全文获取类型
收费全文 | 47031篇 |
免费 | 3873篇 |
国内免费 | 2404篇 |
出版年
2023年 | 429篇 |
2022年 | 1036篇 |
2021年 | 2019篇 |
2020年 | 1271篇 |
2019年 | 1561篇 |
2018年 | 1483篇 |
2017年 | 1148篇 |
2016年 | 1734篇 |
2015年 | 2640篇 |
2014年 | 3032篇 |
2013年 | 3374篇 |
2012年 | 3927篇 |
2011年 | 3717篇 |
2010年 | 2136篇 |
2009年 | 1973篇 |
2008年 | 2365篇 |
2007年 | 2184篇 |
2006年 | 1882篇 |
2005年 | 1707篇 |
2004年 | 1460篇 |
2003年 | 1311篇 |
2002年 | 1134篇 |
2001年 | 903篇 |
2000年 | 784篇 |
1999年 | 781篇 |
1998年 | 509篇 |
1997年 | 520篇 |
1996年 | 500篇 |
1995年 | 462篇 |
1994年 | 415篇 |
1993年 | 363篇 |
1992年 | 495篇 |
1991年 | 435篇 |
1990年 | 367篇 |
1989年 | 285篇 |
1988年 | 266篇 |
1987年 | 241篇 |
1986年 | 178篇 |
1985年 | 233篇 |
1984年 | 166篇 |
1983年 | 152篇 |
1982年 | 137篇 |
1981年 | 117篇 |
1980年 | 113篇 |
1979年 | 95篇 |
1978年 | 112篇 |
1977年 | 78篇 |
1976年 | 83篇 |
1975年 | 67篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
61.
Wayne W. Poon Anthony J. Carlos Brittany L. Aguilar Nicole C. Berchtold Crystal K. Kawano Vahe Zograbyan Tim Yaopruke Michael Shelanski Carl W. Cotman 《The Journal of biological chemistry》2013,288(23):16937-16948
We previously found that BDNF-dependent retrograde trafficking is impaired in AD transgenic mouse neurons. Utilizing a novel microfluidic culture chamber, we demonstrate that Aβ oligomers compromise BDNF-mediated retrograde transport by impairing endosomal vesicle velocities, resulting in impaired downstream signaling driven by BDNF/TrkB, including ERK5 activation, and CREB-dependent gene regulation. Our data suggest that a key mechanism mediating the deficit involves ubiquitin C-terminal hydrolase L1 (UCH-L1), a deubiquitinating enzyme that functions to regulate cellular ubiquitin. Aβ-induced deficits in BDNF trafficking and signaling are mimicked by LDN (an inhibitor of UCH-L1) and can be reversed by increasing cellular UCH-L1 levels, demonstrated here using a transducible TAT-UCH-L1 strategy. Finally, our data reveal that UCH-L1 mRNA levels are decreased in the hippocampi of AD brains. Taken together, our data implicate that UCH-L1 is important for regulating neurotrophin receptor sorting to signaling endosomes and supporting retrograde transport. Further, our results support the idea that in AD, Aβ may down-regulate UCH-L1 in the AD brain, which in turn impairs BDNF/TrkB-mediated retrograde signaling, compromising synaptic plasticity and neuronal survival. 相似文献
62.
Jianyong Wu 《Cytotechnology》1996,22(1-3):103-109
Animal cells in suspension culture can suffer severe mechanical damage from bursting gas bubbles or other hydrodynamic force sources. Certain chemical additives in the culture media, particularly some surface-active chemicals, can effectively protect animal cells against such damage. Previously we proposed that the protective effect is associated with the adsorption of the additives in the cell membrane through hydrophobic binding of the surface-active molecules to the membrane. Adsorption of the additives to the cell membrane may lead to decreased hydrophobicity of the cell surface, thus eliminating cell adhesion to bubbles and reducing cell damage from bursting bubbles. In this study, we measured the hydrophobicity of two insect cell lines based on cell adhesion to hydrocarbon phase and its influence by surface-active chemicals, Pluronic F68, a methylcellulose and a polyethylene glycol. The experimental results showed strong support for the aforecited cell protection mechanism. 相似文献
63.
64.
65.
Journal of Plant Growth Regulation - With the increasing popularity of urban landscaping, there is a greater need to address iron deficiency and chlorosis in Cinnamomum camphora. Beneficial... 相似文献
66.
Elfalem Y. Alemu Joseph W. Carl Jr Héctor Corrada Bravo Sridhar Hannenhalli 《Nucleic acids research》2014,42(6):3503-3514
The amount of tissue-specific expression variability (EV) across individuals is an essential characteristic of a gene and believed to have evolved, in part, under functional constraints. However, the determinants and functional implications of EV are only beginning to be investigated. Our analyses based on multiple expression profiles in 41 primary human tissues show that a gene’s EV is significantly correlated with a number of features pertaining to the genomic, epigenomic, regulatory, polymorphic, functional, structural and network characteristics of the gene. We found that (i) EV of a gene is encoded, in part, by its genomic context and is further influenced by the epigenome; (ii) strong promoters induce less variable expression; (iii) less variable gene loci evolve under purifying selection against copy number polymorphisms; (iv) genes that encode inherently disordered or highly interacting proteins exhibit lower variability; and (v) genes with less variable expression are enriched for house-keeping functions, while genes with highly variable expression tend to function in development and extra-cellular response and are associated with human diseases. Thus, our analysis reveals a number of potential mediators as well as functional and evolutionary correlates of EV, and provides new insights into the inherent variability in eukaryotic gene expression. 相似文献
67.
68.
69.
70.
X. Y. Li C. M. Han Y. Wang H. Z. Liu Z. F. Wu Q. H. Gao S. H. Zhao 《Animal genetics》2010,41(5):537-540
RIG-1 signalling is responsible for the detection of cytoplasmic viral RNA molecules. DEXH (Asp-Glu-X-His) box polypeptide 58 (encoded by DHX58) is a negative regulator of the RIG-1 signalling pathway. In human, the DHX58 gene can be upregulated and can inhibit the RIG-1 signalling pathway during viral infection. In this study, porcine DHX58 gene expression patterns were studied. According to our results, the porcine DHX58 gene was upregulated not only by the stimulation of Poly I:C but also by the stimulation of 1ipopolysaccharides (LPS). One polymorphism (g.4919G>C), detected in the ninth intron, was significantly associated with some blood parameters including the red cell distribution width of 1-day-old pigs and white blood cell counts, lymphocyte absolute counts, and platelet distribution width of 17-day-old pigs (P < 0.05). Moreover, the individuals with the genotype GG have a significantly higher mean white blood cell count than individuals with genotype CC or GC (P < 0.05). Our study indicates that DHX58 is an important gene that is associated with the immune response in swine. 相似文献