全文获取类型
收费全文 | 899篇 |
免费 | 139篇 |
专业分类
1038篇 |
出版年
2022年 | 7篇 |
2021年 | 11篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 31篇 |
2014年 | 39篇 |
2013年 | 45篇 |
2012年 | 59篇 |
2011年 | 63篇 |
2010年 | 45篇 |
2009年 | 36篇 |
2008年 | 54篇 |
2007年 | 51篇 |
2006年 | 55篇 |
2005年 | 49篇 |
2004年 | 57篇 |
2003年 | 51篇 |
2002年 | 58篇 |
2001年 | 6篇 |
1999年 | 6篇 |
1998年 | 21篇 |
1997年 | 8篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 8篇 |
1971年 | 6篇 |
1970年 | 11篇 |
1969年 | 8篇 |
1966年 | 4篇 |
1965年 | 4篇 |
1962年 | 4篇 |
排序方式: 共有1038条查询结果,搜索用时 15 毫秒
101.
Billings L Schwartz IB Shaw LB McCrary M Burke DS Cummings DA 《Journal of theoretical biology》2007,246(1):18-27
This paper investigates the complex dynamics induced by antibody-dependent enhancement (ADE) in multiserotype disease models. ADE is the increase in viral growth rate in the presence of immunity due to a previous infection of a different serotype. The increased viral growth rate is thought to increase the infectivity of the secondary infectious class. In our models, ADE induces the onset of oscillations without external forcing. The oscillations in the infectious classes represent outbreaks of the disease. In this paper, we derive approximations of the ADE parameter needed to induce oscillations and analyze the associated bifurcations that separate the types of oscillations. We then investigate the stability of these dynamics by adding stochastic perturbations to the model. We also present a preliminary analysis of the effect of a single serotype vaccination in the model. 相似文献
102.
Mellman I 《The Journal of cell biology》2007,177(4):570-571
Disease-related research requires a different kind of teamwork, says Ira Mellman. He hopes to find that team at his new home at Genentech. 相似文献
103.
The three basic cell types in the migrating slug of Dictyostelium discoideum show differential chemotactic response to cyclic AMP (cAMP) and differential sensitivity to suppression of the chemotaxis
by ammonia. The values of these parameters indicate a progressive maturation of chemotactic properties during the transdifferentiation
of slug cell types. We present a model that explains the localization of the three cell types within the slug based on these
chemotactic differences and on the maturation of their chemotactic properties. 相似文献
104.
Multistrain diseases have multiple distinct coexisting serotypes (strains). For some diseases, such as dengue fever, the serotypes interact by antibody-dependent enhancement (ADE), in which infection with a single serotype is asymptomatic, but contact with a second serotype leads to higher viral load and greater infectivity. We present and analyze a dynamic compartmental model for multiple serotypes exhibiting ADE. Using center manifold techniques, we show how the dynamics rapidly collapses to a lower dimensional system. Using the constructed reduced model, we can explain previously observed synchrony between certain classes of primary and secondary infectives (Schwartz et al. in Phys Rev E 72:066201, 2005). Additionally, we show numerically that the center manifold equations apply even to noisy systems. Both deterministic and stochastic versions of the model enable prediction of asymptomatic individuals that are difficult to track during an epidemic. We also show how this technique may be applicable to other multistrain disease models, such as those with cross-immunity. 相似文献
105.
Lipids in the heart: a source of fuel and a source of toxins 总被引:1,自引:0,他引:1
PURPOSE OF REVIEW: How do lipids arrive in the heart and other tissues? This review focuses on new information on pathways of lipid uptake into the heart. RECENT FINDINGS: Fatty acids, the major cardiac fuel, are obtained from either lipoproteins or free fatty acids associated with albumin. The heart is the tissue with the most robust expression of lipoprotein lipase, and recent data attest to the importance of this enzyme in supplying optimal amounts of fatty acids for the heart. Genetic deletion of CD36 also shows that this transporter is important for cardiac uptake of lipids. Retinoid acquisition by the heart involves pathways parallel to those used for fatty acid uptake: a pathway for acquisition of core lipoprotein retinyl ester and another for nonlipoprotein retinol. Dilated lipotoxic cardiomyopathy is the consequence of excess lipid uptake. SUMMARY: Genetic modifications that affect lipid uptake, oxidation, and storage are being exploited to elucidate the pathophysiology of cardiomyopathies and to discover how lipids relate to heart failure in humans with obesity and diabetes mellitus. This information is likely to lead to new diagnostic categories of cardiomyopathy and more pathophysiologically appropriate treatments. 相似文献
106.
Ira Vashisht Prashant Mishra Tarun Pal Sreekrishna Chanumolu Tiratha Raj Singh Rajinder Singh Chauhan 《Planta》2015,241(5):1269-1270
107.
108.
109.
110.
New strains of influenza spread around the globe via the movement of infected individuals. The global dynamics of influenza are complicated by different patterns of influenza seasonality in different regions of the world. We have released an open-source stochastic mathematical model of the spread of influenza across 321 major, strategically located cities of the world. Influenza is transmitted between cities via infected airline passengers. Seasonality is simulated by increasing the transmissibility in each city at the times of the year when influenza has been observed to be most prevalent. The spatiotemporal spread of pandemic influenza can be understood through clusters of global transmission and links between them, which we identify using the epidemic percolation network (EPN) of the model. We use the model to explain the observed global pattern of spread for pandemic influenza A(H1N1) 2009-2010 (pandemic H1N1 2009) and to examine possible global patterns of spread for future pandemics depending on the origin of pandemic spread, time of year of emergence, and basic reproductive number (). We also use the model to investigate the effectiveness of a plausible global distribution of vaccine for various pandemic scenarios. For pandemic H1N1 2009, we show that the biggest impact of vaccination was in the temperate northern hemisphere. For pandemics starting in the temperate northern hemisphere in May or April, vaccination would have little effect in the temperate southern hemisphere and a small effect in the tropics. With the increasing interconnectedness of the world's population, we must take a global view of infectious disease transmission. Our open-source, computationally simple model can help public health officials plan for the next pandemic as well as deal with interpandemic influenza. 相似文献