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   3738篇
  免费   524篇
  国内免费   9篇
耳鼻咽喉   10篇
儿科学   127篇
妇产科学   378篇
基础医学   274篇
口腔科学   78篇
临床医学   1079篇
内科学   643篇
皮肤病学   139篇
神经病学   133篇
特种医学   323篇
外科学   287篇
综合类   124篇
一般理论   5篇
预防医学   267篇
眼科学   48篇
药学   238篇
肿瘤学   118篇
  2023年   45篇
  2021年   43篇
  2020年   58篇
  2019年   45篇
  2018年   96篇
  2017年   127篇
  2016年   104篇
  2015年   129篇
  2014年   144篇
  2013年   142篇
  2012年   108篇
  2011年   138篇
  2010年   141篇
  2009年   134篇
  2008年   118篇
  2007年   128篇
  2006年   110篇
  2005年   107篇
  2004年   91篇
  2003年   91篇
  2002年   99篇
  2001年   109篇
  2000年   75篇
  1999年   111篇
  1998年   126篇
  1997年   126篇
  1996年   134篇
  1995年   121篇
  1994年   90篇
  1993年   66篇
  1992年   76篇
  1991年   66篇
  1990年   65篇
  1989年   78篇
  1988年   70篇
  1987年   63篇
  1986年   69篇
  1985年   86篇
  1984年   48篇
  1983年   44篇
  1982年   27篇
  1981年   33篇
  1980年   33篇
  1979年   25篇
  1978年   31篇
  1977年   32篇
  1976年   33篇
  1975年   28篇
  1974年   18篇
  1971年   19篇
排序方式: 共有4271条查询结果,搜索用时 46 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.
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   
4.
Proton nuclear magnetic resonance spectroscopy has been used to monitor changes in urinary metabolites in a patient with propionic acidaemia over a period of 10 months and in a patient with methylmalonic aciduria over a period of 11 days. Results could be obtained within 5-10 min of sample receipt. In the spectra on the patient with propionic acidaemia not only could fluctuations in 3-hydroxypropionate and propionylglycine excretion be followed, but also variations in creatine, glycine and betaine, which were often present at millimolar concentrations. The patient with methylmalonic aciduria had an acute episode of severe ketoacidosis during which the glycine excretion fell but creatine excretion rose and then fell on recovery from the episode. The changes in the creatine excretion may reflect disorders in intracellular energy supply. Nuclear magnetic resonance is a powerful technique for monitoring metabolic perturbations in the organic acidurias in 'real-time', allowing the planning and evaluation of therapy.  相似文献   
5.
6.
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   
7.
8.
In the course of 1 year at a tertiary cancer center, 3 patients (2 men; 1 woman; age 51-75 years) were seen in neurological consultation (1.5% of all consultations). Clinical course in all patients was of a progressive neurologic disorder not consistent with either a primary or secondary malignancy. Magnetic resonance (MR) imaging was most informative with respect to diagnosis and subsequent management. Brain biopsy was performed in all patients to assist in both diagnosis and prognostication. All patients were determined to have progressive multifocal leukoencephalopathy (PML) by brain biopsy.  相似文献   
9.
10.
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