全文获取类型
收费全文 | 247篇 |
免费 | 5篇 |
国内免费 | 10篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 15篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有262条查询结果,搜索用时 31 毫秒
101.
102.
本文报告了从国外引进的五种类杆菌培养,鉴定及其抗血清的制备。结果表明这些类杆菌在牛心脑培养基中容易生长。均为厌氧性革兰氏阴性无芽孢多形态杆菌。经生化反应鉴定结果发现脆弱类杆菌对红霉素(60μg)、利福平(15μg)敏感,而对多粘菌素B(10μg)、青霉素(2IU)、卡那霉素(1000μg),万古霉素(5μg)耐受。用不同接种途径免疫家兔所获得的脆弱类杆菌抗血清的结果表明皮下加不完全佐剂组血清中的抗体滴度明显高于一般皮下组及静脉注射组。 相似文献
103.
本文用2种非选择性培养基和12种选择性培养基对17名北京市成年牙周炎病人和9名健康对照者龈下及龈沟菌斑菌群进行了培养、分离和鉴定。结果,牙周炎患者龈下菌斑的菌群主要由专性厌氧的革兰氏阴性杆菌组成(60.8%),优势菌为牙龈拟杆菌等;而对照组的菌群主要由兼性厌氧的革兰氏阳性球菌组成(69.2%),优势菌为链球菌属等。这种菌群构成,两组样本存在显著性差异,对于我们认识牙周炎的病原及有关微生态学问题可能有重要意义。 相似文献
104.
105.
A rapid method for preparation of rough and smooth lipopolysaccharide from Bacteroides, Porphyromonas and Prevotella 总被引:1,自引:0,他引:1
Abstract We describe a new method for lipopolysaccharide (LPS) preparation by water extraction at 100°C and subsequent digestion with proteinase K. The crude LPS could be reliably used for immunoblotting since it retained a high level of antigenicity, and was free of SDS and proteinase K, both of which can cause problems. Two monoclonal antibodies which failed to react with LPS prepared by two conventional methods reacted well with our preparation. We used the new method to prepare LPS from 44 strains of bacteria formerly classified as Bacteroides , some of which have been reclassified as Porphyromonas or Prevotella . In general, yields were good, and electrophoretic profiles obtained with SDS-PAGE and silver staining enabled strains to be rated rough, semi-rough, or smooth. 相似文献
106.
Katharina Miebach Maurice Finger Alexandra Maria Katarina Scherer Constantin Alexander Maaß Jochen Büchs 《Biotechnology and bioengineering》2023,120(8):2199-2213
H2-producing microorganisms are a promising source of sustainable biohydrogen. However, most H2-producing microorganisms are anaerobes, which are difficult to cultivate and characterize. While several methods for measuring H2 exist, common H2 sensors often require oxygen, making them unsuitable for anaerobic processes. Other sensors can often not be operated at high gas humidity. Thus, we applied thermal conductivity (TC) sensors and developed a parallelized, online H2 monitoring for time-efficient characterization of H2 production by anaerobes. Since TC sensors are nonspecific for H2, the cross-sensitivity of the sensors was evaluated regarding temperature, gas humidity, and CO2 concentrations. The systems' measurement range was validated with two anaerobes: a high H2-producer (Clostridium pasteurianum) and a low H2-producer (Phocaeicola vulgatus). Online monitoring of H2 production in shake flask cultivations was demonstrated, and H2 transfer rates were derived. Combined with online CO2 and pressure measurements, molar gas balances of the cultivations were closed, and an anaerobic respiration quotient was calculated. Thus, insight into the effect of medium components and inhibitory cultivation conditions on H2 production with the model anaerobes was gained. The presented online H2 monitoring method can accelerate the characterization of anaerobes for biohydrogen production and reveal metabolic changes without expensive equipment and offline analysis. 相似文献
107.
Abstract Bacteroides fragilis Bf-2 cells were more sensitive to far-UV radiation, N -methyl- N '-nitrosoguanidine, ethylmethane sulphonate, acriflavine and mitomycin C under aerobic conditions than under anaerobic conditions. The opposite effect was observed with H2 O2 -treated cells and exposure to O2 enhanced the survival of H2 O2 -treated cells. Pretreatment of cells with sublethal concentrations of H2 O2 also increased the survival of H2 O2 -treated cells. Reactivation of UV- and X-irradiated and methylmethane sulphonate and H2 O2 -treated phage b-1 was induced by O2 and H2 O2 in B. fragilis . 相似文献
108.
