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   4224篇
  免费   505篇
  国内免费   9篇
耳鼻咽喉   17篇
儿科学   270篇
妇产科学   364篇
基础医学   374篇
口腔科学   53篇
临床医学   1081篇
内科学   711篇
皮肤病学   83篇
神经病学   224篇
特种医学   272篇
外科学   291篇
综合类   121篇
一般理论   2篇
预防医学   465篇
眼科学   36篇
药学   268篇
肿瘤学   106篇
  2023年   50篇
  2021年   24篇
  2020年   60篇
  2019年   49篇
  2018年   90篇
  2017年   127篇
  2016年   104篇
  2015年   117篇
  2014年   132篇
  2013年   178篇
  2012年   136篇
  2011年   167篇
  2010年   177篇
  2009年   167篇
  2008年   159篇
  2007年   126篇
  2006年   113篇
  2005年   127篇
  2004年   125篇
  2003年   113篇
  2002年   105篇
  2001年   108篇
  2000年   95篇
  1999年   125篇
  1998年   122篇
  1997年   129篇
  1996年   127篇
  1995年   114篇
  1994年   90篇
  1993年   61篇
  1992年   73篇
  1991年   87篇
  1990年   58篇
  1989年   86篇
  1988年   104篇
  1987年   82篇
  1986年   74篇
  1985年   92篇
  1984年   62篇
  1983年   76篇
  1982年   49篇
  1981年   48篇
  1980年   37篇
  1979年   30篇
  1978年   39篇
  1977年   33篇
  1976年   25篇
  1974年   27篇
  1973年   24篇
  1972年   25篇
排序方式: 共有4738条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: Computer-assisted image analysis has been proposed for human hair growth studies. METHODS: The performances of Trichoscan, a commercially available automated system combining epiluminiscence microscopy with digital image analysis, developed for office-based hair growth measurements, have been evaluated comparatively on the same skin sites using standardized photographic equipment and calibrated processing for contrast-enhanced phototrichogram (CE-PTG) analysis. This reference method has been validated with scalp biopsies and histological examination of serial sectioning. RESULTS: Besides edge effects, hair fibres escaped the Trichoscan analysis for various reasons including, but not limited to, thickness, pigmentation, closeness and crossing. CONCLUSION: Most of these problems have been identified in the late 1980s and remain largely unsolved by the processing software that was evaluated in 2004. Therefore claims promoting the Trichoscan method for accurate hair measurements in clinical trials on scalp and body hair are not supported by the present investigation. The speed at which the analysis is performed is outweighed by the errors in signal detection. Therefore we suggest that improvements must be clearly documented before Trichoscan is established for quantified diagnostic purposes and detailed hair cycle monitoring during hair trials.  相似文献   
3.
Uniparental isodisomy (iUPD) is a rare genetic condition caused by non-disjunction during meiosis that ultimately leads to a duplication of either the maternal or paternal chromosome in the affected individual. Two types of disorders can result, those due to imprinted genes and those due to homozygosity of recessive disease-causing mutations. Here, we describe the third known case of complete chromosome 4 iUPD of maternal origin. This condition became apparent during whole genome linkage studies of psychiatric disorders in the Portuguese population. The proband is an adult female with normal fertility and no major medical complaints, but a history of major depressive disorder and multiple suicide attempts. The proband's siblings and parents had normal chromosome 4 genotypes and no history of mood disturbance. A brief review of other studies lends support for the possibility that genes on chromosome 4 might confer risk for mood disorders. We conclude that chromosome 4 maternal uniparental disomy (UPD) is a rare disorder that may present with a major depressive phenotype. The lack of a common disease phenotype between this and two other cases of chromosome 4 iUPD [Lindenbaum et al. [1991] Am J Med Genet 49(Suppl 285):1582; Spena et al. [2004] Eur J Hum Genet 12:891-898) would suggest that there is no vital maternal gene imprinting on chromosome 4. However, since there is no reported case of paternal chromosome 4 UPD, paternal gene imprinting on chromosome 4 cannot be excluded.  相似文献   
4.
双波长紫外分光光度法测定贝母中腺苷和胸苷的含量   总被引:4,自引:0,他引:4  
将4种贝母的甲醇提取物经薄层色谱法粗分离后,直接用双波长紫外分光光度法测定其含量。结果表明,该方法线性关系好,腺苷和胸苷标准曲线的相关系数均为0.9999,同时也发现平贝、炉贝和伊贝中腺苷都占核苷总量60%以上,而浙贝中仅占约40%,提示贝母生药的抗凝血活性可能与贝母中核苷类化合物的种类和含量的差别有关。  相似文献   
5.
