全文获取类型
收费全文 | 1550篇 |
免费 | 153篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 35篇 |
2021年 | 68篇 |
2020年 | 31篇 |
2019年 | 35篇 |
2018年 | 50篇 |
2017年 | 43篇 |
2016年 | 58篇 |
2015年 | 95篇 |
2014年 | 105篇 |
2013年 | 113篇 |
2012年 | 152篇 |
2011年 | 141篇 |
2010年 | 88篇 |
2009年 | 76篇 |
2008年 | 82篇 |
2007年 | 80篇 |
2006年 | 70篇 |
2005年 | 68篇 |
2004年 | 52篇 |
2003年 | 40篇 |
2002年 | 43篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1984年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1965年 | 3篇 |
1964年 | 5篇 |
1961年 | 4篇 |
1960年 | 6篇 |
1930年 | 2篇 |
1902年 | 2篇 |
1899年 | 2篇 |
排序方式: 共有1705条查询结果,搜索用时 375 毫秒
151.
Bieri M Mobbs JI Koay A Louey G Mok YF Hatters DM Park JT Park KH Neumann D Stapleton D Gooley PR 《Biophysical journal》2012,102(2):305-314
AMP-activated protein kinase interacts with oligosaccharides and glycogen through the carbohydrate-binding module (CBM) containing the β-subunit, for which there are two isoforms (β(1) and β(2)). Muscle-specific β(2)-CBM, either as an isolated domain or in the intact enzyme, binds carbohydrates more tightly than the ubiquitous β(1)-CBM. Although residues that contact carbohydrate are strictly conserved, an additional threonine in a loop of β(2)-CBM is concurrent with an increase in flexibility in β(2)-CBM, which may account for the affinity differences between the two isoforms. In contrast to β(1)-CBM, unbound β(2)-CBM showed microsecond-to-millisecond motion at the base of a β-hairpin that contains residues that make critical contacts with carbohydrate. Upon binding to carbohydrate, similar microsecond-to-millisecond motion was observed in this β-hairpin and the loop that contains the threonine insertion. Deletion of the threonine from β(2)-CBM resulted in reduced carbohydrate affinity. Although motion was retained in the unbound state, a significant loss of motion was observed in the bound state of the β(2)-CBM mutant. Insertion of a threonine into the background of β(1)-CBM resulted in increased ligand affinity and flexibility in these loops when bound to carbohydrate. However, these mutations indicate that the additional threonine is not solely responsible for the differences in carbohydrate affinity and protein dynamics. Nevertheless, these results suggest that altered protein dynamics may contribute to differences in the ligand affinity of the two naturally occurring CBM isoforms. 相似文献
152.
153.
The red cell membrane is stabilized by a spectrin/actin-based cortical cytoskeleton connected to the phospholipid bilayer via multiple protein bridges. By virtue of its interaction with ankyrin and adducin, the anion transporter, band 3 (AE1), contributes prominently to these bridges. In a previous study, we demonstrated that an exposed loop comprising residues 175-185 of the cytoplasmic domain of band 3 (cdB3) constitutes a critical docking site for ankyrin on band 3. In this paper, we demonstrate that an adjacent loop, comprising residues 63-73 of cdB3, is also essential for ankyrin binding. Data that support this hypothesis include the following. (1) Deletion or mutation of residues within the latter loop abrogates ankyrin binding without affecting cdB3 structure or its other functions. (2) Association of cdB3 with ankyrin is inhibited by competition with the loop peptide. (3) Resealing of the loop peptide into erythrocyte ghosts alters membrane morphology and stability. To characterize cdB3-ankyrin interaction further, we identified their interfacial contact sites using molecular docking software and the crystal structures of D(3)D(4)-ankyrin and cdB3. The best fit for the interaction reveals multiple salt bridges and hydrophobic contacts between the two proteins. The most important ion pair interactions are (i) cdB3 K69-ankyrin E645, (ii) cdB3 E72-ankyrin K611, and (iii) cdB3 D183-ankyrin N601 and Q634. Mutation of these four residues on ankyrin yielded an ankyrin with a native CD spectrum but little or no affinity for cdB3. These data define the docking interface between cdB3 and ankyrin in greater detail. 相似文献
154.
