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   443749篇
  免费   22430篇
  国内免费   1574篇
耳鼻咽喉   5516篇
儿科学   13864篇
妇产科学   10452篇
基础医学   57731篇
口腔科学   10469篇
临床医学   40317篇
内科学   87730篇
皮肤病学   7891篇
神经病学   35708篇
特种医学   18941篇
外国民族医学   109篇
外科学   67349篇
综合类   4681篇
现状与发展   1篇
一般理论   320篇
预防医学   37588篇
眼科学   10821篇
药学   30358篇
  9篇
中国医学   574篇
肿瘤学   27324篇
  2021年   5643篇
  2020年   3487篇
  2019年   5413篇
  2018年   9336篇
  2017年   8185篇
  2016年   8001篇
  2015年   10494篇
  2014年   12683篇
  2013年   15039篇
  2012年   27447篇
  2011年   23409篇
  2010年   12639篇
  2009年   13133篇
  2008年   18546篇
  2007年   20140篇
  2006年   20244篇
  2005年   27936篇
  2004年   28398篇
  2003年   22965篇
  2002年   17424篇
  2001年   6495篇
  2000年   3388篇
  1999年   8227篇
  1998年   3591篇
  1997年   2831篇
  1996年   2562篇
  1995年   2498篇
  1992年   8193篇
  1991年   8330篇
  1990年   8439篇
  1989年   7996篇
  1988年   7494篇
  1987年   7214篇
  1986年   6943篇
  1985年   6254篇
  1984年   4845篇
  1983年   4071篇
  1982年   2382篇
  1979年   4562篇
  1978年   3150篇
  1977年   2443篇
  1975年   2956篇
  1974年   3607篇
  1973年   3168篇
  1972年   3126篇
  1971年   3032篇
  1970年   2813篇
  1969年   2656篇
  1968年   2385篇
  1967年   2311篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Rhinovirus (RV) infections are linked to the development and exacerbation of allergic diseases including allergic asthma. IgE, another contributor to atopic disease pathogenesis, has been shown to regulate DC antiviral functions and influence T cell priming by monocytes. We previously demonstrated that IgE-mediated stimulation of monocytes alters multiple cellular functions including cytokine secretion, phagocytosis, and influenza-induced Th1 development. In this study, we investigate the effects of IgE-mediated stimulation on monocyte-driven, RV-induced T cell development utilizing primary human monocyte-T cell co-cultures. We demonstrate that IgE crosslinking of RV-exposed monocytes enhances monocyte-driven Th2 differentiation. This increase in RV-induced Th2 development was regulated by IgE-mediated inhibition of virus-induced type I IFN and induction of IL-10. These findings suggest an additional mechanism by which two clinically significant risk factors for allergic disease exacerbations—IgE-mediated stimulation and rhinovirus infection—may synergistically promote Th2 differentiation and allergic inflammation.  相似文献   
102.
103.
104.
IntroductionPeople with Down syndrome (DS) have high respiratory morbidity, evaluating their respiratory health with standardized, objective tests is desirable. Thus, the objective of this study was to evaluate the technical quality of Pulmonary Function Tests (PFTs) to determine which ones are most suitable for this population.MethodsParticipants included children, teenagers and adults with DS, 5 years of age or older (n = 302). The technical quality of the impulse oscillometry system (IOS), forced spirometry, lung-diffusing capacity for carbon monoxide (DLCO), and 6-min walk test (6MWT) were analyzed by age group. Capnography and pulse oximetry were included in the study. Technical quality was determined on the basis of current international PFTs standards.ResultsFifty-one percent of participants were males. A total of 184 participants (71%) who completed the IOS fulfilled the quality criteria, while 210 (70%) completed the 6MWT. Performance on forced spirometry and DLCO was poor. All pulse oximetries and 96% percent heart rates obtained had good quality, but exhaled carbon dioxide (PetCO2) and respiratory rate (RR) showed deficient repeatability.ConclusionsIOS appears to be the most reliable instrument for evaluating lung mechanics in individuals with DS.  相似文献   
105.
106.
107.
108.
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods.  相似文献   
109.
110.
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