首页 | 官方网站   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   242924篇
  免费   22155篇
  国内免费   11435篇
医药卫生   276514篇
  2024年   218篇
  2023年   3355篇
  2022年   4562篇
  2021年   8668篇
  2020年   7779篇
  2019年   7691篇
  2018年   7874篇
  2017年   8225篇
  2016年   8858篇
  2015年   9975篇
  2014年   14967篇
  2013年   15463篇
  2012年   14024篇
  2011年   15745篇
  2010年   12809篇
  2009年   12439篇
  2008年   12994篇
  2007年   13534篇
  2006年   12346篇
  2005年   11213篇
  2004年   9586篇
  2003年   8344篇
  2002年   6877篇
  2001年   6231篇
  2000年   5180篇
  1999年   4511篇
  1998年   4242篇
  1997年   3805篇
  1996年   3017篇
  1995年   2998篇
  1994年   2651篇
  1993年   2103篇
  1992年   1768篇
  1991年   1607篇
  1990年   1286篇
  1989年   1179篇
  1988年   1094篇
  1987年   881篇
  1986年   796篇
  1985年   1100篇
  1984年   928篇
  1983年   650篇
  1982年   695篇
  1981年   551篇
  1980年   472篇
  1979年   361篇
  1978年   257篇
  1977年   188篇
  1976年   151篇
  1975年   64篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
1.
BackgroundTo investigate perioperative complication rates at radical nephrectomy (RN) according to inferior vena cava thrombectomy (IVC-T) status and stage (metastatic vs non-metastatic) within kidney cancer patients.Materials and methodsWe ascertained perioperative complication rates within the National Inpatient Sample database (2016–2019). First, log-link linear Generalized Estimating Equation function (GEE) regression models (adjusted for hospital clustering and weighted for discharge disposition) tested complication rates in IVC-T patients, according to metastatic stage. Subsequently, a subgroup analysis relied on RN patients with or without IVC-T. Here, multivariable logistic regression models tested complication rates in RN patients according to IVC-T status, after propensity score matching including metastatic stage.ResultsOf 26,299 RN patients, 461 (2%) patients underwent IVC-T. Of those, 252 (55%) were non-metastatic vs 209 (45%) were metastatic. Rates of acute kidney injury (AKI), transfusion, cardiac, thromboembolic and other medical complications in non-metastatic vs metastatic patients were 40 vs 40%, 25 vs 22%, 21 vs 23%, 19 vs 14% and 38 vs 40%, respectively (all p ≥ 0.2). Metastatic stage in IVC-T patients did not predict differences in complications in log-link linear GEE regression models (all p > 0.1). However, in logistic regression models with propensity score matching, relying on the overall cohort of RN patients, IVC-T status was associated with higher complication rates (all p < 0.001): AKI (Odds ratio [OR]:2.60; 95%-CI [95%-Confidence interval: 1.97–3.44), transfusions (OR:2.40; 95%-CI: 1.72–3.36), cardiac (OR:2.27; 95%-CI: 1.49–3.47), thromboembolic (OR:9.07; 95%-CI: 5.21–16.58) and other medical complications (OR:2.01; 95%-CI: 1.52–2.66).ConclusionsThe current analyses indicate that presence of concomitant IVC-T is associated with higher complication rate at RN. Conversely, metastatic stage has no effect on recorded complication rates.  相似文献   
2.
孔慧  崔彦 《眼科新进展》2022,(9):753-756
视网膜内皮细胞(REC)是参与糖尿病视网膜病变和许多眼部疾病的主要细胞类型之一。视网膜微血管系统有助于血-视网膜屏障的维持,这对正常的视功能至关重要。REC的改变在视网膜疾病的发生发展中起着关键作用。高血糖是糖尿病微血管损伤的重要原因,通过不同的机制导致REC功能障碍,包括向衰老表型改变、迁移和增殖能力增强、炎性凋亡等,最终导致无细胞毛细血管及病理性新生血管形成。本文对糖尿病视网膜病变中REC的功能障碍作一综述。  相似文献   
3.