Young dentate granule cells mediate pattern separation, whereas old granule cells facilitate pattern completion 总被引:1,自引:0,他引:1
Nakashiba T Cushman JD Pelkey KA Renaudineau S Buhl DL McHugh TJ Rodriguez Barrera V Chittajallu R Iwamoto KS McBain CJ Fanselow MS Tonegawa S 《Cell》2012,149(1):188-201
Adult-born granule cells (GCs), a minor population of cells in the hippocampal dentate gyrus, are highly active during the first few weeks after functional integration into the neuronal network, distinguishing them from less active, older adult-born GCs and the major population of dentate GCs generated developmentally. To ascertain whether young and old GCs perform distinct memory functions, we created a transgenic mouse in which output of old GCs was specifically inhibited while leaving a substantial portion of young GCs intact. These mice exhibited enhanced or normal pattern separation between similar contexts, which was reduced following ablation of young GCs. Furthermore, these mutant mice exhibited deficits in rapid pattern completion. Therefore, pattern separation requires adult-born young GCs but not old GCs, and older GCs contribute to the rapid recall by pattern completion. Our data suggest that as adult-born GCs age, their function switches from pattern separation to rapid pattern completion. 相似文献
155.
Kyoung C. Park Crystal Whitney Jesse C. McNichol Kathryn E. Dickinson Scott MacQuarrie Blair P. Skrupski Jitao Zou Kenneth E. Wilson Stephen J. B. O’Leary Patrick J. McGinn 《Journal of applied phycology》2012,24(3):339-348
Northern regions are generally viewed as unsuitable for microalgal biofuel production due to unfavorable climate and solar insolation levels. However, these conditions can potentially be mitigated by coupling microalgal cultivation to industrial processes such as wastewater treatment. In this study, we have examined the biomass and lipid productivity characteristics of 14 microalgae isolates (Chlorophyta) from the Canadian province of Saskatchewan. Under both photoautotrophic and mixotrophic cultivation, a distinct linear trend was observed between biomass and lipid productivities in the 14 SK isolates. The most productive strain under cultivation in TAP media was Scenedesmus sp.-AMDD which displayed rates of biomass and fatty acid productivities of 80 and 30.7?mg?L?1?day?1, respectively. The most productive strain in B3NV media was Chlamydomonas debaryana-AMLs1b which displayed rates of biomass and fatty acid productivities of 51.7 and 5.9?mg?L?1?day?1, respectively. In 11 of the isolates tested, secondary municipal wastewater (MCWW) supported rates of biomass productivity between 21 and 33?mg?L?1?day?1 with Scenedesmus sp.-AMDD being the most productive. Three strains, Chlamydomonas debaryana-AMB1, Chlorella sorokiniana-RBD8 and Micractinium sp.-RB1b, showed large increases in biomass productivity when cultivated mixotrophically in MCWW supplemented with glycerol. High relative oleic acid content was detected in 10 of the 14 isolates when grown mixotrophically in media supplemented with acetate. There was no detectable effect on the fatty acid profiles in cells cultivated mixotrophically in glycerol-supplemented MCWW. These data indicate that biomass and lipid productivities are boosted by mixotrophic cultivation. Exploiting this response in municipal wastewater is a promising strategy for the production of environmentally sustainable biofuels. 相似文献
156.
Road mortality in freshwater turtles: identifying causes of spatial patterns to optimize road planning and mitigation 总被引:1,自引:0,他引:1
Tom A. Langen Kari E. Gunson Christopher A. Scheiner Jesse T. Boulerice 《Biodiversity and Conservation》2012,21(12):3017-3034
Road mortality of freshwater turtles can be high enough to imperil populations near roads, thus there is a need to efficiently and accurately locate regions of excessive road-kill along road networks for mitigation. Weekly over 2?years, we drove a 160?km highway circuit in northeastern New York State, USA and recorded the location of all detected road-kill of three freshwater turtle species (Chelydra serpentina, Chrysemys picta, Emydoidea blandingii). We then analyzed the spatial dispersion of road-kill and the road and landscape features associated with road-kill locations. Road-kill was most prevalent at a limited number of short road segments, termed ‘hotspots’. The locations of hotspots, as indicated by kernel density analysis, and the peak spatial extent of hotspots (250?m), as indicated by Ripley’s?K, corresponded to the locations and average lengths of causeways (road segments with wetlands within 100?m on both sides). Hotspots were located at causeways that were greater than 200?m length and characterized by high traffic volumes, close proximity to water, and high forest coverage. We conclude that freshwater turtle road mortality is spatially aggregated at short, severe hotspots, and hotspot locations can be predicted when the locations of wetlands, traffic volumes, and the land-uses bordering roads are known. Hotspot models using these predictors can locate sites along a road network that are the most promising for mitigation to reduce excessive road mortality and maintain connectivity. 相似文献
157.
158.
159.
160.