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De Gregorio A Battistutta R Arena N Panzalorto M Francescato P Valentini G Bruno G Zanotti G 《Organic & biomolecular chemistry》2003,1(18):3178-3185
Ornithine transcarbamoylase from ovine liver has been purified to homogeneity. Like all anabolic OTCs, the ovine enzyme is a trimer, constituted by identical subunits of 34 kDa. Sequence analysis of the 54 N-terminal residues of ovine OTC shows a high degree of homology with the human enzyme. The optimum pH and the Michaelis constants for the catalytic reaction were determined. The ovine enzyme is the most thermostable one among mammals OTCs, its critical temperature being 6 degrees C higher than those measured for the other enzymes. The enzyme has been crystallised and the structure determined at 3.5 A resolution. Crystals belong to the cubic P4(3)32 space group, with a = b = c = 184.7 A and a solvent content of about 80%. There is no evidence of any ligand in the active site cavity, indicating that the crystals contain an unliganded or T state of the enzyme. The unliganded OTCase enzyme adopts a trimeric structure which, in the crystal, presents a three-fold axis coincident with the crystallographic one. The conformation of each monomer in the trimer is quite similar to that of the liganded human protein, with the exception of a few loops, directly interacting with the substrate(s), which are able to induce a rearrangement of the quaternary organisation of the trimer, that accounts for the cooperative behaviour of the enzyme following the binding of the substrates. 相似文献
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N.B. Sussman V.C. Arena S. Yu S. Mazumdar B.P. Thampatty 《SAR and QSAR in environmental research》2013,24(2):83-96
Humans are exposed to thousands of environmental chemicals for which no developmental toxicity information is available. Structure-activity relationships (SARs) are models that could be used to efficiently predict the biological activity of potential developmental toxicants. However, at this time, no adequate SAR models of developmental toxicity are available for risk assessment. In the present study, a new developmental database was compiled by combining toxicity information from the Teratogen Information System (TERIS) and the Food and Drug Administration (FDA) guidelines. We implemented a decision tree modeling procedure, using Classification and Regression Tree software and a model ensemble approach termed bagging. We then assessed the empirical distributions of the prediction accuracy measures of the single and ensemble-based models, achieved by repeating our modeling experiment many times by repeated random partitioning of the working database. The decision tree developmental SAR models exhibited modest prediction accuracy. Bagging tended to enhance the accuracy of prediction. Also, the model ensemble approach reduced the variability of prediction measures compared to the single model approach. Further research with data derived from animal species- and endpoint-specific components of an extended and refined FDA/TERIS database has the potential to derive SAR models that would be useful in the developmental risk assessment of the thousands of untested chemicals. 相似文献
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Ubiquitin Associates with the N‐Terminal Domain of Nerve Growth Factor: The Role of Copper(II) Ions
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Dr. Valeria Lanza Dr. Alessio Travaglia Dr. Gaetano Malgieri Prof. Roberto Fattorusso Dr. Giuseppe Grasso Dr. Giuseppe Di Natale Valeria Zito Prof. Giuseppe Arena Dr. Danilo Milardi Prof. Enrico Rizzarelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17767-17775
Many biochemical pathways involving nerve growth factor (NGF), a neurotrophin with copper(II) binding abilities, are regulated by the ubiquitin (Ub) proteasome system. However, whether NGF binds Ub and the role played by copper(II) ions in modulating their interactions have not yet been investigated. Herein NMR spectroscopy, circular dichroism, ESI‐MS, and titration calorimetry are employed to characterize the interactions of NGF with Ub. NGF1–14, which is a short model peptide encompassing the first 14 N‐terminal residues of NGF, binds the copper‐binding regions of Ub (KD=8.6 10?5 m ). Moreover, the peptide undergoes a random coil–polyproline type II helix structural conversion upon binding to Ub. Notably, copper(II) ions inhibit NGF1–14/Ub interactions. Further experiments performed with the full‐length NGF confirmed the existence of a copper(II)‐dependent association between Ub and NGF and indicated that the N‐terminal domain of NGF was a valuable paradigm that recapitulated many traits of the full‐length protein. 相似文献
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Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garbincius PH Garren L Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Torretta D Vittone M Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1994,72(7):961-964
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The thermodynamic parameters for the chelation of cupric ion with 2,2′-dipyridyl have been redetermined at 25°C and I=0.1 M. ΔG values were obtained by potentiometry with a selective ion electrode and ΔH values by direct calorimetry. Similar studies have been made on the relative hydroxocomplexes. The data obtained are compared with those in the literature and the chelate effect of the heterocyclic diimine is described. 相似文献