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   854篇
  免费   50篇
  国内免费   18篇
耳鼻咽喉   12篇
儿科学   23篇
妇产科学   50篇
基础医学   115篇
口腔科学   22篇
临床医学   103篇
内科学   120篇
皮肤病学   8篇
神经病学   119篇
特种医学   72篇
外科学   53篇
综合类   23篇
预防医学   90篇
眼科学   3篇
药学   56篇
肿瘤学   53篇
  2023年   7篇
  2020年   6篇
  2019年   8篇
  2018年   11篇
  2017年   7篇
  2016年   5篇
  2015年   13篇
  2014年   15篇
  2013年   27篇
  2012年   23篇
  2011年   28篇
  2010年   23篇
  2009年   21篇
  2008年   26篇
  2007年   34篇
  2006年   25篇
  2005年   35篇
  2004年   32篇
  2003年   23篇
  2002年   23篇
  2001年   31篇
  2000年   30篇
  1999年   16篇
  1998年   22篇
  1997年   23篇
  1996年   26篇
  1995年   18篇
  1994年   21篇
  1993年   21篇
  1992年   26篇
  1991年   23篇
  1990年   26篇
  1989年   24篇
  1988年   26篇
  1987年   28篇
  1986年   28篇
  1985年   22篇
  1984年   20篇
  1983年   15篇
  1982年   9篇
  1981年   5篇
  1980年   18篇
  1979年   4篇
  1978年   9篇
  1977年   7篇
  1976年   3篇
  1975年   6篇
  1974年   4篇
  1973年   5篇
  1970年   3篇
排序方式: 共有922条查询结果,搜索用时 31 毫秒
1.
2.
目的:以病理活检结果为金标准,评估多普勒超声检查对移植肾排斥反应的诊断价值。方法:选择2003—01/2006—12在中国医科大学附属第一医院器官移植科行肾移植并在术后行超声检查的患者176例,均知情同意。①实验分组:根据术后移植肾功能分为2组,移植肾功能不良组78例,其中30例次行病理活检;移植肾功能正常组98例。②实验方法及评估:对患者移植肾行多普勒超声检查,参数选择峰收缩期流速、平均舒张期流速、阻力指数及血管显示率。血管显示率的评估标准(0~5级):0级为肾动脉及其远侧血管未显示;5级为肾各级血管均显示良好。以病理活检结果为金标准,分别选取阻力指数=0.7,0.75,0.8,0.85为诊断界值进行诊断试验。结果:169例患者进入结果分析,脱落7例。①峰收缩期流速、平均舒张期流速不呈正态分布,无法作为肾功能评价指标。30例次病理活检中共有28例次被确诊为排斥反应,急性排斥反应15例次,慢性排斥反应13例次。②肾功能正常组患者中血管显示率5级者占63.30%,4级者占36.73%。肾功能不良组患者中血管显示率4级者占41.03%,3级者占46.15%,2级者占10.30%,1级者占2.60%。③移植肾功能不良组患者阻力指数显著高于移植肾功能正常组(P〈0.01)。移植肾功能不良组患者移植肾功能恢复后阻力指数显著低于移植肾尚未恢复时(P〈0.01),其中99%以上的患者△(阻力指数)≥0.20。④界值阻力指数=0.75的诊断试验的敏感性、特异性和准确性最高,均达到100%。结论:当移植肾血管阻力指数升高至0.75以上,特别是同一患者自身对照升高超过0.2以上和或血管显示率低于4级,结合临床表现和生化结果,提示可能出现移植肾排斥反应。  相似文献   
3.
As part of a study addressing chronic alcohol consumption and simian immunodeficiency virus, 31 rhesus macaques (Macaca mulatta) were implanted with gastric catheters used to deliver alcohol or isocaloric sucrose (control). Once implanted, the animals wore jackets and were housed in specialized cages modified with swivels and tethers. During the course of the study, 3 animals developed clinical signs indicating possible instability of the implanted gastric catheter. All 3 animals were found to have a string foreign body wrapped around the distal end of the catheter, with 2 of the catheters perforating the intestinal wall. Gastroscopy was used to screen remaining animals to determine catheter position and the presence of a foreign body attached to the end of the catheter. Results of the screening revealed that of the 28 remaining animals, 9 had malpositioned catheters; string foreign bodies were associated with 3 of the 9 malpositioned catheters. We initially hypothesized that the peristaltic motion of the stomach, combined with the attachment of string, which was probably ingested by subjects after manipulating their jackets, led to eventual catheter displacement. We later concluded that the string may have played a secondary role but was not the primary cause of catheter instability, because several malpositioned catheters had no string attached at the time of diagnosis. Subsequent modifications were instituted, including modifying the surgical technique, altering the type of gastric catheter used, and increasing environmental enrichment for animals with known tendency to manipulate their jackets.  相似文献   
4.
Three patients with head injury are described to illustrate certain features of the development, treatment and recovery of hyponatraemia. The hyponatraemia is initially due to water retention but true sodium depletion may develop because of an associated urine sodium loss. The mechanism of the latter is discussed.  相似文献   
5.
A multilaboratory study was conducted to develop a system for standardizing alanine aminotransferase (ALT) acceptability criteria ("cutoffs") for donated blood. Without standardized cutoffs, each laboratory must develop its own cutoff, and this may not make optimal use of ALT testing to reduce transmission of non-A, non-B hepatitis (NANB). Defining an ALT acceptability criterion in absolute terms is necessary because relative cutoffs based on local donor populations may be affected by the prevalence of NANB in each community. This study involved 16 laboratories using 23 different analytic systems. The ALT results of the analysis of a plasma reference sample could be used to translate mathematically a single, absolute cutoff to units applicable to each analytic system. The distribution of ALT results in 1.4 million donations from across the country was established; basing the cutoff on this sample avoids the problems inherent in using a local donor base to establish a cutoff. We propose the implementation of a system to standardize ALT acceptability criteria to an activity level defined by analysis of a nationwide donor sample.  相似文献   
6.

