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排序方式: 共有198条查询结果,搜索用时 15 毫秒
1.
Samples from biogas digesters, sewage ponds, animal house effluents and food processing wastes were used in enrichment systems seeking anaerobic bacteria producing pectinases. Among the 46 anaerobic consortia developed from various samples, four showed high pectinase activity under static anaerobic conditions. Investigation of fermentation variables showed the optimum conditions for pectinase activity were pH 7.0, 45°C and 72 h of growth with 0.5% pectin in the cultivation medium. A 1.4- to 1.6-fold increase in the pectinase activity was achieved under these conditions. The maximum yield of enzymes (62.72 U ml-1 of pectinase, 4.74 U ml-1 of polygalacturonase, 113.30 U ml-1 of pectin lyase, 2.10 U ml-1 of pectinesterase, 0.75 U ml-1 of total cellulase and 9.27 U ml-1 of xylanase) was recorded with the consortia C-S2 developed from decomposed plant samples collected from a pond. 相似文献
2.
P Zhong S D Pratt R P Edalji K A Walter T F Holzman A G Shivakumar L Katz 《Journal of bacteriology》1995,177(15):4327-4332
ErmC' is a methyltransferase that confers resistance to the macrolide-lincosamide-streptogramin B group of antibiotics by catalyzing the methylation of 23S rRNA at a specific adenine residue (A-2085 in Bacillus subtilis; A-2058 in Escherichia coli). The gene for ErmC' was cloned and expressed to a high level in E. coli, and the protein was purified to virtual homogeneity. Studies of substrate requirements of ErmC' have shown that a 262-nucleotide RNA fragment within domain V of B. subtilis 23S rRNA can be utilized efficiently as a substrate for methylation at A-2085. Kinetic studies of the monomethylation reaction showed that the apparent Km of this 262-nucleotide RNA oligonucleotide was 26-fold greater than the value determined for full-size and domain V 23S rRNA. In addition, the Vmax for this fragment also rose sevenfold. A model of RNA-ErmC' interaction involving multiple binding sites is proposed from the kinetic data presented. 相似文献
3.
Naturally occurring macrolide-lincosamide-streptogramin B resistance in Bacillus licheniformis. 总被引:12,自引:8,他引:4
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A Docherty G Grandi R Grandi T J Gryczan A G Shivakumar D Dubnau 《Journal of bacteriology》1981,145(1):129-137
Resistance to the macrolide-lincosamide-streptogramin B (MLS) group of antibiotics is widespread and of clinical importance. B. Weisblum and his coworkers have demonstrated that this resistance is associated with methylation of the 23S ribosomal ribonucleic acid of the large ribosomal subunit which results in a diminished affinity of this organelle for these antibiotics (Lai et al, J. Mol. Biol. 74:67-72, 1973). We report that 10 of 15 natural isolates of Bacillus licheniformis, a common soil organism, are resistant to the MLS antibiotics. The properties of this resistance (high level of tolerance for erythromycin, broad cross-resistance spectrum, and inducibility) suggest that resistance is conferred as described above. The resistance determinant from one of these strains was cloned onto a B. subtilis plasmid vector, and the resulting hybrid plasmid (pBD90) was used to prepare radioactive probe deoxyribonucleic acid for hybridization studies. All of the resistance B. licheniformis strains studied exhibited homology with the pBD90 insert. Plasmid pBD90 showed no homology to the following staphylococcal and streptococcal MLS-resistance plasmids: pE194, pE5, pAM77, pI258. Plasmids pE194 and pE5, on the other hand, carry homologous MLS genes but showed no detectable homology to one another in their replication genes. pBD90 specified a 35,000-dalton erythromycin-inducible protein, detectable in minicells, which therefore appears different from the 29,000-dalton inducible resistance protein specified by pE194. We conclude that there are at least three distinct MLS resistance determinants to be found among gram-positive bacteria. 相似文献
4.
