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51.
A. O. Bazarko C. G. Arroyo K. T. Bachmann T. Bolton C. Foudas B. J. King W. C. Lefmann W. C. Leung S. R. Mishra E. Oltman P. Z. Quintas S. A. Rabinowitz F. J. Sciulli W. G. Seligman M. H. Shaevitz F. S. Merritt M. J. Oreglia B. A. Schumm R. H. Bernstein F. Borcherding H. E. Fisk M. J. Lamm W. Marsh K. W. B. Merritt H. M. Schellman D. D. Yovanovitch A. Bodek H. S. Budd P. de Barbaro W. K. Sakumoto T. Kinnel P. H. Sandler W. H. Smith 《Zeitschrift fur Physik C Particles and Fields》1995,65(2):189-198
We present the first next-to-leading-order QCD analysis of neutrino charm production, using a sample of 6090
– and
-induced opposite-sign dimuon events observed in the CCFR detector at the Fermilab Tevatron. We find that the nucleon strange quark content is suppressed with respect to the non-strange sea quarks by a factor =0.477
–0.053
+0.063
, where the error includes statistical, systematic and QCD scale uncertainties. In contrast to previous leading order analyses, we find that the strange seax-dependence is similar to that of the non-strange sea, and that the measured charm quark mass,m
c
=1.70±0.19 GeV/c2, is larger and consistent with that determined in other processes. Further analysis finds that the difference inx-distributions betweenxs(x) and
is small. A measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V
cd
|=0.232
–0.020
+0.018
is also presented. 相似文献
52.
Abe K Abt I Ahn CJ Akagi T Ash WW Aston D Bacchetta N Baird KG Baltay C Band HR Barakat MB Baranko G Bardon O Barklow T Bazarko AO Ben-David R Benvenuti AC Bienz T Bilei GM Bisello D Blaylock G Bogart JR Bolton T Bower GR Brau JE Breidenbach M Bugg WM Burke D Burnett TH Burrows PN Busza W Calcaterra A Caldwell DO Calloway D Camanzi B Carpinelli M Cassell R Castaldi R Castro A Cavalli-Sforza M Church E Cohn HO Coller JA Cook V Cotton R Cowan RF Coyne DG D'Oliveira A Damerell CJ Dasu S 《Physical review letters》1995,74(15):2895-2899
53.
Bai Z Blaylock GT Bolton T Brient J Browder T Brown JS Bunnell KO Burchell M Burnett TH Cassell RE Coffman D Cook V Coward DH DeJongh F Dorfan DE Drinkard J Dubois GP Eigen G Einsweiler KF Eisenstein BI Freese T Gatto C Gladding G Grab C 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 《Physical review letters》1990,65(6):686-689
54.
55.
Bai Z Blaylock GT Bolton T Brient JC Browder T Brown JS Bunnell KO Burchell M Burnett TH Cassell RE Coffman D Cook V Coward DH DeJongh F Dorfan DE Drinkard J Dubois GP Eigen G Einsweiler KF Eisenstein BI Freese T Gatto C Gladding G Grab C 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 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 《Physical review letters》1990,65(20):2507-2510
56.
Abstract— Using the technique of flash photolysis-electron spin resonance, we have shown, by means of a kinetic analysis, that phenazine methosulfate (PMS) interacts with reaction-center preparations from the blue-green mutant R26 of Rhodopseudomonas spheroides. At intermediate concentrations of PMS, biphasic decay kinetics of the P870+ ESR signal are observed demonstrating that the PMS radical interacts with reaction centers by a specific binding mechanism. With PMS bound to reaction centers, the P870+ ESR signal decays in ˜ 1 ms; whereas, in unbound reaction centers the decay is ˜ 120 ms. A model is proposed involving the interaction of PMS on the donor side of P870. 相似文献
57.
The growth of single wall carbon nanotubes (SWNTs) mediated by metal nanoparticles is considered within (i) the surface diffusion growth kinetics model coupled with (ii) a thermal model taking into account heat release of carbon adsorption-desorption on nanotube surface and carbon incorporation into the nanotube wall and (iii) carbon nanotube-inert gas collisional heat exchange. Numerical simulations performed together with analytical estimates reveal various temperature regimes occurring during SWNT growth. During the initial stage, which is characterized by SWNT lengths that are shorter than the surface diffusion length of carbon atoms adsorbed on the SWNT wall, the SWNT temperature remains constant and is significantly higher than that of the ambient gas. After this stage the SWNT temperature decreases towards that of gas and becomes nonuniformly distributed over the length of the SWNT. The rate of SWNT cooling depends on the SWNT-gas collisional energy transfer that, from molecular dynamics simulations, is seen to be efficient only in the SWNT radial direction. The decreasing SWNT temperature may lead to solidification of the catalytic metal nanoparticle terminating SWNT growth or triggering nucleation of a new carbon layer and growth of multiwall carbon nanotubes. 相似文献
58.
