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   1174篇
  免费   68篇
  国内免费   4篇
耳鼻咽喉   21篇
儿科学   35篇
妇产科学   27篇
基础医学   142篇
口腔科学   67篇
临床医学   104篇
内科学   221篇
皮肤病学   23篇
神经病学   152篇
特种医学   18篇
外科学   80篇
综合类   6篇
预防医学   120篇
眼科学   13篇
药学   108篇
中国医学   12篇
肿瘤学   97篇
  2024年   3篇
  2023年   17篇
  2022年   37篇
  2021年   62篇
  2020年   49篇
  2019年   47篇
  2018年   49篇
  2017年   41篇
  2016年   53篇
  2015年   42篇
  2014年   70篇
  2013年   82篇
  2012年   106篇
  2011年   124篇
  2010年   70篇
  2009年   36篇
  2008年   76篇
  2007年   50篇
  2006年   44篇
  2005年   41篇
  2004年   46篇
  2003年   27篇
  2002年   25篇
  2001年   8篇
  2000年   4篇
  1999年   6篇
  1998年   6篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1985年   1篇
  1979年   4篇
  1975年   1篇
  1973年   1篇
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
1.
Purpose of the study: the aim of this study was to synthesize PFC fNIRS outcomes on the effects of cognitive tasks compared to resting/baseline tasks in healthy adults from studies utilizing a pre/post design.

Material and methods: original research studies were searched from seven databases (MEDLINE, EMBASE, CENTRAL, CINAHL, SCOPUS, PEDro and PubMed). Subsequently, two independent reviewers screened the titles and abstracts followed by full-text reviews to assess the studies' eligibility.

Results: eleven studies met the inclusion criteria and had data abstracted and quality assessed. Methodology varied considerably and yet cognitive tasks resulted in the ΔO2Hb increasing in 8 of the 11 and ΔHHb decreasing in 8 of 8 studies that reported this outcome. The cognitive tasks from 10 of the 11 studies were classified as “Working Memory” and “Verbal Fluency Tasks”.

Conclusions: although, the data comparison was challenging provided the heterogeneity in methodology, the results across studies were similar.  相似文献   

