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   15834篇
  免费   1043篇
  国内免费   236篇
耳鼻咽喉   530篇
儿科学   4665篇
妇产科学   155篇
基础医学   637篇
口腔科学   142篇
临床医学   1541篇
内科学   725篇
皮肤病学   152篇
神经病学   1721篇
特种医学   426篇
外科学   1348篇
综合类   1410篇
预防医学   2534篇
眼科学   137篇
药学   720篇
中国医学   134篇
肿瘤学   136篇
  2024年   16篇
  2023年   264篇
  2022年   605篇
  2021年   731篇
  2020年   600篇
  2019年   518篇
  2018年   521篇
  2017年   561篇
  2016年   636篇
  2015年   578篇
  2014年   1072篇
  2013年   1169篇
  2012年   929篇
  2011年   1062篇
  2010年   838篇
  2009年   888篇
  2008年   909篇
  2007年   846篇
  2006年   667篇
  2005年   610篇
  2004年   515篇
  2003年   368篇
  2002年   340篇
  2001年   305篇
  2000年   249篇
  1999年   176篇
  1998年   155篇
  1997年   107篇
  1996年   87篇
  1995年   87篇
  1994年   64篇
  1993年   74篇
  1992年   61篇
  1991年   43篇
  1990年   29篇
  1989年   39篇
  1988年   49篇
  1987年   35篇
  1986年   40篇
  1985年   48篇
  1984年   34篇
  1983年   19篇
  1982年   17篇
  1981年   23篇
  1980年   21篇
  1979年   27篇
  1978年   15篇
  1977年   14篇
  1976年   16篇
  1974年   15篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
Child benefits are typically paid from birth. This paper asks whether starting universal child benefits in pregnancy leads to improvements in infant health. Leveraging administrative birth registry and hospital microdata from England and Wales, I study the effects of the Health in Pregnancy Grant, a universal conditional cash transfer equivalent to three months of child benefit (190 GBP) as a lump sum to pregnant mothers from 2009 to 2011. I exploit quasi-experimental variation in eligibility with a regression discontinuity design in the date of birth of the baby. I find that the policy increased birth weight by 8–12 grams on average, reduced low birth weight (<2500 g) by 3-6 percent and decreased prematurity by 9–11 percent. Younger mothers, particularly those living in deprived areas, benefit the most. I present evidence that the mechanisms are unlikely to be antenatal care, nutrition or smoking, with reductions in stress remaining a possible explanation.  相似文献   
2.
3.
BackgroundDental caries is the most common chronic childhood disease. Past studies revealed that grandparents provide their grandchildren with cariogenic foods and beverages (eg, those with free sugars and/or modified starches). Qualitative research can help identify what drives this phenomenon.ObjectiveOur aim was to examine mothers’ explanations for why grandparents in north central and central Appalachia give their grandchildren cariogenic foods and beverages.DesignA qualitative study on children’s oral health in Pennsylvania and West Virginia from 2018 through 2020 was performed. In-person, semi-structured interviews were conducted. Qualitative data from interviews were recorded, transcribed, and then coded using NVivo. Data analysis for this study was performed using thematic analysis with iterative theme development.Participants/settingThe participants were 126 mothers of children aged 3-5 years from West Virginia (n = 66) and Pittsburgh, PA (n = 60).Main outcome measuresMothers’ perspectives about why grandparents give their grandchildren cariogenic foods and beverages were analyzed.ResultsIn the study sample, 85% of mothers (n = 107/126) named at least 1 of their children’s grandparents as a member of their social network responsible for their children’s oral health. From these interviews, 85% of mothers (n = 91/107) discussed that grandparents gave their grandchildren cariogenic foods and beverages. The mothers described the following 4 themes to explain why grandparents gave their grandchildren cariogenic foods and beverages: privilege of the grandparent role; responsibilities of the grandparent role; symbol of care and affection; and limited consideration or understanding of the detrimental impact.ConclusionsGrandparents play a role in giving their grandchildren cariogenic foods and beverages, which could potentially contribute to childhood caries. Research is needed to develop effective social interventions to help some grandparents understand the implications of a cariogenic diet on their grandchildren’s oral health and/or decrease their provision of cariogenic foods and beverages.  相似文献   
4.