J E Morley 《Hospital practice (Office ed.)》1988,23(4):139-42, 145-6, 152-3 passim
  相似文献   
6.
7.
Intraperitoneal (i.p.) injection of platelet activating factor (PAF) in guinea pigs caused a dose-related increase in the number of eosinophils recovered from bronchoalveolar lavage fluid (BALF). The prevalence of eosinophils in BALF had significantly increased within 1 hr of i.p. injection of PAF (10 micrograms/animal) and was maximal after 24 hr. Subcutaneous osmotic mini-pumps were used to administer drugs for 5 days prior to i.p. injection of PAF (10 micrograms/animal) and for the subsequent 24 hr. The percentage increase of eosinophils in BALF, due to PAF, was inhibited in animals treated with dexamethasone, aminophylline, cromoglycate, tranilast or ketotifen, but not in animals treated with oxatomide, azelastine, amlexanox, ibudilast or AA-861. These results suggest that inhibition of pulmonary eosinophilia may be a necessary property of prophylactic anti-asthma drugs and provide indirect evidence favoring a role for PAF in eosinophilia of asthma.  相似文献   
8.
The molecular events responsible for controlling cell growth and development, as well as their coordinate interaction is only beginning to be revealed. At the basis of these controlling events are hormones, growth factors and mitogens which, through transmembrane signalling trigger an array of cellular responses, initiated by receptor-associated tyrosine kinases, which in turn either directly or indirectly mediate their effects through serine/threonine protein kinases. Utilizing the obligatory response of activation of protein synthesis in cell growth and development, we describe efforts to work backwards along the regulatory pathway to the receptor, identifying those molecular components involved in modulating the rate of translation. We begin by describing the components and steps of protein synthesis and then discuss in detail the regulatory pathways involved in the mitogenic response of eukaryotic cells and during meiotic maturation of oocytes. Finally we discuss possible future work which will further our understanding of these systems.  相似文献   
9.
This study investigated the use of attentional control strategies in the self-management of pain using daily process design methodology. Twenty six cancer patients with pain completed diaries 3 times daily for 10 days. Diaries incorporated measures of pain intensity, affect, coping, coping efficacy, and the novelty and predictability of pain, and participants completed a cross-sectional measure of catastrophizing. At the across-person level, focusing on pain was associated with increased negative affect, and the use of pain focusing strategies was positively correlated with experiencing pain that was novel in its location or quality. Distractions that were interesting, important and pleasant were positively correlated with positive affect, perceptions of control over pain and ability to decrease pain. Over-prediction of pain was positively correlated with catastrophizing, and negatively correlated with perceptions of control over and ability to decrease pain. The within-person analysis (ARIMA modelling) showed that catastrophizing moderated the effects of pain focusing strategies, novel pain and over-predictions of pain. Meta-analysis of the ARIMA models revealed that the within-person effects of using attentional strategies did not generalize across the sample. These findings indicated that the effects of distraction strategies are influenced by their motivational-affective significance rather than the frequency with which they are used, and provided further evidence that the threat value of pain influences the way in which people cope with their pain. Theoretical and clinical implications are discussed.  相似文献   
10.
BACKGROUND: Based on good results in the treatment of superficial skin tumours, since the early 1990s topical photodynamic therapy with aminolaevulinic acid (ALA PDT) has been used for disseminated, inflammatory dermatoses including psoriasis. However, there is still a lack of well-documented trials. OBJECTIVE: A prospective randomized, double-blind phase I/II intrapatient comparison study was conducted in 12 patients to investigate whether topical ALA PDT is an effective treatment for chronic plaque-type psoriasis. METHODS: In each patient three psoriatic plaques were randomly treated with a light dose of 20 J/cm(2) and 0.1%, 1% and 5% ALA, respectively. Treatment was conducted twice a week until complete clearance or for a maximum of 12 irradiations. Therapeutic efficacy was assessed by weekly determination of the psoriasis severity index (PSI). RESULTS: The mean percentage improvement was 37.5%, 45.6% and 51.2% in the 0.1%, 1% and 5% ALA-treated groups, respectively. Irradiation had to be interrupted several times because of severe burning and pain sensation. CONCLUSION: Topical ALA PDT did not prove to be an appropriate treatment option for plaque-type psoriasis due to disappointing clinical efficacy, the time-consuming treatment procedure and its unfavourable adverse event profile.  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