succeeded in reducing both nutrients to levels similar to those present in the meals selected by people who had been satisfied with their first selection. Customers>> selections for non-starch polysaccharide and energy did not differ between the groups. The main changes made by customers to achieve improved second choices were to omit dishes (44%), add dishes (19%), make changes within a menu category (46%), and make changes from one menu category to another (26%). Conclusion : It was concluded that provision of graphical nutrition information on a computer screen could be used by a subset of the users of both restaurants to enable them to improve their menu selections to a similar composition to that selected by the other people who used the computer system.  相似文献   
997.
998.
为研究包钢的原料中所含天然钍对作业工人健康的影响,对5985人的暴露队列进行了17年的流行病学调查。结果发现,作业工人外周血淋巴细胞染色体畸变率随年附加有效剂量的增加而升高(与对照组比较P<0.01)。工龄为5~14年者增加较快,15年后增加缓慢,趋于平衡。尘肺分析结果提示,天然钍可能增强SiO2的致肺纤维化作用。肿瘤死亡率除胃癌外,其余RR均大于1,但无统计学意义。相距一年的两次植物血球凝集素(PHA)皮试反应均有增强,但外周血淋巴细胞离体照射后,染色体畸变未见适应性。女工妊娠期从事钍作业,其所生子女的智力发育无明显异常。  相似文献   
999.
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