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   812篇
  免费   127篇
  国内免费   46篇
耳鼻咽喉   5篇
儿科学   26篇
妇产科学   9篇
基础医学   136篇
口腔科学   16篇
临床医学   119篇
内科学   184篇
皮肤病学   18篇
神经病学   39篇
特种医学   169篇
外科学   86篇
综合类   20篇
预防医学   63篇
眼科学   3篇
药学   58篇
肿瘤学   34篇
  2021年   8篇
  2020年   4篇
  2019年   5篇
  2016年   9篇
  2015年   18篇
  2014年   13篇
  2013年   17篇
  2012年   22篇
  2011年   24篇
  2010年   11篇
  2009年   15篇
  2008年   25篇
  2007年   52篇
  2006年   14篇
  2005年   28篇
  2004年   17篇
  2003年   22篇
  2002年   18篇
  2001年   19篇
  2000年   17篇
  1999年   30篇
  1998年   34篇
  1997年   40篇
  1996年   36篇
  1995年   33篇
  1994年   24篇
  1993年   27篇
  1992年   30篇
  1991年   23篇
  1990年   19篇
  1989年   29篇
  1988年   35篇
  1987年   20篇
  1986年   25篇
  1985年   29篇
  1984年   12篇
  1983年   22篇
  1982年   12篇
  1981年   10篇
  1980年   13篇
  1979年   9篇
  1978年   13篇
  1977年   20篇
  1976年   14篇
  1975年   10篇
  1974年   9篇
  1972年   4篇
  1971年   6篇
  1969年   4篇
  1967年   3篇
排序方式: 共有985条查询结果,搜索用时 15 毫秒
21.
Acute kidney injury (AKI) is a major risk factor for the development of chronic kidney disease (CKD). Persistent oxidative stress and mitochondrial dysfunction are implicated across diverse forms of AKI and in the transition to CKD. In this study, we applied hyperpolarized (HP) 13C dehydroascorbate (DHA) and 13C pyruvate magnetic resonance spectroscopy (MRS) to investigate the renal redox capacity and mitochondrial pyruvate dehydrogenase (PDH) activity, respectively, in a murine model of AKI at baseline and 7 days after unilateral ischemia reperfusion injury (IRI). Compared with the contralateral sham‐operated kidneys, the kidneys subjected to IRI showed a significant decrease in the HP 13C vitamin C/(vitamin C + DHA) ratio, consistent with a decrease in redox capacity. The kidneys subjected to IRI also showed a significant decrease in the HP 13C bicarbonate/pyruvate ratio, consistent with impaired PDH activity. The IRI kidneys showed a significantly higher HP 13C lactate/pyruvate ratio at day 7 compared with baseline, although the 13C lactate/pyruvate ratio was not significantly different between the IRI and contralateral sham‐operated kidneys at day 7. Arterial spin labeling magnetic resonance imaging (MRI) demonstrated significantly reduced perfusion in the IRI kidneys. Renal tissue analysis showed corresponding increased reactive oxygen species (ROS) and reduced PDH activity in the IRI kidneys. Our results show the feasibility of HP 13C MRS for the non‐invasive assessment of oxidative stress and mitochondrial PDH activity following renal IRI.  相似文献   
22.
23.
Treacher Collins Syndrome (TCS) is the most common of the human mandibulofacial dysostosis disorders. Recently, a partial TCOF1 cDNA was identified and shown to contain mutations in TCS families. Here we present the entire exon/intron genomic structure and the complete coding sequence of TCOF1. TCOF1 encodes a low complexity protein of 1,411 amino acids, whose predicted protein structure reveals repeated motifs that mirror the organization of its exons. These motifs are shared with nucleolar trafficking proteins in other species and are predicted to be highly phosphorylated by casein kinase. Consistent with this, the full-length TCOF1 protein sequence also contains putative nuclear and nucleolar localization signals. Throughout the open reading frame, we detected an additional eight mutations in TCS families and several polymorphisms. We postulate that TCS results from defects in a nucleolar trafficking protein that is critically required during human craniofacial development.  相似文献   
24.
Purified CD34+ Lin- Thy+ stem cells do not contain clonal myeloma cells   总被引:6,自引:0,他引:6  
High-dose therapy with autologous marrow or peripheral blood stem cell (PBSC) rescue has been extensively applied in the treatment of multiple myeloma (MM) patients during the past 10 years resulting in improved event-free and overall survival when compared with standard chemotherapy. However, relapses are common and cure is unlikely in the majority of patients. Because both bone marrow and PBSCs are contaminated with myeloma cells it is conceivable that relapse after autotransplantation originates at least in part from autografted tumor cells. In this study, mobilized PBSCs were examined for the presence of myeloma cells based on immunophenotyping and sensitive polymerase chain reaction (PCR)-based techniques. In addition, CD34+ Lin- Thy+ stem cells were purified from mobilized PBSC harvests of 10 MM patients by sequentially using counterflow elutriation centrifugation, treatment with phenylalanine methylester, and flow sorting, using 5-parameter gating (propidium iodide, forward scatter, side scatter, CD34+ v Lin- and CD34+ v Thy+). Virtually all mobilized unsorted PBSC preparations contained myeloma cells in sufficient quantities (range, < 0.01 to > 10%) potentially causing a disease relapse. Stem cell purification led to an overall enrichment by about 50-fold in all 10 patients; approximately 90% of the final cell population expressed CD34+ Lin- Thy+ with no evidence of myeloma cell contamination based on flow cytometric analysis of CD38bright cells (< 0.1%). Quantitative PCR amplification of patient-specific complementarity determining region III (CDRIII) DNA sequences showed depletion of clonal B cells by 2.7 to 7.3 logs, with the highest log reduction noted in the samples initially containing the most tumor cells. Our results show that purification of CD34+ Lin- Thy+ cells depletes myeloma cells to undetectable levels from up to 10% present in unsorted PBSCs, thus offering a tool to investigate whether MM relapse after autotransplantation can be reduced markedly.  相似文献   
25.
[Purpose] The purpose of this study was to investigate the use of smartphones by university students in selected areas, their musculoskeletal symptoms, and the associated hazard ratio. [Subjects and Methods] This involved the completion of a self-administered questionnaire by dental hygiene students in Seoul, Gyeonggido, and Gyeongsangbukdo. The 292 completed copies of the questionnaire were then analyzed. [Results] The most painful body regions after the use of smartphones were found to be the shoulders and neck. In the musculoskeletal system, back pain was found to have a positive correlation with the size of the smartphone’s liquid crystal display (LCD) screen, and pain in legs and feet were found to have a negative correlation with the length of time that the smartphone was used. As a result, it was revealed that the use of a smartphone was correlated with musculoskeletal symptoms. [Conclusion] Therefore, in today’s environment, where the use of smartphones is on the rise, it is necessary to improve the ways that they are used and to develop a preventive program to alleviate the symptoms of musculoskeletal damage.Key words: Smartphone, Musculoskeletal symptoms, Prevent  相似文献   
26.
27.
28.

