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   3727294篇
  免费   311718篇
  国内免费   13928篇
耳鼻咽喉   51162篇
儿科学   118654篇
妇产科学   97658篇
基础医学   582933篇
口腔科学   103362篇
临床医学   332809篇
内科学   666255篇
皮肤病学   95515篇
神经病学   318780篇
特种医学   149146篇
外国民族医学   497篇
外科学   575002篇
综合类   113797篇
现状与发展   23篇
一般理论   2380篇
预防医学   310221篇
眼科学   85976篇
药学   261013篇
  23篇
中国医学   10169篇
肿瘤学   177565篇
  2021年   55499篇
  2020年   35314篇
  2019年   58330篇
  2018年   71848篇
  2017年   54770篇
  2016年   60646篇
  2015年   74645篇
  2014年   109088篇
  2013年   174351篇
  2012年   98743篇
  2011年   99215篇
  2010年   118471篇
  2009年   122708篇
  2008年   86875篇
  2007年   90152篇
  2006年   101020篇
  2005年   96059篇
  2004年   98594篇
  2003年   88947篇
  2002年   78725篇
  2001年   120946篇
  2000年   115257篇
  1999年   111827篇
  1998年   67130篇
  1997年   64684篇
  1996年   62672篇
  1995年   58272篇
  1994年   52420篇
  1993年   48949篇
  1992年   83018篇
  1991年   79465篇
  1990年   76022篇
  1989年   74690篇
  1988年   69512篇
  1987年   68216篇
  1986年   64990篇
  1985年   64862篇
  1984年   56626篇
  1983年   51326篇
  1982年   44783篇
  1981年   41940篇
  1980年   39539篇
  1979年   48991篇
  1978年   40981篇
  1977年   36794篇
  1976年   34094篇
  1975年   32848篇
  1974年   35555篇
  1973年   34205篇
  1972年   31699篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
猕猴桃汁抗环磷酰胺致突变作用的机理   总被引:12,自引:1,他引:11  
目的用大鼠外周血双核淋巴细胞微核测试法(CBMNT),在哺乳动物整体水平,研究猕猴桃汁抗环磷酰胺(CP)的致突变作用以及生物转化Ⅱ相酶的作用。方法测定大鼠外周血双核淋巴细胞微核细胞率及肝组织中总谷胱甘肽硫转移酶(GST)、尿苷二磷酸葡萄糖醛酸转移酶(UDPGT)、谷氨酰胺转肽酶(γGT)活性。结果猕猴桃汁对CP诱发的大鼠外周血双核淋巴细胞微核细胞率有显著抑制作用,能明显诱导大鼠肝脏总GST、UDGTP活性,但对γGT活性无显著影响。大鼠外周血双核淋巴细胞微核细胞率与总GST、UDGTP活性呈明显负相关。结论猕猴桃汁抗CP致微核形成作用的机理可能是通过诱导机体外来化合物代谢解毒酶系,加速CP的代谢灭活  相似文献   
943.
944.
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   
945.
Parker  Lisa S. 《JAMA》1998,280(20):1798-1799
  相似文献   
946.
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   
947.
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   
948.
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   
949.
Summary: Current peritoneal dialysis solutions are not biocompatible, particularly in respect to low pH, high osmolality and use of lactate. In addition, glucose is not an ideal osmotic agent. Recent advances in the formulation of peritoneal dialysis fluids aim to provide a more physiological environment to preserve membrane integrity. the effects of pH and lactate have been overcome by the use of bicarbonate based solutions whilst icodextrin (glucose polymers) often prolonged ultrafiltration in spite of being isomotic to uraemic plasma. Future formulations will see a combination of osmotic agents (including amino acids) and bicarbonate to achieve a more biocompatible solution whilst still meeting the ultrafiltration needs of the patients. Additives (glycosaminoglycans, procysteine) may protect the peritoneum from free radical injury.  相似文献   
950.
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   
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