ObjectivesThe aim of this meta-analysis was to conduct a contemporary systematic review of high quality non-randomised controlled trials to determine the effect of pre-liver transplantation (LT) transarterial chemoembolisation (TACE) on long-term survival and complications of hepatocellular carcinoma (HCC) patients.BackgroundTACE is used as a neoadjuvant therapy to mitigate waitlist drop-out for patients with HCC awaiting LT. Previous studies have conflicting conclusions on the effect of TACE on long-term survival and complications of HCC patients undergoing LT.MethodsCINAHL, Cochrane Controlled Register of Trials, Embase, PubMed, and Web of Science were systematically searched. Baseline characteristics included number of patients outside Milan criteria, tumour diameter, MELD score, and time on the waiting list. Primary outcomes included 3- and 5-year overall and disease-free survival. Secondary outcomes included tumour recurrence, 30-day postoperative mortality, and hepatic artery and biliary complications.ResultsTwenty-one high-quality NRCTs representing 8242 patients were included. Tumour diameter was significantly larger in TACE patients (3.49 cm vs 3.15 cm, P = 0.02) and time on the waiting list was significantly longer in TACE patients (4.87 months vs 3.46 months, P = 0.05), while MELD score was significantly higher in non-TACE patients (10.81 vs 12.35, P = 0.005). All primary and secondary outcomes displayed non-significant differences.ConclusionPatients treated with TACE had similar survival and postoperative outcomes to non-TACE patients, however, they had worse prognostic features compared to non-TACE patients. These findings strongly support the current US and European clinical practice guidelines that neoadjuvant TACE can be used for patients with longer expected waiting list times (specifically >6 months). Randomised controlled trials would be needed to increase the quality of evidence.  相似文献   
4.
The present letter to the editor is in response to the research “Outcomes of curative liver resection for hepatocellular carcinoma in patients with cirrhosis” by Elshaarawy et al in World J Gastroenterol 2021; 13(5): 424–439. The preoperative assessment of the liver reserve function in hepatocellular carcinoma (HCC) patients with cirrhosis is crucial, and there is no universal consensus on how to assess it. Based on a retrospective study, Elshaarawy et al investigated the impact of various classical clinical indicators on liver failure and the prognosis after hepatectomy in HCC patients with cirrhosis. We recommend that we should strive to explore new appraisal indicators, such as the indocyanine green retention rate at 15 min.  相似文献   
5.
BackgroundThe goal of this study was to characterize contemporary performance benchmarks and risk factors associated with negative appendectomy (NA) in children with suspected appendicitis.MethodsA multicenter retrospective cohort analysis of children undergoing appendectomy for suspected appendicitis was performed using data from the 2016–2021 NSQIP-Pediatric Appendectomy Targeted Public Use Files. Multivariable regression was used to evaluate the influence of year, age, sex, and WBC count on NA rate, and to generate rate estimates for NA based on different combinations of demographic characteristics and WBC profiles.Results100,322 patients were included from 140 hospitals. The overall NA rate was 2.4%, and rates decreased significantly during the study period (2016: 3.1% vs. 2021: 2.3%, p < 0.001). In adjusted analyses, the highest risk for NA was associated with a normal WBC (<9000/mm3; OR 5.31 [95% CI: 4.87–5.80]), followed by female sex (OR 1.55 [95% CI: 1.42–1.68]) and age <5 years (OR 1.64 [95% CI 1.39, 1.94]). Model-estimated risk for NA varied significantly across demographic and WBC strata, with a 14.4-fold range in rates between subgroups with the lowest and highest predicted risk (males 13–17 years with elevated WBC [1.1%] vs. females 3–4 years with normal WBC [15.8%]).ConclusionsContemporary NA rates have decreased over time, however NA risk remains high in children without a leukocytosis, particularly for girls and children <5 years of age. These data provide contemporary performance benchmarks for NA in children with suspected appendicitis and identify high-risk populations where further efforts to mitigate NA risk should be targeted.Level of EvidenceIII.  相似文献   
6.
7.
8.
《Cancer cell》2022,40(8):835-849.e8
  1. Download : Download high-res image (220KB)
  2. Download : Download full-size image
  相似文献   
9.
10.
The endothelium is a single-layered structure that responds to physical and chemical signals with various factors it synthesizes. In the early days of its discovery, as the inner wall of the vessels, the endothelium was thought to be a simple barrier that lays on the surface. Over time it is discovered that endothelium maintains body homeostasis with the molecules it synthesizes, despite its simple single-layer structure. It has been accepted as an important organ that contributes to the maintenance of vascular tone, cell adhesion, inflammation, vascular permeability and coagulation. Any imbalance in these physiological and pathological events causes endothelial dysfunction. This can cause many diseases such as atherosclerosis, hypertension, diabetes, or it can occur because of these. Endothelial related disorders may also complicate hematopoietic stem cell transplantation (HSCT), which is used to treat various hematologic and neoplastic diseases. These life-threatening complications include graft-versus-host disease, hepatic veno-occlussive disease, transplant-associated thrombotic microangiopathy and diffuse alveolar hemorrhage. They share a similar pathophysiology involving endothelial cells with different clinical presentations. Therefore, current researche on the issue is putting the endothelium under the spotlight for novel markers and treatment options that should be used to monitor or treat at least some of these complications following HSCT.  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-23

京公网安备 11010802026262号