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   4199744篇
  免费   340570篇
  国内免费   14971篇
耳鼻咽喉   58972篇
儿科学   135141篇
妇产科学   110754篇
基础医学   644780篇
口腔科学   116069篇
临床医学   378392篇
内科学   758182篇
皮肤病学   103240篇
神经病学   351960篇
特种医学   167392篇
外国民族医学   641篇
外科学   645663篇
综合类   122715篇
现状与发展   24篇
一般理论   2451篇
预防医学   353085篇
眼科学   97830篇
药学   294837篇
  25篇
中国医学   11189篇
肿瘤学   201943篇
  2021年   55950篇
  2020年   35603篇
  2019年   58787篇
  2018年   73673篇
  2017年   56160篇
  2016年   62121篇
  2015年   75743篇
  2014年   110294篇
  2013年   175783篇
  2012年   112209篇
  2011年   115751篇
  2010年   123016篇
  2009年   125506篇
  2008年   102964篇
  2007年   109656篇
  2006年   118843篇
  2005年   114525篇
  2004年   115982篇
  2003年   106615篇
  2002年   96062篇
  2001年   148505篇
  2000年   143567篇
  1999年   133964篇
  1998年   70627篇
  1997年   66899篇
  1996年   65162篇
  1995年   60773篇
  1994年   54947篇
  1993年   51007篇
  1992年   99502篇
  1991年   96130篇
  1990年   92573篇
  1989年   89984篇
  1988年   83915篇
  1987年   81927篇
  1986年   78002篇
  1985年   76838篇
  1984年   64999篇
  1983年   58108篇
  1982年   47652篇
  1981年   44305篇
  1980年   41686篇
  1979年   56695篇
  1978年   46123篇
  1977年   41033篇
  1976年   38074篇
  1975年   38227篇
  1974年   41784篇
  1973年   40138篇
  1972年   37660篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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.
999.
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   
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