全文获取类型
收费全文 | 1143篇 |
免费 | 53篇 |
出版年
2023年 | 11篇 |
2022年 | 8篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 24篇 |
2018年 | 40篇 |
2017年 | 44篇 |
2016年 | 43篇 |
2015年 | 32篇 |
2014年 | 46篇 |
2013年 | 89篇 |
2012年 | 77篇 |
2011年 | 71篇 |
2010年 | 62篇 |
2009年 | 29篇 |
2008年 | 47篇 |
2007年 | 45篇 |
2006年 | 34篇 |
2005年 | 20篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1971年 | 2篇 |
1960年 | 1篇 |
1955年 | 29篇 |
1954年 | 77篇 |
1953年 | 42篇 |
1952年 | 27篇 |
1951年 | 20篇 |
1950年 | 56篇 |
1949年 | 12篇 |
1948年 | 5篇 |
1947年 | 3篇 |
1937年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1196条查询结果,搜索用时 15 毫秒
1.
2.
Kinga Michno David Knight Jorge M. Campussano Diana van de Hoef Gabrielle L. Boulianne 《PloS one》2009,4(9)
Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation. 相似文献
3.
4.
5.
6.
7.
8.
9.
Łukasz Wejnerowski Ewa Poniecka Jakub Buda Piotr Klimaszyk Agnieszka Piasecka Marcin Krzysztof Dziuba Gianmarco Mugnai Nozomu Takeuchi Krzysztof Zawierucha 《Journal of phycology》2023,59(5):939-949
Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers. 相似文献
10.