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   821篇
  免费   48篇
  国内免费   22篇
耳鼻咽喉   4篇
儿科学   64篇
妇产科学   7篇
基础医学   107篇
口腔科学   17篇
临床医学   117篇
内科学   137篇
皮肤病学   19篇
神经病学   31篇
特种医学   116篇
外科学   45篇
综合类   15篇
预防医学   127篇
眼科学   1篇
药学   49篇
肿瘤学   35篇
  2023年   6篇
  2022年   23篇
  2021年   25篇
  2020年   12篇
  2019年   27篇
  2018年   24篇
  2017年   13篇
  2016年   12篇
  2015年   10篇
  2014年   20篇
  2013年   30篇
  2012年   16篇
  2011年   21篇
  2010年   27篇
  2009年   15篇
  2008年   19篇
  2007年   30篇
  2006年   13篇
  2005年   20篇
  2004年   11篇
  2003年   9篇
  2002年   19篇
  2001年   14篇
  2000年   12篇
  1999年   36篇
  1998年   47篇
  1997年   43篇
  1996年   41篇
  1995年   19篇
  1994年   30篇
  1993年   17篇
  1992年   18篇
  1991年   17篇
  1990年   16篇
  1989年   10篇
  1988年   29篇
  1987年   13篇
  1986年   12篇
  1985年   9篇
  1984年   11篇
  1983年   12篇
  1982年   16篇
  1981年   11篇
  1980年   8篇
  1977年   6篇
  1976年   4篇
  1975年   4篇
  1974年   3篇
  1973年   7篇
  1888年   3篇
排序方式: 共有891条查询结果,搜索用时 15 毫秒
81.
Human blood groups: incidental receptors for viruses and bacteria   总被引:2,自引:0,他引:2  
  相似文献   
82.
Purpose: To assess the current status of computerized gait analysis techniques in the management of children with cerebral palsy or spina bifida who have significant walking disorders.

Method: Synthesis of available data from a review of the literature, drawing on MEDLINE, EMBASE, PRE-MEDLINE, HealthStar and PsychInfo. Other information was obtained from persons with expertise in computerized gait analysis. Cost data were obtained from Canadian rehabilitation centres and the provincial health ministry.

Results: This technology seems helpful in detecting gait changes. However, available evidence is insufficient to draw conclusions about the influence of computerized gait analysis on treatment outcomes. Part of the rationale for use of the technology is that costs of gait analysis (of the order of $CAN 2,000 per examination) would be offset by a decrease in followup surgical procedures and associated hospital care. There could also be a major influence on children's independence and quality of life. However, there are as yet no convincing data to support these propositions.

Conclusions: Computerized gait analysis is a potentially useful technology in the management of children with walking disabilities, but its efficacy is not established. It should be regarded as a developing technology and its clinical application linked to systematic collection and assessment of outcomes data.  相似文献   
83.
Although parental volubility, or amount of talk, has received considerable recent attention, infant volubility has received comparatively little attention despite its potential significance for communicative risk status and later linguistic and cognitive outcomes. Volubility of 16 typically developing infants from 2 to 11 months of age was longitudinally investigated in the present study across three social circumstances: parent talking to infant, parent not talking to infant and parent talking to interviewer while the infant was in the room. Results indicated that volubility was least in the Interview circumstance. There were no significant differences in volubility between the parent Talk and No Talk circumstances. Volubility was found to reduce with age. These results suggest that infants vocalise in a variety of circumstances, even when no one talks to or interacts with them. The presence of a stranger or perhaps overhearing adults speaking to each other, however, may significantly reduce infant volubility.  相似文献   
84.