Purpose

The objective of this study was to assess the prognostic value of metabolic tumor burden on 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) positron emission tomography (PET)/CT measured with metabolic tumor volume (MTV) and total lesion glycolysis (TLG), independent of Union Internationale Contra la Cancrum (UICC)/American Joint Committee on Cancer (AJCC) tumor, node, and metastasis (TNM) stage, in comparison with that of standardized uptake value (SUV) in nonsurgical patients with non-small cell lung cancer (NSCLC).

Methods

This study retrospectively reviewed 169 consecutive nonsurgical patients (78 men, 91 women, median age of 68?years) with newly diagnosed NSCLC who had pretreatment 18F-FDG PET/CT scans. The 18F-FDG PET/CT scans were performed in accordance with National Cancer Institute guidelines. The MTV of whole-body tumor (MTVWB), of primary tumor (MTVT), of nodal metastases (MTVN), and of distant metastases (MTVM); the TLG of whole-body tumor (TLGWB), of primary tumor (TLGT), of nodal metastases (TLGN), and of distant metastases (TLGM); the SUVmax of whole-body tumor (SUVmaxWB), of primary tumor (SUVmaxT), of nodal metastases (SUVmaxN), and of distant metastases (SUVmaxM) as well as the SUVmean of whole-body tumor (SUVmeanWB), of primary tumor (SUVmeanT), of nodal metastases (SUVmeanN), and of distant metastases (SUVmeanM) were measured with the PETedge tool on a MIMvista workstation with manual adjustment. The median follow-up among survivors was 35?months from the PET/CT (range 2?C82?months). Statistical methods included Kaplan-Meier curves, Cox regression, and C-statistics.

Results

There were a total of 139 deaths during follow-up. Median overall survival (OS) was 10.9?months [95% confidence interval (CI) 9.0?C13.2?months]. The MTV was statistically associated with OS. The hazard ratios (HR) for 1 unit increase of ln(MTVWB), ??(MTVT), ??(MTVN), and ??(MTVM) before/after adjusting for stage were: 1.47/1.43 (p?p?p?p?=?0.007/0.043), respectively. TLG had statistically significant associations with OS with the HRs for 1 unit increase in ln(TLGWB), ??(TLGT), ??(TLGN), and ??(TLGM) before/after adjusting for stage being 1.36/1.33 (p?p?=?0.001/0.002), 1.05/1.04 (p?p?=?0.003/0.024), respectively. The ln(SUVmaxWB) and ??(SUVmaxN) were statistically associated with OS with the corresponding HRs for a 1 unit increase before/after adjusting for stage being 1.46/1.43 (p?=?0.013/0.024) and 1.22/1.16 (p?=?0.002/0.040). The ??(SUVmeanN) was statistically associated with OS before and after adjusting for stage with HRs for a 1 unit increase of 1.32 (p?p?=?0.015), respectively. The ??(SUVmeanM) and ??(SUVmaxM) were statistically associated with OS before adjusting for stage with HRs for a 1 unit increase of 1.26 (p?=?0.017) and 1.18 (p?=?0.007), respectively, but not after adjusting for stage (p?=?0.127 and 0.056). There was no statistically significant association between OS and ??(SUVmaxT), ln(SUVmeanWB), or ??(SUVmeanT). There was low interobserver variability among three radiologists with intraclass correlation coefficients (ICC) greater than 0.94 for SUVmaxWB, ln(MTVWB), and ln(TLGWB). Interobserver variability was higher for SUVmeanWB with an ICC of 0.806.

