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121.
In the framework of the formalism of Cornwall et al. for composite operators, we develop a new method for the calculation of the effective potential. We apply the method to the study of chiral symmetry breaking in an SU(N) color gauge theory with n massless flavors and derive analytically the complete effective potential at two fermion loops. We find that in this approximation the theory has two phases: the symmetric phase and the broken phase into the diagonal flavor sub-group. 相似文献
122.
We propose a geometrical formulation of complementarity between the Higgs phase and the confining phase of a non-abelian gauge theory, introducing local “vierbein” fields to provide for a one-to-one mapping between the states of the two phases. We investigate the gauge structure when a subgroup of the global symmetry is also gauged. The formalism is used to build up a composite model based on a SU(4) of subcolor complementary to a Pati-Salam SU(4), and allowing for dynamical symmetry breaking of SU(2)L ? U(1). 相似文献
123.
An algorithm for the real time forecast of the outflow from a lake is described. It is assumed that the influent flows of the tributaries, the effluent flow and the lake level are measured hour by hour and used for the outflow prediction in future hours. The proposed method is tested in a real case, the 1957 spring flood of Lake Maggiore. 相似文献
124.
AknT is an activating protein for the glycosyltransferase AknS in L-aminodeoxysugar transfer to the aglycone of aclacinomycin A 总被引:2,自引:0,他引:2
Lu W Leimkuhler C Gatto GJ Kruger RG Oberthür M Kahne D Walsh CT 《Chemistry & biology》2005,12(5):527-534
During biosynthesis of the anthracycline antitumor agents daunomycin, adriamycin, and aclacinomycin, the polyketide-derived tetracyclic aglycone is enzymatically glycosylated at the C7-OH by dedicated glycosyltransferases (Gtfs) that transfer L-2,3,6-trideoxy-3-aminohexoses. In aclacinomycins, the first deoxyhexose is predicted to be transferred via AknS action, then subjected to further elongation to a trisaccharide by the subsequent Gtf, AknK. We report here that purified AknS has very low activity in the absence of the adjacently encoded AknT; however, at a 3:1 ratio, AknT stimulates AknS k(cat) by 40-fold up to 0.22 min(-1) for transfer of L-2-deoxyfucose (2-dF) to the aglycone aklavinone. It is likely that several other Gtfs that glycosylate polyketide aglycones also act as two-component catalytic systems. Incubations of purified AknS/AknT/AknK with two aglycones and two dTDP-2-deoxyhexoses produced previously uncharacterized anthracycline disaccharides. 相似文献
125.
Bai Z Blaylock GT Bolton T Browder TE Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V DeJongh F Dorfan DE Drinkard J Dubois GP Eigen G Einsweiler KF Eisenstein BI Freese T Gatto C Gladding G Hauser J Heusch CA Hitlin DG Izen JM Kim PC Labs J Li A Lockman WS Mallik U Matthews CG Mincer AI Mir R Mockett PM Mozley RF Nemati B Odian A Parrish L Partridge R Pitman D Plaetzer SA Richman JD Sadrozinski HF Scarlatella M Schalk TL Schindler RH Seiden A Simopoulos C Stockdale IE Toki W 《Physical review letters》1990,65(11):1309-1312
126.
Coffman D DeJongh F Dubois G Eigen G Hauser J Hitlin DG Matthews CG Mincer A Richman JD Wisniewski WJ Zhu Y Burchell M Dorfan DE Drinkard J Gatto C Hamilton RP Heusch CA Köpke L Lockman WS Partridge R Sadrozinski HF Scarlatella M Schalk TL Seiden A Weinstein AJ Weseler S Xu R Becker JJ Blaylock GT Eisenstein BI Freese T Gladding G Izen JM Plaetzer SA Simopoulos C Spadafora AL Stockdale IE Tripsas B Mallik U Roco M Wang MZ Adler J Bolton T Brient JC Bunnell KO Cassell RE Coward DH Einsweiler KF 《Physical review D: Particles and fields》1990,41(5):1410-1413
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Roberto Sole Vanessa Gatto Silvia Conca Noemi Bardella Andrea Morandini Valentina Beghetto 《Molecules (Basel, Switzerland)》2021,26(1)
Conventional methods employed today for the synthesis of amides often lack of economic and environmental sustainability. Triazine-derived quaternary ammonium salts, e.g., 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM(Cl)), emerged as promising dehydro-condensation agents for amide synthesis, although suffering of limited stability and high costs. In the present work, a simple protocol for the synthesis of amides mediated by 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) and a tert-amine has been described and data are compared to DMTMM(Cl) and other CDMT-derived quaternary ammonium salts (DMT-Ams(X), X: Cl− or ClO4−). Different tert-amines (Ams) were tested for the synthesis of various DMT-Ams(Cl), but only DMTMM(Cl) could be isolated and employed for dehydro-condensation reactions, while all CDMT/tert-amine systems tested were efficient as dehydro-condensation agents. Interestingly, in best reaction conditions, CDMT and 1,4-dimethylpiperazine gave N-phenethyl benzamide in 93% yield in 15 min, with up to half the amount of tert-amine consumption. The efficiency of CDMT/tert-amine was further compared to more stable triazine quaternary ammonium salts having a perchlorate counter anion (DMT-Ams(ClO4)). Overall CDMT/tert-amine systems appear to be a viable and more economical alternative to most dehydro-condensation agents employed today. 相似文献