全文获取类型
收费全文 | 1086067篇 |
免费 | 74159篇 |
国内免费 | 3386篇 |
专业分类
耳鼻咽喉 | 13603篇 |
儿科学 | 35116篇 |
妇产科学 | 29332篇 |
基础医学 | 159834篇 |
口腔科学 | 29033篇 |
临床医学 | 104813篇 |
内科学 | 208670篇 |
皮肤病学 | 21315篇 |
神经病学 | 90406篇 |
特种医学 | 39105篇 |
外国民族医学 | 306篇 |
外科学 | 148286篇 |
综合类 | 23105篇 |
现状与发展 | 1篇 |
一般理论 | 369篇 |
预防医学 | 92425篇 |
眼科学 | 23357篇 |
药学 | 79935篇 |
32篇 | |
中国医学 | 2584篇 |
肿瘤学 | 61985篇 |
出版年
2021年 | 9033篇 |
2019年 | 9894篇 |
2018年 | 13246篇 |
2017年 | 10007篇 |
2016年 | 10840篇 |
2015年 | 12286篇 |
2014年 | 16800篇 |
2013年 | 25897篇 |
2012年 | 35821篇 |
2011年 | 37760篇 |
2010年 | 21964篇 |
2009年 | 20092篇 |
2008年 | 34618篇 |
2007年 | 36434篇 |
2006年 | 36455篇 |
2005年 | 35115篇 |
2004年 | 33521篇 |
2003年 | 31878篇 |
2002年 | 30782篇 |
2001年 | 49053篇 |
2000年 | 50319篇 |
1999年 | 42125篇 |
1998年 | 11793篇 |
1997年 | 10748篇 |
1996年 | 10681篇 |
1995年 | 10063篇 |
1994年 | 9422篇 |
1993年 | 8807篇 |
1992年 | 33600篇 |
1991年 | 32912篇 |
1990年 | 31788篇 |
1989年 | 30042篇 |
1988年 | 27952篇 |
1987年 | 26995篇 |
1986年 | 25854篇 |
1985年 | 24648篇 |
1984年 | 18447篇 |
1983年 | 15751篇 |
1982年 | 9521篇 |
1979年 | 16682篇 |
1978年 | 11870篇 |
1977年 | 9720篇 |
1976年 | 9530篇 |
1975年 | 9686篇 |
1974年 | 11919篇 |
1973年 | 11718篇 |
1972年 | 10751篇 |
1971年 | 10034篇 |
1970年 | 9234篇 |
1969年 | 8336篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Erin C. Peckham-Gregory Kenneth L. McClain Carl E. Allen Michael E. Scheurer Philip J. Lupo 《Annals of epidemiology》2018,28(8):521-528
Purpose
Potential roles of inherited and environmental risk factors in pathogenesis of Langerhans cell histiocytosis (LCH), a myeloid neoplastic disorder, are undefined. We therefore evaluated the role of parental and perinatal factors on the risk of this childhood cancer.Methods
Information on LCH cases (n = 162) for the period 1995–2011 was obtained from the Texas Cancer Registry. Birth certificate controls were frequency-matched on year of birth at a ratio of 10:1 for the same period. Variables evaluated included parental age, race/ethnicity, size for gestational age, and birth order. Logistic regression was used to generate an adjusted odds ratio (aOR) and 95% confidence interval (CI) testing the association between each factor and LCH.Results
Few perinatal or parental factors were associated with LCH risk, with the exception of race/ethnicity. Mothers of Hispanic ethnicity were more likely to have children who developed LCH compared to non-Hispanic whites (aOR: 1.51; 95% CI: 1.02–2.25). This risk increased when both parents were Hispanic (aOR: 1.80; 95% CI: 1.13–2.87). Non-Hispanic black mothers were suggested as less likely to give birth to offspring who developed LCH compared to non-Hispanic whites (aOR: 0.50; 95% CI: 0.24–1.02).Conclusions
LCH is characterized by somatic mutations in MAPK pathway genes in myeloid precursors. Increased risk for LCH in children of Hispanic parents suggests potential impact of inherited factors on LCH pathogenesis. 相似文献142.
Background
The Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue Scale is an internationally used validated measure. General population–based age- and sex-specific percentile norms are, however, not published to date, although these are needed as reference for the interpretation of clinical research data.Objectives
To assess the FACIT-Fatigue Scale in a large representative sample of the German general population to examine psychometric characteristics and factorial structure and to provide population-based norms.Methods
A nationally representative face-to-face household survey was conducted in Germany using the FACIT-Fatigue Scale. Item characteristics were examined. Internal consistency was determined using the Cronbach α. Dimensionality was analyzed using confirmatory factor analysis (CFA) and bifactor analysis. Scale score differences relating to sex and age were assessed. Sex- and age-specific percentiles were computed for the entire scale range.Results
Of 2426 participants, 55.7% were women, and the mean age was 49.8 ± 17.4 years. The FACIT-Fatigue Scale mean was 43.5 ± 8.3. Cronbach α was high at 0.92. Although fit indices of the CFA were below desired levels (root mean squared error of approximation = 0.144, comparative fit index = 0.846, and Tucker-Lewis index = 0.815), item loadings in the CFA and bifactor analysis confirm the scale’s unidimensionality. Women were more fatigued than men, and participants who were 70 years or older showed higher fatigue scores than younger respondents. Thus, sex- and age-specific population-based percentiles were provided.Conclusions
Reliability and validity of the German translation of the FACIT-Fatigue Scale were confirmed. This study provides general population–based sex- and age-specific FACIT-Fatigue Scale percentile norms for the first time, thereby contributing to a meaningful interpretation of clinical research data. 相似文献143.