-We have carried out a very detailed study, using fluorescence and optical flash photolysis techniques, of the photoreduction of methyl viologen (MV2+) by the electron donor ethylene diamine tetraacetic acid (EDTA) in aqueous solution sensitized by the dye acridine orange (AOH+). A complete mechanism has been proposed which accounts for virtually all of the known observations on this reaction. This reaction is novel in that both the triplet and the singlet state of AOH+ appear to be active photochemically. We have shown that mechanisms previously proposed for this reaction are probably incorrect due to an artifact. At pH 7 the fluorescence quantum yield φs of AOH+ is 0.26 ± 0.02 and the fluorescence lifetime is 1.8 ± 0.2 ns. φs is pH dependent and reaches a maximum of 0.56 at pH 4. The fluorescence of AOH+ is quenched by MV2+ at concentrations above 1 mM and the quenching obeys Stern-Volmer kinetics with a quenching rate constant of (1.0 ± 0.1) × 1010M?1 s?1. The quenching of the AOH+ excited singlet state by MV2+ almost certainly returns the AOH+ to its ground state with no photochemistry occurring. EDTA also quenches the fluorescence of AOH· with Stern-Volmer kinetics but with a smaller rate constant (6.4 ± 0.5) × 108M?1s?1 at pH 7. In this case the quenching is reactive resulting in the formation of semireduced AOH. In the presence of MV2+, flash irradiation of AOH+ does result in the reversible formation of the semireduced MV? which absorbs at 603 nm. We attribute this to a photochemical reaction of the triplet state of AOH+ with MV2+. The initial quantum yield for formation of MV? (φMV:)0 was found to be constant at 0.10 ± 0.05 for [MV2+] from 5 × 10?5 to 1.0 × 10?3 with [AOH+] = 8 × 10?6M. Previous workers had found that (φMV:)0 appears to decrease with decreasing [AOH+]; however, on careful investigation, we found this was most probably due to quenching of the triplet state of AOH+ by trace amounts of oxygen. When EDTA is added to a mixture of AOH + and MV2+ at pH 7, the photochemical formation of MV? becomes irreversible as the [EDTA] is increased. The quantum yield for the irreversible formation of MV? exceeds 0.10 becoming as large as 0.16 for [EDTA] = 0.014M. This fact requires that an alternative photochemical process must be operative and we present evidence that this is a reaction of EDTA with the excited singlet state of AOH+ to produce the semi-reduced AOH- which then reacts with MV2+ to produce MV?. The full kinetic scheme was tested by computer simulation and found to be totally consistent. This also enabled the processing of a full set of rate constants. When colloidal PtO2 was added to the optimal mixture [EDTA] = 3.4 × 10?2M; [MV2+] = 5 × 10?4M; [AOH+] = 4 × 10?5M; pH6 H2 gas was produced at a rate of 0.2μmol H2h?1. Thus, acridine orange should serve as an effective sensitizer in reactions designed to use solar energy to photolyze water. 相似文献
59.
Adler J Bai Z Becker JJ Blaylock GT Bolton T Brient J Brown JS Bunnell KO Burchell M Burnett TH Cassell RE Coffman D Cook V Coward DH DeJongh F Dorfan DE Drinkard J Dubois GP Eigen G Einsweiler KF Eisenstein BI Freese T Gatto C Gladding G Grab C Hamilton RP Hauser J Heusch CA Hitlin DG Izen JM Kim PC Köpke L Labs J Li A Lockman WS Mallik U Matthews CG Mincer AI Mir R Mockett PM Nemati B Odian A Parrish L Partridge R Pitman D Plaetzer SA Richman JD Roco M Sadrozinski HF Scarlatella M Schalk TL 《Physical review letters》1989,63(12):1211-1214
60.
Coffman D Dubois GP 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 Perrier J Sadrozinski HF Scarlatella M Schalk TL Seiden A Weinstein AJ Xu R Becker JJ Blaylock GT Eisenstein BI Freese T Gladding G Izen JM Plaetzer SA Simopoulos C Spadafora AL Stockdale IE Thaler JJ Tripsas B Mallik U Adler J Bolton T Brient JC Bunnell KO Cassell RE Coward DH Einsweiler KF Grab C 《Physical review D: Particles and fields》1989,40(11):3788