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   9159篇
  免费   1089篇
  国内免费   282篇
耳鼻咽喉   52篇
儿科学   142篇
妇产科学   95篇
基础医学   666篇
口腔科学   254篇
临床医学   723篇
内科学   1026篇
皮肤病学   96篇
神经病学   475篇
特种医学   220篇
外国民族医学   1篇
外科学   519篇
综合类   1391篇
预防医学   3086篇
眼科学   168篇
药学   871篇
  3篇
中国医学   262篇
肿瘤学   480篇
  2024年   41篇
  2023年   172篇
  2022年   374篇
  2021年   410篇
  2020年   405篇
  2019年   336篇
  2018年   332篇
  2017年   349篇
  2016年   393篇
  2015年   337篇
  2014年   548篇
  2013年   659篇
  2012年   514篇
  2011年   553篇
  2010年   414篇
  2009年   421篇
  2008年   429篇
  2007年   453篇
  2006年   394篇
  2005年   328篇
  2004年   340篇
  2003年   249篇
  2002年   233篇
  2001年   209篇
  2000年   167篇
  1999年   176篇
  1998年   156篇
  1997年   120篇
  1996年   105篇
  1995年   92篇
  1994年   92篇
  1993年   88篇
  1992年   117篇
  1991年   84篇
  1990年   80篇
  1989年   65篇
  1988年   65篇
  1987年   34篇
  1986年   34篇
  1985年   41篇
  1984年   19篇
  1983年   19篇
  1982年   22篇
  1981年   9篇
  1980年   12篇
  1979年   9篇
  1978年   8篇
  1977年   8篇
  1976年   4篇
  1973年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
职业紧张与冠心病的病例对照研究   总被引:12,自引:0,他引:12  
目的 :(1)探讨男性列车乘务人员职业紧张与冠心病发病的关系。方法 :应用职业紧张因素测试量表 (OSI) ,对男性列车乘务人员中 3 9例冠心病患者进行 1:2的配比病例对照研究并进行多因素条件Logistic回归分析。结果 :(1)在控制和考虑了非职业紧张因素条件下 ,职业紧张与冠心病关系密切 (OR =2 18,95 %CI :1 15 -4 15 ) ,而且随着职业紧张程度的增加 ,患冠心病的危险性显著增加 ;(2 )以铁路乘务人员为对照时 (与病例同工种 ) ,职业紧张仍与冠心病发病有关联 (OR =4 43 ,95 %CI :1 60 -12 2 5 ) ,但其OR值明显低于以其他服务行业人员为对照时的OR值 (OR =9 75 ,95 %CI:3 18-2 9 92 )。结论 :职业紧张是引起男性列车乘务人员冠心病发病的重要危险因素之一。  相似文献   
62.
PROBLEM: We have recently observed that the regression of corpora lutea (CL) in women during the reproductive period of life is accompanied by a diminution of Thy-1 differentiation protein release from vascular pericytes and an accumulation of T lymphocytes and activated macrophages among both degenerating granulosa lutein cells (GLC) and theca lutein cells. These data suggest that the immune system and other stromal factors, representing components of the “tissue control system,” may play a role in regression of the CL. We investigated degenerating CL from climacteric women to address the possibility that the decline of immune functions with advancing age may result in incomplete regression of luteal tissue. This could contribute to the altered hormonal profiles and abnormal uterine bleeding that frequently occur during the climacteric. METHOD: Immunoperoxidase staining and image analysis were used to localize Thy-1 differentiation protein of vascular pericytes, cytokeratin staining of GLC, neural cell adhesion molecule expression by theca lutein cells, CD15 of neutrophils, CD4, CD14, CD68, and leukocyte common antigens of macrophages, and CD3 and CD8 determinants of T lymphocytes. We also investigated the expression of luteinizing hormone receptor (LH receptor) and mitogen activated protein kinases (MAP kinases) in luteal cells. Samples of regressing luteal tissue were obtained during the follicular phase from perimenopausal women (age 45–50) who exhibited prolonged or irregular cycles. For comparison, luteal tissues from women with regular cycles (age 29–45) and CL of pregnancy were also investigated. RESULTS: Corpora lutea of the climacteric women exhibited irregular regression of luteal tissue characterized by a lack of cytoplasmic vacuolization and nuclear pyknosis in GLC, and by a persistence of theca lutein cells exhibiting hyperplasia and adjacent theca externa layers. This was accompanied by a continuing release of Thy-1 differentiation protein from vascular pericytes. Persisting GLC lacked surface expression of macrophage markers (CD4, CD14, CD68 and leukocyte common antigen) as well as nuclear granules exhibiting CD15 of neutrophils, detected in regularly regressing GLC. In addition, such persisting GLC showed weak or no LH receptor expression, and retained the expression of cytokeratin. They also exhibited enhanced staining for MAP kinases. Strong cytoplasmic MAP kinase expression with occasional nuclear translocation was also detected in persisting theca lutein cells, indicating high metabolic activity of these cells. T lymphocytes, although occasionally present in luteal stroma within luteal convolutions, did not invade among persisting GLC and were virtually absent from layers of theca externa and theca lutein cells. CONCLUSIONS: These data indicate that the regressing CL in climacteric women may exhibit persistence of luteal cells, perhaps because of age-induced alterations of the immune system and other local stromal homeostatic mechanisms involved in the elimination of luteal cells. Persisting GLC and/or theca lutein cells may exhibit abnormal hormonal secretion that contributes to the alteration of target tissues, such as the endometrium, resulting in abnormal uterine bleeding, hyperplasia, and neoplasia.  相似文献   
63.
生物学行为是影响胃癌预后的重要因素而核面积是影响因素中最重要一个。本文按生长方式对胃癌作了新的病理生物学分型的尝试,把胃癌分作膨胀型和浸润型,每型又依核面积大小分为大核型和小核型。结果表明,本文的分型较其他分型更能体现肿瘤的生物学特性,值得提倡。  相似文献   
64.
企业员工应对方式与心理健康之间的关系   总被引:3,自引:2,他引:3  
目的:验证不同应对方式对心理健康的单独与共同影响。方法:对4745名被试用分层回归的方法分析不同应对方式对心理健康的单独影响和交互作用。结论:单独使用“消极应对”的应对方式,对心理健康水平存在不利影响;而单独使用“积极应对”的应对方式能在一定程度上改善心理健康水平。“消极应对”与“积极应对”两种应对方式结合使用能显著改善心理健康水平,比单独使用这两种应对方式对心理健康更有利。  相似文献   
65.

