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   1267007篇
  免费   94981篇
  国内免费   1604篇
耳鼻咽喉   16366篇
儿科学   41034篇
妇产科学   35014篇
基础医学   189712篇
口腔科学   34836篇
临床医学   118018篇
内科学   248573篇
皮肤病学   27316篇
神经病学   102177篇
特种医学   46887篇
外国民族医学   265篇
外科学   179034篇
综合类   25755篇
现状与发展   3篇
一般理论   570篇
预防医学   104782篇
眼科学   28096篇
药学   92782篇
  7篇
中国医学   2025篇
肿瘤学   70340篇
  2018年   13598篇
  2017年   10456篇
  2016年   11411篇
  2015年   13174篇
  2014年   18096篇
  2013年   27626篇
  2012年   37785篇
  2011年   40185篇
  2010年   23173篇
  2009年   22363篇
  2008年   37952篇
  2007年   40598篇
  2006年   40171篇
  2005年   39326篇
  2004年   37762篇
  2003年   36170篇
  2002年   35028篇
  2001年   56064篇
  2000年   57062篇
  1999年   48114篇
  1998年   13417篇
  1997年   12236篇
  1996年   12663篇
  1995年   11937篇
  1994年   11137篇
  1993年   10411篇
  1992年   38215篇
  1991年   37679篇
  1990年   36456篇
  1989年   35275篇
  1988年   32700篇
  1987年   32040篇
  1986年   30533篇
  1985年   28796篇
  1984年   21954篇
  1983年   19198篇
  1982年   11376篇
  1981年   10332篇
  1979年   20946篇
  1978年   15396篇
  1977年   12791篇
  1976年   11847篇
  1975年   12813篇
  1974年   15591篇
  1973年   15364篇
  1972年   14515篇
  1971年   13552篇
  1970年   12786篇
  1969年   12066篇
  1968年   11230篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Teeth with white spot lesions (WSL) might be more prone to enamel loss during bracket debonding. This in vitro study compared enamel loss from teeth with (n = 14) and without (n = 14) WSL after polishing with low-speed finishing burs or disks (Sof-Lex, 3M ESPE, St Paul, Minn). Debonded surfaces were analyzed with a contact stylus profilometer, and digitized data were compared with baseline readings by using AnSur NT software (Regents, University of Minnesota, Minneapolis, Minn). Specimen surfaces were also examined with a scanning electron microscope. Two-way analysis of variance was performed to analyze the data. In teeth without WSL, the volume losses were 0.16 mm(3) for the bur group and 0.10 mm(3) for the disk group; the mean maximum depths were 47.7 microm for the bur group and 54.3 microm for the disk group. In teeth with WSL, the volume losses were 0.06 and 0.17 mm(3), and the mean maximum depths were 35.1 and 48.7 microm for the bur and disk groups, respectively. There were no significant differences in enamel loss between the 2 groups of teeth without WSL (P =.12). However, in teeth with WSL, the burs removed less enamel than the disks (P = 0.006). Scanning electron microscope examination showed that any damage on the enamel surface was usually located in the cervical third of the teeth. On most specimens, even though tooth surfaces appeared resin-free to the naked eye, there were remnants of it. The differences between groups were so small that they might be clinically insignificant.  相似文献   
952.
Pleural effusion is a common complication of various diseases. Conventional methods are not always capable of establishing the cause of pleural effusion, so alternative tests are needed. The aim of this study was to explore means of discriminating between different pleural effusion groups, malignant, parapneumonic and tuberculous, based on the combined function of seven biological markers. Adenosine deaminase (ADA), interferon-gamma, C-reactive protein (CRP), carcinoembryonic antigen, interleukin-6, tumour necrosis factor-alpha and vascular endothelial growth factor concentration levels were measured in pleural fluid from 45 patients with malignant, 15 with parapneumonic and 12 with tuberculous pleural effusion. Receiver operating characteristic curve analysis, multinomial logit modelling and canonical variate analysis were applied to discriminate the pleural effusion groups. The three groups could be discriminated successfully using the measured markers. The most important parameters for discrimination were ADA and CRP concentration levels. An individual with an ADA concentration level of >45 U.L(-1) and a CRP concentration of <4 mg.dL(-1) was more likely to belong to the tuberculous pleural effusion group, whereas one with an ADA concentration level of <40 U.L(-1) and a CRP concentration of >6 mg.dL(-1) was more likely to belong to the parapneumonic pleural effusion group, and one with a CRP concentration of <4 mg.dL(-1) to the malignant pleural effusion group. The combination of adenosine deaminase and C-reactive protein levels might be sufficient for discriminating between the three different groups of exudative pleural effusion: malignant, tuberculous and parapneumonic.  相似文献   
953.
954.
This paper outlines the programming model employed by the Soul City Institute for Health and Development Communication, a South African NGO, in using ‘edutainment’ to facilitate social change. The paper refers to the intersection of this model and current thought on health promotion and various social change theories. It also discusses key challenges and factors contributing to sustainability over 12 years.  相似文献   
955.
956.
957.
OBJECTIVE: The purpose of this study was to examine the effect of optimal seated positioning in individually fitted furniture versus suboptimal seated positioning in standard classroom furniture on typical 6- and 7-year-old children's object manipulation skills as measured by the In-hand Manipulation Test (IMT). METHOD: An experimental research design was used to compare IMT performance of two groups of 20 children. One group was positioned in standard, too-large classroom furniture that did not support an optimal seated position, and one group was positioned optimally in furniture fitted to each child for tabletop activities, which allowed for hip flexion to 90 degrees, and foot placement on the floor, and the table to be at flexed elbow height. RESULTS: Independent groups' t tests indicated that children who were optimally positioned performed significantly better (t = -2.77, df = 38, p < .01) than children who were tested in the too-large standard classroom furniture. The difference between groups was greater on the more difficult object manipulation items (t = -3.29, df = 38, p = .001) than on the easier items (t = -1.38, df = 38, p = .08). Age and gender may have differentially affected the results. CONCLUSION: The study's results suggest that the fit of furniture relative to the child's size may have a significant impact on a young, typical child's object manipulation skills. Complex hand skills, such as those involving in-hand manipulation with stabilization, appear to be more affected by the quality of the child's seated position than are simpler, more well-established skills. Findings suggest that test administrators should strive to test young children in the most optimal seated position possible, particularly when the test involves complex hand skills. Further study is needed to assess the impact of the fit of furniture on hand skills in children with disabilities and on children's performance of other tasks.  相似文献   
958.
959.
960.
According to the guidelines, ultrasonography (US) is now established as the cross-sectional imaging technique of choice in postoperative care of colorectal carcinoma. Although conventional percutaneous US is inferior to computed tomography (CT) and magnetic resonance imaging (MRI) for detecting hepatic metastases, the application of specific contrast media has significantly increased sensitivity and specificity to 87% and 88%, respectively. The combination of US and CT/MRI achieves the highest detection rates. During follow-up of rectal carcinoma, in up to 20% of locoregional recurrences are diagnosed solely by endorectal sonography and result in repeat resection with curative intention. In noncolorectal carcinoma, US is recommended in the guidelines for following up hepatocellular carcinoma and malignant thyroid disease, but the available data are insufficient to support those recommendations.  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