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   658篇
  免费   28篇
  国内免费   4篇
儿科学   23篇
妇产科学   27篇
基础医学   43篇
口腔科学   6篇
临床医学   58篇
内科学   151篇
皮肤病学   1篇
神经病学   89篇
特种医学   21篇
外科学   154篇
综合类   11篇
预防医学   41篇
眼科学   2篇
药学   46篇
中国医学   1篇
肿瘤学   16篇
  2024年   1篇
  2023年   5篇
  2022年   15篇
  2021年   23篇
  2020年   12篇
  2019年   18篇
  2018年   17篇
  2017年   17篇
  2016年   16篇
  2015年   26篇
  2014年   25篇
  2013年   27篇
  2012年   61篇
  2011年   56篇
  2010年   29篇
  2009年   19篇
  2008年   34篇
  2007年   33篇
  2006年   37篇
  2005年   43篇
  2004年   34篇
  2003年   28篇
  2002年   14篇
  2001年   10篇
  2000年   12篇
  1999年   8篇
  1998年   6篇
  1997年   3篇
  1995年   2篇
  1994年   5篇
  1993年   3篇
  1992年   3篇
  1991年   6篇
  1990年   7篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1986年   5篇
  1985年   4篇
  1984年   1篇
  1983年   8篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1975年   1篇
  1971年   1篇
排序方式: 共有690条查询结果,搜索用时 187 毫秒
141.
142.
IGF-1 is a key growth factor during fetal life. Using DXA, we found that the concentration of IGF-1 in umbilical cord serum is strongly related to neonatal whole body bone mineral content, lean mass, and fat mass. However IGF-1 did not explain the relationships of maternal smoking, fat mass, and physical activity with neonatal bone mass. The study supports a direct role for circulating IGF-1 in growth of the fetal skeleton. INTRODUCTION: Evidence is accumulating that the risk of osteoporosis in later life may be determined in part by environmental influences during intrauterine and early postnatal life. We previously reported that maternal birthweight, smoking, fat stores, and physical activity during pregnancy predict neonatal bone mass. While the growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis is an important determinant of postnatal skeletal growth, there are few data relating the concentration of growth factors in umbilical cord blood to bone mineral content (BMC) and other indices of body composition in the newborn infant. MATERIALS AND METHODS: We conducted a population-based study in a cohort of full-term, newborn infants whose mothers were characterized for lifestyle, body composition, and nutrition through their normal pregnancies. In a sample of 119 infants from the cohort, we related cord serum IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 concentrations to neonatal body composition measured by DXA and evaluated the extent to which this cytokine mediates the previously reported effects of maternal diet and lifestyle on neonatal bone mass. RESULTS: There were strong positive associations between cord serum IGF-1 concentration and whole body BMC (r = 0.38, p < 0.001), whole body lean mass (r = 0.40, p < 0.001), and whole body fat mass (r = 0.50, p < 0.001) after adjusting for gestational age and sex. There was no association between cord serum IGF-1 and BMC adjusted for bone size. Neither cord serum IGF-1 nor IGFBP-3 explained the relationships that we previously reported between maternal influences and neonatal bone mass. CONCLUSIONS: Cord serum IGF-1 is more closely related to the size of the neonatal skeleton than to its degree of mineralization. Documented maternal determinants of neonatal bone mass seem to mediate their effects independently of variations in cord serum IGF-1 in healthy pregnancies.  相似文献   
143.
To test the hypothesis that 2-phenylethylamine (PEA) modulates affect, plasma levels and urinary excretion of its main metabolite, phenylacetic acid (PAA), were studied in depressed and manic subjects, and the mood-elevating effects of its precursor, L-phenylalanine, were studied in depressed subjects. Mean total plasma PAA concentrations were 491.83 +/- 232.84 ng/ml in 12 healthy volunteers and 300.33 +/- 197.44 ng/ml in 23 drug-free patients with major depression. The 24-hour urinary PAA excretion was also measured in 48 healthy volunteers (141.1 +/- 10.2 mg PAA/24 hr) and in 144 patients with major depression (78.2 +/- 41.0 mg PAA/24 hr). The results suggest that low plasma and urinary PAA may be state markers for depression and are compatible with the PEA hypothesis. In further support, phenylalanine elevated mood in 31 of 40 depressives.  相似文献   
144.
Twenty-four hour urinary phenylacetic acid was high in 12 acutely psychotic schizoaffective patients (240.3 +/- 51.9 mg/day) and low in 16 acutely psychotic schizophrenic patients (53.6 +/- 15.1 mg/day). These results indicate a biochemical difference between these two types of acute psychoses and indicate alterations in phenylalanine metabolism.  相似文献   
145.
146.
147.
The purpose of this study was to identify barriers to and facilitators of human papillomavirus (HPV) vaccination in children aged 9–17 years across Texas. A literature review informed the development of a web-based survey designed for people whose work involves HPV vaccination in settings serving pediatric patients. The survey was used to examine current HPV vaccine recommendation practices among healthcare providers, barriers to HPV vaccination, reasons for parent/caregiver vaccine refusal, staff and family education practices, utilization of reminder and recall systems and status of vaccine administration (payment, ordering and stocking). 1132 responses were received representing healthcare providers, administrative and managerial staff. Respondents identified perceived barriers to HPV vaccination as parental beliefs about lack of necessity of vaccination prior to sexual debut, parental concerns regarding safety and/or side effects, parental perceptions that their child is at low risk for HPV-related disease, and parental lack of knowledge that the vaccine is a series of three shots. Of responding healthcare providers, 94 % (n = 582) reported they recommend the vaccine for 9–12 year olds; however, same-day acceptance of the vaccine is low with only 5 % (n = 31) of providers reporting the HPV vaccine is “always” accepted the same day the recommendation is made. Healthcare providers and multidisciplinary care teams in pediatric care settings must work to identify gaps between recommendation and uptake to maximize clinical opportunities. Training in methods to communicate an effective HPV recommendation and patient education tailored to address identified barriers may be helpful to reduce missed opportunities and increase on-time HPV vaccinations.  相似文献   
148.
Organic light-emitting field-effect transistors (LEFETs) provide the possibility of simplifying the display pixilation design as they integrate the drive-transistor and the light emission in a single architecture. However, in p-type LEFETs, simultaneously achieving higher external quantum efficiency (EQE) at higher brightness, larger and stable emission area, and high switching speed are the limiting factors for to realise their applications. Herein, we present a p-type polymer heterostructure-based LEFET architecture with electron and hole injection interlayers to improve the charge injection into the light-emitting layer, which leads to better recombination. This device structure provides access to hole mobility of ~2.1 cm2 V−1 s−1 and EQE of 1.6% at a luminance of 2600 cd m−2. Most importantly, we observed a large area emission under the entire drain electrode, which was spatially stable (emission area is not dependent on the gate voltage and current density). These results show an important advancement in polymer-based LEFET technology toward realizing new digital display applications.  相似文献   
149.
150.
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