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   1268915篇
  免费   85876篇
  国内免费   2066篇
耳鼻咽喉   17049篇
儿科学   39758篇
妇产科学   32665篇
基础医学   178457篇
口腔科学   33832篇
临床医学   113806篇
内科学   244241篇
皮肤病学   26980篇
神经病学   100428篇
特种医学   49416篇
外国民族医学   215篇
外科学   193196篇
综合类   24983篇
现状与发展   3篇
一般理论   552篇
预防医学   92785篇
眼科学   28511篇
药学   99404篇
  8篇
中国医学   3146篇
肿瘤学   77422篇
  2021年   10563篇
  2019年   10787篇
  2018年   14825篇
  2017年   11781篇
  2016年   13140篇
  2015年   14928篇
  2014年   20750篇
  2013年   30388篇
  2012年   42315篇
  2011年   45275篇
  2010年   26345篇
  2009年   24515篇
  2008年   42391篇
  2007年   45257篇
  2006年   45358篇
  2005年   44233篇
  2004年   42468篇
  2003年   40445篇
  2002年   38985篇
  2001年   61867篇
  2000年   62904篇
  1999年   52910篇
  1998年   15049篇
  1997年   13286篇
  1996年   13078篇
  1995年   12148篇
  1994年   11010篇
  1993年   10409篇
  1992年   38986篇
  1991年   37390篇
  1990年   36769篇
  1989年   35226篇
  1988年   31843篇
  1987年   30990篇
  1986年   29205篇
  1985年   27547篇
  1984年   20619篇
  1983年   17499篇
  1982年   10554篇
  1981年   9234篇
  1979年   17864篇
  1978年   12339篇
  1977年   11129篇
  1976年   9658篇
  1975年   10745篇
  1974年   12328篇
  1973年   11863篇
  1972年   11192篇
  1971年   10465篇
  1970年   9597篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Severe tuberculosis (TB) requiring intensive care unit (ICU) care is rare but commonly known to be of markedly bad prognosis. The present study aimed to describe this condition and to determine the mortality rate and risk factors associated with mortality. Patients with confirmed TB admitted to ICU between 1990 and 2001 were retrospectively identified and enrolled. Clinical, radiological and bacteriological data at admission and during hospital stay were recorded. A multivariate analysis was performed to identify the predictive factors for mortality. A total of 58 TB patients (12 females, mean age 48 yrs) admitted to ICU were included. Mean Acute Physiology and Chronic Health Evaluation (APACHE) II score at admission was 13.1+/-5.6 and 22 of 58 (37.9%) patients required mechanical ventilation. The in-hospital mortality was 15 of 58 (25.9%); 13 (22.4%) patients died in the ICU. The mean survival of patients who died was 53.6 days (range 1-229), with 50% of the patients dying within the first 32 days. The factors independently associated with mortality were: acute renal failure, need for mechanical ventilation, chronic pancreatitis, sepsis, acute respiratory distress syndrome, and nosocomial pneumonia. These data indicate a high mortality of patients with tuberculosis requiring intensive care unit care and identifies new independently associated risk factors.  相似文献   
22.
23.
Although studies have documented underuse of controller medications and overuse of short-acting inhaled ss(2)-agonist among children with persistent asthma in disadvantaged communities, the persistence of oral ss(2)-agonist use in pediatric practice has not been studied since inhaled short-acting ss(2)-agonists became widespread. We describe medications used to treat asthma among children 3 to 5 years of age at 10 Head Start and other subsidized preschool centers in East and Central Harlem, New York City. We interviewed 149 parents/guardians of children who were identified as having probable asthma based on physician's diagnosis, persistent symptoms, hospitalization, and medication use. We classified 86 of the 149 children (58%) as having current persistent asthma. Only 15 of them (17%) were reported to have used controller medications at least 5 days/week in the last 4 weeks-only 2 of whom used inhaled corticosteroids. By contrast, 53 children (62%) used oral ss(2)-agonist in the last 4 weeks, often (72%) in conjunction with nebulized or inhaled short-acting ss(2)-agonist. Use of oral ss(2)-agonist was associated with more severe symptoms. This study documents the continued widespread use of oral ss(2)-agonist for treatment of children in a low-income community with high prevalence of asthma.  相似文献   
24.
25.
26.
