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   71199篇
  免费   4673篇
  国内免费   1200篇
耳鼻咽喉   309篇
儿科学   1481篇
妇产科学   1509篇
基础医学   6131篇
口腔科学   873篇
临床医学   8249篇
内科学   16829篇
皮肤病学   322篇
神经病学   2326篇
特种医学   2544篇
外国民族医学   9篇
外科学   6327篇
综合类   10402篇
预防医学   7962篇
眼科学   369篇
药学   6842篇
  211篇
中国医学   2527篇
肿瘤学   1850篇
  2023年   952篇
  2022年   1570篇
  2021年   2465篇
  2020年   2846篇
  2019年   3512篇
  2018年   2360篇
  2017年   2191篇
  2016年   2122篇
  2015年   2173篇
  2014年   4835篇
  2013年   4766篇
  2012年   4142篇
  2011年   4650篇
  2010年   3600篇
  2009年   3409篇
  2008年   3481篇
  2007年   3374篇
  2006年   2944篇
  2005年   2685篇
  2004年   2175篇
  2003年   1813篇
  2002年   1543篇
  2001年   1360篇
  2000年   1217篇
  1999年   1031篇
  1998年   816篇
  1997年   818篇
  1996年   755篇
  1995年   721篇
  1994年   684篇
  1993年   503篇
  1992年   549篇
  1991年   483篇
  1990年   397篇
  1989年   394篇
  1988年   349篇
  1987年   296篇
  1986年   250篇
  1985年   330篇
  1984年   313篇
  1983年   218篇
  1982年   268篇
  1981年   238篇
  1980年   223篇
  1979年   188篇
  1978年   161篇
  1977年   145篇
  1976年   139篇
  1975年   142篇
  1974年   111篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
2.
Serrated polyps (SPs) are precursors to one-third of colorectal cancers (CRCs), with histological subtypes: hyperplastic polyps (HPs), sessile serrated lesions (SSLs) and traditional serrated adenomas (TSAs). The incidence of early-onset CRC before the age of 50 is increasing, with limited understanding of SPs in younger cohorts. Using a large colonoscopy-based cohort, we characterized epidemiologic profiles of SP subtypes, compared to conventional adenomas, with secondary analysis on early-onset polyps. Ninety-four thousand four hundred and twenty-seven patients underwent screening colonoscopies between 2010 and 2018. Demographic, endoscopic and histopathologic characteristics of each polyp subtype were described. High-risk polyps included SSLs ≥10 mm/with dysplasia and conventional adenomas ≥10 mm/with tubulovillous/villous histology/high-grade dysplasia. We examined polyp prevalence with age and compared early- (age < 50) and late-onset polyps (age ≥ 50). Eighteen thousand one hundred and twenty-five patients had SPs (4357 SSLs, 15 415 HPs, 120 TSAs) and 26 699 had conventional adenomas. High-risk SSLs were enriched in the ascending colon (44.1% vs 2.6-35.8% for other locations; P < .003). Early- and late-onset SPs had similar subsite distribution. Early-onset conventional adenomas were more enriched in the distal colon/rectum (51.8% vs 43.4%, P < .001). Multiple conventional adenomas were more represented in late-onset groups (40.8% vs 33.8%, P < .001), with no difference in SSLs. The prevalence of conventional adenomas/high-risk conventional adenomas increased continuously with age, whereas the prevalence of SSLs/high-risk SSLs was stable from age 40 years onwards. A higher proportion of women were diagnosed with early-onset than late-onset SSLs (62.9% vs 57.6%, P = .03). Conventional adenomas, SSLs, early- and late-onset polyps have distinct epidemiology. The findings have implications for improved colonoscopy screening and surveillance and understanding the etiologic heterogeneity of CRC.  相似文献   
3.
