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   2546篇
  免费   302篇
  国内免费   62篇
  2024年   8篇
  2023年   91篇
  2022年   116篇
  2021年   185篇
  2020年   141篇
  2019年   227篇
  2018年   171篇
  2017年   102篇
  2016年   95篇
  2015年   103篇
  2014年   177篇
  2013年   263篇
  2012年   126篇
  2011年   141篇
  2010年   87篇
  2009年   83篇
  2008年   88篇
  2007年   85篇
  2006年   83篇
  2005年   53篇
  2004年   60篇
  2003年   61篇
  2002年   39篇
  2001年   41篇
  2000年   29篇
  1999年   20篇
  1998年   23篇
  1997年   20篇
  1996年   27篇
  1995年   22篇
  1994年   22篇
  1993年   11篇
  1992年   14篇
  1991年   8篇
  1990年   9篇
  1989年   12篇
  1988年   7篇
  1987年   9篇
  1986年   5篇
  1985年   6篇
  1984年   9篇
  1983年   5篇
  1982年   2篇
  1981年   5篇
  1980年   7篇
  1979年   2篇
  1978年   6篇
  1977年   1篇
  1976年   2篇
  1974年   1篇
排序方式: 共有2910条查询结果,搜索用时 500 毫秒
991.
Context: Acute kidney injury (AKI) could lead to progressive chronic kidney disease (CKD). Objectives: To demonstrate that urinary markers in AKI are associated with the degree of persistent renal injury. Material and methods: Human L-FABP chromosomal transgenic (Tg) mice were subjected to ischemia-reperfusion (I/R) clamping renal pedicle for 20?min or 30?min. Kidneys were obtained at one and 40 days after I/R. Results: Urinary L-FABP, NGAL, Kim-1 and albumin levels increased during the acute phase and were significantly correlated with the degree of tubulointerstitial fibrosis during the chronic phase. Discussion and conclusion: These markers could detect higher risk of progression to CKD.  相似文献   
992.
目的:探讨不同性别腰椎间盘突出症(Lumbar disc herniation,LDH)患者脊柱-骨盆矢状位参数差异特点。方法:回顾性分析2014年1月至2016年3月在第四军医大学西京医院脊柱外科因LDH住院手术治疗,且具有术前脊柱站立位全长X线片的患者共222例,其中男l25例,女97例,年龄20-80岁,平均年龄50.97岁;应用图形分析软件Surgimap进行参数测量,在站立位全长脊柱侧位x线片上测量参数包括:骨盆投射角(Pelvic incidence,PI)、骨盆倾斜角(Pelvic tilt,PT)和骶骨倾斜角(Sacral slope,SS),胸椎后凸角(Thoracic Kyphosis,TK)、腰椎前凸角(Lumbarlordosis,LL)、矢状面垂直轴(Sagittal vertical axis,SVA)。根据性别分组,比较不同性别之间各参数、发病累及节段、不同年龄段发病率之间的差异。应用SPSS 19.0对数据进行统计分析。结果:LDH患者男女性别之间比较发现,男性PI 43.82±8.66°,女性PI 47.75±8.50°,P=0.001(P0.05),具有统计学显著性差异,年龄、PT、SS、LL、TK、SVA无显著性差异;不同性别LDH患者所累及节段分别进行统计,P=0.480(P0.05),无统计学显著性差异;不同性别LDH患者不同年龄段的发病率进行统计,应用Pearson卡方检验进行统计分析,P=0.024(P0.05),具有统计学显著性差异。然后将各年龄段发病率通过u检验进行比较,20-40岁段P=0.023(P0.05),具有统计学显著性差异。结论:PI也可能与LDH的发病有关,男性患者PI小于女性患者,可能是在LDH发病中男性多于女性,且男性更早发病的一个重要原因。  相似文献   
993.
目的:探讨动态仿真直肠排粪造影在诊断盆底痉挛综合征中的应用价值。方法:回顾性选择2014年7月至2016年3月在我院确诊的38例盆底痉挛综合征患者为研究对象,随机分为研究组和对照组,采用全功能数字胃肠机测量患者静息状态下和力排状态下的肛直角,并计算肛直角差。采用t检验进行分析。结果:研究组患者9例合并直肠前突和粘膜脱垂,3例合并直肠前突和内脏下垂,1例合并直肠前突和结肠疝,对照组患者4例合并直肠前突和粘膜脱垂,1例合并直肠前突和内脏下垂,1例合并直肠前突和结肠疝,两组患者的合并症检出率比较,差异有统计学意义(P0.05)。研究组患者的静息状态下肛直角(103.46±8.15)和力排状态下肛直角(93.12±7.51)明显低于对照组(117.62±11.37)、(135.14±12.13),且研究组的肛直角差(10.34±7.25)明显低于对照组(17.52±9.14),差异有统计学意义(P0.01)。结论:动态仿真直肠排粪造影动态观察盆底形态的变化,可为盆底痉挛综合征诊断提供可靠依据。  相似文献   
994.
慢性疼痛是临床常见的病症,给患者和社会都带来极大的负担。其发病机制受生理、心理和社会等多种因素的影响较为复杂,因此,慢性疼痛的治疗一直是临床上的一大难题。单一的治疗手段往往不能取得令人满意的效果,目前常采用多手段联合的方式来治疗慢性疼痛,常见的包括药物治疗、心理治疗、介入治疗以及自我管理等。针对不同类型的慢性疼痛甚至同一类型的不同病人其治疗方案也不尽相同,近年来兴起的跨学科康复计划为慢性疼痛的治疗指明了方向。本文就慢性疼痛治疗的研究进展进行了综述,以期为临床实践提供更多参考和理论依据。  相似文献   
995.