Background

Myositis is a heterogeneous group of muscular auto-immune diseases with clinical and pathological criteria that allow the classification of patients into different sub-groups. Inclusion body myositis is the most frequent myositis above fifty years of age. Diagnosing inclusion body myositis requires expertise and is challenging. Little is known concerning the pathogenic mechanisms of this disease in which conventional suppressive-immune therapies are inefficacious.

Objectives

Our aim was to deepen our understanding of the immune mechanisms involved in inclusion body myositis and identify specific biomarkers.

Methods

Using a panel of thirty-six markers and mass cytometry, we performed deep immune profiling of peripheral blood cells from inclusion body myositis patients and healthy donors, divided into two cohorts: test and validation cohorts. Potential biomarkers were compared to myositis controls (anti-Jo1-, anti-3-hydroxyl-3-methylglutaryl CoA reductase-, and anti-signal recognition particle-positive patients).

Results

Unsupervised analyses revealed substantial changes only within CD8+ cells. We observed an increase in the frequency of CD8+ cells that expressed high levels of T-bet, and containing mainly both effector and terminally differentiated memory cells. The senescent marker CD57 was overexpressed in CD8+T-bet+ cells of inclusion body myositis patients. As expected, senescent CD8+T-bet+ CD57+ cells of both patients and healthy donors were CD28nullCD27nullCD127null. Surprisingly, non-senescent CD8+T-bet+ CD57- cells in inclusion body myositis patients expressed lower levels of CD28, CD27, and CD127, and expressed higher levels of CD38 and HLA-DR compared to healthy donors. Using classification and regression trees alongside receiver operating characteristics curves, we identified and validated a frequency of CD8+T-bet+ cells >51.5% as a diagnostic biomarker specific to inclusion body myositis, compared to myositis control patients, with a sensitivity of 94.4%, a specificity of 88.5%, and an area under the curve of 0.97.

