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   169684篇
  免费   16936篇
  国内免费   10230篇
耳鼻咽喉   1394篇
儿科学   2301篇
妇产科学   2086篇
基础医学   23892篇
口腔科学   2915篇
临床医学   20326篇
内科学   23417篇
皮肤病学   1860篇
神经病学   8229篇
特种医学   5877篇
外国民族医学   75篇
外科学   16912篇
综合类   28497篇
现状与发展   34篇
一般理论   14篇
预防医学   12431篇
眼科学   3924篇
药学   19383篇
  151篇
中国医学   9745篇
肿瘤学   13387篇
  2024年   703篇
  2023年   2741篇
  2022年   6937篇
  2021年   8804篇
  2020年   6488篇
  2019年   5628篇
  2018年   5933篇
  2017年   5520篇
  2016年   5220篇
  2015年   7689篇
  2014年   9433篇
  2013年   9376篇
  2012年   12998篇
  2011年   13660篇
  2010年   9601篇
  2009年   7733篇
  2008年   9225篇
  2007年   9088篇
  2006年   8247篇
  2005年   7444篇
  2004年   5693篇
  2003年   5550篇
  2002年   4746篇
  2001年   3913篇
  2000年   3344篇
  1999年   2931篇
  1998年   1791篇
  1997年   1946篇
  1996年   1365篇
  1995年   1288篇
  1994年   1189篇
  1993年   817篇
  1992年   1074篇
  1991年   986篇
  1990年   878篇
  1989年   800篇
  1988年   731篇
  1987年   626篇
  1986年   582篇
  1985年   460篇
  1984年   394篇
  1983年   322篇
  1982年   279篇
  1981年   239篇
  1980年   214篇
  1979年   214篇
  1978年   205篇
  1977年   221篇
  1976年   199篇
  1974年   163篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
双环[1.1.1]戊烷(BCP)是一种具有三维立体结构的桥环骨架,其作为苯环、叔丁基和炔烃的生物电子等排体,已经在药物化学领域得到广泛的应用。随着BCP应用范围的扩大,BCP及其衍生物的合成日益成为研究的热点。本文对BCP衍生物的主要合成策略和方法进行总结,旨在为新药研发人员提供参考。  相似文献   
65.
66.
A pulmonary artery (PA) sling is a very rare congenital cardiovascular anomaly, and only a few studies have reported PA slings in fetuses. The relationship of the PA, aorta, ductus arteriosus, and trachea can be evaluated in the 3‐vessel and 3‐vessel and trachea views during fetal echocardiography. A PA sling can be detected by abnormal positioning of the left PA in relation to the trachea when sweeping from the 3‐vessel view cranially to the 3‐vessel and trachea view. Here we report 3 cases of fetal PA slings and their follow‐ups. Two cases were confirmed by postnatal echocardiography, and the other case was confirmed by a cardiovascular cast after pregnancy termination. We emphasize that the 3‐vessel and 3‐vessel and trachea views are of crucial importance in the prenatal diagnosis of a PA sling.  相似文献   
67.
68.

Introduction

For never-smokers (smoked <100 lifetime cigarettes), lung cancer (LC) has emerged as an important issue. We aimed to investigate the effects of prevalence changes in tobacco smoking and particulate matter (PM) 2.5 (PM2.5) levels on LC in Taiwan, in relation to contrasting PM2.5 levels, between Northern Taiwan (NT) and Southern Taiwan (ST).

Methods

We reviewed 371,084 patients with LC to assess smoking prevalence and correlations between the incidence of adenocarcinoma lung cancer (AdLC) and non-AdLC. Two subsets were selected to assess different AdLC stage trends and the effect of PM2.5 on survival of patients with AdLC.

Results

From 1995 to 2015, the proportion of male adult ever-smokers decreased from 59.4% to 29.9% whereas the female smoking rate remained low (3.2% to 5.3%). AdLC incidence in males and females increased from 9.06 to 23.25 and 7.05 to 24.22 per 100,000 population, respectively. Since 1993, atmospheric visibility in NT improved (from 7.6 to 11.5 km), but deteriorated in ST (from 16.3 to 4.2 km). The annual percent change in AdLC stages IB to IV was 0.3% since 2009 (95% confidence interval [CI]: -1.9%–2.6%) in NT, and 4.6% since 2007 (95% CI: 3.3%–5.8%) in ST; 53% patients with LC had never smoked. Five-year survival rates for never-smokers, those with EGFR wild-type genes, and female patients with AdLC were 12.6% in NT and 4.5% in ST (hazard ratio: 0.79, 95% CI: 0.70–0.90).

Conclusions

In Taiwan, greater than 50% of patients with LC had never smoked. PM2.5 level changes can affect AdLC incidence and patient survival.  相似文献   
69.
70.
Photobiomodulation (PBM) therapy is based on the exposure of biological tissues to low‐level laser light (coherent light) or light‐emitting diodes (LEDs; noncoherent light), leading to the modulation of cellular functions, such as proliferation and migration, which result in tissue regeneration. PBM therapy has important clinical applications in regenerative medicine. Vitiligo is an acquired depigmentary disorder resulting from disappearance of functional melanocytes in the involved skin. Vitiligo repigmentation depends on available melanocytes derived from (a) melanocyte stem cells located in the bulge area of hair follicles and (b) the epidermis at the lesional borders, which contains a pool of functional melanocytes. Since follicular melanoblasts (MBs) are derived from the melanocyte stem cells residing at the bulge area of hair follicle, the process of vitiligo repigmentation presents a research model for studying the regenerative effect of PBM therapy. Previous reports have shown favourable response for treatment of vitiligo with a low‐energy helium‐neon (He‐Ne) laser. This review focuses on the molecular events that took place during the repigmentation process of vitiligo triggered by He‐Ne laser (632.8 nm, red light). Monochromatic radiation in the visible and infrared A (IRA) range sustains matrix metalloproteinase (MMP), improves mitochondrial function, and increases adenosine triphosphate (ATP) synthesis and O2 consumption, which lead to cellular regenerative pathways. Cytochrome c oxidase in the mitochondria was reported to be the photoacceptor upon which He‐Ne laser exerts its effects. Mitochondrial retrograde signalling is responsible for the cellular events by red light. This review shows that He‐Ne laser initiated mitochondrial retrograde signalling via a Ca2+‐dependent cascade. The impact on cytochrome c oxidase within the mitochondria, an event that results in activation of CREB (cyclic‐AMP response element binding protein)‐related cascade, is responsible for the He‐Ne laser promoting functional development at different stages of MBs and boosting functional melanocytes. He‐Ne laser irradiation induced (a) melanocyte stem cell differentiation; (b) immature outer root sheath MB migration; (c) differentiated outer root sheath MB melanogenesis and migration; and (d) perilesional melanocyte migration and proliferation. These photobiomodulation effects result in perifollocular and marginal repigmentation in vitiligo.  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