2.
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   
3.
Cytokines are important regulators of materno-fetal immunotolerance in mammals. They act within an intricate network, in which the balance among different cytokines contributes to the success of reproductive processes. Despite numerous studies, however, the role of cytokines at the materno-fetal interface remains largely unknown. Interleukin-1 (IL-1) is a proinflammatory cytokine with many functions in the immune system and in defence against infections. There have been very many studies of the presence and role of IL-1 in human and murine reproduction. Although studies on mammals have shown that IL-1 is an essential mediator in embryo implantation and establishment of pregnancy, mice that are transgenic for most components of the IL-1 family breed normally, suggesting that IL-1 acts in concert with other cytokines at the materno-fetal interface. We recently showed that IL-1 is also expressed by the placenta of non-mammalian vertebrates, including some squamate reptiles and elasmobranch fishes. The expression of IL-1 at the materno-fetal interface in the phylogenetically oldest extant placental vertebrates suggests that IL-1 is a fundamental regulator of materno-fetal relationships.  相似文献   
4.
BACKGROUND: The hypo-osmotic swelling (HOS) test evaluates the ability of the functional sperm plasma membrane to stretch following cell swelling when exposed to hypo-osmotic solutions. Sperm samples with low HOS scores show low fertilization and pregnancy rates during assisted reproductive techniques, though data are controversial. The aim of this study was to compare the results of the HOS test in a group of normozoospermic men with those in a group of subjects affected by autoimmune infertility due to the presence of antisperm antibodies (ASA) bound to the sperm surface. METHODS: Sperm from normozoospermic and from infertile subjects affected by autoimmune infertility were exposed to hypo-osmolar conditions to verify the effects on intracellular calcium concentrations and acrosome reaction. RESULTS: Sperm samples from infertile men with ASA showed HOS test scores that were significantly lower than those of normozoospermic subjects despite similar sperm viability percentages. Sperm with ASA bound to their plasma membrane showed a reduced rise in intracellular calcium concentrations and acrosome reaction after hypo-osmotic challenge with respect to sperm from normozoospermic subjects without ASA. CONCLUSIONS: Infertile subjects with ASA have a reduced sperm plasma membrane functional integrity that could explain, at least in part, the low fertilization and pregnancy rates observed in these subjects during assisted reproductive procedures. Evaluation for the presence of ASA in all sperm samples showing low HOS test scores in the presence of normal sperm viability percentages is suggested.  相似文献   
5.
Maternal and Child Health Journal - Dietary patterns can influence maternal and child health outcomes. The study aims to characterize dietary patterns during pregnancy as well as to identify their...  相似文献   
6.
BackgroundObesity has reached epidemic proportions worldwide, affecting life quality and span. Susceptibility to obesity is partly mediated by genetic differences. Indeed, several genes from the clock gene family have already been shown to be intimately associated with obesity in diverse ethnic groups. In the present study, an association between BMI and the rs707467, rs228697 and rs228729 PER3 (Period Circadian Clock 3) polymorphisms in subjects with class II (BMI ≥ 35.0–39.9 kg/m2) and class III obesity (>40 kg/m2, extreme obesity) were carried out using TaqMan real-time PCR. Overall, 259 Brazilian adults were genotyped, of whom 122 had class II or III obesity (BMI ≥ 35.0 kg/m2) and 137 were controls having normal weight (BMI > 18.5 and <24.9 kg/m2).ResultsPER3 tag SNP (rs228729) shows a significant association with extreme obesity (1000 permutation p = 0.03 and p = 0.04), for genotype and allele frequency respectively) and a haplotype among the three assessed SNPs (alleles G/T/A, rs228697, rs228729, and rs707467, respectively, 1000 permutation p = 0.03) was significantly more prevalent in the group with obesity.ConclusionThis exploratory association study suggests that PER3 rs228729 may be associated with extreme obesity in Brazilian adults, however, replication is needed.  相似文献   
7.
OBJECTIVE: To investigate gender differences among older Brazilians in their health status and their use of health services. METHODS: Participants were individuals aged 60 years and older included in a national household survey conducted in Brazil in 1998. Data were analyzed by multiple logistic regression, taking into account the design effect due to multistage sampling. RESULTS: There were differences in the health and living conditions of older men and older women that were not explained by age or place of residence. Older women had worse indicators of schooling and personal income but better indicators of housing standards and per capita household income. The older women also reported more chronic diseases, had poorer indicators of independence and physical mobility, sought health services more often, and reported more medical visits in the previous year. Despite their apparent worse health conditions, elderly women in urban areas had lower hospitalization rates in the previous year (odds ratio = 0.89; 95% confidence interval, 0.82-0.96) than did elderly men in urban areas. CONCLUSIONS: Our results indicate that among older Brazilians there are gender inequalities in health that cannot be explained by age and place of residence. The findings raise questions on how health, socioeconomic, and cultural factors influence gender patterns of seeking and using health care in later life in the country. As pressures on health care and health funding increase in Brazil as a result of the aging of the population, there is a need to take a gender perspective into account.  相似文献   
8.
Few epidemiologic studies have investigated the potential relation between flavonoids and breast cancer risk. We have applied recently published data on the composition of foods and beverages in terms of six principal classes of flavonoids (i.e., flavanones, flavan-3-ols, flavonols, flavones, anthocyanidines, and isoflavones) on dietary information collected in a large-case control study of breast cancer conducted in Italy between 1991 and 1994. The study included 2,569 women with incident, histologically confirmed breast cancer, and 2,588 hospital controls. Odds ratios (OR) and 95% confidence intervals were estimated by multiple logistic regression models. After allowance for major confounding factors and energy intake, a reduced risk of breast cancer was found for increasing intake of flavones (OR, 0.81, for the highest versus the lowest quintile; P-trend, 0.02), and flavonols (OR, 0.80; P-trend, 0.06). No significant association was found for other flavonoids, including flavanones (OR, 0.95), flavan-3-ols (OR, 0.86), anthocyanidins (OR, 1.09), as well as for isoflavones (OR, 1.05). The findings of this large study of an inverse association between flavones and breast cancer risk confirm the results of a Greek study.  相似文献   
9.
Spinal cord signal abnormality resulting from alterations in cerebrospinal fluid flow at the craniocervical junction has been termed a presyrinx state. This condition has been described in the adult literature in association with a variety of conditions that cause obstruction to normal cerebrospinal fluid flow. We present a case of presyrinx in a child in the setting of acquired Chiari I malformation caused by lumboperitoneal overshunting. Awareness of the potentially reversible nature of this condition might allow for intervention before irreversible neurological damage has occurred.  相似文献   
10.
Supplementation with olive and fish oils reverses the effects of stress on behavioral activities and adrenal activation. However, previous studies have not shown whether supplementation with olive and fish oil could inhibit the effects of stress on cutaneous wound healing. Thus, this study investigated the effects of supplementation with fish or olive oil on cutaneous healing in stressed mice. Mice were subjected to rotational stress and treated with olive or fish oil daily until euthanasia. An excisional lesion was created on each mouse, and 14 days later, the lesions were analyzed. In addition, murine skin fibroblasts were exposed to elevated epinephrine levels plus olive oil, and fibroblast activity was evaluated. In the in vivo studies, administration of olive oil, but not fish oil, inhibited stress‐induced reduction in wound contraction, reepithelialization, hydroxyproline levels, and blood vessel density. Stress‐induced increases in vascular endothelial growth factor expression and the numbers of macrophages and neutrophils were reversed only by olive oil. Both oils reversed stress‐induced increase in catecholamine levels and oxidative damage. In in vitro studies, olive oil treatment reversed the reduction in fibroblast migration and collagen deposition and the increase in lipid peroxidation induced by epinephrine. In conclusion, supplementation with olive oil, but not fish oil, improves cutaneous wound healing in chronically stressed mice.  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