Heike  A.  Bischoff-Ferrari  Waiter  C.  Willett  John  B.  Wong  苗峥 《美国医学会杂志》2006,25(4):248-248
背景:对于脊椎以外的骨折而言,补充口服维生素D的预防作用和用量仍无定论。 目的:评估补充维生素D在预防老年髋骨骨折和非脊椎骨折方面的效果。 数据来源:使用MEDLINE、Cochrance对照试验记录(1960~2005年)以及EMBASE(1991-2005年),对英文和非英文文章进行系统回顾。通过与临床专家接触,通过检索美国社会骨和骨矿研究协会提供的参考文献和摘要(1995~2004年).进一步寻找更多的研究。检索词包括随机对照试验(randomized controlled trial,RCT)、临床对照试验、随机分配、双盲法、维生素D3、维生素D2;25-羟基维生素D、骨折、人类、老年、摔倒和骨密度。 研究选取:纳入的研究仅限于口服补充维生素D(维生素D3、维生素D2、补钙或不补钙)与补钙或安慰剂比较的双盲RCTs。试验于检查髋部骨折或非脊椎骨折的老年人(年龄≥60岁)中进行。数据提取:两位作者根据预先规定独立提取相关数据,其中包括研究质量指标。 数据综合:所有的汇总分析均以随机效应模型为基础。5项有关髋部骨折的RCTs(n=9294)和7项有关非脊椎骨折危险的RCTs(n=9820)符合我们的纳入标准。所有试验均使用了维生素D3。对髋部和非脊椎骨折预防研究的异质性亦进行观察,用低剂量(400IU/d)和高剂量(700~800IU/d)分别合并RCTs后异质性消失。与补钙或安慰剂相比,每天服700~800IU的维生素D可使髋部骨折的相对危险(relative risk,aa)下降26%(3项RCTs共计5572人;RR,0.74;95%可信区间[confidence interval,CI],0.61~0.88),使非脊椎骨折的相对危险下降23%(5项RCTs共计6098人;RR,0.77;95%CI,0.68~0.87)。每天服400IU的维生素D(2项RCTs共计3722人;髋部骨折RR,1.15;95%CI,0.88~1.50;非脊椎骨折RR,1.03;95%CI,0.86—1.24)未见明显获益。 结论:口服补充维生素D(700~800IU/d)可以降低尚能活动的老人或慈善机构收容的老年人发生髋部骨折和脊椎以外骨折的危险,每天口服400IU维生素D并不足以预防骨折。  相似文献   
27.
目的:描述胚胎种植前遗传诊断在1例携带Ⅰ型白细胞黏附缺陷病(LAD-1)携带者并完成健康妊娠夫妇中的应用。设计:病例报道。机构:大学医院生殖中心。患者:1例男女双方都是LAD-1携带者的夫妇,女方CD18基因的外显子4携带有G400A置换,男方的外显子5携带有C562T置换。干预:标准体外受精(IVF)后第3天行卵裂期活检和分裂球遗传分析以检测2处突变以及21号染色体标记物。主要观察指标:1个未罹患LAD-1婴儿的出生。结果:得到15个卵母细胞,其中10个受精。8个胚胎适宜胚胎活组织检查。  相似文献   
28.
OBJECTIVE: To illustrate the safety and efficacy of the endoscopic laser approach for cricopharyngeal myotomy (CPM) compared to the traditional transcervical approach. STUDY DESIGN AND SETTING: Retrospective chart review of 22 patients undergoing CPM from 1996 to 2003 at the Mayo Clinic, Jacksonville. RESULTS: The laser CPM technique was used in 14 patients, and an open approach in 8. The mean hospital stay and operative times were shorter for the laser group. Functional outcome analyses showed improvement in both groups. There were no major complications in the laser group, while 1 patient in the transcervical group had a pharyngocutaneous fistula. CONCLUSIONS: The laser technique is at least as effective as the transcervical approach for CPM to improve dysphagia symptoms in the properly selected patient, with a low risk of major complications. SIGNIFICANCE: In this report, we provide the reader with data to support the safety and efficacy of laser CPM. EBM rating: B-3b.  相似文献   
29.
Using the SF-12 to measure physical and mental functioning, the authors examine the intra-individual changes in health-related quality of life (HRQOL) 6 months post-discharge for depressed older adults. In addition, they examine three sets of predictors that might influence these changes. The sample of depressed older adults was recruited from an inpatient geropsychiatry unit. Although their physical and mental health scores on the SF-12 were lower than comparable norms, the sample showed an average increase in their mental functioning but a decrease in the physical functioning over the 6 months. Negative life-events were significant predictors of people who reported no change in their mental health functioning and decreases in their physical health functioning. Interestingly, those who experienced positive life events were more likely to report declines and younger participants were more likely to report no change in their physical functioning. The findings indicate that the effects of depression on HRQOL can have enduring effects on a sample of previously hospitalized older adults. The significance of life event changes might signify the importance of taking into account non-traditional areas of medical interventions. Further, the findings indicate the usefulness of the SF-12 quantifying HRQOL outcomes.  相似文献   
30.
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