福建省高校贫困大学生心理健康水平与人格特征   总被引:1,自引:0,他引:1  
目的:了解贫困生的心理健康现状和人格特征。方法:于2005-09/11随机抽取福州大学、福建师范大学、福建农林大学、福建中医学院、闽江学院2002-2004级学生2400名。男1478名,女922名,平均(20±1)岁。根据2004-11-04福建省福州市政府办公厅正式下发的《福州市人民政府关于提高城区城镇及农村居民最低生活保障标准的通知》中的规定,即城镇多人户每人每个月210元、单人户230元;农村多人户每人每月155元、单人户175元,本文把家庭人均月收入较少,有一定数额债务,只能缴纳部分学杂费,基本生活费接近于当地居民最低生活保障线(如上规定,本文以230元为基准)的学生定为“贫困生”。采用精神症状自评量表和16种人格因素问卷对高校贫困生的心理健康和人格特征进行调查。结果:发放问卷2400份,收回有效问卷2111份。其中贫困生539份。①贫困生精神症状自评量表的躯体化、强迫、人际敏感、抑郁、焦虑、敌对、恐怖、偏执、精神病性、其他、总症状指数得分均高于非贫困生(贫困生:1.61±0.56,2.02±0.64,1.92±0.63,1.71±0.56,1.65±0.58,1.73±0.68,1.57±0.62,1.81±0.65,1.67±0.54,1.76±0.63,1.74±0.49;非贫困生:1.48±0.45,1.89±0.56,1.79±0.57,1.61±0.51,1.54±0.50,1.61±0.56,1.44±0.49,1.66±0.54,1.54±0.46,1.61±0.53,1.62±0.41,P<0.01)。男女贫困生之间各因子分差异均不显著(P>0.05)。②福建省高校贫困大学生的心理问题检出率为24.5%,其中轻度心理问题(2≤因子分<3)为22.6%;中度心理问题(3≤因子分<4)为1.7%;重度心理问题(4≤因子分<5)为0.2%。心理问题以强迫、人际敏感、偏执、忧郁、敌对、焦虑等心理问题最为突出。③16种人格因素问卷中,贫困生乐群性、聪慧性、兴奋性、敏感性、怀疑性上得分低于非贫困生,有恒性、忧虑性、独立性得分高于非贫困生(贫困生:5.20±1.77,4.70±1.93,5.49±1.87,6.46±1.79,4.29±1.71,4.60±1.63,6.64±1.82,5.07±1.82;非贫困生:5.39±1.74,4.95±1.99,5.82±1.91,6.66±1.75,4.55±1.77,4.36±1.69,6.43±1.94,4.89±1.77,P<0.05~0.01)。④影响贫困生心理健康水平的主要人格因素按其影响作用从大到小有怀疑性、忧虑性、稳定性、兴奋性、自律性。结论:福建省高校贫困大学生的心理健康状况令人担忧,其人格特征对心理健康水平有重要影响。  相似文献   
85.
目的:探讨体外诱导骨髓间充质干细胞向胰岛素分泌细胞分化的可能性,并观察其动态变化。方法:实验于2005-09/2007-03在山东大学齐鲁医院完成。①标本来源:骨髓标本15例来自山东大学齐鲁医院成人骨髓检查结果正常者,均签署捐献同意书。②实验方法:无菌条件下取骨髓2.0~5.0mL,采用percoll分离液和贴壁法获得纯化的成人骨髓间充质干细胞。③实验评估:流式细胞仪行细胞表面抗原检测,在适当的条件下诱导其分化为成骨细胞和脂肪细胞。采用两步法向胰岛素分泌细胞诱导,观察其在碱性成纤维细胞生长因子、活化素A、胰岛素样生长因子、尼克酰胺等因子刺激下向胰岛素分泌细胞分化的动态变化。双硫踪染色鉴定胰岛样细胞团,酶联免疫吸附试验检测细胞分泌胰岛素的情况,RT-PCR检测胰岛细胞特异基因的表达。结果:①骨髓间充质干细胞的生长特性及免疫表型:分离培养获得的贴壁细胞,呈形态均一的梭形,流式细胞仪检测CD34、CD45表达阴性,CD29、CD44表达阳性。②向成骨细胞和脂肪细胞的诱导分化:此类细胞经茜素红染色、油红O染色均呈阳性,可诱导分化为成骨细胞和脂肪细胞。③向胰岛素分泌细胞的诱导分化:第1步诱导后出现细胞簇,双硫腙染色不着色,胰岛素分泌量少,仅检测到PDX-1基因的表达,证实其为胰岛前体细胞。第2步诱导后细胞簇数目逐渐上升,至诱导14d大部分细胞簇经双硫腙染色都呈红色。④诱导后培养上清中胰岛素含量:诱导第3,7,14,21天的胰岛素分泌量分别为(15.3±4.9),(34.1±5.6),(40.4±5.3),(39.8±5.1)mU/L。⑤胰岛细胞特异基因的表达:诱导7d仅检测到PDX-1基因的表达,insulin1、insulin2和Glut2基因均不表达。诱导14,21d检测到insulin2、PDX-1基因表达,insulin1基因弱表达,Glut2基因不表达。结论:体外分离、纯化得到的骨髓间充质干细胞诱导7d可分化出胰岛前体细胞,不具功能性;诱导14d后可成功地分化出成熟的具有功能性的胰岛素分泌细胞。  相似文献   
86.
87.
