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   2566篇
  免费   154篇
  国内免费   62篇
耳鼻咽喉   19篇
儿科学   84篇
妇产科学   52篇
基础医学   253篇
口腔科学   46篇
临床医学   335篇
内科学   571篇
皮肤病学   125篇
神经病学   149篇
特种医学   270篇
外科学   306篇
综合类   47篇
一般理论   1篇
预防医学   197篇
眼科学   16篇
药学   129篇
中国医学   3篇
肿瘤学   179篇
  2023年   20篇
  2022年   40篇
  2021年   112篇
  2020年   46篇
  2019年   75篇
  2018年   87篇
  2017年   58篇
  2016年   61篇
  2015年   69篇
  2014年   87篇
  2013年   125篇
  2012年   137篇
  2011年   160篇
  2010年   86篇
  2009年   70篇
  2008年   120篇
  2007年   146篇
  2006年   112篇
  2005年   100篇
  2004年   98篇
  2003年   99篇
  2002年   66篇
  2001年   22篇
  2000年   15篇
  1999年   25篇
  1998年   55篇
  1997年   40篇
  1996年   65篇
  1995年   49篇
  1994年   44篇
  1993年   51篇
  1992年   14篇
  1991年   20篇
  1990年   24篇
  1989年   34篇
  1988年   42篇
  1987年   49篇
  1986年   33篇
  1985年   34篇
  1984年   24篇
  1983年   16篇
  1982年   17篇
  1981年   29篇
  1980年   25篇
  1979年   9篇
  1978年   11篇
  1977年   16篇
  1976年   9篇
  1975年   10篇
  1927年   3篇
排序方式: 共有2782条查询结果,搜索用时 62 毫秒
1.
2.
3.
The present study explores the construct and ecological validity of the Biber Cognitive Estimation Test (BCET) in a traumatic brain injury (TBI) sample. Participants completed the BCET in the course of a neuropsychological evaluation at 1-15 years after injury. BCET scores correlated moderately with other standard measures of executive functioning, and contrary to our hypotheses, at least as high with neuropsychological tests with minimal demands on executive functioning. Moreover, partialing out the portion of BCET variance not attributable to executive functioning markedly attenuated the former correlations. With respect to ecological validity, BCET scores did not predict concurrent functional status, as measured by the Disability Rating Scale. By comparison, standard measures of executive functioning strongly correlated with each other, correlated less strongly with nonexecutive functioning measures, and predicted functional status. In conclusion, unlike standard measures of executive functioning, the BCET demonstrated poor construct and ecological validity in TBI patients.  相似文献   
4.
The political disintegration of former Yugoslavia inaugurated in 1991 resulted in the decentralization of health systems in the federation's successor nation-states. Efforts by the Open Society Institute improved public health planning and management needs consequent to health sector changes. Beginning in Croatia in 2001, the Institute developed ongoing collaborations between Andrija Stampar School of Public Health and the US Centers for Disease Control and Prevention. In 2003 and 2004, it expanded its project to include the republics of Macedonia and of Serbia and Montenegro.  相似文献   
5.
Glucose is provided to cells by a family of glucose transport facilitators known as GLUTs. These transporters are expressed in a tissue specific manner and are overexpressed in many primary tumors of these tissues. Regulation of glucose transport facilitator expression has been demonstrated in endometrial tissue and endometrial adenocarcinoma. The following experiments were conducted to quantify and localize the expression of GLUT1 and GLUT8 in benign endometrium and compare this expression to endometrial cancer. Endometrial tissue samples were obtained from random hysterectomy specimens of patients with benign indications for surgery and endometrial cancer. Immunoblot and immunolocatization studies were performed using GLUT1 and GLUT8 specific antisera. Endometrial samples from 65 women who had undergone hysterectomy were examined (n=38 benign, n=27 malignant). A 44 and a 35.4 kDa immunoreacive species was demonstrated in endometrium and endometrial cancer for GLUT1 and GLUT8, respectively. Upregulation of GLUT1 expression was demonstrated with increasing grade of tumors (P<0.002). GLUT8 expression was increased in all tumor subtypes compared to atrophic endometrium (P<0.001). Apical localization by GLUT1 and GLUT8 was demonstrated in endometrial glands. GLUT1 and GLUT8 demonstrated diffuse intracellular localization in the cancer subtypes. GLUT1 and GLUT8 are expressed in both human endometrium and endometrial cancer. There appears to be a step-wise progression in GLUT1 and GLUT8 expression as tumor histopathology worsens. GLUT1 and GLUT8 may be important markers in tumor differentiation, as well as providing energy to rapidly dividing tumor cells.  相似文献   
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.
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