全文获取类型
收费全文 | 4921篇 |
免费 | 287篇 |
国内免费 | 999篇 |
出版年
2024年 | 7篇 |
2023年 | 77篇 |
2022年 | 103篇 |
2021年 | 128篇 |
2020年 | 145篇 |
2019年 | 154篇 |
2018年 | 127篇 |
2017年 | 132篇 |
2016年 | 180篇 |
2015年 | 174篇 |
2014年 | 193篇 |
2013年 | 374篇 |
2012年 | 217篇 |
2011年 | 242篇 |
2010年 | 185篇 |
2009年 | 232篇 |
2008年 | 210篇 |
2007年 | 256篇 |
2006年 | 279篇 |
2005年 | 280篇 |
2004年 | 264篇 |
2003年 | 285篇 |
2002年 | 241篇 |
2001年 | 199篇 |
2000年 | 187篇 |
1999年 | 146篇 |
1998年 | 114篇 |
1997年 | 152篇 |
1996年 | 132篇 |
1995年 | 101篇 |
1994年 | 94篇 |
1993年 | 80篇 |
1992年 | 70篇 |
1991年 | 64篇 |
1990年 | 67篇 |
1989年 | 44篇 |
1988年 | 50篇 |
1987年 | 36篇 |
1986年 | 15篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有6207条查询结果,搜索用时 15 毫秒
181.
182.
183.
Altered expression of the PTR/NRT1 homologue OsPTR9 affects nitrogen utilization efficiency,growth and grain yield in rice 总被引:2,自引:0,他引:2
Zhongming Fang Kuaifei Xia Xin Yang Marianne Suter Grotemeyer Stefan Meier Doris Rentsch Xinlan Xu Mingyong Zhang 《Plant biotechnology journal》2013,11(4):446-458
The plant PTR/NRT1 (peptide transporter/nitrate transporter 1) gene family comprises di/tripeptide and low‐affinity nitrate transporters; some members also recognize other substrates such as carboxylates, phytohormones (auxin and abscisic acid), or defence compounds (glucosinolates). Little is known about the members of this gene family in rice (Oryza sativa L.). Here, we report the influence of altered OsPTR9 expression on nitrogen utilization efficiency, growth, and grain yield. OsPTR9 expression is regulated by exogenous nitrogen and by the day‐night cycle. Elevated expression of OsPTR9 in transgenic rice plants resulted in enhanced ammonium uptake, promotion of lateral root formation and increased grain yield. On the other hand, down‐regulation of OsPTR9 in a T‐DNA insertion line (osptr9) and in OsPTR9‐RNAi rice plants had the opposite effect. These results suggest that OsPTR9 might hold potential for improving nitrogen utilization efficiency and grain yield in rice breeding. 相似文献
184.
185.
186.
187.
188.
189.
Dipti Verma Mohammad Wahid Ansari Ganesh Kumar Agrawal Randeep Rakwal Alok Shukla Narendra Tuteja 《Plant signaling & behavior》2013,8(4)
Drought is the major environmental stress that limits rice productivity worldwide. In vitro somaclonal variation using different selection agents has been used for crop improvement. Here, rice plants of cv PR113 were selected in vitro on 30, 50 and 70 g L-1 polyethylene glycol 6,000 (PEG). Callus growth, proliferation, calli volume (first and second culture) and plantlet regeneration (third culture) were found to be decreased upto a certain level to acquire tolerance to PEG-induced drought. From the field data, 30 g L-1 PEG lines showed higher vegetative growth (plant height, tiller number, leaf number, shoot weight and root growth) as compared with 50 g L-1 PEG selected somaclone lines under limited irrigation. The yield parameters-panicle length, panicle weight, grains per panicle, 1,000-grain weight, grain yield per plant, harvest index and grain straw ratio were also higher in 30 g L-1 PEG lines as compared with 50 g L-1 PEG lines. The results, therefore indicate that 30 g L-1 PEG selected somaclone lines were more suited than 50 g L-1 PEG selected somaclone lines under stress as compared with WT. The finding suggests that rice cv PR113 somaclones generated on PEG are found to be drought tolerant under field condition with better yield. 相似文献
190.
Mutations in the LMNA gene, which encodes lamin A and C (lamin A/C), cause a diverse spectrum of tissue-selective diseases termed laminopathies. The most prevalent form affects striated muscles as dilated cardiomyopathy with variable skeletal muscle involvement, which includes autosomal Emery-Dreifuss muscular dystrophy. Mechanisms underlying the disease pathogenesis are beginning to be understood and they point toward defects in cell signaling. We therefore assessed putative signaling defects in a mouse model carrying a point mutation in Lmna (LmnaH222P/H222P) that faithfully recapitulates human Emery-Dreifuss muscular dystrophy. We found that AKT-mechanistic target of rapamycin (MTOR) signaling was hyperactivated in hearts of LmnaH222P/H222P mice and that reducing MTOR activity by pharmacological intervention ameliorated cardiomyopathy. Given the central role of MTOR in regulating autophagy, we assessed fasting-induced autophagic responses and found that they were impaired in hearts of these mice. Moreover, the improved heart function associated with pharmacological blockade of MTOR was correlated with enhanced autophagy. These findings demonstrated that signaling defects that impair autophagy underlie pathogenesis of dilated cardiomyopathy arising from LMNA mutation. 相似文献