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   4159220篇
  免费   302086篇
  国内免费   10044篇
耳鼻咽喉   56388篇
儿科学   135342篇
妇产科学   113549篇
基础医学   586868篇
口腔科学   117804篇
临床医学   388157篇
内科学   804413篇
皮肤病学   93462篇
神经病学   343982篇
特种医学   160305篇
外国民族医学   1182篇
外科学   613883篇
综合类   90371篇
现状与发展   8篇
一般理论   1880篇
预防医学   335586篇
眼科学   95097篇
药学   304534篇
  16篇
中国医学   7829篇
肿瘤学   220694篇
  2019年   33863篇
  2018年   46664篇
  2017年   35678篇
  2016年   40654篇
  2015年   46050篇
  2014年   64284篇
  2013年   97608篇
  2012年   130216篇
  2011年   138728篇
  2010年   82982篇
  2009年   79158篇
  2008年   129627篇
  2007年   138019篇
  2006年   139057篇
  2005年   134907篇
  2004年   129799篇
  2003年   124508篇
  2002年   120240篇
  2001年   184363篇
  2000年   189012篇
  1999年   160151篇
  1998年   48672篇
  1997年   43091篇
  1996年   43332篇
  1995年   41741篇
  1994年   38583篇
  1993年   36267篇
  1992年   127152篇
  1991年   123615篇
  1990年   120040篇
  1989年   115626篇
  1988年   106785篇
  1987年   104992篇
  1986年   99194篇
  1985年   95092篇
  1984年   71903篇
  1983年   61456篇
  1982年   37157篇
  1981年   33484篇
  1979年   65596篇
  1978年   47185篇
  1977年   40031篇
  1976年   37097篇
  1975年   39800篇
  1974年   47622篇
  1973年   45924篇
  1972年   43024篇
  1971年   40051篇
  1970年   37146篇
  1969年   35288篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
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   
152.
153.
154.
155.
156.
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   
157.
158.
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   
159.
160.
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   
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