全文获取类型
收费全文 | 368篇 |
免费 | 24篇 |
专业分类
392篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 21篇 |
2014年 | 23篇 |
2013年 | 32篇 |
2012年 | 30篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 16篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1950年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有392条查询结果,搜索用时 15 毫秒
1.
A full-length zebrafish cDNA clone and a partial mouse cDNA clone similar to chick DM-GRASPwere isolated and analyzed. The nucleotide sequence of the full-length zebrafish clone shares 54% identity, and predicts 39% amino acid identity, with chick DM-GRASP. The partial mouse clone shares 76% nucleotide identity, and predicts 76% amino acid identity, with chick DM-GRASP. The predicted proteins encoded by both of these clones exhibit conserved structural domains that are characteristic of the chick protein. These features may identify them as a distinct subfamily within the immunoglobulin superfamily of cell adhesion molecules. Express of the zebrafish DM-GRASP protein is similar to chick DM-GRASP and is principally restricted to a small subset of developing sensory and motor neurons during axonogenesis. Zebrafish DM-GRASP expression was temporally regulated and limited to specific axon domains. This regional expression correlated with fasciculated axon domains. These results suggest that the zebrafish and mouse cDNA clones represent the respective fish and mammalian homologs of thick DM-GRASP. The highly selective expression of zebrafish DM-GRASP suggests that it is involved in the selective fasciculation and guidance of axons along their normal pathways. 1994 John Wiley & Sons, Inc. 相似文献
2.
Halothane (1%) was administered to twenty-two gram female Swiss-Albino mice which were sacrificed at times of 15 seconds, 45 seconds, 79 seconds and 5 minutes. Additional animals were exposed for 5 minutes and sacrificed 10 minutes after removal from halothane (recovery). Selected energy metabolites were measured in 100–500 nanogram samples from the inferior colliculus and the ascending reticular activating system.Results from this study showed an increase in glucose levels at 79 seconds, when the animals first lost their righting response. The glucose increase was similar in the inferior colliculus and reticular formation. ATP and phosphocreatine were increased at 45 seconds, and during the sleep period in the ascending reticular activiting system, and returned to normal during the recovery period. In the inferior colliculus, ATP was similarly increased from 45 seconds throughout the time course, whereas phosphocreatine was elevated at 79 seconds, and during recovery only. These data suggest a decrease in utilization of energy metabolities during halothane anesthesia, both in cells of the inferior colliculus and ascending reticular activating system. 相似文献
3.
Summary C-6 glioma and C-1300 neuroblastoma cells were cultured in thiamine deficient and control media. Thiamine levels, transketolase and pyruvate decarboxylase activities, and high energy phosphate metabolites were all measured in deficient and control cells. Thiamine levels in the deficient cells were found to be below the level of detectability. Pyruvate decarboxylase activity was more susceptible to thiamine deficiency in both cell lines than transketolase. In spite of the large decrease in pyruvate decarboxylase activity, high energy phosphate metabolites were not decreased in either cell line. These data indicate that C-6 glioma and C-1300 neuroblastoma cells have the capacity to maintain normal energy metabolites in the presence of large changes in thiamine levels and thiamine dependent enzyme activity.Supported in part by USPHS grant AA 01391. 相似文献
4.
5.
6.
7.
8.
Persistence of Swidden Cultivation in the Face of Globalization: A Case Study from Communities in Calakmul, Mexico 总被引:1,自引:0,他引:1
Birgit Schmook Nathalie van Vliet Claudia Radel María de Jesús Manzón-Che Susannah McCandless 《Human ecology: an interdisciplinary journal》2013,41(1):93-107
Over the last decades, political, economic and environmental pressures have encouraged changes from swidden to more intensive agricultural practices, resulting in the hypothesis that swidden cultivation systems are disappearing. In Calakmul, southeastern Mexico, communities decreased the area under milpa, the traditional maize swidden system, but a collapse did not occur. To document and explain the persistence of swidden we employ a variety of data: (1) 59 standardized household surveys from 2003 and 2010 in five villages, (2) in-depth interviews in one village, and (3) coupled human–environmental timelines in this same village. Droughts, hurricanes, and remittances were important drivers of decreases in milpa cultivation. Market crop profitability and conservation programs were also reported to affect the area under milpa. Off-farm employment and governmental transfers have tended to stabilize household economies and decrease dependency on agricultural production, but have also allowed households to maintain their milpas for subsistence and cultural reproduction. Findings in Calakmul point to the need to consider swidden as an evolving and active response to changing policy, economic, and environmental conditions. 相似文献
9.
David M. Wilson James Apps Nicholas Bailey Mark J. Bamford Isabel J. Beresford Michael A. Briggs Andrew R. Calver Barry Crook Robert P. Davis Susannah Davis David K. Dean Leanne Harris Tom D. Heightman Terry Panchal Christopher A. Parr Nigel Quashie Jon G.A. Steadman Joanne Schogger Andrew D. Medhurst 《Bioorganic & medicinal chemistry letters》2013,23(24):6897-6901
This Letter describes the discovery of a novel series of H3 receptor antagonists. The initial medicinal chemistry strategy focused on deconstructing and simplifying an early screening hit which rapidly led to the discovery of a novel series of H3 receptor antagonists based on the benzazepine core. Employing an H3 driven pharmacodynamic model, the series was then further optimised through to a lead compound that showed robust in vivo functional activity and possessed overall excellent developability properties. 相似文献
10.
Jason J Flowers Shaomei He Stephanie Malfatti Tijana Glavina del Rio Susannah G Tringe Philip Hugenholtz Katherine D McMahon 《The ISME journal》2013,7(12):2301-2314
Members of the genus Candidatus Accumulibacter are important in many wastewater treatment systems performing enhanced biological phosphorus removal (EBPR). The Accumulibacter lineage can be subdivided phylogenetically into multiple clades, and previous work showed that these clades are ecologically distinct. The complete genome of Candidatus Accumulibacter phosphatis strain UW-1, a member of Clade IIA, was previously sequenced. Here, we report a draft genome sequence of Candidatus Accumulibacter spp. strain UW-2, a member of Clade IA, assembled following shotgun metagenomic sequencing of laboratory-scale bioreactor sludge. We estimate the genome to be 80–90% complete. Although the two clades share 16S rRNA sequence identity of >98.0%, we observed a remarkable lack of synteny between the two genomes. We identified 2317 genes shared between the two genomes, with an average nucleotide identity (ANI) of 78.3%, and accounting for 49% of genes in the UW-1 genome. Unlike UW-1, the UW-2 genome seemed to lack genes for nitrogen fixation and carbon fixation. Despite these differences, metabolic genes essential for denitrification and EBPR, including carbon storage polymer and polyphosphate metabolism, were conserved in both genomes. The ANI from genes associated with EBPR was statistically higher than that from genes not associated with EBPR, indicating a high selective pressure in EBPR systems. Further, we identified genomic islands of foreign origins including a near-complete lysogenic phage in the Clade IA genome. Interestingly, Clade IA appeared to be more phage susceptible based on it containing only a single Clustered Regularly Interspaced Short Palindromic Repeats locus as compared with the two found in Clade IIA. Overall, the comparative analysis provided a genetic basis to understand physiological differences and ecological niches of Accumulibacter populations, and highlights the importance of diversity in maintaining system functional resilience. 相似文献