全文获取类型
收费全文 | 3121篇 |
免费 | 207篇 |
出版年
2024年 | 3篇 |
2023年 | 25篇 |
2022年 | 63篇 |
2021年 | 97篇 |
2020年 | 44篇 |
2019年 | 75篇 |
2018年 | 93篇 |
2017年 | 77篇 |
2016年 | 120篇 |
2015年 | 199篇 |
2014年 | 193篇 |
2013年 | 210篇 |
2012年 | 337篇 |
2011年 | 267篇 |
2010年 | 166篇 |
2009年 | 157篇 |
2008年 | 199篇 |
2007年 | 205篇 |
2006年 | 163篇 |
2005年 | 140篇 |
2004年 | 106篇 |
2003年 | 91篇 |
2002年 | 105篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1967年 | 4篇 |
排序方式: 共有3328条查询结果,搜索用时 15 毫秒
61.
62.
The use of dried and re-hydrated biomass of the seagrass Posidonia oceanica was investigated as an alternative and –low-cost biomaterial for removal of vanadium(III) and molybdenum(V) from wastewaters. Initial characterisation of this biomaterial identified carboxylic groups on the cuticle as potentially responsible for cation sorption, and confirmed the toxic-metal bioaccumulation. The combined effects on biosorption performance of equilibrium pH and metal concentrations were investigated in an ideal single-metal system and in more real-life multicomponent systems. There were either with one metal (vanadium or molybdenum) and sodium nitrate, as representative of high ionic strength systems, or with the two metals (vanadium and molybdenum). For the single-metal solutions, the optimum was at pH 3, where a significant proportion of vanadium was removed (ca. 70%) while there was ca. 40% adsorption of molybdenum. The data obtained from the more real-life multicomponent systems showed that biosorption of one metal was improved both by the presence of the other metal and by high ionic strength, suggesting a synergistic effect on biosorption rather than competition. There data ware used for the development of a simple multi-metal equilibrium model based on the non-competitive Langmuir approach, which was successfully fitted to experimental data and represents a useful support tool for the prediction of biosorption performance in such real-life systems. Overall, the results suggest that biomass of P. oceanica can be used as an efficient biosorbent for removal of vanadium(III) and molybdenum(V) from aqueous solutions. This process thus offers an eco-compatible solution for the reuse of the waste material of leaves that accumulate on the beach due to both human activities and to storms at sea. 相似文献
63.
Silvia Rossi Valeria Studer Alessandro Moscatelli Caterina Motta Giancarlo Coghe Giuseppe Fenu Stacy Caillier Fabio Buttari Francesco Mori Francesca Barbieri Maura Castelli Valentina De Chiara Fabrizia Monteleone Raffaele Mancino Giorgio Bernardi Sergio E. Baranzini Maria G. Marrosu Jorge R. Oksenberg Diego Centonze 《PloS one》2013,8(6)
Synaptic transmission and plasticity mediated by NMDA receptors (NMDARs) could modulate the severity of multiple sclerosis (MS). Here the role of NMDARs in MS was first explored in 691 subjects carrying specific allelic variants of the NR1 subunit gene or of the NR2B subunit gene of this glutamate receptor. The analysis was replicated for significant SNPs in an independent sample of 1548 MS subjects. The C allele of rs4880213 was found to be associated with reduced NMDAR-mediated cortical excitability, and with increased probability of having more disability than the CT/TT MS subjects. MS severity was higher in the CC group among relapsing-remitting MS (RR-MS) patients, while primary progressive MS (PP-MS) subjects homozygous for the T allele had more pronounced clinical worsening. Mean time to first relapse, but not to an active MRI scan, was lower in the CC group of RR-MS patients, and the number of subjects with two or more clinical relapses in the first two years of the disease was higher in CC compared to CT/TT group. Furthermore, the percentage of relapses associated with residual disability was lower in subjects carrying the T allele. Lesion load at the MRI was conversely unaffected by the C or T allele of this SNP in RR-MS patients. Axonal and neuronal degeneration at the optical coherence tomography was more severe in the TT group of PP-MS patients, while reduced retinal nerve fiber thickness had less consequences on visual acuity in RR-MS patients bearing the T allele. Finally, the T allele was associated with preserved cognitive abilities at the Rao’s brief repeatable neuropsychological battery in RR-MS. Signaling through glutamate NMDARs enhances both compensatory synaptic plasticity and excitotoxic neurodegeneration, impacting in opposite ways on RR-MS and PP-MS pathophysiological mechanisms. 相似文献
64.
Oecologia - Fluctuations in the abundance of main prey species might shape animal communities, by inducing numerical responses and dietary shifts in predators. Whether numerical responses and... 相似文献
65.
66.
67.
68.
69.
70.