全文获取类型
收费全文 | 310篇 |
免费 | 17篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 31篇 |
2011年 | 14篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 13篇 |
2006年 | 16篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1944年 | 1篇 |
1934年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有327条查询结果,搜索用时 15 毫秒
321.
On the origins of esterases 总被引:8,自引:0,他引:8
Comparisons among the primary sequences of five cloned eukaryotic esterases
reveal two distinct lineages, neither bearing any significant overall
sequence similarity to the functionally related serine protease multigene
family. We have not eliminated the possibility that the esterases may have
residual conformational similarities to the serine proteases. However, our
profile analysis and analyses of the predicted conformations of the
esterases reveal little similarity to the serine proteases. Four of the
esterase proteins share 27%-53% overall sequence similarity and evidence of
a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge
relay. We propose that these four esterases, three of them cholinesterases,
form part of a multigene family essentially separate from the serine
proteases.
相似文献
322.
João Soeiro Teodoro Filipe Valente Duarte Ana Patrícia Gomes Ana Teresa Varela Francisco Manuel Peixoto Anabela Pinto Rolo Carlos Marques Palmeira 《Mitochondrion》2013,13(6):637-646
Berberine is an isoquinoline alkaloid with anti-diabetic properties. Despite the central role of liver and thus hepatic mitochondria in whole-body metabolism, berberine effects on hepatic mitochondrial function in an obesity model are still unknown. Here, we demonstrate that berberine treatment recovers mitochondrial efficiency when altered by a high-fat feeding. Mitochondria isolated from the liver of high-fat fed rats exhibited decreased capacity to accumulate calcium and impaired oxidative phosphorylation (OXPHOS) capacity, as shown by impaired mitochondrial membrane potential, oxygen consumption and cellular ATP levels. Interestingly, the recovery of mitochondrial function by berberine was associated with an increased activity of the mitochondrial sirtuin 3 (SirT3). In conclusion, berberine potent protective effects against metabolic syndrome may rely on increasing mitochondrial SirT3 activity, normalizing mitochondrial function and preventing a state of energetic deficit caused by impaired OXPHOS. 相似文献
323.
Aims Both human and non‐human determinants have shaped Mediterranean forest structure over the last few millennia. The effects of recent human activities on forest composition, however, remain poorly understood. We quantified changes in forest composition during the past century in the mixed forests of Quercus suber (cork oak) and Q. canariensis (Algerian oak), and explored the effects of forest management and environmental (climate, topography) factors on forest structure at various spatial and temporal scales. Location Mountains north of the Strait of Gibraltar (southern Spain). Methods First, we quantified 20th‐century changes in species composition from a series of inventories in nine mixed forests (c. 40,000 ha), and examined them in terms of the management practices and environmental conditions. Second, we analysed present‐day Q. suber and Q. canariensis stand structure along environmental gradients at two spatial scales: (1) that of the forest landscape (c. 284 ha), combining local inventories and topographic variables and using a digital elevation model; and (2) regional (c. 87,600 km2), combining data from the Spanish Forest Inventory for the Andalusia region and estimates of climatic variables. Results Historical data indicate anthropogenic changes in stand composition, revealing a sharp increase in the density of cork oaks over the last century. Forest management has favoured this species (for cork production) at the expense of Q. canariensis. The impact of management is imprinted on the present‐day forest structure. The abundance of both species increases with annual mean precipitation, and they coexist above 800 mm (the minimum threshold for Q. canariensis). Quercus suber dominates in most of the stands, and species segregation in the landscape is associated with the drainage network, Q. canariensis being clearly associated with moister habitats near streams. Main conclusions Our study quantitatively exemplifies a recent human‐mediated shift in forest composition. As a result of forest management, the realized niche of the cork oak has been enlarged at the expense of that of Q. canariensis, providing further evidence for humans as major drivers of oak forest composition across the Mediterranean. Recent regeneration problems detected in Q. suber stands, a reduced demand for wood products, conservation policies, and climate change augur new large‐scale shifts in forest composition. 相似文献
324.
de Almeida Teodoro Isnard Ribeiro do Amaral Cibele Hummel Botelho Moreno Ribeiro Eduardo Francisco Penatti Natasha Costa 《Wetlands Ecology and Management》2019,27(1):171-185
Wetlands Ecology and Management - The Pantanal is located in the center of South America in a tectonically active sedimentary basin of Quaternary age. Even though the relief is flat and the... 相似文献
325.
326.
Nicholas JG Webster Lui-Guojing Evans Matt Caples Laura Erker Shern L Chew 《BMC molecular biology》2004,5(1):7-15
Background
Incorporation of exon 11 of the insulin receptor gene is both developmentally and hormonally-regulated. Previously, we have shown the presence of enhancer and silencer elements that modulate the incorporation of the small 36-nucleotide exon. In this study, we investigated the role of inherent splice site strength in the alternative splicing decision and whether recognition of the splice sites is the major determinant of exon incorporation. 相似文献327.