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   4241403篇
  免费   344858篇
  国内免费   15510篇
耳鼻咽喉   58216篇
儿科学   132878篇
妇产科学   112060篇
基础医学   649833篇
口腔科学   118814篇
临床医学   383447篇
内科学   762601篇
皮肤病学   106303篇
神经病学   353439篇
特种医学   166592篇
外国民族医学   425篇
外科学   652435篇
综合类   129256篇
现状与发展   24篇
一般理论   2501篇
预防医学   350183篇
眼科学   100764篇
药学   298686篇
  26篇
中国医学   12339篇
肿瘤学   210949篇
  2021年   55900篇
  2020年   35580篇
  2019年   58706篇
  2018年   73755篇
  2017年   56374篇
  2016年   62431篇
  2015年   75779篇
  2014年   110112篇
  2013年   175657篇
  2012年   117292篇
  2011年   121038篇
  2010年   124149篇
  2009年   126100篇
  2008年   107176篇
  2007年   114058篇
  2006年   122553篇
  2005年   117386篇
  2004年   119038篇
  2003年   108767篇
  2002年   97878篇
  2001年   155893篇
  2000年   150549篇
  1999年   139152篇
  1998年   71122篇
  1997年   67082篇
  1996年   64837篇
  1995年   60323篇
  1994年   54449篇
  1993年   50656篇
  1992年   100988篇
  1991年   96810篇
  1990年   92655篇
  1989年   90571篇
  1988年   83794篇
  1987年   81823篇
  1986年   77588篇
  1985年   76189篇
  1984年   64589篇
  1983年   57586篇
  1982年   47187篇
  1981年   44030篇
  1980年   41418篇
  1979年   55903篇
  1978年   45467篇
  1977年   40774篇
  1976年   37422篇
  1975年   37146篇
  1974年   41001篇
  1973年   39468篇
  1972年   37068篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
21.
22.
Journal of Behavioral Medicine - Evidence supports the use of graphic warnings to educate the public about the health harms of smoking and suggests warnings eliciting negative emotional responses...  相似文献   
23.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T2-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T2-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis.  相似文献   
24.
25.
Collagens are the most abundant proteins in the extracellular matrix. They provide a framework to build organs and tissues and give structural support to make them resistant to mechanical load and forces. Several intra‐ and extracellular modifications are needed to make functional collagen molecules, intracellular post‐translational modifications of proline and lysine residues having key roles in this. In this article, we provide a review on the enzymes responsible for the proline and lysine modifications, that is collagen prolyl 4‐hydroxylases, 3‐hydroxylases and lysyl hydroxylases, and discuss their biological functions and involvement in diseases.  相似文献   
26.
27.
28.
29.
Coronavirus disease-19 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is now a pandemic threat. This virus is supposed to be spread by human to human transmission. Cellular angiotensin-converting enzyme 2 (ACE2) is the receptor of SARS-CoV-2 which is identical or similar in different species of animals such as pigs, ferrets, cats, orangutans, monkeys, and humans. Moreover, a recent study predicted that dogs might be secondary hosts during the evolution of SARS-CoV-2 from bat to human. Therefore, there is a possibility of spreading SARS-CoV-2 through domestic pets. There are now many reports of SARS-CoV-2 positive cases in dogs, cats, tigers, lion, and minks. Experimental data showed ferrets and cats are highly susceptible to SARS-CoV-2 as infected by virus inoculation and can transmit the virus directly or indirectly by droplets or airborne routes. Based on these natural infection reports and experimental data, whether the pets are responsible for SARS-CoV-2 spread to humans; needs to be deeply investigated. Humans showing clinical symptoms of respiratory infections have been undergoing for the COVID-19 diagnostic test but many infected people and few pets confirmed with SARS-CoV-2 remained asymptomatic. In this review, we summarize the natural cases of SARS-CoV-2 in animals with the latest researches conducted in this field. This review will be helpful to think insights of SARS-CoV-2 transmissions, spread, and demand for seroprevalence studies, especially in companion animals.  相似文献   
30.
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