全文获取类型
收费全文 | 247篇 |
免费 | 2篇 |
国内免费 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 15 毫秒
81.
82.
83.
In dry films of bacteriorhodopsin-containing purple membranes from Halobacterium halobium the external electric field (104–105 V · cm?1) induces the appearance of a product spectrally close to the initial intermediate of bacteriorhodopsin (BR) photochromic cycle (batho form, K). This result and also preliminary data of the electret-thermal analysis of the preparations suggest that the dielectric polarization in chromophore-protein-lipid complexes might be an essential step of the primary stabilization of light energy in photo-bioenergetic processes. 相似文献
84.
1. Dry weight yields from mixed cultures ofProsthecochloris aestuarii orChlorobium limicola with the sulfur reducingDesulfuromonas acetoxidans were determined on different growth limiting amounts of acetate, ethanol or propanol. The obtained yields agreed well with values predicted from stoichiometric calculations. 2. From mixed cultures of twoChlorobium limicola strains withDesulfovibrio desulfuricans orD. gigas on ethanol as the growth limiting substrate, dry weight yields were obtained as calculated for the complete utilization of the ethanol by the mixed cultures. 3. Dry weight yield determinations for two pure cultures ofChlorobium limicola with different growth limiting amounts of sulfide in the absence and presence of excess acetate confirmed that acetate is incorporated byChlorobium in a fixed proportion to sulfide; compared to the yield in the absence of acetate the yield is increased two to threefold in the presence of acetate. 4. The lowest possible sulfide concentrations necessary for optimal growth of mixed cultures of eitherProsthecochloris orChlorobium withDesulfuromonas on acetate were 7–8 mg H2S per liter of medium. 5. Doubling times at the growth rate limiting light intensities of 5, 10, 20, 50, 100 and 200 lux were determined under optimal growth conditions for the following phototrophic bacteria:Prosthecochloris aestuarii, Chlorobium phaeovibriodes, Chromatium vinosum andRhodopseudomonas capsulata. Reasonably good growth was still obtained withProsthecochloris at 10 and 5 lux light intensity at which no growth of the purple bacteria could be observed. 相似文献
85.
Walther Stoeckenius Richard H. Lozier Werner Niederberger 《European biophysics journal : EBJ》1977,3(1):65-68
Bacteriorhodopsin is a membrane-bound light energy transducer which generates an electrochemical proton gradient. It undergoes a cyclic photoreaction in which five intermediates have been identified. During the cycle it releases a proton from one surface of the membrane and takes up a proton on the opposite surface. The active chromophore consists of retinal bound through a Schiff base to the protein. The Schiff base is deprotonized during the photoreaction cycle and appears to be involved in the transport of protons through the membrane. The retinal may also undergo an isomerization.Presented at the EMBO-Workshop on Transduction Mechanism of Photoreceptors, Jülich, Germany, October 4–8, 1976This work was supported by NASA Grant NSG-7151 and NHLI Grant HL-06285 相似文献
86.
The marine green sulfur bacterium Chlorobium vibrioforme strain 1930 produced H2 and elemental sulfur from sulfide or thiosulfate under N limitation in the light. H2 production depended on nitrogenase and occurred only in the absence of ammonia. Methionine sulfoximine, an inhibitor of glutamine synthetase, prevented the switch-off by ammonia. In defined syntrophic cocultures of the acetate-oxidizing, sulfur-reducing bacterium Desulfuromonas acetoxidans with green sulfur bacteria, H2 was produced from acetate via a light-driven sulfur cycle. The sulfur-reducing bacterium could not be replaced by sulfate-reducing bacteria in these experiments. In a coculture of the marine Chlorobium vibrioforme strain 1930 and the sulfur-reducing bacterium Desulfuromonas acetoxidans strain 5071, optimum long-term H2 production from acetate was obtained with molecular nitrogen as N source, at low light intensity (110 mol · m-2 · s-1), in sulfide-reduced mineral medium (2 mM Na2S) at pH 6.8. Traces of sulfide (10 M) were sufficient to keep the sulfur cycle running. The coculture formed no poly--hydroxyalkanoates (PHA), but 20%–40% polysaccharide per cell dry mass. Per mol acetate added, the coculture formed 3.1 mol of H2 (78% of the theoretical maximum). Only 8% of the reducing equivalents was incorporated into biomass. The maximum rate of H2 production was 1300 ml H2 per day and g cell dry mass.Non-standard abbrevations MOPS
2-(N-morpholino) propane sulfonic acid
- MSX
Methionine sulfoximine
- PHA
poly--hydroxyalkanoates 相似文献
87.