Conclusion

Baseline metabolic tumor burdens at the level of whole-body tumor, primary tumor, nodal metastasis, and distant metastasis as measured with MTV and TLG on FDG PET are prognostic measures independent of clinical stage with low inter-observer variability and may be used to further stratify nonsurgical patients with NSCLC. This study also suggests MTV and TLG are better prognostic measures than SUVmax and SUVmean. These results will need to be validated in larger cohorts in a prospective study.  相似文献   
7.

Background:

17β-Oestradiol (E2)-induced reactive oxygen species (ROS) have been implicated in regulating the growth of breast cancer cells. However, the underlying mechanism of this is not clear. Here we show how ROS through a novel redox signalling pathway involving nuclear respiratory factor-1 (NRF-1) and p27 contribute to E2-induced growth of MCF-7 breast cancer cells.

Methods:

Chromatin immunoprecipitation, qPCR, mass spectrometry, redox western blot, colony formation, cell proliferation, ROS assay, and immunofluorescence microscopy were used to study the role of NRF-1.

Results:

The major novel finding of this study is the demonstration of oxidative modification of phosphatases PTEN and CDC25A by E2-generated ROS along with the subsequent activation of AKT and ERK pathways that culminated in the activation of NRF-1 leading to the upregulation of cell cycle genes. 17β-Oestradiol-induced ROS by influencing nuclear proteins p27 and Jab1 also contributed to the growth of MCF-7 cells.

Conclusions:

Taken together, our results present evidence in the support of E2-induced ROS-mediated AKT signalling leading to the activation of NRF-1-regulated cell cycle genes as well as the impairment of p27 activity, which is presumably necessary for the growth of MCF-7 cells. These observations are important because they provide a new paradigm by which oestrogen may contribute to the growth of breast cancer.  相似文献   
8.
Human subjects ingested daily 5- to 20-mg doses of technical DDT, p,p′-DDE, or p,p′-DDD for 81 to 183 days. Serum and adipose concentrations of DDT and DDT metabolites in response to these dosings have indicated that the initial dechlorination of DDT is of critical importance to its metabolic fate. Conversion to the saturated p,p′-DDD makes possible further degradation to the readily excreted p,p′-DDA. Dehydrochlorination, on the other hand, yields p,p′-DDE, a stable metabolite that is avidly retained in adipose storage. In two subjects ingesting technical DDT, conversion to DDE has been extremely limited, while conversion to DDD has been regularly demonstrable during and after dosing. Tissue stores of p,p′-DDE in general population probably originate mainly from preformed dietary p,p′-DDE in the diet, rather than from p,p′-DDT.  相似文献   
9.
10.
Objective: Globally, depression is one of the most prevalent and burdensome conditions in older adults. However, there are few population-based studies of depression in older adults in developing countries. In this paper, we examine the prevalence of depressive symptoms and explore possible contributory risk factors in older adults living in Nepal.

Methods: A cross-sectional study was conducted in two semi-urban communities in Kathmandu, Nepal. Depression was assessed using the 15-item Geriatric Depression Scale in 303 participants, aged 60 years and over. Multivariate logistic regression was then used to assess associations between potential risk factors and depression.

Results: More than half of the participants (n = 175, 60.6%) had significant depressive symptomatology, with 27.7% having scores suggesting mild depression. Illiteracy (aOR = 2.01, 95% CI: 1.08–3.75), physical immobility (aOR = 5.62, 95% CI: 1.76–17.99), the presence of physical health problems (aOR = 1.97, 95% CI: 1.03–3.77), not having any time spent with family members (aOR = 3.55, 95% CI: 1.29–9.76) and not being considered in family decision-making (aOR = 4.02, 95% CI: 2.01–8.04) were significantly associated with depression in older adults.

Conclusion: The prevalence of depression was significant in older adults. There are clear associations of depression with demographic, social support and physical well-being factors in this population. Strategies that increase awareness in the community along with the health and social care interventions are needed to address the likely drivers of depression in older adults.  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