Conclusion

Using a panel of thirty-six markers by mass cytometry, we identify an activated cell population (CD8+T-bet+ CD57- CD28lowCD27lowCD127low CD38+ HLA-DR+) which could play a role in the physiopathology of inclusion body myositis, and identify CD8+T-bet+ cells as a predominant biomarker of this disease.  相似文献   
66.
 To improve our understanding of the role of extracellular matrix (ECM) proteins and integrins during the processes of granuloma formation in sarcoidosis, we examined the distribution of ECM proteins and the expression of integrins in sarcoid lymph nodes by immunohistochemical methods. We also examined the expression of transforming growth factor-β1 (TGF-β1), which is one of major regulators for synthesis of ECM proteins. Most ECM proteins were detected in the periphery of the granulomas in a concentric pattern, and fibronectin was diffusely detected from an early to a regressive stage. Compared with normal lymph nodes, most β1-integrin subfamilies (α1, α4, α5 and α6) were more strongly expressed on lymphocytes around the granulomas. Epithelioid cells exhibited strong expression of the α5 molecule. Fibroblasts exhibited the expression of the α2 and α5 molecules surrounding ECM proteins. The α5β1 molecule had a distribution similar to that of fibronectin. TGF-β1 was detected in epithelioid cells throughout the various evolutional stages and its expression was especially marked in mature granulomas. Interaction of fibronectin and the α5β1 molecule may have an important role in the process of formation of sarcoid granuloma. The expression of TGF-β1 may be involved in the regression of sarcoid granuloma by initiating fibrosis and atrophy of epithelioid cells. Received: 2 December 1997 / Accepted: 19 February 1998  相似文献   
67.
利用脉搏波特征参数连续测量血压的方法研究   总被引:11,自引:0,他引:11  
通过研究血压与脉搏波特征参数的关系,提出了一个选择多个与血压相关的脉搏波特征参数,通过回归分析建立适合不同人的特征方程,进行血压的连续测量的新方法,为了验证测量结果的准确性;研制了张力计。实验结果表明:该方法具有较高的测量精度,可以应用于临床危重病人的血压监护和一般医学研究中,经过进一步地改进和完善后可应用于载人航天和日常动态环境。  相似文献   
68.
BACKGROUND: Asthma is becoming increasingly prevalent and a number of research groups are investigating its genetic and environmental basis. OBJECTIVE: To produce a brief screening tool suitable for determining phenotype in asthma research. METHODS: The scores from eight questions on symptoms and history were obtained from 678 adults and 244 children from high asthma-incidence caucasian families. An independent physician diagnosis was also obtained with the use of a modified NHLBI-CSGA questionnaire and pulmonary function test. Stepwise logistic regression was applied to determine which of the eight questions had greatest predictive value for asthma, and the quality of the resultant models was evaluated using an independent set of 643 adults and 239 children. RESULTS: For adults, the most parsimonious model used responses from three of the eight questions. It had sensitivity and specificity of 0.94 and 0.96, respectively. For children, responses to two questions gave a model with sensitivity and specificity of 0.97. For both age groups, negative predictive values were above 0.87. Positive predictive values were 0.58 and 0.78 for adults and children respectively. The latter emphasize the need for conformation, by physician, of "affected" calls made by this initial screen. CONCLUSION: The brief questionnaires described are potentially useful in a research setting, as a preliminary screening mechanism of low cost. Their use will reduce the numbers of subjects that must undergo detailed phenotyping.  相似文献   
69.
对1980.9~1982.8江苏省6个城市172例围产儿羊水吸入性肺炎临床病理多因素回归分析研究,以探讨其发病机制。目的是筛选能影响肺炎和羊水吸入的临床参数。结果:(1)男婴占52.91%,女婴47.09%。(2)组织学:肺的炎症和羊水大多数是混合性、弥漫性分布,病变较一致,纤维素渗出很少,这说明本病可能是在出生前或分娩过程中吸入感染的羊水所致。(3)影响本病发生的主要因素为剖腹产、胎吸术、羊水吸入以及胎龄。(4)影响羊水吸入性的因素为胎儿体重(4000g以上)和胎龄(42周以上)。而体重、胎龄和胎吸术又和产程延长有关。  相似文献   
70.
健康婴幼儿早期教育的效果及影响因素   总被引:1,自引:1,他引:1  
目的:探讨健康足月婴幼儿早期教育(简称早教)的效果及其影响因素,为开展健康足月婴幼儿早教工作提供理论和实践依据.方法:以自愿来早教中心进行早教的健康足月婴幼儿52名为实验组.另选择与其基本条件相同的婴幼儿52名为对照组.实验组除进行早教的各项培训工作外,还于培训前和培训3、6、9个月后各测评发育商(DQ)1次,以评定早教的效果.对照组无早教,于入组时和9个月后各测评DQ 1次.结果:①实验组经培训9个月后,其DQ平均值提高21.9±13.6分,高于对照组观察9个月后DQ平均值提高分3.0±3.0,差异有统计学意义(t=9.757,P<0.001).②实验组培训前DQ值有23例低于中等水平;培训后有27例高于中等水平,其中8例DQ≥130.③多元逐步回归分析结果表明,影响DQ增加的主要因素是完成家庭训练作业的程度(R2=0.57),其次是到早教中心训练的次数(R2=0.019),再次是性别(R2=0.016).结论:早教对健康足月婴幼儿的大脑发育、智能发展、运动发育具有显著效果,是提高婴幼儿DQ的有效措施.  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