Introduction

Fine needle aspiration (FNA) is a safe and quick method of diagnosing superficial lumps, which aids preoperative planning. However, FNA of the parotid gland has not gained the widespread acceptance noted in other head and neck lumps. The aim of this study was to determine the ability of FNA of the parotid gland to differentiate benign and malignant disease, and to determine the impact on surgical outcome.

Methods

A retrospective analysis of 201 consecutive parotid operations with preoperative FNA in a large district hospital in the UK was performed. The diagnostic characteristics were calculated for benign and malignant disease, and the impact on surgical procedure was determined.

Results

In identifying benign disease, FNA has a sensitivity of 85% and a specificity of 76%. In detecting malignant disease, FNA has a sensitivity and specificity of 52% and 92% respectively. A false positive on FNA was associated with a higher incidence of neck dissection.

Conclusions

FNA is a useful diagnostic test. However, owing to low sensitivity, it is necessary to interpret it in the context of all other clinical information.  相似文献   
29.
Background: Visual alcohol cues are often used to elicit craving (e.g., cue-reactivity), and selection of appropriate comparison cues is important to isolate the specific effect of craving for alcohol. Objectives: In the current study, via the development of a new set of non-alcoholic beverage cues, we examine measurement and methodological choices in testing alcohol images for cue-reactivity studies. Methods: The current project combined two independent studies of hazardous (Study 1; n = 80) and recent drinkers (Study 2; n = 244) recruited from Amazon Mechanical Turk. Participants viewed either alcohol cues (Lovett, Ham, &; Veilleux, 2015 Lovett, D. E., Ham, L. S., &; Veilleux, J. C. (2015). Psychometric evaluation of a standardized set of alcohol cue photographs to assess craving. Addictive Behaviors, 48, 5861. doi: 10.1016/j.addbeh.2015.05.002[Crossref], [PubMed], [Web of Science ®] [Google Scholar]) or newly developed non-alcoholic beverage cues. We also randomly assigned people to rate the cues regarding motivational (e.g., affect, craving for alcohol, resistance to alcohol) responses or non-motivational features (e.g., artistry). Results: In Study 1, we included presentation of non-beverage objects, and found that beverages were rated as more positive, less negative and with higher craving than non-beverage objects. In the combined sample, we found that the alcohol beverage cues were associated with greater craving than non-alcoholic beverage cues, and that there were no differences between cue types on either positive or negative affect. We also found an interaction between drinking experience and cue type in predicting resistance to drinking. Conclusions: We conclude that the choice of control cues in alcohol cue-reactivity studies is important, and that the currently developed non-alcoholic beverage cue set provides an adequate control for alcohol beverage cues for use in cue-reactivity paradigms.  相似文献   
30.

Background

Men having sex with men (MSM) remain the largest high-risk group involved in on-going transmission of sexually transmitted infections (STI), including HIV, in the Netherlands. As risk behaviour may change with age, it is important to explore potential heterogeneity in risks by age. To improve our understanding of this epidemic, we analysed the prevalence of and risk factors for selected STI in MSM attending STI clinics in the Netherlands by age group.

Methods

Analysis of data from the national STI surveillance system for the period 2006–2012. Selected STI were chlamydia, gonorrhoea, infectious syphilis and/or a new HIV infection. Logistic regression was used to identify factors associated with these selected STI and with overall STI positivity. Analyses were done separately for MSM aged younger than 25 years and MSM aged 25 years and older.

Results

In young MSM a significant increase in positivity rate was seen over time (p?<?0.01), mainly driven by increasing gonorrhoea diagnoses, while in MSM aged 25 and older a significant decrease was observed (p?<?0.01). In multivariate analyses for young MSM, those who were involved in commercial sex were at higher risk (OR: 1.5, 95% CI: 1.2-1.9). For MSM aged 25 years and older this was not the case. Having a previous negative HIV test was protective among older MSM compared to those not tested for HIV before (OR: 0.8, 95% CI: 0.8-0.8), but not among younger MSM.

Conclusions

MSM visiting STI clinics remain a high-risk group for STI infections and transmission, but are not a homogenous group. While in MSM aged older than 25 years, STI positivity rate is decreasing, positivity rate in young MSM increased over time. Therefore specific attention needs to be paid towards targeted counselling and reaching particular MSM sub-groups, taken into account different behavioural profiles.
  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