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   232603篇
  免费   9915篇
  国内免费   487篇
耳鼻咽喉   3275篇
儿科学   6730篇
妇产科学   5325篇
基础医学   33145篇
口腔科学   8032篇
临床医学   13789篇
内科学   52313篇
皮肤病学   6526篇
神经病学   18976篇
特种医学   5675篇
外国民族医学   2篇
外科学   27146篇
综合类   1107篇
一般理论   54篇
预防医学   26826篇
眼科学   5936篇
药学   17743篇
中国医学   999篇
肿瘤学   9406篇
  2023年   1233篇
  2022年   859篇
  2021年   3664篇
  2020年   2033篇
  2019年   4181篇
  2018年   7436篇
  2017年   4602篇
  2016年   4529篇
  2015年   5088篇
  2014年   5606篇
  2013年   8642篇
  2012年   14959篇
  2011年   15843篇
  2010年   7864篇
  2009年   5634篇
  2008年   12986篇
  2007年   13976篇
  2006年   13180篇
  2005年   12876篇
  2004年   11742篇
  2003年   11038篇
  2002年   10462篇
  2001年   6968篇
  2000年   7823篇
  1999年   5994篇
  1998年   1007篇
  1992年   2942篇
  1991年   2578篇
  1990年   2488篇
  1989年   2101篇
  1988年   1972篇
  1987年   1863篇
  1986年   1887篇
  1985年   1730篇
  1984年   1259篇
  1983年   1065篇
  1979年   1386篇
  1978年   906篇
  1977年   885篇
  1976年   866篇
  1975年   1020篇
  1974年   1304篇
  1973年   1372篇
  1972年   1283篇
  1971年   1256篇
  1970年   1165篇
  1969年   1224篇
  1968年   1267篇
  1967年   1120篇
  1966年   992篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
93.
94.
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   
95.
The concept of participation was reviewed as a component of children's citizenship in order to promote a programme for Integral Development. A narrative revision of the literature was carried out as well as a group discussion was organized along with the staff of an Integral Care Programme, in order to identify notions of democracy and child citizenship related to care and rearing. Some elements that favoured the child participation and some parenting skills were identified. Among the elements that must be encouraged in children are: the development of emotional, cognitive and communicative skills and promotion of decision-making; among the parent skills development included are: sensitivity and responsivity; establishing routines and participation experiences. It is important to stand out that the identified elements to promote child participation and parental competences should be adapted to every specific cultural context.  相似文献   
96.
97.
98.
99.
100.
Studies on the exposure of children to sugar-sweetened beverages (SSBs) at an early age may contribute to better understand the common causes and the temporal order of the relationships between obesity and asthma in early childhood. The objective of this study was to estimate the association between SSB and child asthma traits in the 2nd year of life, modeling direct and indirect pathways mediated by the highest BMI-z of the child and allergic inflammation. Data from the BRISA cohort, São Luís-MA, Brazil (n = 1140), were obtained from the baseline and from the follow-up performed at the 2nd year of life. The main explanatory variable was the calories from added sugars in SSBs as a percentage of the total daily energy intake. The outcome child asthma traits was a latent variable deduced from four indicators: medical diagnosis of asthma, wheezing, emergency visit due to intense wheezing, and medical diagnosis of rhinitis. A high percentage of daily calories from sugars added to SSBs was directly associated with higher values of child asthma traits (standardized coefficient (SC = 0.073; P = .030)). High levels of eosinophils were also directly associated with child asthma traits (SC = 0.118; P = .049). No mediation pathways were observed via greater BMI-z or eosinophil counts. Therefore, early exposure of children to SSB may contribute to increased risk of childhood asthma, preceding the link between sugar consumption and overweight/obesity, not yet evident in children in the first 2 years of life.  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