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   2195099篇
  免费   151424篇
  国内免费   3238篇
耳鼻咽喉   31334篇
儿科学   71883篇
妇产科学   62268篇
基础医学   315512篇
口腔科学   61904篇
临床医学   190574篇
内科学   422489篇
皮肤病学   47386篇
神经病学   169135篇
特种医学   86582篇
外国民族医学   565篇
外科学   336390篇
综合类   45414篇
现状与发展   2篇
一般理论   559篇
预防医学   157518篇
眼科学   50339篇
药学   171240篇
  8篇
中国医学   4907篇
肿瘤学   123752篇
  2018年   21563篇
  2016年   18736篇
  2015年   21311篇
  2014年   29155篇
  2013年   43825篇
  2012年   60041篇
  2011年   64059篇
  2010年   37849篇
  2009年   35556篇
  2008年   61070篇
  2007年   65879篇
  2006年   66906篇
  2005年   64832篇
  2004年   62231篇
  2003年   60260篇
  2002年   58864篇
  2001年   107318篇
  2000年   110122篇
  1999年   92694篇
  1998年   24951篇
  1997年   22169篇
  1996年   22267篇
  1995年   21055篇
  1994年   19561篇
  1993年   18241篇
  1992年   72475篇
  1991年   70522篇
  1990年   69575篇
  1989年   67242篇
  1988年   61884篇
  1987年   60493篇
  1986年   57434篇
  1985年   54403篇
  1984年   40129篇
  1983年   34458篇
  1982年   19845篇
  1981年   17543篇
  1979年   37104篇
  1978年   25581篇
  1977年   22457篇
  1976年   20433篇
  1975年   22793篇
  1974年   26704篇
  1973年   25790篇
  1972年   24634篇
  1971年   22985篇
  1970年   21238篇
  1969年   20579篇
  1968年   18870篇
  1967年   16703篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  相似文献   
46.
We report the case of a 38-year-old woman who presented with chronic lower abdominal pain. Her past medical history included a splenectomy due to abdominal trauma. Ultrasound examination revealed four pelvic tumors which, upon laparotomy, were found to be the result of splenosis. Approximately 100 cases of splenosis have been reported but only a minority of them have been published in the gynecological literature. Our case indicates that those involved in pelvic scanning (even of asymptomatic women) and/or treating those complaining of lower abdominal pain or presenting with pelvic tumors should be aware of splenosis as a possible diagnosis.  相似文献   
47.
48.
Although surgical lung resection could improve prognosis in some patients with multidrug-resistant tuberculosis (MDR-TB), there are no reports on the optimal candidates for this surgery. The aim of the present study was to elucidate the prognostic factors for surgery in patients with MDR-TB. Patients who underwent lung resection for the treatment of MDR-TB between March 1993 and December 2004 were included in the present study. Treatment failure was defined as greater than or equal to two of the five cultures recorded in the final 12 months of treatment being positive, any one of the final three cultures being positive, or the patient having died during treatment. The variables that affected treatment outcomes were identified through univariate and multivariate logistic regression analysis. In total, 79 patients with MDR-TB were included in the present study. The treatment outcomes of 22 (27.8%) patients were classified as failure. A body mass index <18.5 kg x m(-2), primary resistance, resistance to ofloxacin and the presence of a cavitary lesion beyond the range of the surgical resection were associated with treatment failure. Low body mass index, primary resistance, resistance to ofloxacin and cavitary lesions beyond the range of resection are possible poor prognostic factors for surgical lung resection in multidrug-resistant tuberculosis patients.  相似文献   
49.
50.
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