目的:探讨乳腺癌组织中核呼吸因子-1(NRF-1)蛋白表达与乳腺癌发生、发展及临床病理特征的关系。方法:采用免疫组化EnVision二步法,对211例乳腺癌组织和50例乳腺良性病变组织中NRF-1蛋白表达进行检测。结果:NRF-1蛋白表达定位于细胞核,着色呈棕黄色,乳腺癌中阳性表达(82.7%)低于乳腺良性病变组织阳性表达(100%),χ2=100.288,P=0.000;高分化乳腺癌NRF-1阳性率明显高于中、低分化乳腺癌(χ2=16.242,P=0.001;χ2=72.802,P=0.000),中分化乳腺癌也明显高于低分化乳腺癌,χ2=30.190,P=0.000。乳腺癌淋巴结转移患者NRF-1蛋白阳性表达率明显低于未转移者,χ2=12.025,P=0.007;TNM分期中I期NRF-1蛋白阳性表达率明显高于Ⅱ、Ⅲ期,χ2=12.025,P=0.007。结论:NRF-1蛋白的表达可能与乳腺癌的发生发展密切相关,可作为乳腺癌患者疾病进展监控和预后观测的指标,具有临床应用价值。  相似文献   
88.
A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in rats. Groups of 100 male and 100 female F344/N rats were exposed continuously to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female F344/N rats received intermittent (1 hr on/1 hr off) exposure to 10 G fields. Mortality patterns, body weight gains throughout the study, and the total incidence and number of malignant and benign tumors in all groups exposed to magnetic fields were similar to those found in sex-matched sham controls. Statistically significant increases in the combined incidence of C-cell adenomas and carcinomas of the thyroid were seen in male rats chronically exposed to 20 mG and 2 G magnetic fields. These increases were not seen in male rats exposed continuously or intermittently to 10 G fields or in female rats at any magnetic field exposure level. No increases in the incidence of neoplasms, which have been identified in epidemiology studies as possible targets of magnetic field action (leukemia, breast cancer, and brain cancer), were found in any group exposed to magnetic fields. There was a decrease in leukemia in male rats exposed to 10 G intermittent fields. The occurrence of C-cell tumors at the 2 lower field intensities in male rats is interpreted as equivocal evidence of carcinogenicity; data from female rats provides no evidence of carcinogenicity in that sex. These data, when considered as a whole, are interpreted as indicating that chronic exposure to pure linearly polarized 60 Hz magnetic fields has little or no effect on cancer development in the F344/N rat.  相似文献   
89.
Histopathology is a major diagnostic tool in dermatology, particularly in psoriasiform diseases. Morphological studies showed that the initial event in psoriatic lesions is perivascular infiltrate, followed by dilatation of superficial papillary vessels. Proliferation of keratinocytes and neutrophil exocytosis are secondary events. Fully developed psoriasis has a very characteristic pattern, which includes elongation of rete ridges leading to regular acanthosis, oedema of the papillary dermis associated with tortuous dilated vessels, thinning of suprapapillar area, decreased thickness of granular layer, and exocytosis of neutrophils in the spinous layer (Kogoj's pustule) or in the cornified parakeratotic layer (Munro microabscesses). Pustular psoriasis is characterized by large or confluent intra‐epidermal multilocular pustules. Whatever the clinical variant of psoriasis, common morphological signs suggest that it is basically a unique pathological process, with many possible presentations according to various factors such as age, size and localization of lesions, or therapy. Similar microscopic elementary lesions indicate that Hallopeau's acrodermatitis continua, Reiter's disease and geographical tongue are variants of psoriasis. Because of the many faces of the disease, psoriasis can resemble many other squamous or pustular disorders. Differential diagnosis by microscopic analysis is based on pattern analysis, PAS (Periodic Acid Schiff) staining to rule out fungal infection, and immunohistochemistry to characterize lymphocytic infiltrate. Psoriasis is one of the most common inflammatory skin diseases. In its characteristic presentation, psoriasis comprises well‐circumscribed red scaly papules and plaques. In this form, the disease is generally easy to identify, especially when the elbows, knees and scalp are affected. Nevertheless, the term ‘psoriasis’ includes more clinical variants than any other inflammatory dermatosis: psoriasis vulgaris vs. pustular, localized vs. generalized, topographic variants, mucous membranes involvement, hair and nail lesions. Although some of these conditions might be extremely different from psoriasis vulgaris, common pathological findings can be identified in all of them. Microscopic analysis of psoriatic lesions may therefore help clinicians to make the diagnosis and to understand that, whatever the clinical presentation, signs and symptoms are mainly due to a unique pathological process.  相似文献   
90.
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