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   2560篇
  免费   212篇
  国内免费   1篇
  2023年   13篇
  2022年   44篇
  2021年   73篇
  2020年   31篇
  2019年   43篇
  2018年   51篇
  2017年   53篇
  2016年   89篇
  2015年   162篇
  2014年   154篇
  2013年   176篇
  2012年   249篇
  2011年   229篇
  2010年   130篇
  2009年   118篇
  2008年   154篇
  2007年   159篇
  2006年   158篇
  2005年   137篇
  2004年   129篇
  2003年   123篇
  2002年   108篇
  2001年   12篇
  2000年   10篇
  1999年   18篇
  1998年   16篇
  1997年   12篇
  1996年   12篇
  1995年   12篇
  1994年   14篇
  1993年   10篇
  1992年   5篇
  1991年   8篇
  1990年   5篇
  1989年   4篇
  1988年   8篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   7篇
  1983年   3篇
  1982年   3篇
  1981年   4篇
  1980年   3篇
  1979年   4篇
  1978年   3篇
  1974年   2篇
  1973年   3篇
  1971年   1篇
  1969年   1篇
排序方式: 共有2773条查询结果,搜索用时 15 毫秒
991.

Background

Apolipoprotein E (APOE) polymorphism is associated with lipid levels. Some studies have reported that blood lipid response to diet or obesity varies depending on APOE genotypes. The aim of this study was to assess the effect of APOE genotypes, the intake of saturated fatty acids (SFA), and obesity on serum lipid levels in Lithuanian adult population.

Methodology/Principal Findings

A cross-sectional health survey was carried out in five municipalities of Lithuania. The random sample was obtained from lists of 25–64 year-old inhabitants registered at primary health care centres. The data from 996 subjects (416 men and 580 women) were analysed in this study. Two single-nucleotide polymorphisms (rs429358 and rs7412) were assessed using a real-time polymerase chain reaction. 24-hour recall and food frequency questionnaire were used for evaluation of dietary habits. Serum lipids were determined using enzymatic methods.Men and women with the APOE2 genotype had the lowest level of total cholesterol (TC) (p = 0.002 for men, and p = 0.02 for women) and low-density lipoprotein cholesterol (LDL-C) (p<0.001). Multivariate linear regression analysis showed that age, genotype APOE2, SFA intake, and body mass index (BMI) were significant determinants of TC and LDL-C level (with p values ranging from 0.043 to 0.001). Our data did not reveal any statistically significant interactions between APOE genotype and SFA intake or between APOE genotype and BMI regarding TC and LDL-C level (all p>0.05). However, the predictive power of the regression model for LDL-C improved when gene-BMI interaction and gene-BMI interaction plus gene-nutrient interaction were added (p = 0.04 and p = 0.032 for R2 change, respectively).

Conclusions/Significance

APOE genotypes, SFA intake, and obesity were found to be associated with blood lipid levels in Lithuanian adult population. Analysis of gene-diet and gene-obesity interactions did not confirm that the effects of diet and obesity on TC and LDL-C level significantly depended on APOE genotype.  相似文献   
992.
Knowledge of factors that trigger human response to climate change is crucial for effective climate change policy communication. Climate change has been claimed to have low salience as a risk issue because it cannot be directly experienced. Still, personal factors such as strength of belief in local effects of climate change have been shown to correlate strongly with responses to climate change and there is a growing literature on the hypothesis that personal experience of climate change (and/or its effects) explains responses to climate change. Here we provide, using survey data from 845 private forest owners operating in a wide range of bio-climatic as well as economic-social-political structures in a latitudinal gradient across Europe, the first evidence that the personal strength of belief and perception of local effects of climate change, highly significantly explain human responses to climate change. A logistic regression model was fitted to the two variables, estimating expected probabilities ranging from 0.07 (SD ±0.01) to 0.81 (SD ±0.03) for self-reported adaptive measures taken. Adding socio-demographic variables improved the fit, estimating expected probabilities ranging from 0.022 (SD ±0.008) to 0.91 (SD ±0.02). We conclude that to explain and predict adaptation to climate change, the combination of personal experience and belief must be considered.  相似文献   
993.

Background

Certain immune-mediated diseases (IMDs), such as rheumatoid arthritis and systemic lupus erythematosus, have been linked to cardiovascular disorders. We examined whether there is an association between 32 different IMDs and risk of subsequent hospitalization for coronary heart disease (CHD) related to coronary atherosclerosis in a nationwide follow up study in Sweden.

Methods and Findings

All individuals in Sweden hospitalized with a main diagnosis of an IMD (n = 336,479) without previous or coexisting CHD, between January 1, 1964 and December 31 2008, were followed for first hospitalization for CHD. The reference population was the total population of Sweden. Standardized incidence ratios (SIRs) for CHD were calculated. Overall risk of CHD during the first year after hospitalization for an IMD was 2.92 (95% CI 2.84–2.99). Twenty-seven of the 32 IMDs studied were associated with an increased risk of CHD during the first year after hospitalization. The overall risk of CHD decreased over time, from 1.75 after 1–5 years (95% CI 1.73–1.78), to 1.43 after 5–10 years (95% CI 1.41–1.46) and 1.28 after 10+ years (95% CI 1.26–1.30). Females generally had higher SIRs than males. The IMDs for which the SIRs of CDH were highest during the first year after hospitalization included chorea minor 6.98 (95% CI 1.32–20.65), systemic lupus erythematosus 4.94 (95% CI 4.15–5.83), rheumatic fever 4.65 (95% CI 3.53–6.01), Hashimoto''s thyroiditis 4.30 (95% CI 3.87–4.75), polymyositis/dermatomyositis 3.81 (95% CI 2.62–5.35), polyarteritis nodosa 3.81 (95% CI 2.72–5.19), rheumatoid arthritis 3.72 (95% CI 3.56–3.88), systemic sclerosis 3.44 (95% CI 2.86–4.09), primary biliary cirrhosis 3.32 (95% CI 2.34–4.58), and autoimmune hemolytic anemia 3.17 (95% CI 2.16–4.47).

