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   1031164篇
  免费   81371篇
  国内免费   5618篇
耳鼻咽喉   13396篇
儿科学   34853篇
妇产科学   29028篇
基础医学   148428篇
口腔科学   28383篇
临床医学   94966篇
内科学   197276篇
皮肤病学   23337篇
神经病学   80219篇
特种医学   39897篇
外国民族医学   320篇
外科学   153127篇
综合类   32279篇
现状与发展   18篇
一般理论   390篇
预防医学   80891篇
眼科学   23469篇
药学   76341篇
  52篇
中国医学   4692篇
肿瘤学   56791篇
  2019年   8646篇
  2018年   11943篇
  2017年   9685篇
  2016年   10635篇
  2015年   12514篇
  2014年   16793篇
  2013年   24438篇
  2012年   32232篇
  2011年   34219篇
  2010年   21019篇
  2009年   19576篇
  2008年   31169篇
  2007年   32871篇
  2006年   33185篇
  2005年   31693篇
  2004年   30731篇
  2003年   29807篇
  2002年   28473篇
  2001年   48207篇
  2000年   48824篇
  1999年   40757篇
  1998年   11014篇
  1997年   9944篇
  1996年   9794篇
  1995年   9988篇
  1994年   9298篇
  1993年   8580篇
  1992年   32349篇
  1991年   31588篇
  1990年   31103篇
  1989年   29948篇
  1988年   27210篇
  1987年   27366篇
  1986年   25456篇
  1985年   24628篇
  1984年   18386篇
  1983年   15483篇
  1982年   9259篇
  1981年   8342篇
  1979年   16834篇
  1978年   12197篇
  1977年   10290篇
  1976年   9725篇
  1975年   10154篇
  1974年   12305篇
  1973年   11834篇
  1972年   10884篇
  1971年   10106篇
  1970年   9372篇
  1969年   8715篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
41.
Objective:To evaluate CT-ventilation imaging (CTVI) within a well-characterized, healthy cohort with no respiratory symptoms and examine the correlation between CTVI and concurrent pulmonary function test (PFT).Methods:CT scans and PFTs from 77 Caucasian participants in the NORM dataset (clinicaltrials.gov NCT00848406) were analyzed. CTVI was generated using the robust Integrated Jacobian Formulation (IJF) method. IJF estimated total lung capacity (TLC) was computed from CTVI. Bias-adjusted Pearson’s correlation between PFT and IJF-based TLC was computed.Results:IJF- and PFT-measured TLC showed a good correlation for both males and females [males: 0.657, 95% CI (0.438–0.797); females: 0.667, 95% CI (0.416–0.817)]. When adjusting for age, height, smoking, and abnormal CT scan, correlation moderated [males: 0.432, 95% CI (0.129–0.655); females: 0.540, 95% CI (0.207–0.753)]. Visual inspection of CTVI revealed participants who had functional defects, despite the fact that all participant had normal high-resolution CT scan.Conclusion:In this study, we demonstrate that IJF computed CTVI has good correlation with concurrent PFT in a well-validated patient cohort with no respiratory symptoms.Advances in knowledge:IJF-computed CTVI’s overall numerical robustness and consistency with PFT support its potential as a method for providing spatiotemporal assessment of high and low function areas on volumetric non-contrast CT scan.  相似文献   
42.
IntroductionOrgan-based tube current modulation (OBTCM) is designed for anterior dose reduction in Computed Tomography (CT). The purpose was to assess dose reduction capability in chest CT using three organ dose modulation systems at different kVp settings. Furthermore, noise, diagnostic image quality and tumour detection was assessed.MethodsA Lungman phantom was scanned with and without OBTCM at 80–135/140 kVp using three CT scanners; Canon Aquillion Prime, GE Revolution CT and Siemens Somatom Flash. Thermo-luminescent dosimeters were attached to the phantom surface and all scans were repeated five times. Image noise was measured in three ROIs at the level of the carina. Three observers visually scored the images using a fivestep scale. A Wilcoxon Signed-Rank test was used for statistical analysis of differences.ResultsUsing the GE revolution CT scanner, dose reductions between 1.10 mSv (12%) and 1.56 mSv (24%) (p < 0.01) were found in the anterior segment and no differences posteriorly and laterally. Total dose reductions between 0.64 (8%) and 0.91 mSv (13%) were found across kVp levels (p < 0.00001). Maximum noise increase with OBTCM was 0.8 HU. With the Canon system, anterior dose reductions of 6–10% and total dose reduction of 0.74–0.76 mSv across kVp levels (p < 0.001) were found with a maximum noise increase of 1.1 HU. For the Siemens system, dose increased by 22–51% anteriorly; except at 100 kVp where no dose difference was found. Noise decreased by 1 to 1.5 HU.ConclusionOrgan based tube current modulation is capable of anterior and total dose reduction with minimal loss of image quality in vendors that do not increase posterior dose.Implications for practiceThis research highlights the importance of being familiar with dose reduction technologies.  相似文献   
43.
44.
45.
46.
目的分析并探究双侧延髓内侧梗死(BMMI)的血管病因、临床表现、MRI特征和预后,以期提高BMMI的早期诊断率.方法对青岛大学附属烟台毓璜顶医院诊治的14例BMMI患者临床资料进行分析.结果BMMI血管病因以动脉粥样硬化为主;临床症状表现为四肢瘫痪、舌瘫、感觉异常、头晕、构音障碍、饮水呛咳等,危重时出现呼吸衰竭.头颅DWI示双侧延髓内侧可呈特征性"心型"、"Y"字型、"V"字型或倒"八"字型高信号影.出院NIHSS评分、卒中进展(尤其呼吸衰竭)为BMMI的预后不良因素.结论BMMI临床少见,临床表现多样,预后较差;头颅MRI为其主要的影像学检查,有助于早期诊断.  相似文献   
47.
IntroductionThe main challenge of Parkinson's disease in women of childbearing age is managing symptoms and drugs during pregnancy and breastfeeding. The increase in the age at which women are having children makes it likely that these pregnancies will become more common in future.ObjectivesThis study aims to define the clinical characteristics of women of childbearing age with Parkinson's disease and the factors affecting their lives, and to establish a series of guidelines for managing pregnancy in these patients.ResultsThis consensus document was developed through an exhaustive literature search and a discussion of the available evidence by a group of movement disorder experts from the Spanish Society of Neurology.ConclusionsParkinson's disease affects all aspects of sexual and reproductive health in women of childbearing age. Pregnancy should be well planned to minimise teratogenic risk. A multidisciplinary approach should be adopted in the management of these patients in order to take all relevant considerations into account.  相似文献   
48.
49.
50.
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