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   3084篇
  免费   230篇
  国内免费   20篇
耳鼻咽喉   39篇
儿科学   179篇
妇产科学   30篇
基础医学   308篇
口腔科学   94篇
临床医学   343篇
内科学   518篇
皮肤病学   76篇
神经病学   348篇
特种医学   366篇
外科学   336篇
综合类   72篇
预防医学   169篇
眼科学   33篇
药学   125篇
  1篇
肿瘤学   297篇
  2020年   22篇
  2019年   32篇
  2018年   52篇
  2016年   37篇
  2015年   44篇
  2014年   70篇
  2013年   113篇
  2012年   80篇
  2011年   94篇
  2010年   90篇
  2009年   86篇
  2008年   83篇
  2007年   102篇
  2006年   100篇
  2005年   92篇
  2004年   80篇
  2003年   74篇
  2002年   72篇
  2001年   72篇
  2000年   61篇
  1999年   100篇
  1998年   104篇
  1997年   90篇
  1996年   82篇
  1995年   72篇
  1994年   55篇
  1993年   58篇
  1992年   57篇
  1991年   81篇
  1990年   52篇
  1989年   86篇
  1988年   78篇
  1987年   74篇
  1986年   67篇
  1985年   78篇
  1984年   55篇
  1983年   44篇
  1982年   37篇
  1981年   33篇
  1980年   44篇
  1979年   51篇
  1978年   52篇
  1977年   42篇
  1976年   35篇
  1975年   35篇
  1974年   34篇
  1973年   30篇
  1972年   23篇
  1971年   33篇
  1970年   37篇
排序方式: 共有3334条查询结果,搜索用时 109 毫秒
1.
BACKGROUND & AIMS: Breath methane measurements reflect the in situ activity of the methanogenic colonic flora. Thirty-five years ago we found that 34% of healthy adult subjects were methane producers (breath methane level >1 ppm above atmospheric methane levels). The current study presents a new survey of breath methane levels designed to determine if the activity of the methanogenic flora has changed over the past 35 years. In addition, we review insights into the methanogenic flora that have resulted from breath methane measurements. METHODS: The end-alveolar breath methane concentrations of 212 healthy adults living in the Minneapolis area were determined via gas chromatography. The influence of sex, age, and bowel movement frequency on methane production was assessed. RESULTS: The findings that 36.4% of participants were methane producers, with a mean methane concentration in these producers of 16.6 ppm, are strikingly similar to the values of 33.6% and 15.2 ppm observed 35 years ago. Neither sex nor age showed a statistically significant relationship to methane production. There was a negative correlation between frequency of bowel movements and breath methane concentration in methane producers. CONCLUSIONS: The activity of the methanogenic flora of healthy adults remained remarkably stable over the past 35 years despite widespread antibiotic use and dietary changes. A literature review revealed that many associations have been shown between methane production and clinical states, but it remains to be determined if methanogens actively influence human physiology or are simply a marker of colonic function.  相似文献   
2.
3.
4.
Pyomyositis: characteristics at CT and MR imaging   总被引:9,自引:0,他引:9  
Gordon  BA; Martinez  S; Collins  AJ 《Radiology》1995,197(1):279
  相似文献   
5.
SUMMARY A case is reported of pseudohyperphosphataemia in association with a monoclonal gammopathy of undetermined significance.  相似文献   
6.
7.
BACKGROUND: Diagnosis of atopic dermatitis (AD) depends on clinical features because no definitive diagnostic test exists. Criteria proposed by Hanifin and Rajka (Acta Derm Venereol (Stockh) 1980; Suppl 92: 44-47) were acceptable for hospital-based studies but were found not to be suitable for field studies. A UK working party formulated clinical diagnostic criteria that could be used in both hospital and epidemiological settings. Validation studies of the criteria showed widely variable results, probably due to different clinical settings and ethnicity. AIM AND OBJECTIVE: This study was undertaken to validate Hanifin and Rajka's criteria and to assess the comparative efficacy of their criteria and the UK working party's diagnostic criteria in the diagnosis of AD in a hospital setting in North India. SUBJECTS AND METHODS: This study serially included 101 patients with AD and 48 controls of paediatric age group. The study period was from July 2003 to December 2004. RESULTS: Hanifin and Rajka's criteria (sensitivity 96%, specificity 93.75%, positive predictive value 97% (PPV) and negative predictive value (NPV) 91.84%) had a statistical advantage over the UK working party's diagnostic criteria (sensitivity 86%, specificity 95.83%, PPV 97.75% and NPV 76.67%), with a P-value < 0.005.  相似文献   
8.
SUMMARY Impotence is a common symptom which can cause considerable distress to both the sufferer and his partner. The use of pharmacotherapy to improve erectile function will continue to increase as safe and effective drugs are developed. However, restoring erectile function should not be the only treatment objective. It is also essential to address personal and emotional factors in the sufferer, conflicts in his relationship with his partner, and sexual problems in his partner, all of which may be instrumental in causing or maintaining the presenting impotence. We advocate a combined approach with appropriate medical treatment and sex and couple therapy  相似文献   
9.
Acute appendicitis: CT and US correlation in 100 patients   总被引:19,自引:1,他引:18  
  相似文献   
10.
Although postoperative beta irradiation for prevention of pterygium recurrence is widely used, its complication rate has not been widely appreciated. Thirty-six patients underwent pterygium excision followed by irradiation with 90Sr to between 1600 and 5300 cGy (median 2400) in two to four fractions over 7 to 27 days. A median of three fields were used in each treatment course (range two to 10). Most patients had undergone previous treatment for their pterygia, including surgery alone (25 patients), or both surgery and irradiation (5 patients). Overall, recurrences developed in 10 eyes (28%). Recurrence occurred in one eye after re-irradiation (20%), compared to 9 of 31 (29%) previously non-irradiated eyes (p greater than 0.1). There was no association with number of excisions and recurrences, although all but 6 patients had undergone more than one excision. Thirteen patients (36%) developed complications including: epithelial defect or corneal thinning (3), symblepharon (5), cataract (4) and corneal ulceration (1). Complications developed in 4 of the 5 (80%) re-irradiated eyes compared to 9 of 31 (29%) previously non-irradiated eyes (p less than 0.05). The power of the statistical analysis was limited by sample size, but no significant association was observed between the development of complications or recurrences and total dose, number of abutting fields, number of previous surgical excisions or patient age, even when re-irradiated patients were excluded. Recently described calibration uncertainties with the 90Sr applicator may explain in part these complications. Alternatively, technical factors such as the number of fields or volume treated may play a role. Excessive complications and recurrences with the use of postoperative beta irradiation in this series emphasize the danger of re-treatment and the need for alternative safe and effective therapies.  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