Conclusions

Most IMDs are associated with increased risk of CHD in the first year after hospital admission. Our findings suggest that many hospitalized IMDs are tightly linked to coronary atherosclerosis.  相似文献   
994.
995.

Background

Earlier studies have suggested that sickness presenteeism (SP) may be a risk factor for future health problems. The purpose of the present study was to test this in a nationally representative prospective study of Swedish workers.

Methods

Prospective cohort with a representative sample of the Swedish working population surveyed in 2008 and 2010. Odds ratios (OR) with 95% confidence intervals (CI) were calculated using logistic regression.

Results

Those who reported more than 7 days of SP had higher risk of suboptimal SRH compared to those who reported no SP (OR = 5.95; 95% CI 4.98–7.12), also after adjustment for confounders (OR = 1.64; 95% CI 1.30–2.06). Those who reported 1–7 days of SP also had an increased risk before and after adjustments. Inclusion of self-rated physical and psychological work capacity did not attenuate the associations, whereas of emotional exhaustion attenuated the ORs to non-significance for both outcomes, indicating that the health consequences associated with SP are largely related to mental health.

Conclusion

The results strengthen earlier findings suggesting that SP can be a risk factor for future suboptimal general health and sickness absence, particularly through mental health problems. This indicates that asking about SP could yield important information for employers, occupational health practitioners and GPs, possibly leading to more timely intervention that could decrease the risk of future sickness absence and more serious health problems, especially in the mental domain. Further studies of the possible causal pathways between SP and future health development are also warranted, especially since going to work is often seen as desirable also for those with poor health.  相似文献   
996.
997.
998.
Ecosystems are simultaneously affected by biodiversity loss and climate change, but we know little about how these factors interact. We predicted that climate warming and CO (2) -enrichment should strengthen trophic cascades by reducing the relative efficiency of predation-resistant herbivores, if herbivore consumption rate trades off with predation resistance. This weakens the insurance effect of herbivore diversity. We tested this prediction using experimental ocean warming and acidification in seagrass mesocosms. Meta-analyses of published experiments first indicated that consumption rate trades off with predation resistance. The experiment then showed that three common herbivores together controlled macroalgae and facilitated seagrass dominance, regardless of climate change. When the predation-vulnerable herbivore was excluded in normal conditions, the two resistant herbivores maintained top-down control. Under warming, however, increased algal growth outstripped control by herbivores and the system became algal-dominated. Consequently, climate change can reduce the relative efficiency of resistant herbivores and weaken the insurance effect of biodiversity.  相似文献   
999.
Children respond positively to individuals who favor them and also to individuals who are fair. The present studies examine the interaction between these two preferences by presenting children with two distributors who share resources with the child participant and another recipient. Children are asked whom they like better: the distributor who was unfair but favored the child participant or the distributor who was fair and showed no (or reduced) favoritism. In Study 1, we find that when fairness and favoritism are in conflict, children are split on whom they prefer. In Study 2, we find that placing children in a competitive context leads to a stronger preference for the distributor who favored the child participant. In Study 3, we examine whether children's preference for favoritism persists when both distributors gave the child the same number of rewards, but one distributor gave the child participant relatively more than the other recipient. In this situation, we find that children prefer the fair distributor. However, we again find that creating a competitive context reduces children's preference for the fair distributor. Finally we find that in a third-party context, children value fairness over generosity. Taken together, these results show how children balance competing concerns for fairness and favoritism.  相似文献   
1000.
The brain function depends on a continuous supply of blood. The blood–brain barrier (BBB), which is formed by vascular cells and glia, separates components of the circulating blood from neurons and maintains the precisely regulated brain milieu required for proper neuronal function. A compromised BBB alters the transport of molecules between the blood and brain and has been associated with or shown to precede neurodegenerative disease. Blood components immediately leak into the brain after mechanical damage or as a consequence of a compromised BBB in brain disease changing the extracellular environment at sites of vascular damage. It is intriguing how blood-derived components alter the cellular and molecular constituents of the neurovascular interface after BBB opening. We recently identified an unexpected role for the blood protein fibrinogen, which is deposited in the nervous system promptly after vascular damage, as an initial scar inducer by promoting the availability of active TGF-β. Fibrinogen-bound latent TGF-β interacts with astrocytes, leading to active TGF-β formation and activation of the TGF-β/Smad signaling pathway. Here, we discuss the pleiotropic effects of potentially vascular-derived TGF-β on cells at the neurovascular interface and we speculate how these biological effects might contribute to degeneration and regeneration processes. Summarizing the effects of the components derived from the brain vascular system on nervous system regeneration might support the development of new therapeutic approaches.  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