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   4323752篇
  免费   347851篇
  国内免费   14063篇
耳鼻咽喉   59880篇
儿科学   138081篇
妇产科学   112679篇
基础医学   665949篇
口腔科学   115828篇
临床医学   394184篇
内科学   782615篇
皮肤病学   107505篇
神经病学   360821篇
特种医学   167238篇
外国民族医学   512篇
外科学   663540篇
综合类   121297篇
现状与发展   23篇
一般理论   2782篇
预防医学   362241篇
眼科学   102360篇
药学   303050篇
  28篇
中国医学   11535篇
肿瘤学   213518篇
  2021年   57127篇
  2020年   36330篇
  2019年   59687篇
  2018年   75476篇
  2017年   57310篇
  2016年   63525篇
  2015年   76417篇
  2014年   111380篇
  2013年   177257篇
  2012年   131073篇
  2011年   137951篇
  2010年   129136篇
  2009年   129344篇
  2008年   123070篇
  2007年   131472篇
  2006年   139692篇
  2005年   134823篇
  2004年   134553篇
  2003年   124379篇
  2002年   113022篇
  2001年   150323篇
  2000年   145052篇
  1999年   134901篇
  1998年   70736篇
  1997年   66715篇
  1996年   64820篇
  1995年   60034篇
  1994年   54107篇
  1993年   50331篇
  1992年   96357篇
  1991年   92883篇
  1990年   89291篇
  1989年   87073篇
  1988年   80271篇
  1987年   78775篇
  1986年   74099篇
  1985年   73238篇
  1984年   61939篇
  1983年   55663篇
  1982年   46273篇
  1981年   43363篇
  1980年   40712篇
  1979年   53262篇
  1978年   44192篇
  1977年   39010篇
  1976年   36391篇
  1975年   36377篇
  1974年   39528篇
  1973年   37752篇
  1972年   35364篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
21.
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   
22.
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   
23.
24.
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   
25.
26.
27.
28.
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   
29.
30.
Anaplastic thyroid carcinoma (ATC) is an aggressive thyroid malignancy with high mortality rate. This malignancy arises in thyroid follicular cells either denovo or with an associated differentiated thyroid carcinoma component. Clinically, it usually presents as a rapidly enlarging mass, pain and locally compressive symptoms. Histopathologic variability and heterogeneity often pose diagnostic challenges, especially in scant and paucicellular specimens. This article describes the clinical, histopathologic and molecular features of ATC and also addresses the associated diagnostic limitations and challenges.  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