目的:比较自然分娩和剖宫产产妇术后发生腰背痛的情况差异及其相关影响因素。方法:选择2014年10月~2016年10月于我院就诊的400例产妇。按照分娩方式的不同分为自然分娩组和剖宫产组,每组各200例。比较两组产妇产后2、3、4个月腰背痛的发生率及疼痛(VAS)评分,并通过logistic回归分析探讨发生产后腰背痛的影响因素。结果:剖宫产组术后2、3、4个月产妇腰背痛的发生率均明显高于自然分娩组(P0.05);术后2个月,两组产妇腰背痛的VAS评分接近,术后3、4月剖宫产组产妇的VAS评分均显著高于自然分娩组(P0.05);生育超过3次、腰背痛史、剖宫产与产后腰背痛的发生密切相关(P0.05)。结论:剖宫产后腰背痛的发病率显著高于采取自然分娩方式的产妇,既往腰背痛史、分娩方式、生育次数、胎儿体重均与是产后腰背痛相关影响因素。  相似文献   
996.
Prion diseases are transmissible spongiform encephalopathies (TSEs) characterized by fatal, progressive neurologic diseases with prolonged incubation periods and an accumulation of infectious misfolded prion proteins. Antemortem diagnosis is often difficult due to a long asymptomatic incubation period, differences in the pathogenesis of different prions, and the presence of very low levels of infectious prion in easily accessible samples. Chronic wasting disease (CWD) is a TSE affecting both wild and captive populations of cervids, including mule deer, white-tailed deer, elk, moose, muntjac, and most recently, wild reindeer. This study represents a well-controlled evaluation of a newly developed real-time quaking-induced conversion (RT-QuIC) assay as a potential CWD diagnostic screening test using rectal biopsy sections from a depopulated elk herd. We evaluated 69 blinded samples of recto-anal mucosa-associated lymphoid tissue (RAMALT) obtained from USDA Veterinary Services. The results were later un-blinded and statistically compared to immunohistochemical (IHC) results from the USDA National Veterinary Services Laboratories (NVSL) for RAMALT, obex, and medial retropharyngeal lymph node (MRPLN). Comparison of RAMALT RT-QuIC assay results with the IHC results of RAMALT revealed 92% relative sensitivity (95% confidence limits: 61.52–99.8%) and 95% relative specificity (95% confidence limits: 85.13–99%). Collectively, our results show a potential utility of the RT-QuIC assay to advance the development of a rapid, sensitive, and specific prion diagnostic assay for CWD prions.  相似文献   
997.
Chronic wasting disease (CWD) is a prion disease found in deer, elk and moose in North America and since recently, wild reindeer in Norway. Caribou are at-risk to encounter CWD in areas such as Alberta, Canada, where the disease spreads toward caribou habitats. CWD susceptibility is modulated by species-specific polymorphisms in the prion protein gene (Prnp). We sequenced Prnp of woodland caribou from 9 Albertan populations. In one population (Chinchaga) a significantly higher frequency of the 138N allele linked to reduced CWD susceptibility was observed. These data are relevant for developing CWD management strategies including conservation of threatened caribou populations.  相似文献   
998.
In chronic inflammatory airway diseases, mucins display disease-related alterations in quantity, composition and glycosylation. This opens the possibility to diagnose and monitor inflammatory airway disorders and their exacerbation based on mucin properties. For such an approach to be reasonably versatile and diagnostically meaningful, the mucin of interest must be captured in a reliable, patient-independent way. To identify appropriate mucin-specific reagents, we tested anti-mucin antibodies on mucin-content-standardized, human bronchoalveolar lavage fluid samples in immunoblot assays. All commercially available monoclonal antibodies against the major airway mucin MUC5AC were screened, except for those with known specificity for carbohydrates, as glycosylation patterns are not mucin-specific. Our results indicated considerable inter-patient and inter-antibody variability in mucin recognition for all antibodies and samples tested. The best results in terms of signal strength and reproducibility were obtained with antibodies Mg-31, O.N.457 and 45M1. Additional epitope mapping experiments revealed that only one of the antibodies with superior binding to MUC5AC recognized linear peptide epitopes on the protein backbone.  相似文献   
999.
Several studies on birds have proposed that a lack of invertebrate prey in urbanized areas could be the main cause for generally lower levels of breeding success compared to rural habitats. Previous work on house sparrows Passer domesticus found that supplemental feeding in urbanized areas increased breeding success but did not contribute to population growth. Here, we hypothesize that supplementary feeding allows house sparrows to achieve higher breeding success but at the cost of lower nestling quality. As abundant food supplies may permit both high‐ and low‐quality nestlings to survive, we also predict that within‐brood variation in proxies of nestling quality would be larger for supplemental food broods than for unfed broods. As proxies of nestling quality, we considered feather corticosterone (CORTf), body condition (scaled mass index, SMI), and tarsus‐based fluctuating asymmetry (FA). Our hypothesis was only partially supported as we did not find an overall effect of food supplementation on FA or SMI. Rather, food supplementation affected nestling phenotype only early in the breeding season in terms of elevated CORTf levels and a tendency for more variable within‐brood CORTf and FA. Early food supplemented nests therefore seemed to include at least some nestlings that faced increased stressors during development, possibly due to harsher environmental (e.g., related to food and temperature) conditions early in the breeding season that would increase sibling competition, especially in larger broods. The fact that CORTf was positively, rather than inversely, related to nestling SMI further suggests that factors influencing CORTf and SMI are likely operating over different periods or, alternatively, that nestlings in good nutritional condition also invest in high‐quality feathers.  相似文献   
1000.
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