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91.
Regioselective Dichlorination of a Non‐Activated Aliphatic Carbon Atom and Phenolic Bismethylation by a Multifunctional Fungal Flavoenzyme
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Pranatchareeya Chankhamjon Dr. Yuta Tsunematsu Dr. Mie Ishida‐Ito Yuzuka Sasa Florian Meyer Dr. Daniela Boettger‐Schmidt Barbara Urbansky Klaus‐Dieter Menzel Dr. Kirstin Scherlach Prof. Dr. Kenji Watanabe Prof. Dr. Christian Hertweck 《Angewandte Chemie (International ed. in English)》2016,55(39):11955-11959
The regioselective functionalization of non‐activated carbon atoms such as aliphatic halogenation is a major synthetic challenge. A novel multifunctional enzyme catalyzing the geminal dichlorination of a methyl group was discovered in Aspergillus oryzae (Koji mold), an important fungus that is widely used for Asian food fermentation. A biosynthetic pathway encoded on two different chromosomes yields mono‐ and dichlorinated polyketides (diaporthin derivatives), including the cytotoxic dichlorodiaporthin as the main product. Bioinformatic analyses and functional genetics revealed an unprecedented hybrid enzyme (AoiQ) with two functional domains, one for halogenation and one for O‐methylation. AoiQ was successfully reconstituted in vivo and in vitro, unequivocally showing that this FADH2‐dependent enzyme is uniquely capable of the stepwise gem‐dichlorination of a non‐activated carbon atom on a freestanding substrate. Genome mining indicated that related hybrid enzymes are encoded in cryptic gene clusters in numerous ecologically relevant fungi. 相似文献
92.
Diego A. Sampietro Emilio F. Lizarraga Zharkyn A. Ibatayev Akerke B. Omarova Yerlan M. Suleimen Cesar A. N. Catalán 《Natural product research》2016,30(17):1950-1955
Essential oils from aerial parts of Acantholippia deserticola, Artemisia proceriformis, Achillea micrantha and Libanotis buchtormensis were analysed by GC–MS. The major compounds identified were β-thujone (66.5 ± 0.2%), and trans-sabinyl acetate (12.1 ± 0.2%) in A. deserticola; α-thujone (66.9 ± 0.4%) in A. proceriformis; 1,8-cineole (26.9 ± 0.5%), and camphor (17.7 ± 0.3%) in A. micrantha and cis-β-ocimene (23.3 ± 0.3%), and trans-β-ocimene (18.4 ± 0.2%) in L. buchtormensis. The oils showed a weak antimicrobial effect (MIC100 > 1.5 mg/ml) on most phytopathogens tested. A moderate antimicrobial activity (MIC100 between 0.5 and 1.5 mg/ml) was displayed by the oils of A. deserticola, A. micrantha and L. buchtormensis on Septoria tritici and by the oil of A. deserticola on Septoria glycine. The antimicrobial activity was associated to the contents of β-thujone, trans-sabinyl acetate and trans-sabinol. Our results indicate that the tested essential oils have little inhibitory potency not suitable for use as plant protection products against the phytopathogens assayed. 相似文献
93.
Seven new prenylated indole diketopiperazine alkaloids, including compound 1, 3 spirotryprostatins C-E (2-4), 2 derivatives of fumitremorgin B (5 and 6), and 13-oxoverruculogen (7), have been isolated from the holothurian-derived fungus Aspergillus fumigatus, along with 12 known ones (8-19). The structures of the new compounds were determined on the basis of extensive spectroscopic data and amino acid analysis. All new compounds were evaluated for their cytotoxic activities on MOLT-4, A549, HL-60, and BEL-7420 cell lines by the MTT and SRB methods. 相似文献
94.
