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   2566923篇
  免费   189204篇
  国内免费   7527篇
耳鼻咽喉   34244篇
儿科学   84941篇
妇产科学   71559篇
基础医学   360663篇
口腔科学   69573篇
临床医学   232844篇
内科学   510776篇
皮肤病学   62414篇
神经病学   211929篇
特种医学   99781篇
外国民族医学   736篇
外科学   385255篇
综合类   50231篇
现状与发展   5篇
一般理论   967篇
预防医学   194384篇
眼科学   56460篇
药学   187468篇
  8篇
中国医学   5152篇
肿瘤学   144264篇
  2019年   20617篇
  2018年   29282篇
  2017年   22597篇
  2016年   26235篇
  2015年   29516篇
  2014年   40455篇
  2013年   60429篇
  2012年   80253篇
  2011年   84504篇
  2010年   51017篇
  2009年   49156篇
  2008年   79044篇
  2007年   83860篇
  2006年   85607篇
  2005年   81773篇
  2004年   78757篇
  2003年   75894篇
  2002年   73170篇
  2001年   128196篇
  2000年   131027篇
  1999年   109805篇
  1998年   29621篇
  1997年   26198篇
  1996年   26432篇
  1995年   27232篇
  1994年   24936篇
  1993年   23291篇
  1992年   85063篇
  1991年   81550篇
  1990年   78744篇
  1989年   76010篇
  1988年   69406篇
  1987年   67956篇
  1986年   63509篇
  1985年   60472篇
  1984年   44886篇
  1983年   37847篇
  1982年   22370篇
  1981年   19908篇
  1979年   38893篇
  1978年   27372篇
  1977年   23168篇
  1976年   21419篇
  1975年   22757篇
  1974年   26739篇
  1973年   25333篇
  1972年   23730篇
  1971年   21935篇
  1970年   20155篇
  1969年   19408篇
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
91.
92.

Background

Health-related quality of life (HRQoL) is frequently assessed in randomised clinical trials (RCTs) in the intensive care unit (ICU), but data are limited regarding the proportions of patients without responses or not surviving to HRQoL follow-up and the handling of this. We aimed to describe the extent and pattern of missing HRQoL data in intensive care trials and describe how these data and deaths were handled statistically.

Methods

We conducted a systematic review and meta-analysis following a published protocol. We searched PubMed, EMBASE, CINAHL and Cochrane Library for RCTs involving adult ICU patients reporting HRQoL as an outcome and excluded RCTs unobtainable in full text. We performed risk of bias assessment independently and in duplicate.

Results

We included 196 outcomes from 88 RCTs published in the years 2002–2022; the numbers of patients alive and eligible to respond HRQoL were reported in 76% of trials. At follow-up, median 27% (interquartile range 14%–39%) of patients had died, and median 20% (9%–38%) of survivors did not respond across outcomes. Analyses of 80% of outcomes were restricted to complete cases only. The handling of non-survivors in analyses were reported for 46% of outcomes, with 26% of all outcomes reported as including non-survivors (using the value zero or the worst possible score).

Conclusion

For HRQoL outcomes in ICU trials, we found that mortality at time of follow-up was high and non-response among survivors frequent. The reporting and statistical handling of these issues were insufficient, which may have biased results.  相似文献   
93.
Myocardial injury due to ischaemia within 30 days of non-cardiac surgery is prognostically relevant. We aimed to determine the discrimination, calibration, accuracy, sensitivity and specificity of single-layer and multiple-layer neural networks for myocardial injury and death within 30 postoperative days. We analysed data from 24,589 participants in the Vascular Events in Non-cardiac Surgery Patients Cohort Evaluation study. Validation was performed on a randomly selected subset of the study population. Discrimination for myocardial injury by single-layer vs. multiple-layer models generated areas (95%CI) under the receiver operating characteristic curve of: 0.70 (0.69–0.72) vs. 0.71 (0.70–0.73) with variables available before surgical referral, p < 0.001; 0.73 (0.72–0.75) vs. 0.75 (0.74–0.76) with additional variables available on admission, but before surgery, p < 0.001; and 0.76 (0.75–0.77) vs. 0.77 (0.76–0.78) with the addition of subsequent variables, p < 0.001. Discrimination for death by single-layer vs. multiple-layer models generated areas (95%CI) under the receiver operating characteristic curve of: 0.71 (0.66–0.76) vs. 0.74 (0.71–0.77) with variables available before surgical referral, p = 0.04; 0.78 (0.73–0.82) vs. 0.83 (0.79–0.86) with additional variables available on admission but before surgery, p = 0.01; and 0.87 (0.83–0.89) vs. 0.87 (0.85–0.90) with the addition of subsequent variables, p = 0.52. The accuracy of the multiple-layer model for myocardial injury and death with all variables was 70% and 89%, respectively.  相似文献   
94.
Münch  F.  Purbojo  A.  Wenzel  F.  Kohl  M.  Dittrich  S.  Rauh  M.  Zimmermann  R.  Kwapil  N. 《Der Anaesthesist》2022,71(11):882-892
Die Anaesthesiologie - Die Transfusion von Erythrozytenkonzentraten (EK) ist mit verschiedenen Nebenwirkungen assoziiert, die u. a. durch Lagerungsschäden an Erythrozyten hervorgerufen...  相似文献   
95.

