全文获取类型
收费全文 | 510篇 |
免费 | 42篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 33篇 |
2017年 | 23篇 |
2016年 | 16篇 |
2015年 | 24篇 |
2014年 | 49篇 |
2013年 | 42篇 |
2012年 | 53篇 |
2011年 | 52篇 |
2010年 | 31篇 |
2009年 | 24篇 |
2008年 | 17篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有552条查询结果,搜索用时 125 毫秒
1.
2.
3.
Nitrogen mineralization, nitrification potentials, pH, total N, C, extractable P and cations were measured in soils under 4-year-old, mono-specific stands of six fast-growing, native tree species, an abandoned pasture, and a 20-year-old secondary forest, as part of a study on the use of indigenous tree species for rehabilitation of soil fertility on degraded pastures at the La Selva Biological Station in the Atlantic humid lowlands of Costa Rica. Soil net nitrification potential rates were higher under two N-fixing, leguminous species,Stryphnodendron microstachyum Poepp. et Endl. (1.1–1.9 mg kg–1 day–1) andDalbergia tucurensis Donn. Smith (0.7–1.5 mg kg–1 day–1), than under the non-N-fixing trees in the plantation,Vochysia guatemalesis Don. Sm.,Vochysia ferruginea Mart,Dipteryx panamensis (Pittier) Record and Mell andHyeronima alchorneoides Fr. Allemao (0.2–0.8 mg kg–1 day–1). Values under the N-fixing trees were comparable to those found in secondary forest. There were no statistically significant differences in soil total N or in other nurtients between the species. Results of pH measurements done before and after incubation did not show any clear evidence of a pH drop attributable to nitrification. 相似文献
4.
Alejandro P. Pariani Evangelina Almada Florencia Hidalgo Carla Borini-Etichetti Rodrigo Vena Leandra Marín Cristián Favre James R. Goldenring Maria Cecilia Larocca 《Journal of cellular physiology》2023,238(1):227-241
The elimination of transformed and viral infected cells by natural killer (NK) cells requires a specialized junction between NK and target cells, denominated immunological synapse (IS). After initial recognition, the IS enables the directed secretion of lytic granules content into the susceptible target cell. The lymphocyte function-associated antigen (LFA)-1 regulates NK effector function by enabling NK-IS assembly and maturation. The pathways underlying LFA-1 accumulation at the IS in NK cells remained uncharacterized. A kinase anchoring protein 350 (AKAP350) is a centrosome/Golgi-associated protein, which, in T cells, participates in LFA-1 activation by mechanisms that have not been elucidated. We first evaluated AKAP350 participation in NK cytolytic activity. Our results showed that the decrease in AKAP350 levels by RNA interference (AKAP350KD) inhibited NK-YTS cytolytic activity, without affecting conjugate formation. The impairment of NK effector function in AKAP350KD cells correlated with decreased LFA-1 clustering and defective IS maturation. AKAP350KD cells that were exclusively activated via LFA-1 showed impaired LFA-1 organization and deficient lytic granule translocation as well. In NK AKAP350KD cells, activation signaling through Vav1 was preserved up to 10 min of interaction with target cells, but significantly decreased afterwards. Experiments in YTS and in ex vivo NK cells identified an intracellular pool of LFA-1, which partially associated with the Golgi apparatus and, upon NK activation, redistributed to the IS in an AKAP350-dependent manner. The analysis of Golgi organization indicated that the decrease in AKAP350 expression led to the disruption of the Golgi integrity in NK cells. Alteration of Golgi function by BFA treatment or AKAP350 delocalization from this organelle also led to impaired LFA-1 localization at the IS. Therefore, this study characterizes AKAP350 participation in the modulation of NK effector function, revealing the existence of a Golgi-dependent trafficking pathway for LFA-1, which is relevant for LFA-1 organization at NK-lytic IS. 相似文献
5.
María Florencia Pignataro María Georgina Herrera Natalia Brenda Fernández Martín Aran Hernán Gustavo Gentili Fernando Battaglini Javier Santos 《Biotechnology and bioengineering》2023,120(2):409-425
Frataxin is a kinetic activator of the mitochondrial supercomplex for iron-sulfur cluster assembly. Low frataxin expression or a decrease in its functionality results in Friedreich's Ataxia (FRDA). With the aim of creating new molecular tools to study this metabolic pathway, and ultimately, to explore new therapeutic strategies, we have investigated the possibility of obtaining small proteins exhibiting a high affinity for frataxin. In this study, we applied the ribosome display approach, using human frataxin as the target. We focused on Affi_224, one of the proteins that we were able to select after five rounds of selection. We have studied the interaction between both proteins and discussed some applications of this specific molecular tutor, concerning the modulation of the supercomplex activity. Affi_224 and frataxin showed a KD value in the nanomolar range, as judged by surface plasmon resonance analysis. Most likely, it binds to the frataxin acidic ridge, as suggested by the analysis of chemical shift perturbations (nuclear magnetic resonance) and computational simulations. Affi_224 was able to increase Cys NFS1 desulfurase activation exerted by the FRDA frataxin variant G130V. Importantly, Affi_224 interacts with frataxin in a human cellular model. Our results suggest quaternary addition may be a new tool to modulate frataxin function in vivo. Nevertheless, more functional experiments under physiological conditions should be carried out to evaluate Affi_224 effectiveness in FRDA cell models. 相似文献
6.
Modifications of major aspects of myocardial ribonucleic acid metabolism as a response to noradrenaline. Behaviour of polyadenylate polymerase and ribonucleic acid polymerase, acetylation of histones and rate of synthesis of polyamines. 下载免费PDF全文
A Casti A Corti N Reali G Mezzetti G Orlandini Caldarer tcm 《The Biochemical journal》1977,168(3):333-340
Noradrenaline added to perfused rabbit heart previously perfused with labelled precursors causes, after 2.5 and 5.0 min, a general increase of specific radioactivity or RNA in subcellular fractions, but no augmentation of acetylation of F2a2 and F2a1 histone fractions and no stimulation of DNA-dependent RNA polymerase activities. Synthesis of spermidine and spermine is enhanced at 10.0 min of treatment, when there is also a fall in specific radioactivity of RNA. The cytoplasmic Mn2+-stimulated polyadenylate polymerase activity is strongly enhanced 30s to 2.5 min after injection of noradrenaline or of dibutyryl cyclic AMP. Both the cyclic nucleotide and noradrenaline have no influence in vitro on the polyadenylate polymerase reaction. 相似文献
7.
8.
9.
10.
M. Florencia Grandi Damián G. Vales Enrique A. Crespo Rocío Loizaga 《Marine Mammal Science》2021,37(1):314-327
Difference among colonies in the population structure of otariids can be driven by philopatry and/or by specializations in the foraging ecology of females. In northern Patagonia, the South American sea lion (SASL) shows some degree of spatial genetic structure among colonies from north and south zones. This study aims to explore the isotopic niche of SASL females in the last period of the pregnancy from different colonies of northern Patagonia and to consider whether the fine scale genetic spatial structuring is potentially related to variation in trophic resources. Stable isotope analysis was performed on 101 skin samples of newborn pups in 10 colonies, as a proxy for the feeding ecology of their mothers. Differences among colonies in the metrics studied revealed the plasticity of the species and support individual trophic specialization of SASL females at a small geographic scale. Also, significant differences were found in all isotopic metrics between the north and south zones. Several hypotheses were proposed to explain the differences in SASL females' isotope values (e.g., use of different foraging areas or prey, isotopic baseline variation). Nonetheless, further research is needed to better understand the relation between fine scale genetic structuring and the foraging ecology of SASL females. 相似文献