收费全文 | 1757篇 |
免费 | 164篇 |
2023年 | 21篇 |
2022年 | 29篇 |
2021年 | 59篇 |
2020年 | 44篇 |
2019年 | 55篇 |
2018年 | 64篇 |
2017年 | 61篇 |
2016年 | 75篇 |
2015年 | 97篇 |
2014年 | 100篇 |
2013年 | 175篇 |
2012年 | 115篇 |
2011年 | 116篇 |
2010年 | 100篇 |
2009年 | 84篇 |
2008年 | 84篇 |
2007年 | 92篇 |
2006年 | 72篇 |
2005年 | 75篇 |
2004年 | 68篇 |
2003年 | 46篇 |
2002年 | 35篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 25篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 14篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1978年 | 5篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1897年 | 2篇 |
1883年 | 3篇 |
1882年 | 5篇 |
1881年 | 2篇 |
1879年 | 6篇 |
1878年 | 2篇 |
1877年 | 2篇 |
Parkinson’s disease (PD) signs and symptoms regularly include tremor. Interestingly, the nucleoside guanosine (GUO) has already proven to be effective in reducing reserpine-induced tremulous jaw movements (TJMs) in rodent models, thus becoming a promising antiparkinsonian drug. Here, we aimed at revealing the mechanism behind GUO antiparkinsonian efficacy by assessing the role of adenosine A1 and A2A receptors (A1R and A2AR) on GUO-mediated anti-tremor effects in the reserpinized mouse model of PD. Reserpinized mice showed elevated reactive oxygen species (ROS) production and cellular membrane damage in striatal slices assessed ex vivo and GUO treatment reversed ROS production. Interestingly, while the simultaneous administration of sub-effective doses of GUO (5 mg/kg) and SCH58261 (0.01 mg/kg), an A2AR antagonist, precluded reserpine-induced TJMs, these were ineffective on reverting ROS production in ex vivo experiments. Importantly, GUO was able to reduce TJM and ROS production in reserpinized mouse lacking the A2AR, thus suggesting an A2AR-independent mechanism of GUO-mediated effects. Conversely, the administration of DPCPX (0.75 mg/kg), an A1R antagonist, completely abolished both GUO-mediated anti-tremor effects and blockade of ROS production. Overall, these results indicated that GUO anti-tremor and antioxidant effects in reserpinized mice were A1R dependent but A2AR independent, thus suggesting a differential participation of adenosine receptors in GUO-mediated effects.
相似文献The potential impact of the soil seed bank of a given species and subsequent population persistence will depend on the robustness of the seeds against depletion. Invasiveness is frequently linked to this behavior and successful control of invasive species depends on reducing the size of their seed banks. We propose a hybrid model that simulates the seed bank dynamics in association with their physical dormancy (PD) based on experimental data on seed bank depletion of a Leucaena leucocephala population during the dispersal phase. The hybrid model uses cellular automata (CA) and Monte Carlo techniques. The sensitivity analysis revealed that the model delivers reproducible and reliable results. Then, we discuss the ability of the hybrid model to predict the effect of seasonal climate change. A 2.0 °C increase in temperature was enough to cause a considerable impact in the seed depletion curve, and after 1 year, ~?75% of the seeds had already disappeared from the seed bank. The proposed hybrid CA model can be used to study soil-stored seed banks with physical dormancy, and could be applied to other Fabaceae species with similar seed traits. We believe that this computational model contributes to a better understanding of seed bank dynamics and will aid in the control of invasive species and for testing different scenarios to reduce or eliminate seed banks that have already been formed.
相似文献