Abstract Ribulose-1,5-biphosphate carboxylase (RuBPCase) partially purified from the thermophilic purple bacterium Chromatium tepidum displayed maximum carboxylase activity at 50°C, while enzyme from a related mesophilic species, Chromatium vinosum , was completely inactive at 50°C. RuBPCase from C. tepidum showed ribulose-1,5- bisphosphate-dependent oxygenase activity, and, in addition, O2 was found to partially destroy carboxylase activity. It is concluded that thermophilic purple bacteria produce heat-stable RuBPCase and that all RuBPCases, even those from an obligate anaerobe such as C. tepidum , have associated oxygenase activity. 相似文献
88.
紫金山含明党参早春草本层的群落学分析 总被引:7,自引:0,他引:7
在1 ̄7月对紫金山紫薇-山胡椒群落(Form.Lagerstroemis indica-Lindera glauca)的早春草本层进行了定位连续的群落学调查统计。结果表明,生于落叶林下的含明党参(Changium smyrnioides smyrnioids Wolff.)早春草本层植物通常2月萌芽,在早春落叶乔木尚未展叶林内透光好的条件下旺盛生长,在6月初落叶乔木展叶郁闭度增高后完成生活史。早春 相似文献
89.
N-glycosylation influences the latency and catalytic properties of mammalian purple acid phosphatase
Purple acid phosphatase (PAP), also known as tartrate-resistant acid phosphatase or uteroferrin, contains two potential consensus N-glycosylation sites at Asn(97) and Asn(128). In this study, endogenous rat bone PAP was found to possess similar N-glycan structures as rat recombinant PAP heterologously expressed in baculovirus-infected Sf9 insect cells. PAP from Sf9 cells was shown to contain two N-linked oligosaccharides, whereas PAP expressed by mammalian CHO-K1 cells was less extensively glycosylated. The extent of N-glycosylation affected the catalytic properties of the enzyme, as N97Q and N128Q mutants, containing a single oligosaccharide chain, exhibited a lower substrate affinity and catalytic activity compared to those of the fully glycosylated PAP in the native, monomeric state. The differences in substrate affinity and catalytic activity were abolished and partially restored, respectively, by proteolytic cleavage in the loop domain, indicating that the extent of N-glycosylation influences the interaction of the repressive loop domain with catalytically important residues. 相似文献
90.
The universal occurrence and abundance of nematodes provides opportunities to investigate ecological factors that may influence biodiversity. Clarke and Warwick (2001) have proposed diversity indices average taxonomic distance(AvTD), variation in taxonomic distinctness (VarTD) for computing marine nematode biodiversity based on classification trees. Faith [Biological Conservation 61 (1992) 1] had previously proposed a diversity index based on phylogenetic trees, though not applied to nematodes. Clarke and Warwick (2001) also considered an index AvPD analogous to AvTD. These indices have been applied to five very large collections of free-living nematodes from three exposed sandy beaches in Australia. Two were from a beach close to Darwin in northern Australia, two from the temperate southeast coast of Australia and one from the south of the Australian mainland. The collections extend over a considerable range of latitude, from 12°26S to 38°33S and the controversial hypothesis that latitudinal gradients per se influence the biodiversity of marine nematode assemblages is examined. AvTD did not vary among collections and its value for any collection was indistinguishable from that of random samples of the same size drawn from the total species pool. VarTD showed no variation for three of the collections, but was slightly higher than expected for the mid-latitude beach, attributed to unevenness in the classification trees. AvTD and VarTD were not greatly affected by differences in sampling intensity. PD varied directly with the number of species found but observed PD did not differ from the PD of random samples of the same number of species taken from the total species pool. Thus, the observed variation in PD is wholly accounted for by variations in species richness. The number of species found increased with decreasing latitude. It appears that species richness by itself is an adequate index of biodiversity for the free-living nematodes of these sandy beaches, and more complex indices such as AvTD, VarTD and PD are unnecessary. 相似文献