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   2197篇
  免费   340篇
  国内免费   8篇
耳鼻咽喉   4篇
儿科学   89篇
妇产科学   286篇
基础医学   149篇
口腔科学   49篇
临床医学   876篇
内科学   213篇
皮肤病学   63篇
神经病学   69篇
特种医学   277篇
外科学   108篇
综合类   73篇
一般理论   1篇
预防医学   101篇
眼科学   18篇
药学   71篇
肿瘤学   98篇
  2023年   44篇
  2021年   7篇
  2020年   35篇
  2019年   25篇
  2018年   59篇
  2017年   93篇
  2016年   80篇
  2015年   103篇
  2014年   106篇
  2013年   109篇
  2012年   72篇
  2011年   86篇
  2010年   113篇
  2009年   111篇
  2008年   63篇
  2007年   73篇
  2006年   65篇
  2005年   42篇
  2004年   37篇
  2003年   49篇
  2002年   36篇
  2001年   54篇
  2000年   34篇
  1999年   58篇
  1998年   101篇
  1997年   111篇
  1996年   106篇
  1995年   95篇
  1994年   72篇
  1993年   51篇
  1992年   27篇
  1991年   35篇
  1990年   19篇
  1989年   40篇
  1988年   42篇
  1987年   27篇
  1986年   31篇
  1985年   36篇
  1984年   16篇
  1983年   16篇
  1982年   19篇
  1981年   17篇
  1980年   22篇
  1979年   13篇
  1978年   19篇
  1977年   21篇
  1976年   22篇
  1975年   14篇
  1973年   3篇
  1971年   3篇
排序方式: 共有2545条查询结果,搜索用时 156 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.
We describe 2 renal transplant patients with increasing plasma creatinine levels after resolution of acute rejection episodes. Antegrade pyelography demonstrated adherence of the ureter to the inferior pole of the kidney with partial obstruction in both cases, which was confirmed at operation.  相似文献   
5.
It is known that low glucose concentrations increase the aspartate and decrease the glutamate content of brain tissue both in vivo and in vitro. To see whether these changes occur in the transmitter compartment or not, the release of aspartate and glutamate evoked by electrical-field stimulation or by high K+ was followed in slices of rat hippocampus superfused with 5 or 0.2 mM glucose. Superfusion with 0.2 mM glucose increased the evoked release of aspartate about ten times and that of glutamate about threefold. This shift in the ratio of aspartate to glutamate released was accompanied by a similar increase in the relative amount of aspartate contained in the slices. The high evoked release of aspartate and glutamate was well maintained, provided 0.5 mM glutamine was added to the medium. Changing the concentration of glucose after the first period of stimulation rapidly altered the relative amounts of aspartate and glutamate released but not the enhanced release of glutamate. The large evoked release of both aspartate and glutamate in 0.2 mM glucose was almost entirely Ca2+-dependent. The relative amounts of aspartate and glutamate released by 50 mM K+ also changed when the glucose concentration was reduced. Results suggest two effects of low glucose concentrations: an increase in the overflow of synaptically released glutamate due to a decreased uptake and an increase in the proportion of aspartate to glutamate formed and released from the transmitter pool. These observations are consistent with the interpretation that these two transmitters can be released in different proportions from the same terminals.  相似文献   
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.
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