Wild type (WT) DNA sequence, which encoded a mature β-mannanase of Aspergillus sulphureus, composed of 1,152 nucleotides (nt), was amplified from pUCm-T-mann by polymerase chain reaction (PCR). Based on this DNA
fragment, mutants designated as E206G and E314G were constructed by overextension PCR (OE-PCR). Glutamic acids of the 206th and 314th sites in the amino acid sequence of
β-mannanase were separately replaced by glycine in these two mutants. The WT and mutant genes were ligated into prokaryotic
vector pET-28a (+) and transformed into the Escherichia coli BL21 strain, respectively. The recombinant enzyme proteins were expressed by IPTG induction and detected by Western blot.
The recombinant proteins purified with Ni-NTA column were dialyzed to correctly refold. The WT recombinant β-mannanase showed
optimal activity at 50 °C and pH 2.4. The kinetic parameters of K
m and V
max for purified β-mannanase were 1.38 mg/ml and 72.99 U/mg, respectively. However, the mutant proteins did not show any activity.
It was demonstrated that E206 and E314 were the catalytic residues of β-mannanase. 相似文献
95.
Dutra JC da C Terzi S Bevilaqua JV Damaso MC Couri S Langone MA Senna LF 《Applied biochemistry and biotechnology》2008,147(1-3):63-75
The aim of this study was to monitor the biomass growth of Aspergillus niger in solid-state fermentation (SSF) for lipase production using digital image processing technique. The strain A. niger 11T53A14 was cultivated in SSF using wheat bran as support, which was enriched with 0.91% (m/v) of ammonium sulfate. The addition of several vegetable oils (castor, soybean, olive, corn, and palm oils) was investigated
to enhance lipase production. The maximum lipase activity was obtained using 2% (m/m) castor oil. In these conditions, the growth was evaluated each 24 h for 5 days by the glycosamine content analysis and digital
image processing. Lipase activity was also determined. The results indicated that the digital image process technique can
be used to monitor biomass growth in a SSF process and to correlate biomass growth and enzyme activity. In addition, the immobilized
esterification lipase activity was determined for the butyl oleate synthesis, with and without 50% v/v hexane, resulting in 650 and 120 U/g, respectively. The enzyme was also used for transesterification of soybean oil and ethanol
with maximum yield of 2.4%, after 30 min of reaction. 相似文献
96.
Fahmy AS El-Beih FM Mohamed SA Abdel-Gany SS Abd-Elbaky EA 《Applied biochemistry and biotechnology》2008,149(3):205-217
Polygalacturonase (PGI) from Aspergillus niger NRRL3 was purified about 12.0-fold from the cell-free broth using diethylaminoethyl-Sepharose and Sephacryl S-200 columns. The molecular weight of the PGI was 32,000 Da as estimated by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PGI had an isoelectric point of 7.6 and an optimum pH of 5.0. PGI was active on polygalacturonic acid and esterified pectins, but the activity on pectin decreased with an increase in degree of esterification. PGI had higher affinity (low Km) and turnover number (Vmax/Km and Kcat/Km) toward polygalacturonic acid. PGI was found to have a temperature optimum at 40 degrees C and was approximately stable up to 30 degrees C. All the examined metal cations had partial inhibitory effects on PGI, while Mn+2 at 5 mM caused a complete inhibition for the enzyme. Comparison of viscosity reduction rates with release of reducing sugars indicated that the enzyme from A. niger is exoacting. The storage stability study of PGI showed that the enzyme in powder form retained 56% of its activity after 9 months of storage at 4 degrees C. The above properties of PGI may be suitable for food processing. 相似文献
97.
Evaluation of the Oxo‐bridged Dinuclear Ruthenium Ammine Complex as Redox Mediator in an Electrochemical Biosensor
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Paulo A. Raymundo‐Pereira Ana C. V. Mascarenhas Marcos F. S. Teixeira 《Electroanalysis》2016,28(3):562-569
The mediation of electron‐transfer by oxo‐bridged dinuclear ruthenium ammine [(bpy)2(NH3)RuIII(µ‐O)RuIII(NH3)(bpy)2]4+ for the oxidation of glucose was investigated by cyclic voltammetry. These ruthenium (III) complexes exhibit appropriate redox potentials of 0.131–0.09 V vs. SCE to act as electron‐transfer mediators. The plot of anodic current vs. the glucose concentration was linear in the concentration range between 2.52×10?5 and 1.00×10?4 mol L?1. Moreover, the apparent Michaelis‐Menten kinetic (KMapp) and the catalytic (Kcat) constants were 8.757×10?6 mol L?1 and 1,956 s?1, respectively, demonstrating the efficiency of the ruthenium dinuclear oxo‐complex [(bpy)2(NH3)RuIII(µ‐O)RuIII(NH3)(bpy)2]4+ as mediator of redox electron‐transfer. 相似文献
98.