Raju V. Kumar M. Yariswamy Vikram Joshi K.K. Dharmappa Shivaprasad H. Venkatesha B.K. Sharath Bannikuppe S. Vishwanath 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2013,164(2):111-116
In the present study we describe the purification and characterization of Malabarase, a serine protease from Trimeresurus malabaricus venom. Purification was achieved by gel-permeation chromatography on Sephadex G-75 followed by ion-exchange chromatography on CM Sephadex C-25. Homogeneity of Malabarase was confirmed by RP-HPLC. Malabarase is a monomer that migrated as a single protein band on SDS-PAGE under both reducing and non-reducing conditions. The molecular mass of Malabarase was determined to be 23.4 kDa using MALDI-TOF mass spectrometry. Malabarase is the first serine protease purified from T. malabaricus venom and is selective for fibrinogen. Malabarase hydrolyzes Aα and Bβ but not γ-chains of fibrinogen similar to the metalloproteases, Malabarin and Trimarin, isolated from the same venom. However, the action of Malabarase on plasma coagulation is opposite than those of Malabarin, Trimarin and the whole venom. Malabarase significantly prolonged plasma coagulation time from 152–341 s; whereas Malabarin, Trimarin, and whole venom, greatly reduce plasma clotting time from 152 to 12, 48, and 14 s, respectively. Malabarase did not show hemorrhagic or myotoxic activity. In contrast, Malabarin, Trimarin and whole venom are highly hemorrhagic and myotoxic. These observations support the specificity of Malabarase towards fibrinogen and its non-toxic nature. In conclusion, Malabarase is a fibrinogen-specific, anti-coagulant, and non-toxic serine protease. Its selective action and non-toxic nature might make it useful for treating thrombotic disorders. 相似文献
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Vicuna Requesens Deborah Gonzalez Romero Maria Elena Devaiah Shivakumar P. Chang Yeun-Kyung Flory Ashley Streatfield Stephen Ring Rebecca Phillips Cassie Hood Nathan C. Marbaniang Cyrus Dean Howard John A. Hood Elizabeth E. 《Transgenic research》2019,28(5-6):537-547
Transgenic Research - Expression of recombinant proteins in plants is a technology for producing vaccines, pharmaceuticals and industrial enzymes. For the past several years, we have produced... 相似文献
8.
Kumaran C Shivakumar K 《American journal of physiology. Heart and circulatory physiology》2002,282(5):H1855-H1862
Substance P is released from nerve endings in the heart under pathological conditions like ischemia, but its action on cardiac cells has not been investigated. This study tested the hypothesis that substance P is mitogenic to adult cardiac fibroblasts and delineated the underlying mechanism(s). Substance P, acting via neurokinin-1 (NK-1) receptors, stimulated cellular hyperplasia over a range of 1-10 micromol/l. It elicited no change in net collagen production, total protein synthesis, or cell protein content but increased (45)Ca uptake and superoxide generation. EGTA, N-acetyl-cysteine, and superoxide dismutase attenuated the hyperplastic response to substance P. A combination of substance P and EGTA enhanced superoxide generation without an increase in DNA synthesis, showing that an increase in superoxide production does not result in hyperplasia when extracellular Ca(2+) is chelated. Together, the data suggest that substance P may activate, via NK-1 receptors, a hyperplastic but not hypertrophic response in adult cardiac fibroblasts and that alterations in redox state and Ca(2+) homeostasis may act in concert to mediate its mitogenic action. 相似文献
9.
Cerium (Ce), a rare earth element, has been postulated to play a role in the pathogenesis of tropical endomyocardial fibrosis (EMF). Investigations carried out recently in pursuance of the postulation furnished histological evidence of EMF and increased cardiac collagen content in rats on prolonged administration of Ce. The present study was undertaken to understand the molecular basis of myocardial injury and fibrosis produced by the element. This article presents evidence of increased lipid peroxidation and elevated rates of fibroblast proliferation and collagen deposition in the heart in Ce-treated rats. It is suggested that the element may trigger a wound-healing response in the cardiac tissue leading to cardiac fibrosis. 相似文献
10.
Kumaravel Ilangovan Sharath Burugina Nagaraja Ramya Ananthakrishnan Anil G. Jacob Jaya Prasad Tripathy Deepak Tamang 《PloS one》2015,10(4)