收费全文 | 15674篇 |
免费 | 1356篇 |
国内免费 | 1951篇 |
18981篇 |
2024年 | 52篇 |
2023年 | 286篇 |
2022年 | 594篇 |
2021年 | 908篇 |
2020年 | 706篇 |
2019年 | 816篇 |
2018年 | 760篇 |
2017年 | 556篇 |
2016年 | 727篇 |
2015年 | 1038篇 |
2014年 | 1262篇 |
2013年 | 1288篇 |
2012年 | 1582篇 |
2011年 | 1445篇 |
2010年 | 912篇 |
2009年 | 734篇 |
2008年 | 812篇 |
2007年 | 749篇 |
2006年 | 610篇 |
2005年 | 532篇 |
2004年 | 391篇 |
2003年 | 304篇 |
2002年 | 281篇 |
2001年 | 191篇 |
2000年 | 187篇 |
1999年 | 178篇 |
1998年 | 120篇 |
1997年 | 115篇 |
1996年 | 118篇 |
1995年 | 97篇 |
1994年 | 91篇 |
1993年 | 67篇 |
1992年 | 86篇 |
1991年 | 56篇 |
1990年 | 57篇 |
1989年 | 50篇 |
1988年 | 36篇 |
1987年 | 27篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1950年 | 3篇 |
Overexpression of cotton cellulose synthase like D3 (GhCSLD3) gene partially rescued growth defect of atcesa6 mutant with restored cell elongation and cell wall integrity mainly by enhancing primary cellulose production.
AbstractAmong cellulose synthase like (CSL) family proteins, CSLDs share the highest sequence similarity to cellulose synthase (CESA) proteins. Although CSLD proteins have been implicated to participate in the synthesis of carbohydrate-based polymers (cellulose, pectins and hemicelluloses), and therefore plant cell wall formation, the exact biochemical function of CSLD proteins remains controversial and the function of the remaining CSLD genes in other species have not been determined. In this study, we attempted to illustrate the function of CSLD proteins by overexpressing Arabidopsis AtCSLD2, -3, -5 and cotton GhCSLD3 genes in the atcesa6 mutant, which has a background that is defective for primary cell wall cellulose synthesis in Arabidopsis. We found that GhCSLD3 overexpression partially rescued the growth defect of the atcesa6 mutant during early vegetative growth. Despite the atceas6 mutant having significantly reduced cellulose contents, the defected cell walls and lower dry mass, GhCSLD3 overexpression largely restored cell wall integrity (CWI) and improved the biomass yield. Our result suggests that overexpression of the GhCSLD protein enhances primary cell wall synthesis and compensates for the loss of CESAs, which is required for cellulose production, therefore rescuing defects in cell elongation and CWI.
相似文献Amyloid-β (Aβ) plays an important role in Alzheimer’s disease (AD) pathogenesis, and growing evidence has shown that poor sleep quality is one of the risk factors for AD, but the mechanisms of sleep deprivation leading to AD have still not been fully demonstrated. In the present study, we used wild-type (WT) rats to determine the effects of chronic sleep restriction (CSR) on Aβ accumulation. We found that CSR-21d rats had learning and memory functional decline in the Morris water maze (MWM) test. Meanwhile, Aβ42 deposition in the hippocampus and the prefrontal cortex was high after a 21-day sleep restriction. Moreover, compared with the control rats, CSR rats had increased expression of β-site APP-cleaving enzyme 1 (BACE1) and sAPPβ and decreased sAPPα levels in both the hippocampus and the prefrontal cortex, and the BACE1 level was positively correlated with the Aβ42 level. Additionally, in CSR-21d rats, low-density lipoprotein receptor-related protein 1 (LRP-1) levels were low, while receptor of advanced glycation end products (RAGE) levels were high in the hippocampus and the prefrontal cortex, and these transporters were significantly correlated with Aβ42 levels. In addition, CSR-21d rats had decreased plasma Aβ42 levels and soluble LRP1 (sLRP1) levels compared with the control rats. Altogether, this study demonstrated that 21 days of CSR could lead to brain Aβ accumulation in WT rats. The underlying mechanisms may be related to increased Aβ production via upregulation of the BACE1 pathway and disrupted Aβ clearance affecting brain and peripheral Aβ transport.
相似文献Communicated by Ramaswamy H. Sarma 相似文献