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   1076142篇
  免费   71615篇
  国内免费   1370篇
耳鼻咽喉   15019篇
儿科学   34623篇
妇产科学   28625篇
基础医学   153492篇
口腔科学   29576篇
临床医学   95016篇
内科学   203995篇
皮肤病学   24399篇
神经病学   81531篇
特种医学   43062篇
外国民族医学   201篇
外科学   163272篇
综合类   21707篇
现状与发展   1篇
一般理论   263篇
预防医学   74637篇
眼科学   24605篇
药学   86195篇
  7篇
中国医学   2808篇
肿瘤学   66093篇
  2019年   7778篇
  2018年   11314篇
  2017年   8921篇
  2016年   10118篇
  2015年   11282篇
  2014年   15285篇
  2013年   22226篇
  2012年   30591篇
  2011年   32338篇
  2010年   18985篇
  2009年   17836篇
  2008年   30000篇
  2007年   32134篇
  2006年   32783篇
  2005年   31102篇
  2004年   29796篇
  2003年   28613篇
  2002年   27590篇
  2001年   60062篇
  2000年   61502篇
  1999年   50942篇
  1998年   12452篇
  1997年   11009篇
  1996年   11030篇
  1995年   10330篇
  1994年   9343篇
  1993年   8867篇
  1992年   37809篇
  1991年   36294篇
  1990年   35762篇
  1989年   34310篇
  1988年   30885篇
  1987年   30002篇
  1986年   28228篇
  1985年   26465篇
  1984年   19198篇
  1983年   16122篇
  1982年   8830篇
  1979年   17037篇
  1978年   11406篇
  1977年   10236篇
  1976年   8841篇
  1975年   10074篇
  1974年   11654篇
  1973年   11279篇
  1972年   10756篇
  1971年   10092篇
  1970年   9257篇
  1969年   8941篇
  1968年   7919篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Sugar and tooth decays are bound closely. The mechanisms of destruction of the tooth from the glycolyse are known. The role played by the food in the development of the caries is unique. Foods sweetened of all ways, rich in sucrose are responsible of the intervening of the carious lesions. The transformation of the fermentable sugars in lactic with the absence of hygiene and the action conjugated of the bacteria leads to tooth decays in temporary and permanent denture that evolve very quickly in the absence of treatment. Reasons for which the authors put in evidence in this survey, the influence of the food sweetened on the teeth at the children while showing the cases of caries and its complications due to the excessive consumption of fermentable hydrates of carbon.  相似文献   
92.
93.
94.
95.
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   
96.
97.
98.
99.
100.
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   
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