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   9862篇
  免费   831篇
  国内免费   16篇
耳鼻咽喉   139篇
儿科学   359篇
妇产科学   252篇
基础医学   1225篇
口腔科学   148篇
临床医学   1263篇
内科学   1660篇
皮肤病学   229篇
神经病学   1291篇
特种医学   197篇
外科学   1046篇
综合类   53篇
一般理论   16篇
预防医学   1450篇
眼科学   103篇
药学   518篇
  1篇
中国医学   5篇
肿瘤学   754篇
  2024年   38篇
  2023年   225篇
  2022年   326篇
  2021年   637篇
  2020年   417篇
  2019年   604篇
  2018年   655篇
  2017年   416篇
  2016年   443篇
  2015年   425篇
  2014年   535篇
  2013年   703篇
  2012年   916篇
  2011年   859篇
  2010年   441篇
  2009年   340篇
  2008年   489篇
  2007年   423篇
  2006年   423篇
  2005年   349篇
  2004年   265篇
  2003年   222篇
  2002年   228篇
  2001年   26篇
  2000年   14篇
  1999年   32篇
  1998年   32篇
  1997年   23篇
  1996年   28篇
  1995年   17篇
  1994年   15篇
  1993年   19篇
  1992年   10篇
  1991年   9篇
  1990年   9篇
  1989年   7篇
  1988年   6篇
  1987年   5篇
  1986年   6篇
  1985年   9篇
  1984年   5篇
  1983年   5篇
  1982年   7篇
  1981年   4篇
  1980年   7篇
  1979年   7篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
  1971年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
PurposeTo explore the impact of the extent of reticular pseudodrusen (RPD) on mesopic visual sensitivity in individuals with intermediate age-related macular degeneration (AMD).MethodsIn total, 570 eyes from 285 participants with bilateral large drusen underwent microperimetry testing to assess the visual sensitivity of the central 3.6-mm region and multimodal imaging to determine the extent of RPD in the central 20° × 20° region (at the eye level). Mean visual sensitivity within five sectors in the central 3.6-mm region sampled on microperimetry and the extent of RPD in these sectors were derived. Linear mixed models were used to examine the association between the extent of RPD on overall mean visual sensitivity and sector-based mean sensitivity.ResultsAn increasing extent of RPD at the eye level and within sectors was associated with a significant reduction in overall and sector-based mean sensitivity, respectively (P < 0.001 for both). However, when both RPD parameters were considered together in a multivariable model, only an increasing extent of RPD at the eye level (P < 0.001) and not within each sector (P = 0.178) was independently associated with reduced sector-based mean sensitivity.ConclusionsMesopic visual sensitivity is generally reduced in eyes with large drusen and coexistent RPD compared to eyes without RPD, with greater reductions with an increasing extent of RPD. However, reduced sector-based visual sensitivities are explained by the overall extent of RPD present, rather than their extent within the sector itself. These findings suggest that there are generalized pathogenic changes in eyes with RPD accounting for the observed mesopic visual dysfunction.  相似文献   
32.
The objective of this study was to calculate an oxidative balance score (OBS) utilizing diet and lifestyle information collected from 1322 women during the second trimester of pregnancy in the Conditions Affecting Neurocognitive Development and Learning in Early Childhood study. An energy-adjusted OBS was calculated using nutrient information from a Food Frequency Questionnaire (FFQ), lifestyle measures, and plasma folate and vitamin D levels. Using the least absolute shrinkage and selection operator method, 91 food items from the FFQ were selected and they accounted for 82% of the variance in the OBS, with cruciferous vegetables, citrus fruits, fruit juice, and coffee being among the highest anti-oxidant predictors, and red meats and alcohol among the highest pro-oxidant contributors. Urinary F2-isoprostane, an objective indicator of oxidative stress, was lower with increasing OBS quintiles in a stairstep manner (p for trend = 0.0003), suggesting the possible utility of the OBS as an indicator of oxidative stress. The OBS was moderately correlated with the Healthy Eating Index (correlation coefficient = 0.6076), suggesting it provides a distinct measure of a healthy diet. In conclusion, the OBS may serve as a valid reflective indicator of urinary F2-isoprostanes and an epidemiological tool to inform intervention studies, in order to minimize oxidative stress during pregnancy.  相似文献   
33.
34.
Introduction:HIV confers increased risk of myocardial infarction (MI), but there has been little study of ischemic electrocardiogram (ECG) findings among people with HIV in sub-Saharan Africa.Objectives:To compare the prevalence of ischemic ECG findings among Tanzanians with and without HIV and to identify correlates of ischemic ECG changes among Tanzanians with HIV.Methods:Consecutive adults presenting for routine HIV care at a Tanzanian clinic were enrolled. Age- and sex-matched HIV-uninfected controls were enrolled from a nearby general clinic. All participants completed a standardized health questionnaire and underwent 12-lead resting ECG testing, which was adjudicated by independent physicians. Prior MI was defined as pathologic Q-waves in contiguous leads, and myocardial ischemia was defined as ST-segment depression or T-wave inversion in contiguous leads. Pearson’s chi-squared test was used to compare the prevalence of ECG findings among those with and without HIV and multivariate logistic regression was performed to identify correlates of prior MI among all participants.Results:Of 497 participants with HIV and 497 without HIV, 272 (27.8%) were males and mean (sd) age was 45.2(12.0) years. ECG findings suggestive of prior MI (11.1% vs 2.4%, OR 4.97, 95% CI: 2.71–9.89, p < 0.001), and myocardial ischemia (18.7% vs 12.1% OR 1.67, 95% CI: 1.18–2.39, p = 0.004) were significantly more common among participants with HIV. On multivariate analysis, ECG findings suggestive of prior MI among all participants were associated with HIV infection (OR 4.73, 95% CI: 2.51–9.63, p = 0.030) and self-reported family history of MI or stroke (OR 1.96, 95% CI: 1.08–3.46, p = 0.023).Conclusions:There may be a large burden of ischemic heart disease among adults with HIV in Tanzania, and ECG findings suggestive of coronary artery disease are significantly more common among Tanzanians with HIV than those without HIV.  相似文献   
35.
36.
37.
38.
39.
40.
Blood products are scarce resources requiring prudent and reasoned allocation. The utilization of red blood cells and platelets in terminally ill patients can be complicated and requires guidelines tempered by individualized considerations. Representative cases are discussed in which blood products are requested or utilized by patients at the end of life. Relevant literature is reviewed and ethical issues pertaining to each case are discussed. A practical approach to blood product utilization at the end of life is suggested.  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