Formal multidisciplinary team (MDT) discussions in clinical practice require time and space but have unclear survival benefits for advanced gastrointestinal cancer patients. Our study aimed to investigate the long-term survival of patients with advanced gastrointestinal cancer after MDT decision. From June 2017 to June 2019, continuous MDT discussions on advanced gastrointestinal cancer were conducted in 13 medical centers in China. MDT decisions and actual treatment received by patients were prospectively recorded. The primary endpoint was the difference in overall survival (OS) between patients in the MDT decision implementation and nonimplementation groups. The secondary endpoints included the implementation rate of MDT decisions and subgroup survival analysis. A total of 461 MDT decisions of 455 patients were included in our study. The implementation rate of MDT decisions was 85.7%. Previous treatment had an impact on MDT decision-making. The OS was 24.0 months and 17.0 months in the implementation and nonimplementation groups, respectively. The implementation of MDT decisions significantly reduced the risk of death in multivariate analyses (hazard ratio = 0.518; 95% confidence interval: 0.304-0.884, P = .016). Subgroup analysis showed a significant difference in survival of patients with colorectal cancer, but not in survival of patients with gastric cancer. The rate of secondary MDT discussion was only 5.6% among patients who the MDT decisions were discontinued due to changes in their condition. MDT discussion can prolong the OS of patients with advanced gastrointestinal cancer, especially those with colorectal cancer. Timely scheduling of the subsequent MDT discussion is necessary when the disease condition changes.  相似文献   
4.
5.
Background and objectiveThere is a growing body of evidence that the equations used to estimate the glomerular filtration rate (GFR) are not suitable in critically ill patients, a population whose GFR fluctuates continuously. Glomerular filtration is usually estimated by measuring urine creatinine clearance (CrCl) at various time points. The aim of our study was to evaluate the performance of the most widely used GFR calculators in the subpopulation of critically ill patients admitted for severe trauma, and to compare the results against determinations of CrCl in urine collected over a 4-hour period (4h-CrCl).Material and methodsObservational study in patients hospitalized for severe trauma. We measured the 4h-CrCl and estimated GFR using the Cockcroft-Gault, modified Jelliffe, MDRD, t-MDRD, and CKD-EPI equations, adjusting the results for body surface area (BSA) (ml/min/1.73m2). Data were analysed using R version 4.0.4.ResultsA total of 85 patients were included. Median age was 51 years, and 68 were men (78.82%). The mean BSA-adjusted 4h-CrCl (4h-ClCr/1.73 m2) was 84.5 ml/min/1.73 m2. We found that GFR estimated using the t-MDRD equation correlated significantly with 4h-CrCl/1.73 m2. The Cockcroft-Gault equation correlated significantly with 4h-CrCl/1.73 m2 when GFR was greater than 130 ml/min/m2.ConclusionsIn ICU patients, glomerular filtration can be reliably estimated by determining urine CrCl, but GFR calculators are not accurate in this population.  相似文献   
6.
Renal sodium and water retention with resulting extracellular volume expansion and redistribution are hallmark features of heart failure syndromes. However, congestion assessment, monitoring, and treatment represent a real challenge in daily clinical practice. This document reviewed historical and contemporary evidence of available methods for determining volume status and discuss pharmacological aspects and pathophysiological principles that underlie diuretic use.  相似文献   
7.
目的研究医联体背景下射血分数中间值的中老年急性失代偿心力衰竭(心衰)住院患者临床特征及1年内发生主要心血管事件的风险。方法回顾性队列研究, 连续收集天津市胸科医院心内科和天津河西医院诊区急性失代偿心衰住院患者180例, 根据入院后左心室射血分数(LVEF)将心衰患者分为射血分数低(HFrEF, LVEF< 40%)组70例(38.9%)、射血分数中间值(HFmEF, LVEF 40%~49%)组50例(27.8%)和射血分数保留(HFpEF, LVEF≥50%)组60例(33.3%), 比较3组患者临床特征及1年预后差异。结果 1年全因死亡和心血管死亡单因素Cox回归分析, HFrEF组与HFmEF组、HFpEF组与HFmEF组患者比较, 差异无统计学意义(均P>0.05);1年心衰再入院分析, HFrEF组47.1%(33例)较HFmEF组48.3%(29例)高、HFpEF组24.0%(12例)较HFmEF组高(HR分别为2.307、2.368, 95%CI:0.187~4.480、1.207~4.644, 均P<0.05);1年主要心血管事件HFrEF组57.1%...  相似文献   
8.
