全文获取类型
收费全文 | 3476篇 |
免费 | 167篇 |
出版年
2023年 | 23篇 |
2022年 | 10篇 |
2021年 | 81篇 |
2020年 | 66篇 |
2019年 | 78篇 |
2018年 | 111篇 |
2017年 | 97篇 |
2016年 | 140篇 |
2015年 | 162篇 |
2014年 | 177篇 |
2013年 | 256篇 |
2012年 | 295篇 |
2011年 | 286篇 |
2010年 | 179篇 |
2009年 | 137篇 |
2008年 | 216篇 |
2007年 | 232篇 |
2006年 | 174篇 |
2005年 | 179篇 |
2004年 | 129篇 |
2003年 | 107篇 |
2002年 | 96篇 |
2001年 | 22篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1992年 | 2篇 |
1991年 | 9篇 |
1989年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1971年 | 2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3643条查询结果,搜索用时 390 毫秒
1.
2.
3.
4.
5.
Ernest I. Onyishi Piotr Sorokowski Agnieszka Sorokowska R. Nathan Pipitone 《Evolution and human behavior》2012,33(6):771-774
Previous research has demonstrated that having more children decreases marital satisfaction among parents. However, the universality of these findings is limited since the vast majority of the studies have been conducted in Western countries. In the present study, 374 people from the Igbo ethnic group (Nigeria) were assessed for levels of marital satisfaction and the number of children. In contrast to almost all previous findings, we found a positive relationship between the number of children and marital satisfaction among parents. Number of children was the strongest predictor of marital satisfaction even when compared to other variables like wealth and education. Our results suggest that the negative relationship between the number of children and marital satisfaction is not culturally universal and probably only characterizes developed, individualistic Western countries. We discuss our findings from a sociocultural and evolutionary perspective. 相似文献
6.
7.
8.
Tadeusz Janas Agnieszka Janiak-Osajca Teresa Janas 《Journal of biological physics》1993,19(4):295-308
The study presents an application of the theory of homeomorphic transformations of topological manifolds and the operation of the connected sum of manifolds for topological analysis of membrane transformations during the fusion process between cellular and subcellular compartments. The biological cell and the subcellular structures in the form of vesicles are modelled by an arrangement of two concentric spheres corresponding to the inner and outer layer of the membrane bounding the vesicles. The analysis shows eight succeeding topological stages of membrane transformations during the fusion process and these stages are characterized. It is concluded that there is a vectorial translocation of lipid molecules from the outer layers of the membranes before the fusion process to the internal layer of the membrane bounding the vesicle after the fusion process and there is no lipid translocation in the reverse direction. 相似文献
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.