全文获取类型
收费全文 | 633篇 |
免费 | 10篇 |
国内免费 | 28篇 |
专业分类
671篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 3篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 31篇 |
2013年 | 44篇 |
2012年 | 32篇 |
2011年 | 22篇 |
2010年 | 15篇 |
2009年 | 39篇 |
2008年 | 41篇 |
2007年 | 35篇 |
2006年 | 30篇 |
2005年 | 26篇 |
2004年 | 44篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 29篇 |
1998年 | 32篇 |
1997年 | 25篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有671条查询结果,搜索用时 15 毫秒
661.
AbstractThe use of hyperhalophilic microorganisms is emerging as a sustainable alternative to clean hydrocarbon-polluted hypersaline water bodies. In line with this practice, this work reports on the ability of the archaeon Halobacterium salinarum to develop biofilms on a solid surface conditioned by the presence of phenanthrene crystals, which results in the removal of the contaminating compound. The cell surface hydrophobicity does not change during the removal process and this organism is shown to constitutively produce a surfactant molecule with specific action on aromatic hydrocarbons, both indicating that phenanthrene removal might proceed through a non-contact mechanism. A new approach is presented to follow the process in situ through epifluorescence microscopy by monitoring phenanthrene auto-fluorescence. 相似文献
662.
Uncultured archaeal anaerobic methanotrophs (ANMEs) are known to operate the anaerobic oxidation of methane process, an important sink for the greenhouse gas methane in natural environments. In this study, we designed 16S rRNA gene-specific primers for each of the phylogenetic groups of ANMEs (ANME-1, Guaymas Basin hydrothermal sediment clones group within the ANME-1, ANME-2a, ANME-2b, ANME-2c and ANME-3) based on previously reported sequences. The newly designed primers were used for the detection of the various groups of ANMEs in the sulphate-limited anaerobic environmental samples, i.e. methanogenic sludges, rice field soils, lotus field sediments and natural gas fields. The ANME 16S rRNA gene sequences were detected only in a natural gas field sample among the environments examined in this study and were of the ANME-1 and -2c groups. In addition, the quantitative real-time PCR analysis using the designed primers showed that abundances of ANME-1 and -2c were estimated to be <0.02% of the total prokaryotic 16S rRNA gene community. The newly designed ANME group-specific primers in this study may be useful to survey the distribution and quantitative determination of ANMEs. 相似文献
663.
《Systematic and applied microbiology》2023,46(1):126388
The family Thermodesulfobiaceae, comprising one genus Thermodesulfobium with two validly published species, is currently assigned to order Thermoanaerobacterales within the class Clostridia of the phylum Bacillota. At the same time, the very first 16S rRNA gene sequence-based phylogenetic studies of representatives of the genus pointed out great differences between Thermodesulfobium and other members of the phylum Bacillota. Subsequent studies of new Thermodesulfobium representatives supported deep phylogenetic branching of this lineage within bacterial tree, implying that it represents a novel phylum. The results of the phylogenomic analysis performed in the frames of the present work confirm previous findings and suggest that Thermodesulfobium represents a distinct phylum-level lineage. Thus, we propose the transfer of the family Thermodesulfobiaceae to the new order Thermodesulfobiales within the new class Thermodesulfobiia and the new phylum Thermodesulfobiota. 相似文献
664.
Whole community lipids and pigments have been examined over a 3–5-year period in commercial salterns located in the United States, Israel, and Spain. There were significant differences in the types of lipids and pigments within the California saltern system during the 5-year period. These patterns differed seasonally despite examination of ponds with approximately the same salinities. The solar saltern in Eilat, Israel had fewer lipids on the thin-layer chromatography plates and confirmed previous analyses. The biota in the crystallizer pond in Alicante, Spain, resembled the microbial community in Israel. In the crystallizers at all three locations, phosphatidyl glycerol, methyl-phosphatidyl glycerophosphate, phosphatidyl glycerosulfate, and the sulfated diglycosyldiether lipid were identified regardless of season. This was not true for pans with salinities below 25% where no distinctive pattern was observed. Thus, we hypothesize that the more eutrophic inlet waters of the California saltern and the cooler temperatures, which result in longer retention times of water in the different pans, allow for the more diverse microbial community to develop. This is reflected then in more complex lipid and pigment patterns. However, the oligotrophic inlet waters to the Eilat saltern coupled with a drier and warmer climate result in a shorter retention time of water in the pans and a less diverse microbial community as evidenced by fewer extractable lipids and pigments. 相似文献
665.
