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   4282273篇
  免费   361973篇
  国内免费   15323篇
耳鼻咽喉   61168篇
儿科学   133303篇
妇产科学   112146篇
基础医学   657391篇
口腔科学   119268篇
临床医学   388905篇
内科学   777283篇
皮肤病学   103758篇
神经病学   368140篇
特种医学   171318篇
外国民族医学   913篇
外科学   655292篇
综合类   126253篇
现状与发展   23篇
一般理论   2645篇
预防医学   360769篇
眼科学   100754篇
药学   303029篇
  21篇
中国医学   11400篇
肿瘤学   205790篇
  2021年   56118篇
  2020年   35758篇
  2019年   58917篇
  2018年   73653篇
  2017年   55857篇
  2016年   62294篇
  2015年   75527篇
  2014年   110388篇
  2013年   175813篇
  2012年   119399篇
  2011年   122520篇
  2010年   123562篇
  2009年   126572篇
  2008年   109255篇
  2007年   115898篇
  2006年   125225篇
  2005年   120206篇
  2004年   121047篇
  2003年   111725篇
  2002年   102268篇
  2001年   154474篇
  2000年   150638篇
  1999年   139697篇
  1998年   71387篇
  1997年   67813篇
  1996年   65697篇
  1995年   61538篇
  1994年   55624篇
  1993年   51646篇
  1992年   103677篇
  1991年   99029篇
  1990年   94138篇
  1989年   91747篇
  1988年   85380篇
  1987年   83830篇
  1986年   79532篇
  1985年   77986篇
  1984年   65997篇
  1983年   58897篇
  1982年   48172篇
  1981年   44898篇
  1980年   42208篇
  1979年   57895篇
  1978年   47071篇
  1977年   41632篇
  1976年   38695篇
  1975年   37882篇
  1974年   42485篇
  1973年   40599篇
  1972年   38066篇
排序方式: 共有10000条查询结果,搜索用时 31 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