144.
145.
146.
Nichole L. Hodges Lara B. McKenzie Sarah E. Anderson Mira L. Katz 《Maternal and child health journal》2018,22(8):1111-1117
Objectives The purpose of this qualitative study was to explore the infant safe sleep beliefs and occupational practices of lactation consultants and to determine if lactation consultants give advice to clients that is consistent with the American Academy of Pediatrics’ recommendations on this topic. Methods Focus groups were conducted with certified lactation consultants in two cities in Ohio. Participants discussed the role of lactation consultants, the infant sleep advice they provide to women, their views on the American Academy of Pediatrics’ infant safe sleep recommendations and related policies, and perceived benefits and barriers associated with providing infant safe sleep education as part of their work. A member-checking session was held to ensure the credibility of the findings. Results Four focus groups were conducted with 22 certified lactation consultants between September and November 2015. Major themes that emerged included: lactation consultants’ beliefs regarding the importance of bedsharing for supporting breastfeeding success; their disagreement with the infant safe sleep recommendations of the American Academy of Pediatrics; their frustration with policies that restrict consultants’ ability to discuss bedsharing; and the impact of infant safe sleep policies on their work and the advice they provide. Conclusions for Practice Lactation consultants interact with mothers of newborns at a critical time for infant safe sleep decision-making and may influence a woman’s choices related to this topic. Women may not be receiving messages from lactation consultants that are consistent with the infant safe sleep recommendations of the American Academy of Pediatrics. 相似文献
147.
148.
149.
Wei-Guang Zhang Linpei Jia J. Ma S.-Y. Zhu S.-S. Nie K.-K. Song X.-M. Liu Y.-P. Zhang D. Cao X.-P. Yang D.-L. Zhao M.-J. Xiu L. Lin Z.-X. Li Q. Huang X.-Z. Chen L. Chen P. Wang X.-J. Bai Z. Feng B. Fu J. Huang J.-P. Zhang Guangyan Cai X.-F. Sun Xiangmei Chen 《The journal of nutrition, health & aging》2018,22(2):276-281
Objectives
We aimed to evaluate the relationship between baseline renal function and changes in telomere length in Han Chinese.Methods
The telomere restriction fragment (TRF) length of leukocytes in the peripheral blood was measured in healthy volunteers recruited in 2014. The estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine (Scr) and serum cystatin C (CysC)-eGFRcys and eGFRScr-cys through the Cockcroft-Gault formula (eGFRC-G) or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI / eGFRCKD-EPI) equation. The correlation between telomere length changes over time and renal function was analyzed.Results
Leukocyte TRF lengths were negatively correlated to age (r = -0.393, p < 0.001) and serum CysC (r = -0.180, p < 0.01), while positively associated with eGFRCKD-EPI, eGFRC-G, eGFRcys, and eGFRScr-cys (r = 0.182, 0.122, 0.290, and 0.254 respectively, p < 0.01). The 3-year change of telomere length was 46 bp/years. When adjusted for age, the associations between telomere length changes and baseline, subsequent TRF lengths, and serum CysC were no longer present. No association was observed between TRF length changes and renal function.Conclusion
The rate of telomere length changes was affected by age and baseline telomere length. The telomere length changes might be important markers for aging.150.
Ann M. Vuong Kimberly Yolton Kendra L. Poston Changchun Xie Glenys M. Webster Andreas Sjödin Joseph M. Braun Kim N. Dietrich Bruce P. Lanphear Aimin Chen 《International journal of hygiene and environmental health》2018,221(1):87-94
Prenatal exposure to polybrominated diphenyl ethers (PBDEs) have been reported to impair executive function in children, but little is known whether childhood PBDE exposures play a role. Using the Health Outcomes and Measures of the Environment (HOME) Study, a prospective birth cohort in the greater Cincinnati area, we investigated the association between repeated measures of PBDEs during childhood and executive function at 8 years in 208 children and whether effect modification by child sex was present. We used child serum collected at 1, 2, 3, 5, and 8 years to measure PBDEs. The Behavior Rating Inventory of Executive Function was completed by parents to assess executive function at 8 years. We used multiple informant models to examine childhood PBDEs during several exposure windows. Null associations were observed between early childhood PBDEs and executive function. However, we observed significant adverse associations between a 10-fold increase in concurrent concentrations of BDE-28 (β = 4.6, 95% CI 0.5, 8.7) and BDE-153 (β = 4.8, 95% CI 0.8, 8.8) with behavioral regulation. In addition, PBDEs at 8 years were significantly associated with poorer emotional and impulse control. No associations were noted between childhood PBDEs and metacognition or global executive function. However, child sex significantly modified the associations, with significantly poorer executive function among males with higher concurrent BDE-153, and null associations in females. Our study findings suggest that concurrent PBDE exposures during childhood may be associated with poorer executive function, specifically behavior regulation. Males may also be more sensitive to adverse associations of concurrent PBDEs on executive function. 相似文献