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   3263246篇
  免费   226740篇
  国内免费   8445篇
耳鼻咽喉   44887篇
儿科学   108100篇
妇产科学   90369篇
基础医学   458974篇
口腔科学   89745篇
临床医学   296854篇
内科学   634722篇
皮肤病学   78138篇
神经病学   263931篇
特种医学   125827篇
外国民族医学   918篇
外科学   486525篇
综合类   65631篇
现状与发展   6篇
一般理论   1178篇
预防医学   246631篇
眼科学   73797篇
药学   243853篇
  13篇
中国医学   7095篇
肿瘤学   181237篇
  2019年   25589篇
  2018年   36109篇
  2017年   27968篇
  2016年   32310篇
  2015年   36270篇
  2014年   49765篇
  2013年   74402篇
  2012年   99281篇
  2011年   104981篇
  2010年   63140篇
  2009年   60289篇
  2008年   97786篇
  2007年   104059篇
  2006年   105946篇
  2005年   101546篇
  2004年   97552篇
  2003年   94083篇
  2002年   90879篇
  2001年   159469篇
  2000年   163521篇
  1999年   137621篇
  1998年   38934篇
  1997年   34538篇
  1996年   34736篇
  1995年   33566篇
  1994年   30575篇
  1993年   28699篇
  1992年   106472篇
  1991年   102514篇
  1990年   99678篇
  1989年   96432篇
  1988年   88096篇
  1987年   86085篇
  1986年   80992篇
  1985年   77076篇
  1984年   57183篇
  1983年   48191篇
  1982年   28345篇
  1981年   25122篇
  1979年   50637篇
  1978年   35314篇
  1977年   30646篇
  1976年   27827篇
  1975年   30175篇
  1974年   35424篇
  1973年   33817篇
  1972年   31907篇
  1971年   29679篇
  1970年   27274篇
  1969年   26258篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
112.
The aim of the present study was to explore differences in the clinical expression, clinical diagnoses and management of airway diseases in a primary-care setting. Patients aged >or=35 yrs who had ever smoked were enrolled when they presented for any reason to one of eight rural primary-care practices. Respiratory symptom questionnaires and spirometry were administered. In total, 1,034 patients had acceptable and reproducible spirometry, of whom 550 (53%) were males and 484 (47%) were females. Males smoked more than females (41.2 versus 29.2 pack-yrs) respectively, and were more likely to have a pre-bronchodilator forced expiratory volume in one second/forced vital capacity <0.70 at 22.4 versus 11.8%, respectively. However, more females than males reported breathlessness (51.0 versus 42.8%, respectively), a prior diagnosis compatible with airflow obstruction and taking respiratory medications (23.4 versus 14.9%, respectively). In conclusion, the current results suggest that females are more likely than males to report breathlessness and be prescribed respiratory medications independent of differences in the severity of airflow obstruction.  相似文献   
113.
There are no data available combining transbronchial needle aspiration (TBNA) of mediastinal lymph nodes and positron emission tomography (PET) in the staging of nonsmall cell lung cancer (NSCLC). The aim of the current study was to determine if these two methods can enhance the negative predictive value of the individual modality alone, for a specific lymph node station, and if this integrated approach can reduce the number of mediastinoscopies. A total of 113 patients with enlarged mediastinal lymph nodes (> or = 1 cm), who underwent both TBNA and PET scanning, were included. In 51 patients, histopathology, confirmed by surgical lymph node dissection, was compared with PET results and TBNA. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy to detect malignant lymphadenopathy was 68 (13/19), 89 (119/134), 46 (13/28), 95 (119/125) and 86% (132/152) for PET, respectively; 54% (6/11), 100 (53/53), 100 (6/6), 91 (53/58) and 92% (59/64), respectively for TBNA; and 100 (11/11), 94 (50/53), 79 (11/14), 100 (50/50) and 95 (61/64) for combined TBNA and PET, respectively. Combination of transbronchial needle aspiration and positron emission tomography has the potential to allow adequate mediastinal staging of nonsmall cell lung cancer with enlarged lymph nodes in most patients without the need for mediastinoscopy.  相似文献   
114.
115.
116.
117.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  相似文献   
118.
119.
A new semi-empirical formula for the evaluation of (n,(3)He) reaction cross-sections at the energy of 14.6 and 20 MeV is presented. Formula was derived using the analytical expression for the evaluation of the (3)He spectrum within the frame of pre-equilibrium exciton model. The systematics obtained is compared with the empirical formula for the (n,(3)He) reaction cross-section.  相似文献   
120.
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