首页 | 官方网站   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   2754442篇
  免费   190761篇
  国内免费   7562篇
医药卫生   2952765篇
  2021年   20264篇
  2019年   20913篇
  2018年   49656篇
  2017年   38745篇
  2016年   45117篇
  2015年   30643篇
  2014年   41405篇
  2013年   61433篇
  2012年   86975篇
  2011年   104328篇
  2010年   68314篇
  2009年   60091篇
  2008年   97877篇
  2007年   105557篇
  2006年   86366篇
  2005年   84479篇
  2004年   82896篇
  2003年   81409篇
  2002年   76734篇
  2001年   128816篇
  2000年   131964篇
  1999年   110765篇
  1998年   31538篇
  1997年   28239篇
  1996年   28405篇
  1995年   27574篇
  1994年   25278篇
  1993年   23587篇
  1992年   85301篇
  1991年   81759篇
  1990年   78974篇
  1989年   76190篇
  1988年   69579篇
  1987年   68111篇
  1986年   63642篇
  1985年   60639篇
  1984年   45022篇
  1983年   38023篇
  1982年   22569篇
  1981年   20006篇
  1979年   39063篇
  1978年   27506篇
  1977年   23270篇
  1976年   21527篇
  1975年   22771篇
  1974年   26779篇
  1973年   25344篇
  1972年   23737篇
  1971年   21937篇
  1970年   20187篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
71.
Henna, derived from a combination of natural leaves and coloring additives, is a common decorative dye traditionally used in many Islamic religious celebrations. Para‐phenylenediamine (PPD), a major component of black henna tattoo, is a strong sensitizer and common allergen. We report a case of severe connubial allergic contact dermatitis after black henna heterotransfer in a girl.  相似文献   
72.
73.
74.
75.
Acne vulgaris (acne) is a chronic inflammatory disease of the sebaceous gland, characterized by follicular hyperkeratinization, excessive colonization by Propionibacterium acnes (Pacnes) as well as immune reactions and inflammation. Despite an armamentarium of topical treatments available including benzoyl peroxide, retinoids and azelaic acid, topical antibiotics in monotherapies, especially erythromycin and clindamycin, are still used in Europe to treat acne. This intensive use led to antimicrobial‐resistant P. acnes and staphylococci strains becoming one of the main health issues worldwide. This is an update on the current topical acne treatments available in Europe, their mechanism of action, their potential to induce antimicrobial resistance and their clinical efficacy and safety.  相似文献   
76.
We report on a child with several café au lait spots in association with a lumbar lipomeningomyelocele as an apparently new association. Cutaneous markers, the identification of which plays a crucial role in the early diagnosis and management of spinal malformations, can accompany occult spinal dysraphism. Herein we report a case of lumbar lipomeningomyelocele associated with an overlying café au lait spot that served as a marker of occult spinal dysraphism. The patient also had segmental café au lait spots on the face, making the association unique.  相似文献   
77.
78.
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation.  相似文献   
79.
80.
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-23

京公网安备 11010802026262号