全文获取类型
收费全文 | 1087篇 |
免费 | 67篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 14篇 |
2018年 | 29篇 |
2017年 | 36篇 |
2016年 | 33篇 |
2015年 | 27篇 |
2014年 | 34篇 |
2013年 | 70篇 |
2012年 | 64篇 |
2011年 | 70篇 |
2010年 | 55篇 |
2009年 | 25篇 |
2008年 | 51篇 |
2007年 | 27篇 |
2006年 | 28篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1995年 | 6篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 6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 |
排序方式: 共有1154条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
Summary Applying a double-immunofluorescence technique, the porcine ovary is demonstrated to receive two populations of NPY-immunoreactive nerve fibres originating from the inferior mesenteric ganglion: one with colocalized tyrosine hydroxylase and supplying predominantly the ovarian vasculature, and a second, solely NPY-immunoreactive and almost exclusively associated with growing follicles. A third group of tyrosine hydroxylase-and dopamine--hydroxylase-positive, but NPY-negative nerve fibres is associated with ovarian blood vessels and, to a minor extent, with ovarian follicles. As revealed by retrograde tracing, the vast majority of postganglionic neurons projecting to the ovary is located in a discrete area of the ganglion, suggesting a somatotopic organization of the porcine inferior mesenteric ganglion. Moreover, the finding indicate that three subpopulations of postganglionic sympathetic neurons with different chemical codes supply different target components of the porcine ovary. The physiological relevance of the described neurons in the nervous control of ovarian functions remains to be elucidated.A portion of these results has been presented in abstract form (Majewski et al. 1991) 相似文献
8.
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
9.
10.