A positive relationship between treatment volume and outcome quality has been demonstrated in the literature and is thus evident for a variety of procedures. Consequently, policy makers have tried to translate this so-called volume–outcome relationship into minimum volume regulation (MVR) to increase the quality of care—yet with limited success. Until today, the effect of strict MVR application remains unclear as outcome quality gains cannot be estimated adequately and restrictions to application such as patient travel time and utilization of remaining hospital capacity are not considered sufficiently. Accordingly, when defining MVR, its effectiveness cannot be assessed. Thus, we developed a mixed integer programming model to define minimum volume thresholds balancing utility in terms of outcome quality gain and feasibility in terms of restricted patient travel time and utilization of hospital capacity. We applied our model to the German hospital sector and to four surgical procedures. Results showed that effective MVR needs a minimum volume threshold of 125 treatments for cholecystectomy, of 45 and 25 treatments for colon and rectum resection, respectively, of 32 treatments for radical prostatectomy and of 60 treatments for total knee arthroplasty. Depending on procedure type and incidence as well as the procedure’s complication rate, outcome quality gain ranged between 287 (radical prostatectomy) and 977 (colon resection) avoidable complications (11.7% and 11.9% of all complications). Ultimately, policy makers can use our model to leverage MVR’s intended benefit: concentrating treatment delivery to improve the quality of care.

  相似文献   
96.
Prevention Science - As evidence-based interventions (EBIs) become more widely disseminated, fidelity of implementation (FOI) often wanes. This study explores the association between FOI and...  相似文献   
97.
The impact of vaccination and new SARS-CoV-2 variants on peri-operative outcomes is unclear. We aimed to update previously published consensus recommendations on timing of elective surgery after SARS-CoV-2 infection to assist policymakers, administrative staff, clinicians and patients. The guidance remains that patients should avoid elective surgery within 7 weeks of infection, unless the benefits of doing so exceed the risk of waiting. We recommend individualised multidisciplinary risk assessment for patients requiring elective surgery within 7 weeks of SARS-CoV-2 infection. This should include baseline mortality risk calculation and assessment of risk modifiers (patient factors; SARS-CoV-2 infection; surgical factors). Asymptomatic SARS-CoV-2 infection with previous variants increased peri-operative mortality risk three-fold throughout the 6 weeks after infection, and assumptions that asymptomatic or mildly symptomatic omicron SARS-CoV-2 infection does not add risk are currently unfounded. Patients with persistent symptoms and those with moderate-to-severe COVID-19 may require a longer delay than 7 weeks. Elective surgery should not take place within 10 days of diagnosis of SARS-CoV-2 infection, predominantly because the patient may be infectious, which is a risk to surgical pathways, staff and other patients. We now emphasise that timing of surgery should include the assessment of baseline and increased risk, optimising vaccination and functional status, and shared decision-making. While these recommendations focus on the omicron variant and current evidence, the principles may also be of relevance to future variants. As further data emerge, these recommendations may be revised.  相似文献   
98.
99.
100.
Quantitative susceptibility mapping (QSM) has the potential for being a biomarker for various diseases because of its ability to measure tissue susceptibility related to iron deposition, myelin, and hemorrhage from the phase signal of a T2*-weighted MRI. Despite its promise as a quantitative marker, QSM is faced with many challenges, including its dependence on preprocessing of the raw phase data, the relatively weak tissue signal, and the inherently ill posed relationship between the magnetic dipole and measured phase. The goal of this study was to evaluate the effects of background field removal and dipole inversion algorithms on noise characteristics, image uniformity, and structural contrast for cerebral microbleed (CMB) quantification at both 3T and 7T. We selected four widely used background phase removal and five dipole field inversion algorithms for QSM and applied them to volunteers and patients with CMBs, who were scanned at two different field strengths, with ground truth QSM reference calculated using multiple orientation scans. 7T MRI provided QSM images with lower noise than did 3T MRI. QSIP and VSHARP + iLSQR achieved the highest white matter homogeneity and vein contrast, with QSIP also providing the highest CMB contrast. Compared with ground truth COSMOS QSM images, overall good correlations between susceptibility values of dipole inversion algorithms and the COSMOS reference were observed in basal ganglia regions, with VSHARP + iLSQR achieving the susceptibility values most similar to COSMOS across all regions. This study can provide guidance for selecting the most appropriate QSM processing pipeline based on the application of interest and scanner field strength.  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