收费全文 | 8459篇 |
免费 | 568篇 |
国内免费 | 2篇 |
2023年 | 88篇 |
2022年 | 140篇 |
2021年 | 265篇 |
2020年 | 196篇 |
2019年 | 258篇 |
2018年 | 313篇 |
2017年 | 257篇 |
2016年 | 353篇 |
2015年 | 526篇 |
2014年 | 529篇 |
2013年 | 616篇 |
2012年 | 715篇 |
2011年 | 660篇 |
2010年 | 399篇 |
2009年 | 357篇 |
2008年 | 420篇 |
2007年 | 434篇 |
2006年 | 383篇 |
2005年 | 305篇 |
2004年 | 249篇 |
2003年 | 234篇 |
2002年 | 204篇 |
2001年 | 149篇 |
2000年 | 135篇 |
1999年 | 104篇 |
1998年 | 55篇 |
1997年 | 40篇 |
1996年 | 38篇 |
1995年 | 35篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 48篇 |
1991年 | 41篇 |
1990年 | 25篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 39篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1975年 | 16篇 |
1974年 | 14篇 |
1973年 | 15篇 |
Oral mucositis is an inflammation of the oral mucosa mainly resulting from the cytotoxic effect of 5-fluorouracil (5-FU). The literature shows anti-inflammatory action of l-cysteine (l-cys) involving hydrogen sulfide (H2S). In view of these properties, we investigate the effect of l-cys in oral mucositis induced by 5-FU in hamsters. The animals were divided into the following groups: saline 0.9%, mechanical trauma, 5-FU 60–40 mg/kg, l-cys 10/40 mg and NaHS 27 µg/kg. 5-FU was administered on days 1st to 2nd; 4th day excoriations were made on the mucosa; 5th–6th received l-cys and NaHS. For data analysis, histological analyses, mast cell count, inflammatory and antioxidants markers, and immunohistochemistry (cyclooxygenase-2(COX-2)/inducible nitric oxide synthase (iNOs)/H2S) were performed. Results showed that l-cys decreased levels of inflammatory markers, mast cells, levels of COX-2, iNOS and increased levels of antioxidants markers and H2S when compared to the group 5-FU (p < 0.005). It is suggested that l-cys increases the H2S production with anti-inflammatory action in the 5-FU lesion.
相似文献Caffeine, a stimulant largely consumed around the world, is a non-selective adenosine receptor antagonist, and therefore caffeine actions at synapses usually, but not always, mirror those of adenosine. Importantly, different adenosine receptors with opposing regulatory actions co-exist at synapses. Through both inhibitory and excitatory high-affinity receptors (A1R and A2R, respectively), adenosine affects NMDA receptor (NMDAR) function at the hippocampus, but surprisingly, there is a lack of knowledge on the effects of caffeine upon this ionotropic glutamatergic receptor deeply involved in both positive (plasticity) and negative (excitotoxicity) synaptic actions. We thus aimed to elucidate the effects of caffeine upon NMDAR-mediated excitatory post-synaptic currents (NMDAR-EPSCs), and its implications upon neuronal Ca2+ homeostasis. We found that caffeine (30–200 μM) facilitates NMDAR-EPSCs on pyramidal CA1 neurons from Balbc/ByJ male mice, an action mimicked, as well as occluded, by 1,3-dipropyl-cyclopentylxantine (DPCPX, 50 nM), thus likely mediated by blockade of inhibitory A1Rs. This action of caffeine cannot be attributed to a pre-synaptic facilitation of transmission because caffeine even increased paired-pulse facilitation of NMDA-EPSCs, indicative of an inhibition of neurotransmitter release. Adenosine A2ARs are involved in this likely pre-synaptic action since the effect of caffeine was mimicked by the A2AR antagonist, SCH58261 (50 nM). Furthermore, caffeine increased the frequency of Ca2+ transients in neuronal cell culture, an action mimicked by the A1R antagonist, DPCPX, and prevented by NMDAR blockade with AP5 (50 μM). Altogether, these results show for the first time an influence of caffeine on NMDA receptor activity at the hippocampus, with impact in neuronal Ca2+ homeostasis.
相似文献