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   2446721篇
  免费   191036篇
  国内免费   9789篇
耳鼻咽喉   33699篇
儿科学   80942篇
妇产科学   67885篇
基础医学   345911篇
口腔科学   65931篇
临床医学   221810篇
内科学   480857篇
皮肤病学   54271篇
神经病学   195380篇
特种医学   94696篇
外国民族医学   1083篇
外科学   365983篇
综合类   66658篇
现状与发展   18篇
一般理论   793篇
预防医学   190129篇
眼科学   55809篇
药学   179972篇
  83篇
中国医学   9361篇
肿瘤学   136275篇
  2021年   20811篇
  2019年   20764篇
  2018年   28708篇
  2017年   22121篇
  2016年   24285篇
  2015年   28207篇
  2014年   39092篇
  2013年   56493篇
  2012年   77655篇
  2011年   82405篇
  2010年   49166篇
  2009年   46128篇
  2008年   75552篇
  2007年   80003篇
  2006年   80243篇
  2005年   78046篇
  2004年   74449篇
  2003年   71230篇
  2002年   69306篇
  2001年   117906篇
  2000年   121520篇
  1999年   102593篇
  1998年   29346篇
  1997年   26598篇
  1996年   26736篇
  1995年   25403篇
  1994年   23355篇
  1993年   21605篇
  1992年   78436篇
  1991年   75704篇
  1990年   73107篇
  1989年   69656篇
  1988年   64019篇
  1987年   62791篇
  1986年   58600篇
  1985年   56034篇
  1984年   42462篇
  1983年   35804篇
  1982年   21369篇
  1981年   19190篇
  1979年   37755篇
  1978年   26449篇
  1977年   22137篇
  1976年   20854篇
  1975年   22070篇
  1974年   26190篇
  1973年   25284篇
  1972年   23466篇
  1971年   21291篇
  1970年   20226篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: The incidence of malignant melanoma of the skin has risen in every part of the world where reliable cancer registration data are found. OBJECTIVE: Our study aims to describe the changing incidence of and survival from invasive cutaneous malignant melanoma in Malta, by analysing the data from the 211 cases that were registered at the Malta National Cancer Registry between 1993 and 2002. RESULTS: The age standardized incidence rates for invasive cutaneous malignant melanoma rose from 3.7 per 100,000 population per year for males and 5.1 for females in the first 5-year period, to 8.0 per 100,000 population per year for males and 5.9 for females in the second 5-year period. In both sexes, numbers of thin (< or = 1.0 mm) invasive melanomas increased significantly between 1993 and 2002; males also registered a significant increase in intermediate-thickness (1.01-4.0 mm) melanomas. The increase in numbers of thin and intermediate-thickness melanomas between the two 5-year periods was greatest in patients aged 60 years and over. The overall absolute 5-year survival rate for the first period was 74% and for the second period 92%. CONCLUSION: Numbers of reported cases of invasive cutaneous malignant melanoma in Malta have more than doubled during the 10-year study period. This is mostly due to a marked rise in the diagnosis of thin melanomas in both sexes, occurring mainly in patients aged 60 years and over. As thin melanomas are of low metastasizing potential, this has resulted in an increase in survival between the two 5-year study periods.  相似文献   
82.
OBJECTIVE: To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life. METHODS: This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers. RESULTS: In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted. CONCLUSIONS: RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.  相似文献   
83.
AIMS: To report clinical outcomes of a large series of cases with advanced thyroid cancer. STUDY DESIGN: Three hundred and eighty-five patients at the UICC stages III and IV were selected for the study with thyroid cancer. RESULTS: Papillary carcinoma and sclerosing carcinoma have better survival than the Hürthle cell and insular types. Lymphatic metastasis does not appear to worsen the prognosis. All the tumour forms offer the chance of long survival. CONCLUSIONS: Surgical treatment is the primary treatment of thyroid carcinoma. The combined treatments of surgery, metabolic beam therapy, suppressive hormone therapy, radiotherapy and chemotherapy cure a high percentage of patients with the tumour at an advanced stage.  相似文献   
84.
INTRODUCTION: Autoimmune hepatitis (AIH) is a well-defined entity in the West but there are sparse Indian data on this disease. AIM: To study the clinical profile and response to treatment of Indian patients with AIH. METHODS: This is a part retrospective and part prospective study of 50 patients (median age 48 years, range 11-82; 43 women) seen between 1995 to 2001, diagnosed to have AIH as per the revised scoring system. Clinical and laboratory profile, response to treatment, and complications of treatment were analyzed. RESULTS: AIH accounted for 6% of all patients with liver disease seen during the period. The presenting symptoms were gastrointestinal in 43 and non-gastrointestinal in 7, with median symptom duration of 6 months (range 2 weeks to 40 years). Forty patients (80%) had chronic liver disease. Associated illnesses were present in 28 patients. Twenty-six patients were classified as definite and the rest as probable AIH. Forty-nine patients had Type 1 AIH. Five patients had overlap syndrome. Forty-five patients (90%) received immunosuppressive therapy. Twelve of 18 patients receiving only prednisolone and 21 of 27 patients receiving prednisolone and azathioprine combination responded. Thirteen (26%) patients had therapy-related complications (infectious 5, non infectious 8) with two treatment-related deaths. CONCLUSION: Type 1 AIH was the predominant type of AIH. The majority of patients with AIH presented with chronic liver disease. There was good response to immunosuppressive therapy. Therapy-related complications occurred in one-fourth of patients.  相似文献   
85.
灾难的时代错误:灾害医学的过去、现在和将来(一)   总被引:1,自引:0,他引:1  
灾难,特别是地震、火山、洪水以及与战争有关的事件如饥饿和流行性传染病,是人类有记录的经历的一部分。从意大利庞贝的火山爆发,到约翰斯顿的洪水、第二次世界大战和黑色瘟疫,到西班牙流感,都发生了灾难,这不会被传说和历史书籍长期忘却。不过,在20世纪中叶以前,那些灾难的发生相对较少,且相距时间较长。从20世纪中叶以来,灾难的本质发生了变化。从恐怖分子使用“新技术”,到与气候有关的导致亿万美元经济损失的事件,表明这个世界正在发生变化。仅仅在最近的50~60年间,造成多种多样的伤亡事件,其危险性和频率的增加引人注目,并且注定要在接…  相似文献   
86.
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   
87.
88.
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   
89.
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   
90.
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