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211.
Oksana M Subach Anton V Khoroshaev Dmitrii N Gerasimov Vladimir B Baskunov Anna K Shchyolkina Elizaveta S Gromova 《European journal of biochemistry》2004,271(12):2391-2399
EcoRII DNA methyltransferase (M.EcoRII) recognizes the 5' em leader CC*T/AGG em leader 3' DNA sequence and catalyzes the transfer of the methyl group from S-adenosyl-l-methionine to the C5 position of the inner cytosine residue (C*). Here, we study the mechanism of inhibition of M.EcoRII by DNA containing 2-pyrimidinone, a cytosine analogue lacking an NH(2) group at the C4 position of the pyrimidine ring. Also, DNA containing 2-pyrimidinone was used for probing contacts of M.EcoRII with functional groups of pyrimidine bases of the recognition sequence. 2-Pyrimidinone was incorporated into the 5' em leader CCT/AGG em leader 3' sequence replacing the target and nontarget cytosine and central thymine residues. Study of the DNA stability using thermal denaturation of 2-pyrimidinone containing duplexes pointed to the influence of the bases adjacent to 2-pyrimidinone and to a greater destabilizing influence of 2-pyrimidinone substitution for thymine than that for cytosine. Binding of M.EcoRII to 2-pyrimidinone containing DNA and methylation of these DNA demonstrate that the amino group of the outer cytosine in the EcoRII recognition sequence is not involved in the DNA-M.EcoRII interaction. It is probable that there are contacts between the functional groups of the central thymine exposed in the major groove and M.EcoRII. 2-Pyrimidinone replacing the target cytosine in the EcoRII recognition sequence forms covalent adducts with M.EcoRII. In the absence of the cofactor S-adenosyl-l-methionine, proton transfer to the C5 position of 2-pyrimidinone occurs and in the presence of S-adenosyl-l-methionine, methyl transfer to the C5 position of 2-pyrimidinone occurs. 相似文献
212.
Dissimilatory Reduction of Fe(III) by Thermophilic Bacteria and Archaea in Deep Subsurface Petroleum Reservoirs of Western Siberia 总被引:3,自引:0,他引:3
Alexander I. Slobodkin Christian Jeanthon Stéphane L'Haridon Tamara Nazina Margarita Miroshnichenko Elizaveta Bonch-Osmolovskaya 《Current microbiology》1999,39(2):99-102
Twenty-five samples of stratal fluids obtained from a high-temperature (60–84°C) deep subsurface (1700–2500 m) petroleum
reservoir of Western Siberia were investigated for the presence of dissimilatory Fe(III)-reducing microorganisms. Of the samples,
44% and 76% were positive for Fe(III) reduction with peptone and H2 respectively as electron donors. In most of these samples, the numbers of culturable thermophilic H2-utilizing iron reducers were in the order of 10–100 cells/ml. Nine strains of thermophilic anaerobic bacteria and archaea
isolated from petroleum reservoirs were tested for their ability to reduce Fe(III). Eight strains belonging to the genera
Thermoanaerobacter, Thermotoga, and Thermococcus were found capable of dissimilatory Fe(III) reduction, with peptone or H2 as electron donor and amorphous Fe(III) oxide as electron acceptor. These results demonstrated that Fe(III) reduction may
be a common feature shared by a wide range of anaerobic thermophiles and hyperthermophiles in deep subsurface petroleum reservoirs.
Received: 1 March 1999 / Accepted: 5 April 1999 相似文献
213.
214.
Tamara M. Polyanskaya Elizaveta P. Simonenko Nikolay T. Kuznetsov 《Inorganica chimica acta》2009,362(15):5133-5138
The trans-[M(18-crown-6)(C5HO2F6)2] (M = Ca, Sr, Ba, Pb) complexes have been synthesized and identified. The crystal structure of the Sr complex has been determined by X-ray diffraction. The basic structural unit is the mononuclear complex trans-[Sr(18-crown-6)(C5HO2F6)2]. The thermal properties of the complexes have been correlated to their structure. The melting and decomposition ranges of the Ca, Sr and Ba complexes and their sublimation temperatures at ∼10−2 mm Hg have been determined. Experimental evidence is presented that the complexes are similar in volatility. 相似文献
215.