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   923篇
  免费   49篇
  国内免费   61篇
耳鼻咽喉   14篇
儿科学   54篇
妇产科学   10篇
基础医学   49篇
口腔科学   14篇
临床医学   136篇
内科学   246篇
皮肤病学   29篇
神经病学   31篇
特种医学   232篇
外科学   80篇
综合类   29篇
预防医学   40篇
眼科学   9篇
药学   35篇
中国医学   2篇
肿瘤学   23篇
  2022年   4篇
  2021年   10篇
  2020年   4篇
  2019年   7篇
  2018年   16篇
  2017年   7篇
  2016年   5篇
  2015年   14篇
  2014年   15篇
  2013年   30篇
  2012年   14篇
  2011年   10篇
  2010年   22篇
  2009年   20篇
  2008年   18篇
  2007年   53篇
  2006年   20篇
  2005年   20篇
  2004年   15篇
  2003年   9篇
  2002年   13篇
  2001年   18篇
  2000年   13篇
  1999年   18篇
  1998年   52篇
  1997年   39篇
  1996年   62篇
  1995年   44篇
  1994年   40篇
  1993年   49篇
  1992年   14篇
  1991年   13篇
  1990年   21篇
  1989年   27篇
  1988年   37篇
  1987年   39篇
  1986年   32篇
  1985年   44篇
  1984年   16篇
  1983年   11篇
  1982年   13篇
  1981年   23篇
  1980年   20篇
  1979年   10篇
  1978年   10篇
  1977年   18篇
  1976年   8篇
  1975年   9篇
  1972年   2篇
  1963年   1篇
排序方式: 共有1033条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
Activated granulocytes release highly active enzymes such as myeloperoxidase and lactoferrin, which can be involved in tissue destruction mediated by oxygen free radicals. Cardiopulmonary bypass has been reported to activate granulocytes. Bypass circuits coated with heparin have been shown to reduce release of granulocyte factors in experimental studies. In the present study, heparin-coated circuits were compared with noncoated circuits. In seven patients undergoing coronary bypass, heparin-coated circuits were used (group HC), and seven served as control patients (group C). In group HC the heparin dose was reduced to 75% (225 IU/kg). Group C had the standard dose of 300 IU/kg. No preoperative differences in myeloperoxidase and lactoferrin were observed between the groups. At the end of bypass in both groups, there was a significant increase of these enzymes (p less than 0.001) followed by a later decrease. In group HC, however, the release of myeloperoxidase was significantly lower than in group C (215 +/- 24 versus 573 +/- 133 micrograms/L, mean +/- standard error of the mean). The release of lactoferrin was significantly lower in group HC than in group C both at the end of cardiopulmonary bypass (659 +/- 79 versus 1448 +/- 121 micrograms/L) and 3 hours after bypass (224 +/- 37 versus 536 +/- 82 micrograms/L). Granulocytes as well as total number of leukocytes continued to increase until 1 hour after bypass (p less than 0.001) and then manifested a slow decrease. It was concluded that the use of heparin-coated circuits reduced the release of granulocyte factors because of lower activation of leukocytes.  相似文献   
7.
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.  相似文献   
8.
Goei  R; Baeten  C; Arends  JW 《Radiology》1988,168(2):303-306
Sixteen cases of histopathologically proved solitary rectal ulcer syndrome were encountered. Fifteen patients underwent barium enema study; in nine cases the findings--including rectal stricture, granularity of the mucosa, and thickened rectal folds-were nonspecific. In six cases the study was normal. All patients had a long history of defecation disorders, and defecography was performed in all. In seven cases, intussusception of the rectal wall was seen; in another case the intussusception was accompanied by a rectocele. One case showed rectal prolapse. In four cases, failed relaxation of the puborectalis occurred and prevented the passage of the bolus; in another case there was abnormal perineal descent. In two patients studies were normal. In patients with defecation disorders, the possibility of this syndrome should be considered. Defecography is the method of choice for establishing the diagnosis.  相似文献   
9.
10.
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