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   2593692篇
  免费   185429篇
  国内免费   7601篇
耳鼻咽喉   34363篇
儿科学   85388篇
妇产科学   71732篇
基础医学   364399篇
口腔科学   69814篇
临床医学   235027篇
内科学   517103篇
皮肤病学   62716篇
神经病学   213919篇
特种医学   100092篇
外国民族医学   736篇
外科学   387318篇
综合类   50424篇
现状与发展   5篇
一般理论   970篇
预防医学   196695篇
眼科学   56733篇
药学   188325篇
  8篇
中国医学   5363篇
肿瘤学   145592篇
  2021年   20239篇
  2019年   20838篇
  2018年   29549篇
  2017年   22726篇
  2016年   26341篇
  2015年   29667篇
  2014年   40712篇
  2013年   60733篇
  2012年   80566篇
  2011年   84877篇
  2010年   51236篇
  2009年   49397篇
  2008年   79325篇
  2007年   84157篇
  2006年   85876篇
  2005年   82058篇
  2004年   79046篇
  2003年   76348篇
  2002年   73622篇
  2001年   128526篇
  2000年   131451篇
  1999年   110611篇
  1998年   31304篇
  1997年   27959篇
  1996年   28266篇
  1995年   27412篇
  1994年   25099篇
  1993年   23446篇
  1992年   85219篇
  1991年   81618篇
  1990年   78846篇
  1989年   76126篇
  1988年   69525篇
  1987年   68054篇
  1986年   63584篇
  1985年   60548篇
  1984年   44971篇
  1983年   37976篇
  1982年   22466篇
  1981年   19992篇
  1979年   38987篇
  1978年   27451篇
  1977年   23267篇
  1976年   21514篇
  1975年   22829篇
  1974年   26811篇
  1973年   25383篇
  1972年   23767篇
  1971年   21964篇
  1970年   20194篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
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   
92.
93.
94.
95.
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   
96.
97.
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   
98.
99.
Although melanocytic skin lesions have been recognized since antiquity, their literature was limited to Caucasians. To date, the clinicopathologic features of these lesions in Egyptians are still unknown. To define these features, diagnostic records of the melanocytic skin lesions received at the Pathology Department, Assuit University Hospitals (1989-2004) were reviewed. The lesions examined included 12 benign naevi (BN), 10 dysplastic naevi (DN), and 21 cutaneous malignant melanomas (CMMs). The DN and CMMs were more common in men than in women (2 : 1 and 1.5 : 1, respectively) while BN were more common in women (2 : 1). The average age incidence was 33+/-5, 38+/-7 and 54+/-3 years, for BN, DN and CMM, respectively. The lower limb (13/21, 62%), head and neck (7/21, 33%) were the most common sites for CMMs. The average size (mm) was 2+/-0.3, 4+/-0.6 and 21+/-0.3 for BN, DN and CMMs, respectively. Recurrence occurred in 10% of CMMs. Histologically, CMMs were of nodular type and composed of epithelioid (7/21, 33%), spindle cells (1/21, 5%), or mixed cells (13/21, 62%). The mean tumour thickness (Breslow) was 6+/-0.5 mm. CMMs included two of 21(9%), three of 21(14%), six of 21(38%), and 10 of 21(38%) with Clark level II, III, IV and V. In Egypt, CMM is the third most common cutaneous neoplasm following squamous and basal cell carcinomas. Compared with Western societies, melanoma has a male sex predilection, similar histological features but different topographical distribution and rare incidence. The striking difference from Western series is the incidence of nodular melanoma - in the West this represents 15-30% of melanomas, with superficial spreading being the majority. Another key difference from the West is the 'sun-bed' culture of the West and the desire to have suntans. This is the first study that reports the clinicopathologic features of melanocytic skin lesions in Egypt.  相似文献   
100.
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