The effects of triphenyl tetrazolium chloride (TTC) concentration, cell age, and presence of O2 on the dehydrogenase activity of Aspergillus niger as measured by triphenyl formazan (TF) yield were investigated. The results indicated that increasing TTC concentration initially
increased the TF yield and then decreased it. The maximum TF yield was observed at a TTC concentration of 30 g/L for young
cells (4 d old) and 20 g/L for old cells (12 d old). Conducting the test under anaerobic conditions increased the TF yield.
About 18% of the TF produced was converted back into TTC in the presence of oxygen. The relationship between dehydrogenase
activity of A. niger (as measured by TF yield) and cell mass was found to be linear. A kinetic model describing the relationship between reaction
rate (micromoles of TF formed per hour) and TTC concentration while accounting for substrate inhibition was developed, and
the model constants were calculated. The optimum TTC-test conditions for dehydrogenase activity measurement of A. niger were
a TTC concentration of 20 g/L, a pH of 9.0, a temperature of 55°C, an incubation time of 3 h, and anaerobic conditions. 相似文献
99.
Hatzinikolaou DG Mamma D Christakopoulos P Kekos D 《Applied biochemistry and biotechnology》2007,142(1):29-43
Two glucose oxidase (GOX) isoforms where purified to electrophoretic homogeneity from the mycelium extract (GOXI) and the extracellular medium (GOXII) of Aspergillus niger BTL cultures. Both enzymes were found to be homodimers with nonreduced molecular masses of 148 and 159 kDa and pI values
of 3.7 and 3.6 for GOXI and GOXII, respectively. The substrate specificity and the kinetic characteristics of the two GOX forms, as expressed through their
apparent K
m values on glucose, as well as pH and T activity optima, were almost identical. The only structural difference between the
two enzymes was in their degrees of glycosylation, which were determined equal to 14.1 and 20.8% (w/w) of their molecular
masses for GOXI and GOXII, respectively. The above difference in the carbohydrate content between the two enzymes seems to influence their pH and thermal
stabilities. GOXII proved to be more stable than GOXI at pH values 2.5, 3.0, 8.0, and 9.0. Half-lives of GOXI at pH 3.0 and 8.0 were 8.9 and 17.5 h, respectively, whereas the corresponding values for GOXII were 13.5 and 28.1 h. As far as the thermal stability is concerned, GOXII was also more thermostable than GOXI as judged by the deactivation constants determined at various temperatures. More specifically, the half-lives of GOXI and GOXII, at 45°C, were 12 and 49 h, respectively. These results suggest A. niger BTL probably possesses a secondary glycosylation mechanism that increases the stability of the excreted GOX. 相似文献
100.
The lead (II) biosorption potential of Aspergillus parasiticus fungal biomass has been investigated in a batch system. The initial pH, biosorbent dosage, contact time, initial metal ion
concentrations and temperature were studied to optimize the biosorption conditions. The maximum lead (II) biosorption capacity
of the fungal biosorbent was found as 4.02 × 10−4 mol g−1 at pH 5.0 and 20°C. The biosorption equilibrium was reached in 70 min. Equilibrium biosorption data were followed by the
Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. In regeneration experiments, no significant loss of sorption
performance was observed during four biosorption-desorption cycles. The interactions between lead (II) ions and biosorbent
were also examined by FTIR and EDAX analysis. The results revealed that biosorption process could be described by ion exchange
as dominant mechanism as well as complexation for this biosorbent. The ion exchange mechanism was confirmed by E value obtained from D-R isotherm model as well. 相似文献