Cloning vectors that yield high levels of single-stranded DNA for rapid DNA sequencing 总被引:71,自引:0,他引:71
We have constructed chimeric plasmid vectors with the origin and intergenic region from M13 phage cloned into the PvuII ( pZ145 ) and AhaIII ( pZ150 , pZ152 ) sites of pBR322. In the absence of M13 phage, these plasmids replicate like any other ColE1-derived plasmid and confer both ampicillin and tetracycline resistance (Amp, Tet). Upon infection with M13 phage, the viral origin present on the plasmids permits phage-directed plasmid replication and results in high yields of single-stranded (ss) plasmid DNA in M13-like particles. This ssDNA, which represents only one of the plasmid strands, is useful as a substrate for rapid DNA sequence determination by the dideoxy sequencing method described by Sanger et al. (1977). Since these plasmids contain an intact pBR322, the intergenic region can be transferred onto most pBR322 derivatives to yield ss plasmid DNA without affecting the recipient plasmid for further studies. We also constructed a deletion derivative of pZ145 , plasmid pZ146 , that does not exhibit interference with the growth of the M13 helper, although this plasmid is encapsidated into phage particles. This result confirms the theory that the intergenic region consists of two domains: one domain being a segment involved in phage morphogenesis and the other being a region of functional origin which interferes with M13 replication. 相似文献
109.
The effect of CO2 concentration on growth and glucose fermentation of Bacteroides fragilis was studied in a defined mineral medium. Batch culture experiments were done in closed tubes containing CO2 concentrations ranging from 10% to 100% (with appropriate amounts of bicarbonate added to maintain the pH at 6.7). These experiments revealed that CO2 had no influence on growth rate or cell yield when the CO2 concentration was above 30% CO2 (minimum available CO2–HCO
3
-
, 25.5 mM), whereas a slight decrease in these parameters was observed at 20% and 10% CO2 (available CO2–HCO
3
-
, 17 and 8.5 mM, respectively). If CO2–HCO
3
-
concentrations were below 10 mM, the lag phase lengthened and a decrease in maximal growth rate and cell yield were observed. The amount of acetate made decreased, while d-lactate concentration increased. A net production of CO2 allowed growth under conditions of extremely low concentrations of added CO2.When B. fragilis was grown in continuous culture with 100% CO2 or 100% N2, the dilution rate influenced the concentrations of acetate, succinate, propionate, d-lactate, l-malate and formate formed. Decreasing the dilution rate favored propionate and acetate production under both conditions. When the organism was grown with 100% N2, the amount of propionate formed was greater than the amount of succinate formed at all dilution rates. Except at slow dilution rates the reverse was true when 100% CO2 was used. B. fragilis was unable to grow at dilution rates faster than 0.154 h-1 when grown with 100% N2; the Y
glc
max
was 67.9 g DW cells/mol glucose and m
s was 0.064 mmol glucose/g DW·h. If the gas atmosphere was 100% CO2 the organism was washed out of the culture when the dilution rate exceeded 0.38 h-1; the Y
glc
max
was 59.4 g DW cells/mol glucose and m
s was 0.094 mmol glucose/g DW·h.Measurement of the phosphoenolpyruvate (PEP) carboxykinase (E.C. 4.1.1.49) with whole, permeabilized cells of B. fragilis showed an increase of specific enzyme activity with decreasing CO2 concentrations. The mechanisms used by B. fragilis to adjust to low levels of CO2 are discussed. 相似文献
110.
Sensitive detection of RNA using strand-specific M13 probes 总被引:11,自引:0,他引:11
We have extended the method of Hu and Messing (Gene 17 (1982) 271-277) to prepare highly radioactive M13 probes suitable for use in RNA-DNA hybridization experiments. Single strands of M13 DNA carrying cloned sequences are rendered partially double-stranded by primed synthesis using a synthetic oligonucleotide primer complementary to a region 5' to the cloning site. The newly synthesized radioactive complementary strand is then covalently cross-linked to the M13 phage DNA by UV irradiation in the presence of 4,5,8-trimethylpsoralen (trioxsalen). Since the cross-linked probe is stable to heat denaturation, and the region of cloned sequence is kept single-stranded, these complexes may be used as strand-specific hybridization probes to detect RNA sequences under conditions which would denature DNA-DNA duplexes. 相似文献