全文获取类型
收费全文 | 867篇 |
免费 | 57篇 |
出版年
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 27篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 41篇 |
2014年 | 44篇 |
2013年 | 59篇 |
2012年 | 60篇 |
2011年 | 56篇 |
2010年 | 35篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 41篇 |
2006年 | 32篇 |
2005年 | 38篇 |
2004年 | 35篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 13篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1978年 | 9篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1970年 | 5篇 |
1969年 | 9篇 |
1968年 | 7篇 |
排序方式: 共有924条查询结果,搜索用时 15 毫秒
81.
82.
83.
Spermidine is the most abundant polyamine in dormant turions of Hydrocharis morsus-ranae and Utricularia intermedia, and it is also the dominant polyamine in sprouts of U. intermedia. The putrescine level is high in young leaves of H. morsus-ranae. Cadaverine and homospermidine occur respectively in vernalized turions of H. morsus-ranae and of U. intermedia. 相似文献
84.
Robyn L. Poerschke Karen White Scott R. Florell Robert H. I. Andtbacka Joycelyn Tross Madeleine Anderson Sancy A. Leachman Philip J. Moos 《Pigment cell & melanoma research》2015,28(6):685-695
Although significant progress has been made in targeted and immunologic therapeutics for melanoma, many tumors fail to respond, and most eventually progress when treated with the most efficacious targeted combination therapies thus far identified. Therefore, alternative approaches that exploit distinct melanoma phenotypes are necessary to develop new approaches for therapeutic intervention. Tissue microarrays containing human nevi and melanomas were used to evaluate levels of the antioxidant protein thioredoxin reductase 1 (TR1), which was found to increase as a function of disease progression. Melanoma cell lines revealed metabolic differences that correlated with TR1 levels. We used this new insight to design a model treatment strategy that creates a synthetic lethal interaction wherein targeting TR1 sensitizes melanoma to inhibition of glycolytic metabolism, resulting in a decrease in metastases in vivo. This approach holds the promise of a new clinical therapeutic strategy, distinct from oncoprotein inhibition. 相似文献
85.
Why are mitochondria almost always inherited from one parent during sexual reproduction? Current explanations for this evolutionary mystery include conflict avoidance between the nuclear and mitochondrial genomes, clearing of deleterious mutations, and optimization of mitochondrial-nuclear coadaptation. Mathematical models, however, fail to show that uniparental inheritance can replace biparental inheritance under any existing hypothesis. Recent empirical evidence indicates that mixing two different but normal mitochondrial haplotypes within a cell (heteroplasmy) can cause cell and organism dysfunction. Using a mathematical model, we test if selection against heteroplasmy can lead to the evolution of uniparental inheritance. When we assume selection against heteroplasmy and mutations are neither advantageous nor deleterious (neutral mutations), uniparental inheritance replaces biparental inheritance for all tested parameter values. When heteroplasmy involves mutations that are advantageous or deleterious (non-neutral mutations), uniparental inheritance can still replace biparental inheritance. We show that uniparental inheritance can evolve with or without pre-existing mating types. Finally, we show that selection against heteroplasmy can explain why some organisms deviate from strict uniparental inheritance. Thus, we suggest that selection against heteroplasmy explains the evolution of uniparental inheritance. 相似文献
86.
Mohamed Alburaki Sébastien Boutin Pierre-Luc Mercier Yves Loublier Madeleine Chagnon Nicolas Derome 《PloS one》2015,10(5)
Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads. 相似文献
87.
88.
Justin Maire Sam K. Girvan Sophie E. Barkla Alexis Perez-Gonzalez David J. Suggett Linda L. Blackall Madeleine J. H. van Oppen 《The ISME journal》2021,15(7):2168
Corals house a variety of microorganisms which they depend on for their survival, including endosymbiotic dinoflagellates (Symbiodiniaceae) and bacteria. While cnidarian–microorganism interactions are widely studied, Symbiodiniaceae–bacteria interactions are only just beginning to receive attention. Here, we describe the localization and composition of the bacterial communities associated with cultures of 11 Symbiodiniaceae strains from nine species and six genera. Three-dimensional confocal laser scanning and electron microscopy revealed bacteria are present inside the Symbiodiniaceae cells as well as closely associated with their external cell surface. Bacterial pure cultures and 16S rRNA gene metabarcoding from Symbiodiniaceae cultures highlighted distinct and highly diverse bacterial communities occur intracellularly, closely associated with the Symbiodiniaceae outer cell surface and loosely associated (i.e., in the surrounding culture media). The intracellular bacteria are highly conserved across Symbiodiniaceae species, suggesting they may be involved in Symbiodiniaceae physiology. Our findings provide unique new insights into the biology of Symbiodiniaceae.Subject terms: Symbiosis, Microbiome, Marine microbiology 相似文献
89.
90.
Lejour M 《Plastic and reconstructive surgery》2007,120(7):2106-2109