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   100433篇
  免费   6323篇
  国内免费   435篇
耳鼻咽喉   1113篇
儿科学   2514篇
妇产科学   1783篇
基础医学   12465篇
口腔科学   1753篇
临床医学   10653篇
内科学   20252篇
皮肤病学   1339篇
神经病学   10081篇
特种医学   3898篇
外国民族医学   3篇
外科学   16341篇
综合类   1082篇
一般理论   131篇
预防医学   8228篇
眼科学   2080篇
药学   6486篇
中国医学   105篇
肿瘤学   6884篇
  2023年   563篇
  2022年   935篇
  2021年   2093篇
  2020年   1325篇
  2019年   2098篇
  2018年   2549篇
  2017年   1824篇
  2016年   1986篇
  2015年   2275篇
  2014年   3443篇
  2013年   4726篇
  2012年   7562篇
  2011年   7974篇
  2010年   4584篇
  2009年   4132篇
  2008年   7127篇
  2007年   7448篇
  2006年   7176篇
  2005年   6890篇
  2004年   6716篇
  2003年   6050篇
  2002年   5707篇
  2001年   838篇
  2000年   555篇
  1999年   892篇
  1998年   1219篇
  1997年   924篇
  1996年   748篇
  1995年   682篇
  1994年   589篇
  1993年   578篇
  1992年   440篇
  1991年   399篇
  1990年   322篇
  1989年   291篇
  1988年   277篇
  1987年   276篇
  1986年   241篇
  1985年   277篇
  1984年   305篇
  1983年   252篇
  1982年   333篇
  1981年   281篇
  1980年   221篇
  1979年   93篇
  1978年   127篇
  1977年   106篇
  1976年   78篇
  1975年   66篇
  1973年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
A 68-year-old patient was scheduled for a thoracotomy. A double-lumen endobronchial tube was requested by the surgeon to facilitate operating conditions. Initial attempts at intubation by conventional methods were unsuccessful. The proximal ends of a 37F double-lumen tube were then shortened and a 4-mm fibreoptic bronchoscope was passed through the bronchial lumen. The patient's larynx was easily visualized and the bronchoscope was passed into the trachea. The double lumen tube was then advanced over the bronchoscope and correctly positioned. Shortening a double-lumen tube allows the use of a fibreoptic bronchoscope to aid in tracheal intubation in a patient whose larynx is difficult to visualize by conventional methods.  相似文献   
103.
104.
The purpose of this study is to assess the sensitivity and specificity of magnetic resonance imaging (MRI) in the diagnosis of anterolateral impingement of the ankle and to assess the most helpful sequence in making the diagnosis. Twenty-four patients who had undergone ankle arthroscopy were chosen. Twelve patients had arthroscopically documented anterolateral impingement, and 12 patients with no impingement on arthroscopy served as controls. Two musculoskeletal radiologists and an orthopedic surgeon, blinded to the operative diagnosis, retrospectively reviewed selective MRI images in the sagittal, axial, and coronal planes. The sensitivities and specificities were calculated for all 3 reviewers. The Kendall coefficient of concordance was calculated for overall agreement among reviewers. Sensitivities varied from 0.75 to 0.83, whereas specificities varied from 0.75 to 1.00. Using the Fisher exact test of contingency, the sensitivities and specificities showed that all reviewers' interpretations were statistically significant with P = .039, .001, and .012, respectively. The axial images were felt to be most helpful in making the diagnosis. The physicians felt that the sagittal images were helpful in 67%, 83%, and 100%, respectively. MRI is a useful tool that can aid the clinician in the diagnosis of anterolateral impingement of the ankle. T1 sagittal images demonstrating displacement of the normal fat signal anterior to the fibula by scar can be useful and help to confirm the diagnosis.  相似文献   
105.
106.
107.
Cerebrospinal fluid (CSF) from 7 patients with infantile spasms (mean age: 6.7 months) was collected before and after treatment with adrenocorticotropic hormone (ACTH). The concentration of neurotransmitter metabolites was analyzed using high-performance liquid chromatography and compared to the metabolite concentration in the CSF from 7 age-matched controls (mean age: 6.1 months). Pretreatment levels of CSF 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid, 3-methoxy-4-hydroxyphenyl glycol (MHPG), and kynurenine were significantly lower in infantile spasm patients compared to controls. Following treatment, marked increases in 5-HIAA and decreases in kynurenine levels were observed in the CSF of the 5 infants whose seizures were eliminated or reduced by ACTH. In the 2 nonresponders 5-HIAA levels decreased. The level of MHPG was reduced slightly in 5 infants, including the 2 nonresponders, and was increased in 2 responders. CSF homovanillic acid levels increased in 4 infantile spasm infants and decreased in 3 following ACTH. These data demonstrate that the presence of seizures in infantile spasms is associated with a significant decrease in serotonergic activity and that elimination of seizures by ACTH is accompanied by increased serotonin turnover. The simultaneous increase of 5-HIAA and decrease of kynurenine, an alternate metabolite of tryptophan, suggests an underlying disturbance of tryptophan metabolism in infantile spasms. The possibility that elimination of seizures by ACTH may be related to decreased production of certain kynurenine metabolites, particularly quinolinic acid, is discussed.  相似文献   
108.
109.
OBJECTIVES: To determine whether the increase in the incidence of injury found for the first summer season in which rugby league (RL) was played in the UK was repeated in subsequent summer seasons. DESIGN: A retrospective and prospective cohort study design. SETTING AND PARTICIPANTS: Injuries were recorded from all players who took part in 141 games over 3 summer seasons (1997 to 1999) for 1 professional team. These were compared against rates from previously collected data for 3 earlier winter and 1 summer season. ASSESSMENT OF RISK FACTORS: For each injury it was recorded in which season it occurred; how many games or training sessions, if any, were subsequently missed; the type, site and severity of injury. MAIN OUTCOME MEASURES: Injuries were reported as rate per 1000 hours, also broken down into severity according to the number of games missed and whether subsequent training sessions were missed. RESULTS: A sustained increase in injury incidence has been found comparing summer RL over RL played in the winter. There was an increase in injury rates for all sites and types, but not all reached significance. CONCLUSIONS: Data collected over 6 seasons indicate a higher risk of sustaining an injury playing summer RL, but the cause may be related to a combination of factors. These may include the ground or weather conditions associated with summer rugby, player characteristics or changes in the game itself and future research needs to investigate these further.  相似文献   
110.
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