BackgroundThe MAGGIC risk score has been validated to predict mortality in patients with heart failure (HF).ObjectivesTo assess the score ability to predict hospitalization and death and to compare with natriuretic peptides.MethodsNinety-three consecutive patients (mean age 62±10 years) with chronic HF and left ventricular ejection fraction (EF) <50% were studied. The MAGGIC score was applied at baseline and the patients were followed for 219±86 days. MAGGIC score was compared with NT-proBNP in the prediction of events. The primary end point was the time to the first event, which was defined as cardiovascular death or hospitalization for HF.ResultsThere were 23 (24.7%) events (3 deaths and 20 hospitalizations). The median score in patients with and without events was, respectively, 20 [interquartile range 14.2–22] vs. 15.5 [11/21], p=0.16. A ROC curve was performed and a cutoff point of 12 points showed a sensitivity of 87% and specificity of 37% with an area under the curve of 0.59 (95% CI 0.48–0.69) which was lower than that of NT-proBNP (AUC 0.67; 95% CI 0.56–0.76). The mean event-free survival time for patients above and below this cutpoint was 248.8±13 vs. 290±13.7 days (log rank test with p=0.044). Using the COX proportional hazard model, age (p=0.004), NT-proBNP >1000 pg/mL (p=0.014) and the MAGGIC score (p=0.025) were independently associated with the primary outcome.ConclusionThe MAGGIC risk score was an independent predictor of events, including heart failure hospitalization. The addition of biomarkers improved the accuracy of the score.  相似文献   
9.
Background and aimsIn the absence of a gold standard or scientific consensus regarding the nutritional evaluation of heart failure (HF) patients, this study aimed to summarize and systematically evaluate the prognostic value of nutritional screening and assessment tools used for all-cause mortality in HF patients.Methods and resultsRelevant studies were retrieved from major databases (PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), WanFang Data, and China Biology Medicine disc (CMB)) and searched from the earliest available date until July 2021. If three or more studies used the same tool, meta-analysis using RevMan 5.3 was performed. This systematic review was registered at PROSPERO (number CRD42021275575). A total of 36 articles involving 25,141 HF patients were included for qualitative analysis and 31 studies for quantitative analysis. Meta-analysis of these studies indicated, poor nutritional status evaluated by using 5 nutritional screening tools (Prognostic Nutritional Index (PNI), Geriatric Nutritional Risk Index (GNRI), Controlling Nutritional Status Score (CONUT), Nutritional Risk Index (NRI), and Short Form Mini Nutritional Assessment (MNA-SF)) or 2 nutritional assessment tools (the Mini Nutritional Assessment (MNA) and Generated Subjective Global Assessment (SGA)) predicted all-cause mortality in HF patients. Of all tools analyzed, MNA had the maximum HR for mortality [HR = 2.62, 95%CI 1.11–6.20, P = 0.03] and MNA-SF [HR = 1.94, 95%CI 1.40–2.70, P<0.001] was the best nutritional screening tools.ConclusionPoor nutritional status predicted all-cause mortality in HF patients. MNA may be the best nutritional assessment tool, and MNA-SF is most recommended for HF patient nutritional screening. The application value of MNA, especially in patients with reduced left ventricular ejection fraction (LVEF), needs to be further confirmed. The clinical application value of Mini-Nutrition Assessment Special for Heart Failure (MNA-HF) and Global Leadership Initiative on Malnutrition (GLIM) in HF patients needs to be confirmed.  相似文献   
10.
Background and aimHeart failure (HF) and diabetes mellitus (DM) are burdensome chronic diseases with high lifetime risks and numerous studies indicate associations between HF and DM. The objective of this study was to investigate the direct and indirect costs of HF patients with and without DM.Methods and resultsPatients with a first-time diagnosis of HF from 1998 to 2016 were identified through nationwide Danish registries and stratified according to DM status into HF with or without DM. The economic healthcare cost analysis was based on both direct costs, including hospitalization, procedures, medication and indirect costs including social welfare and lost productivity. The economic burden was investigated prior to, at, and following diagnosis of HF. Patients with concomitant HF and DM were younger (median age 74 vs. 77), had more comorbidities and fewer were female as compared to patients with HF but without DM. The socioeconomic burden of concomitant HF and DM compared to HF alone was substantially higher; 45% in direct costs (€16,237 vs. €11,184), 35% in home care costs (€3123 vs. €2320), 8% in social transfer income (€17,257 vs. €15,994) and they had 27% lower income (€10,136 vs. €13,845). The economic burden peaked at year of diagnosis, but the difference became increasingly pronounced in the years following the HF diagnosis.ConclusionPatients with concomitant HF and DM had a significantly higher economic burden compared to patients with HF but without DM.  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