BackgroundOverweight and obesity have been observed in children with type 1 diabetes (T1D). This further increases their future risk of Cardiovascular Disease (CVD) as well as the development of other risk factors, such as dyslipidemia.AimsTo compare lipid profiles in children and adolescents with Type 1 diabetes and lean mass (T1L), Type 1 diabetes and overweight or obese (T1OW/OB), and type 2 diabetes (T2D).MethodsThis was a cross-sectional study of 669 patients with T1D or T2D aged 2–19 years using retrospective data collected from 2003 to 2014. Included patients were categorized into lean (BMI < 85th ile and overweight or Obese (BMI ≥ 85th ile). Patients were subcategorized into three age groups: < 10 years, 10–14 years, and 15–19 years.Results7.6% of patients had T2D. Of the patients with T1D, 58.9% were lean, 26.4% were overweight, and 14.7% were obese. Total Cholesterol (TC), Low-density lipoprotein cholesterol (LDL-C) and Non-HDL-C levels were similar across groups. In the 15–19 years group, Triglycerides (TG) levels were significantly higher in T1OW/OB and similar to T2D. High-density lipoprotein Cholesterol (HDL-C) was significantly lower in T2D. Weight status significantly correlated with TG and HDL-C levels in T1D and T2D groups.ConclusionsT1OW/OB constitutes a significant proportion of the T1D population. Patients with obesity and T1D, especially if in their late adolescence, have an adverse lipid profile pattern that is comparable to adolescents with T2D. Based on these findings, risk for future CVD in T1OW/OB and T2D may be equivalent.  相似文献   
5.
6.
There are an estimated 56 million orphans and vulnerable children across sub-Saharan Africa. Communities typically care for orphan children through informal caring arrangements – either within or outside of kinship networks. Within Kenya, an estimated 250,000 children live on the streets. There is less research related to fostering attitudes of this special population than orphans and vulnerable children generally. Important research over the past decade has illuminated multiple ways in which children are made more vulnerable because of HIV, including parental death and street-migration from HIV-affected households. As HIV transitions from a terminal illness to a chronic, manageable one, research is also required to establish how parents living with HIV can be an asset to children. In this study, we assess whether mothers living with HIV were very willing to foster biologically-related children, and street-involved children, how these fostering attitudes differed from mothers not living with HIV, and whether differences in fostering attitudes by reported HIV status were mediated by social support, family functioning and general self-rated health. Approximately 40% of mothers living with HIV were very willing to provide long-term foster care to biologically-related or street-involved children. This was less than the percentage of mothers not living with HIV, who were very willing to foster biologically-related children (61%) or street-involved children (58%). Significant portions of these differences were explained by social support, family functioning and general self-rated health. Multi-sectoral approaches are suggested by these findings in order to improve the child-fostering capacity of mothers living with HIV. Improving social support, family functioning and general self-rated health among HIV-infected mothers may not only provide protective benefits for the mothers and their children, but also expand the community’s capacity to care for orphan and vulnerable children.  相似文献   
7.
8.
《Vaccine》2020,38(42):6508-6516
BackgroundPneumococcal conjugate vaccine (PCV) effectiveness against radiographic pneumonia in South Asia is unknown. Bangladesh introduced PCV10 in 2015 using a three dose primary series (3 + 0). We sought to measure PCV10 effectiveness for two or more vaccine doses on radiographic pneumonia among vaccine-eligible children in rural Bangladesh.MethodsWe conducted a matched case-control study over two years from 2015 to 2017 using clinic and community controls in three subdistricts of Sylhet, Bangladesh. Cases were vaccine eligible 3–35 month olds at Upazila Health Complex outpatient clinics with World Health Organization-defined radiographic primary endpoint pneumonia (radiographic pneumonia). Clinic controls were matched to cases within a one week time window by age, sex, and clinic and had an illness unlikely to be Streptococcus pneumoniae; community controls were healthy and similarly matched within a one week time window by age and sex, and distance from the clinic. We estimated adjusted vaccine effectiveness (aVE) using conditional logistic regression.ResultsWe matched 1262 cases with 2707 clinic and 2461 community controls. Overall, aVE using clinic controls was 21.4% (95% confidence interval, −0.2%, 38.4%) for ≥2 PCV10 doses and among 3–11 month olds was 47.3% (10.5%, 69.0%) for three doses. aVE increased with higher numbers of doses in clinic control sets (p = 0.007). In contrast, aVE using community controls was 7.6% (95% confidence interval, −22.2%, 30.0%) for ≥2 doses. We found vaccine introduction in the study area faster and less variable than expected with 75% coverage on average, which reduced power. Information bias may also have affected community controls.ConclusionsClinic control analyses show PCV10 prevented radiographic pneumonia in Bangladesh, especially among younger children receiving three doses. While both analyses were underpowered, community control enrollment – compared to clinic controls – was more difficult in a complex, pluralistic healthcare system. Future studies in comparable settings may consider alternative study designs.  相似文献   
9.
10.
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