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   1119149篇
  免费   75286篇
  国内免费   1475篇
耳鼻咽喉   15357篇
儿科学   36387篇
妇产科学   29866篇
基础医学   159769篇
口腔科学   30485篇
临床医学   101078篇
内科学   212050篇
皮肤病学   25236篇
神经病学   85976篇
特种医学   44134篇
外国民族医学   202篇
外科学   166976篇
综合类   22082篇
现状与发展   1篇
一般理论   325篇
预防医学   80039篇
眼科学   25182篇
药学   88659篇
  9篇
中国医学   2849篇
肿瘤学   69248篇
  2021年   8701篇
  2019年   9044篇
  2018年   12712篇
  2017年   10002篇
  2016年   11328篇
  2015年   12558篇
  2014年   16940篇
  2013年   24647篇
  2012年   33912篇
  2011年   35778篇
  2010年   20877篇
  2009年   19539篇
  2008年   32828篇
  2007年   34993篇
  2006年   35616篇
  2005年   33775篇
  2004年   32378篇
  2003年   31020篇
  2002年   29748篇
  2001年   60392篇
  2000年   61761篇
  1999年   51244篇
  1998年   12954篇
  1997年   11381篇
  1996年   11347篇
  1995年   10643篇
  1994年   9603篇
  1993年   9112篇
  1992年   37982篇
  1991年   36443篇
  1990年   35890篇
  1989年   34397篇
  1988年   30991篇
  1987年   30085篇
  1986年   28317篇
  1985年   26549篇
  1984年   19283篇
  1983年   16211篇
  1982年   8943篇
  1979年   17090篇
  1978年   11467篇
  1977年   10277篇
  1976年   8881篇
  1975年   10103篇
  1974年   11691篇
  1973年   11306篇
  1972年   10787篇
  1971年   10126篇
  1970年   9273篇
  1969年   8954篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
We have recently shown that HPV-positive tonsillar carcinoma in young patients exhibits nonkeratinizing basaloid morphology and a characteristic immunophenotype. The purpose of this study was to review a large number of cases of oropharyngeal carcinomas, in all age groups, and to identify tumors with nonkeratinizing morphology. Using polymerase chain reaction (PCR) the prevalence and type of HPV DNA was determined in representative cases and in a control group of conventional keratinizing squamous cell carcinomas. The tumors were further characterized with a panel of immunohistochemical stains. A total of 235 carcinomas were reviewed; 141 of the tonsils and 94 in the base of tongue. Ninety (36%) of the tonsillar and 30 (32%) of the base of tongue carcinomas were nonkeratinizing (NKCa) with basal cell features; the rest were classical keratinizing squamous cell carcinomas (KSCC). HPV DNA, particularly type 16, was identified in 10 (100%) of 10 of NKCA and in only 2 (20%) of 10 of KSCC (P = .0014). NKCas were strongly reactive to p16 antibodies while KSCC showed weak and focal reactivity. Higher Ki67 and lower p53 staining scores were observed in NKCa as compared to KSCC. It is concluded that NKCa of the tonsils and base of tongue is a distinct subtype of squamous cell carcinoma of the head and neck with high prevalence of HPV DNA and a characteristic immunophenotype.  相似文献   
45.
46.
47.
48.
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   
49.
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   
50.
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   
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