High biological activity and volumetric productivity are considered as prerequisites for efficient bioprocesses, extreme halophilic Archaea have, however, lower growth rates, for which reason halophilic Archaea are so far not used in industrial bioprocesses. To overcome this physiological limit and to achieve increased volumetric productivity, the produced biomass must be retained in a bioreactor, for example equipped with an external cell retention system. In this study, the characterization and parameterization of a bioreactor setup with cell retention was carried out with an extreme halophilic archaeon. Bioprocess quantification was used to demonstrate the process controllability. Focussing on maximizing the volumetric productivity; 10-fold productivity increase was achieved compared to chemostat continuous cultures. Circulation of the broth between the bioreactor and the membrane unit can be however challenging from physiological points-of-view. Hence, operating the system with external cell retention at optimal cross flow rate is physiologically essential: at lower cross flow rates, higher extracellular protein concentrations were measured due to oxygen limitation. In turn, at higher cross flow rates, shear stress reasoned higher concentrations of DNA fragments. This work contributes in a pioneering way to the bioprocess development of extreme halophilic Archaea by optimizing continuous laboratory scale processes regarding robustness and scalability. 相似文献
666.
Membrane-related processes in archaea, the third and most-recently described domain of life, are in general only poorly understood.
One obstacle to a functional understanding of archaeal membrane-associated activities corresponds to a lack of archaeal model
membrane systems. In the following, characterization of inverted archaeal membrane vesicles, prepared from the halophilic
archaeon Haloferax volcanii, is presented. The inverted topology of the vesicles was revealed by defining the orientation of membrane-bound enzymes that
in intact cells normally face the cytoplasm or of other protein markers, known to face the exterior medium in intact cells.
Electron microscopy, protease protection assays and lectin-binding experiments confirmed the sealed nature of the vesicles.
Upon alkalinization of the external medium, the vesicles were able to generate ATP, reflecting the functional nature of the
membrane preparation. The availability of preparative scale amounts of inverted archaeal membrane vesicles provides a platform
for the study of various membrane-related phenomena in archaea.
Received: 27 March 2001/Revised: 13 June 2001 相似文献
667.
Hyperthermophilic microorganisms grow at temperatures of 90 °C and above and are a recent discovery in the microbial world. They are considered to be the most ancient of all extant life forms, and have been isolated mainly from near shallow and deep sea hydrothermal vents. All but two of the nearly twenty known genera are classified asArchaea (formerly archaebacteria). Virtually all of them are strict anaerobes. The majority are obligate heterotrophs that utilize proteinaceous materials as carbon and energy sources, although a few species are also saccharolytic. Most also depend on the reduction of elemental sulfur to hydrogen sulfide (H2S) for significant growth. Peptide fermentation involves transaminases and glutamate dehydrogenase, together with several unusual ferredoxin-linked oxidoreductases not found in mesophilic organisms. Similarly, a novel pathway based on a partially non-phosphorylated Entner-Doudoroff scheme has been postulated to convert carbohydrates to acetate, H2 and CO2, although a more conventional Embden-Meyerhof pathway has also been identified in one saccharolytic species. The few hyperthermophiles known that can assimilate CO2 do so via a reductive citric acid cycle. Two So-reducing enzymes termed sulfhydrogenase and sulfide dehydrogenase have been purified from the cytoplasm of a hyperthermophile that is able to grow either with or without So. A scheme for electron flow during the oxidation of carbohydrates and peptides and the reduction of So has been proposed. However, the mechanisms by which So reduction is coupled to energy conservation in this organism and in obligate So-reducing hyperthermophiles is not known.Abbreviations ADH
alcohol dehydrogenase (ADH)
- AOR
aldehyde ferredoxin oxidoreductase
- FMOR
formate ferredoxin oxidoreductase
- FOR
formaldehyde ferredoxin oxidoreductase
- GAPDH
glyceraldehyde-3-phosphate dehydrogenase
- GDH
glutamate dehydrogenase
- GluOR
glucose ferredoxin oxidoreductase
- KGOR
2-ketoglutarate ferredoxin oxidoreductase
- IOR
indolepyruvate ferredoxin oxidoreductase
- LDH
lactate dehydrogenase
- MPT
molybopterin
- POR
pyruvate ferredoxin oxidoreductase
- PLP
pyridoxal-phosphate
- PS
polysulfide
- TPP
thiamin pyrophosphate
- So
elemental sulfur
- VOR
isovalerate ferredoxin oxidoreductase 相似文献
668.
669.
R. S. Ronimus A.-L. Reysenbach D. R. Musgrave H. W. Morgan 《Archives of microbiology》1997,168(3):245-248
The 16S rRNA gene from the Thermococcus New Zealand isolate AN1 was cloned and sequenced. Analysis of the gene revealed the presence of signature sequences, indicating
that strain AN1 represents a new species of the genus Thermococcus. Since the isolate AN1 differed from other thermococci in both its lower optimal NaCl concentration and generally lower optimal
temperature for growth, in its unusual lipid membrane composition, and in its sensitivity to antibiotics, we propose that
strain AN1 represents a new species of Thermococcus. The proposed name is Thermococcus zilligii, and the type strain is DSM 2770.
Received: 13 February 1997 / Accepted: 30 May 1997 相似文献
670.
Abstract Studies on three representative species of methane-utilizing bacteria revealed high intracellular levels of inorganic pyrophosphate (5 mM) in contrast to low levels of ATP (0.5 mM) as well as the differences in the sets of enzymes utilizing pyro- and polyphosphates as phosphate and metabolic energy donors. 相似文献