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   1859篇
  免费   115篇
  国内免费   60篇
耳鼻咽喉   14篇
儿科学   135篇
妇产科学   68篇
基础医学   233篇
口腔科学   28篇
临床医学   259篇
内科学   393篇
皮肤病学   29篇
神经病学   65篇
特种医学   255篇
外科学   145篇
综合类   48篇
一般理论   2篇
预防医学   128篇
眼科学   18篇
药学   121篇
中国医学   3篇
肿瘤学   90篇
  2021年   29篇
  2019年   12篇
  2018年   24篇
  2017年   14篇
  2016年   13篇
  2015年   24篇
  2014年   36篇
  2013年   57篇
  2012年   68篇
  2011年   57篇
  2010年   42篇
  2009年   44篇
  2008年   52篇
  2007年   86篇
  2006年   52篇
  2005年   53篇
  2004年   45篇
  2003年   48篇
  2002年   44篇
  2001年   41篇
  2000年   49篇
  1999年   50篇
  1998年   60篇
  1997年   45篇
  1996年   66篇
  1995年   50篇
  1994年   48篇
  1993年   54篇
  1992年   25篇
  1991年   39篇
  1990年   44篇
  1989年   52篇
  1988年   54篇
  1987年   55篇
  1986年   45篇
  1985年   47篇
  1984年   28篇
  1983年   24篇
  1982年   18篇
  1981年   29篇
  1980年   25篇
  1979年   20篇
  1978年   19篇
  1977年   26篇
  1976年   15篇
  1975年   20篇
  1973年   13篇
  1970年   12篇
  1969年   14篇
  1966年   18篇
排序方式: 共有2034条查询结果,搜索用时 14 毫秒
1.
2.
3.
对57例内膜刮出组织和宫内流出组织均未检出绒毛膜绒毛。用抗血清标记绒毛滋养层的人绒毛膜促性腺激素(HCG)、人胎盘催乳素(HPL)和妊娠特异糖蛋白(SPI),结果18例被标记,37例未被标记。临床证明未被标记的37例为异位妊娠。表明用激素标记子宫内膜可提高异位妊娠的诊断率。  相似文献   
4.
5.
6.
7.
8.
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   
9.
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   
10.
Riddelliine alters hepatocellular and endothelial cell kinetics and function including stimulating an increase in hepatocytic vascular endothelial growth factor (VEGF) in the absence of increased serological levels of VEGF (Nyska etal. 2002). The objective of this study was to further assess hepatic VEGF and KDR/flk-1 synthesis and expression by hepatic cells under riddelliine treatment conditions. Forty-two male F344/N rats were dosed by gavage with riddelliine (0, 1.0, and 2.5 mg/kg/day) for 6 weeks. Seven animals/group were sacrificed after 8 consecutive daily doses; remaining rats were terminated after 30 daily doses, excluding weekends. Hepatic tissues were evaluated by immunohistochemistry and in situ hybridization. The results showed that VEGF mRNA expression was observed in control and treated animals; however, qualitative differences were noted. Treated animals exhibited VEGF mRNA in clustered, focal hepatocytes and bile duct epithelium, whereas VEGF mRNA in hepatocytes from vehicle control rats was distributed evenly across all hepatocytes. Results evaluating the distribution of the VEGF cognate receptor, KDR/flk-1 showed that randomly distributed, rare sinusoidal endothelium, including those demonstrating karyomegaly and cytomegaly expressed KDR/flk-1. Phosphorylation of KDR/flk-1 at pTyr996 and pTyr1054/1059, but not pTyr951, was also detected, evidence that endothelial cell KDR/flk-1 was activated. These results suggest that both hepatocytes and endothelial cells are targets of riddelliine-induced injury. We speculate that damage to both populations of cells may lead to dysregulated VEGF synthesis by hepatocytes and activation of KDR/flk-1 by endothelium leading to the induction of sustained endothelial cell proliferation, culminating in the development of hepatic hemangiosarcoma.  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