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   9650篇
  免费   622篇
  国内免费   62篇
耳鼻咽喉   65篇
儿科学   198篇
妇产科学   149篇
基础医学   1252篇
口腔科学   183篇
临床医学   1016篇
内科学   2236篇
皮肤病学   241篇
神经病学   928篇
特种医学   473篇
外科学   1449篇
综合类   37篇
一般理论   6篇
预防医学   765篇
眼科学   75篇
药学   650篇
中国医学   42篇
肿瘤学   569篇
  2024年   7篇
  2023年   42篇
  2022年   84篇
  2021年   193篇
  2020年   145篇
  2019年   251篇
  2018年   296篇
  2017年   178篇
  2016年   216篇
  2015年   251篇
  2014年   380篇
  2013年   541篇
  2012年   715篇
  2011年   776篇
  2010年   431篇
  2009年   400篇
  2008年   631篇
  2007年   735篇
  2006年   635篇
  2005年   627篇
  2004年   620篇
  2003年   533篇
  2002年   511篇
  2001年   94篇
  2000年   100篇
  1999年   109篇
  1998年   97篇
  1997年   79篇
  1996年   73篇
  1995年   62篇
  1994年   51篇
  1993年   53篇
  1992年   33篇
  1991年   47篇
  1990年   32篇
  1989年   36篇
  1988年   31篇
  1987年   27篇
  1986年   31篇
  1985年   32篇
  1984年   25篇
  1983年   18篇
  1982年   15篇
  1981年   15篇
  1980年   10篇
  1979年   13篇
  1976年   6篇
  1970年   5篇
  1967年   4篇
  1966年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Notch1 proteins are involved in binary cell fate decisions. To determine the role of Notch1 in the differentiation of CD4(+) Th1 versus Th2 cells, we have compared T helper polarization in vitro in naive CD4(+) T cells isolated from mice in which the N1 gene is specifically inactivated in all mature T cells. Following activation, Notch1-deficient CD4(+) T cells transcribed and secreted IFN-gamma under Th1 conditions and IL-4 under Th2 conditions at levels similar to that of control CD4(+) T cells. These results show that Notch1 is dispensable for the development of Th1 and Th2 phenotypes in vitro. The requirement for Notch1 in Th1 differentiation in vivo was analyzed following inoculation of Leishmania major in mice with a T cell-specific inactivation of the Notch1 gene. Following infection, these mice controlled parasite growth at the site of infection and healed their lesions. The mice developed a protective Th1 immune response characterized by high levels of IFN-gamma mRNA and protein and low levels of IL-4 mRNA with no IL-4 protein in their lymph node cells. Taken together, these results indicate that Notch1 is not critically involved in CD4(+) T helper 1 differentiation and in resolution of lesions following infection with L. major.  相似文献   
82.
The relations between structure and isothermal, dielectric properties of poly(α-acetoxystyrene)s substituted in para position by ? OCOCH3 ( 1a ), ? OCOCH2CH3 ( 1b ), ? OCOCH2CH2CH3 ( 1c ), ? OCOC6H5 ( 1d ), ? OCOCH2CH2Cl ( 1f ) and ? OCOOCH3 ( 1g ) were studied. The dielectric constants, at 105 Hz and 20 ± 2°C, were found to be: 3,79 ( 1a ), 3,36 ( 1b ), 3,18 ( 1c ), 3,51 ( 1d ), 3,36 ( 1e ), 3,65 ( 1f ) and 3,07 ( 1g ). The polymers 1a – 1g do not show any α- or β-transition. Increasing bulkiness of the para substituent gives rise to a decreasing dielectric constant due to an increase of the degree of syndiotacticity, as determined from 1H and 13C NMR spectra.  相似文献   
83.
Advances in Health Sciences Education - Spaced education is a learning strategy to improve knowledge acquisition and retention. To date, no robust evidence exists to support the utility of spaced...  相似文献   
84.
International Urology and Nephrology - Biomarkers for the diagnosis and monitoring treatment response of kidney cancer are urgently needed. Neutrophil gelatinase-associated lipocalin (NGAL) is a...  相似文献   
85.
Antihuman leukocyte antigen (HLA) antibodies restrict the access to cardiac allografts. Desensitization therapy is a major challenge in patients with cardiogenic shock waiting for urgent heart transplantation (HT). We retrospectively reviewed six patients (mean age of 37.5 years [16–70]) who underwent plasmapheresis (PP) under extracorporeal membrane oxygenation (ECMO) before transplant between January 2017 and September 2018. The average duration of follow‐up was 25 months [20–32]. Mean fluorescence intensity (MFI) of HLA‐specific antibodies was reported as follows: score 4 for MFI < 1000, score 6 for 1000 < MFI < 3000 and score 8 for MFI > 3000. The mean duration of ECMO support was 29 days [1–74] and 6.8 [1–29] PP sessions were performed per patient before transplant. The mean number of HLA‐specific antibodies before HT was 9.6 for score 6 [4–13] and 5.8 for score 8 [1–12]. Four patients had major complications after transplantation (2 hemorrhagic shocks, 5 infectious events). Mean MFI reduction rate was 94% [79–100] for Class I and 44.2% for Class II [0–83]. Hospital survival was 100%, and early antibody‐mediated rejection was diagnosed in one patient at 7 days after HT. Plasmapheresis under ECMO support was associated with favorable early outcomes in highly sensitized candidates for urgent heart transplantation.  相似文献   
86.
87.
88.
Biosecurity is crucial for infectious disease prevention, more importantly in the absence of vaccination. The need for improving the implementation of biosecurity practices was highlighted in French duck farms following the 2016–2017 H5N8 Highly Pathogenic Avian Influenza (HPAI) epidemic. Farmers have multiple reasons for not implementing biosecurity practices: external (time, money) and internal (socio‐psychological). The purpose of this study was to determine how sets of socio‐psychological factors (i.e. knowledge on biosecurity and avian influenza transmission, attitudes, personality traits, social background) affect the adoption of on‐farm biosecurity practices. Biosecurity practices and socio‐psychological determinants were assessed during 127 duck farm visits, in South West France, using both questionnaires and on‐farm observations. Factorial analysis of mixed data (FAMD) and hierarchical clustering analysis (HCA) identified three groups of farmers with different socio‐psychological profiles: the first group was characterized by minimal knowledge, negative attitudes towards biosecurity, little social pressure and a low level of conscientiousness. The second group was characterized by more extensive experience in poultry production, higher stress and social pressure. The third group was characterized by less experience in poultry production, better knowledge and positive attitudes towards biosecurity, increased self‐confidence and orientation towards action. The first group had a significantly lower adoption of biosecurity measures than the two other groups. A better understanding of the factors involved in farmers' decision‐making could improve the efficiency of interventions aiming at improving and maintaining the level of on‐farm biosecurity in the duck industry.  相似文献   
89.
90.
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