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71.
G. R. Mason G. A. Beer M. S. Dixit S. K. Kim J. A. MacDonald A. Olin R. M. Pearce 《Nuclear Physics A》1980,340(2):240-248
Energies and lorentzian widths of pionic K X-ray transitions have been measured in liquid 3He with improved accuracy. The strong interaction on the π3He 1s level is found to be attractive and to produce an increase in the K transition energies of 34 ± 4 eV; the measured lorentzian width is 36 ±7 eV. Measured values are also presented for K X-ray energies in liquid π4He and μ4He, the lorentzian width of the 1s level in π4He, and relative intensities of K X-ray transitions in π3He, π4He and μ4He. The measurements are compared with those of others and with recent theoretical calculations. 相似文献
72.
D. P. Barber J. B. Dainton L. C. Y. Lee R. Marshall J. C. Thompson D. T. Williams T. J. Brodbeck G. Frost G. N. Patrick G. F. Pearce D. Newton T. Sloan G. R. Brookes W. J. Haynes P. B. Wilkes LAMP Group 《Zeitschrift fur Physik C Particles and Fields》1984,26(3):343-351
The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ+ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ+ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed. 相似文献
73.
74.
R.E. Ballard S.L. Barker J.J. Gunnell W.P. Hagan S.J. Pearce R.H. West A.R. Saunders 《Journal of Electron Spectroscopy and Related Phenomena》1978,14(5):331-339
Nine bands in the He(I) gas-phase photoelectron spectrum of 1,2-ethanediol are assigned by means of ab initio calculation and by comparison with the sp 相似文献
75.
The conversion of picrotoxinin () to picrotin (), which completes the total synthesis of the latter, is described. 相似文献
76.
M. S. Lin B. J. Bulkin E. M. Pearce 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2773-2797
Phenolphthalein polycarbonate underwent complicated thermal degradation which included random scission, rearrangement, hydrolysis, Friedel-Crafts acylation, and cross-linking. The carbonate group and lactone ring were both susceptible to thermal deterioration. Kinetic parameters were determined from the dynamic TGA thermograms. During early stages of degradation the measured reaction order was nearly 1, which suggested a random chain scission mechanism. The measured activation energy was 42.6 kcal/mol, compared with 41.2 kcal/mol calculated from isothermal aging. The Arrhenius preexponential constant was 3.09 × 1011 min?1. Below 80% weight residue the plot of fractional weight against 1/T revealed that complicated reactions with different activation energies occurred simultaneously and resulted in a final overlap of TGA curves for different heating rates indicative of cross-linking and a lower preexponential constant. The reaction order changed and kept increasing in the last stages of degradation. Pyrolysis of this polymer was performed at 350°C under vacuum, followed by GC-mass spectroscopic identification of products. The volatile products (17.5%) contained CO2, CO, O2, H2O, phenol, fluorenone, diphenyl carbonate, xanthone, anthraquinone, 2-hydroxylanthraquinone, 2-benzoxyanthraquinone, phenolphthalein, and trace amounts of benzoxyphenol and hydroquinone; the other 82.5% of products was insoluble gel. Functional group changes were examined by Fourier transform infrared spectroscopy (FT-IR). Lactone, carbonate, and aromatic absorptions decreased during degradation. Increasing absorptions at 1739, 1728, 1280–1200, and 1138–1075 cm?1 were believed to result from aromatic ester (1728 cm?1) and phenyl aromatic ester (1739 cm?1) cross-linkages ortho to the aromatic ether group (increases at 1155 cm?1 and 1280–1200 cm?1). Existence of 2-hydroxyanthraquinone and xanthone contained in the crosslinked polymer matrix were also detected. Mechanisms for random scission, rearrangement, Friedel-Crafts acylation, hydrolysis, and cross-linking were suggested. 相似文献
77.
Pearce BC Sofia MJ Good AC Drexler DM Stock DA 《Journal of chemical information and modeling》2006,46(3):1060-1068
A process for objective identification and filtering of undesirable compounds that contribute to high-throughput screening (HTS) deck promiscuity is described. Two methods of mapping hit promiscuity have been developed linking SMARTS-based structural queries with historical primary HTS data. The first compares an expected assay hit rate to actual hit rates. The second examines the propensity of an individual compound to hit multiple assays. Statistical evaluation of the data indicates a correlation between the resultant functional group filters and compound promiscuity. These data corroborate a number of commonly applied filters as well as producing some unexpected results. Application of these models to HTS collection triage reduced the number of in-house compounds considered for screening by 12%. The implications of these findings are further discussed in the context of the HTS screening set and combinatorial library design as well as compound acquisition. 相似文献
78.
Surasak Kuimalee Torranin Chairuangsri John T.H. Pearce David V. Edmonds Andrew P. Brown Rik M.D. Brydson 《Micron (Oxford, England : 1993)》2010,41(5):423-429
In this work, a method to determine the atomic ratio of Mo and C within complex metal carbides using EELS in the TEM has been developed. The method is based on the determination of k-factors for given experimental conditions from the EEL spectra of Mo2C and MoO3 standards, which had been independently checked by XRD and EPMA. Factors affecting the kMo/C value of the Mo2C standard were also investigated and the value was shown to be insensitive to background subtraction window width but sensitive to prolonged irradiation and specimen thicknesses above a critical value. The method and k-factor obtained from the Mo2C standard was applied to spectra from a complex metal carbide precipitate formed during furnace cooling of a cast duplex stainless steel. Using EELS and EDS in the TEM, the composition was estimated to be (Cr1.52Fe2.33Mo1.25Ni0.17Si0.46)C, which is close to M6C stoichiometry, and the structure was confirmed by electron diffraction. 相似文献
79.
José Rivera-Chávez Lindsay K. Caesar Juan J. Garcia-Salazar Huzefa A. Raja Nadja B. Cech Cedric J. Pearce Nicholas H. Oberlies 《Tetrahedron letters》2019,60(8):594-597
A new 8,8?-binaphthopyranone (mycopyranone, 1) was isolated from a solid fermentation of Phialemoniopsis sp. (fungal strain MSX61662), and the structure was elucidated via analysis of the NMR and HRESIMS data. The axial chirality of 1 was determined to be M by ECD. The central chirality at C-4/C-4? was assigned through a modified Mosher’s method, while the absolute configuration at C-3/C-3? was deduced based on analysis of the 3JH-3-H-4 values and NOESY correlations. Compound 1 was evaluated for its antimicrobial properties against Staphylococcus aureus SA1199 and a clinically relevant methicillin-resistant S. aureus strain (MRSA USA300 LAC strain AH1263). Compound 1 inhibited the growth of both strains in a concentration dependent manner with IC50 values in the low μM range. Molecular docking indicated that compound 1 binds to the FtsZ (tubulin-like) protein in the same pocket as viriditoxin (2), suggesting that 1 targets bacterial cell division. 相似文献
80.
Th. v. Fellenberg R. S. Alcock M. S. Lukjanowitsch N. P. Fedorow D. N. Bidenko E. Thomae J. Deshusses O. L. Evenson J. A. Kime S. S. Forrest Gesellschaft für Linde Eismaschinen A. S. Wetrow A. M. Kogan K. M. Nassyrowa J. P. Pusstylnikowa W. A. Gluchowzewa W. R. Tschertok Bláhá Láska E. Waser S. Janett B. Hazslinszky A. K. Fitger und CI. R. Dumble 《Fresenius' Journal of Analytical Chemistry》1938,113(5-6):226-235
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