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   3778篇
  免费   9篇
  国内免费   1篇
电工技术   4篇
化学工业   56篇
金属工艺   1篇
机械仪表   3篇
建筑科学   12篇
能源动力   35篇
轻工业   19篇
水利工程   9篇
石油天然气   1篇
无线电   50篇
一般工业技术   72篇
冶金工业   3507篇
自动化技术   19篇
  2023年   3篇
  2020年   3篇
  2019年   8篇
  2018年   8篇
  2017年   3篇
  2016年   6篇
  2015年   5篇
  2014年   4篇
  2013年   14篇
  2012年   9篇
  2011年   13篇
  2010年   12篇
  2009年   13篇
  2008年   9篇
  2007年   10篇
  2006年   7篇
  2005年   8篇
  2004年   14篇
  2003年   10篇
  2002年   11篇
  2001年   7篇
  2000年   9篇
  1999年   104篇
  1998年   977篇
  1997年   589篇
  1996年   366篇
  1995年   211篇
  1994年   193篇
  1993年   215篇
  1992年   35篇
  1991年   50篇
  1990年   58篇
  1989年   68篇
  1988年   67篇
  1987年   62篇
  1986年   61篇
  1985年   59篇
  1983年   10篇
  1982年   23篇
  1981年   26篇
  1980年   40篇
  1979年   5篇
  1978年   15篇
  1977年   110篇
  1976年   228篇
  1975年   13篇
  1974年   2篇
  1973年   2篇
  1970年   2篇
  1955年   4篇
排序方式: 共有3788条查询结果,搜索用时 15 毫秒
11.
12.
13.
OBJECTIVE: To evaluate the diagnostic accuracy and clinical usefulness of high-resolution transvaginal duplex Doppler ultrasound in postpartum and post-abortion patients with excessive hemorrhage who are suspected of having residual trophoblast. METHODS: Forty-eight women with excessive hemorrhage referred for possible residual trophoblastic tissue were evaluated by transvaginal duplex Doppler ultrasonography. Based on two-dimensional imaging, the patients were divided prospectively into groups: women who had an empty uterus with a normal uterine cavity, those with a pure endometrial fluid collection and no echogenic foci, those who had a mixed endometrial fluid collection with foci of echogenicity, and those with intracavitary heterogeneous material with mixed echo patterns of fluid and solid components. In each group, Doppler studies were performed and the resistance index (RI) was calculated. The two-dimensional patterns and Doppler results were correlated with clinical and pathologic follow-up. RESULTS: Twenty-eight subjects had a normal uterine cavity and seven had a pure endometrial fluid collection; all were treated conservatively and none showed later clinical evidence of residual trophoblastic tissue. In 13 women, residual trophoblast was strongly suggested from the images of two-dimensional ultrasonography: Five showed an endometrial fluid collection with some echogenic foci, and eight exhibited intracavitary mixed echogenic material. All underwent curettage, and residual trophoblastic tissue was found in ten of the 13. The mean (+/- standard deviation) RI to flow in the myometrial arteries was 0.54 +/- 0.15 in women without residual trophoblast and 0.35 +/- 0.1 in those with residual trophoblastic tissue (P < .01). CONCLUSION: Our experience suggests that transvaginal duplex Doppler ultrasonography is an effective noninvasive method for evaluating patients with excessive postpartum and post-abortion hemorrhage who are suspected of having residual trophoblastic tissue. Its use enhances the positive preoperative diagnosis of residual trophoblastic tissue and may reduce unnecessary curettage procedures.  相似文献   
14.
15.
The role of geriatrics and geriatricians in family medicine remains unsettled. Despite a rapidly aging population, a tremendous shortage now exists of faculty with interest and expertise in geriatrics. Relatively few family practice residents choose to enter geriatric fellowship programs, and federal funding for such programs has been reduced. Despite accreditation requirements, residency programs are not always able to provide the range of geriatric experiences needed to properly prepare graduates to provide care for the broad range of older patients. Medical students' exposure to geriatrics remains limited. The Group on Geriatric Education of the Society of Teachers of Family Medicine believes that family medicine faculty must recognize and be committed to the notion that geriatrics is integral to family medicine. Both undergraduate and residency training programs should emphasize experience with geriatric patients in multiple settings. In particular, the nursing home should not be the main focus of geriatric training. The small number of certified geriatric faculty will be able to provide leadership, but a broad range of faculty must become involved in teaching geriatrics. Faculty development activities and continuing education programs to foster the necessary expertise will be essential to the accomplishment of this task.  相似文献   
16.
17.
18.
19.
20.
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