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排序方式: 共有2211条查询结果,搜索用时 0 毫秒
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S. Banerjee S. N. Ganguli A. Gurtu R. Raghavan A. Subramanian Y. Goldschmidt-Clermont R. T. Ross S. Squarcia K. Dziunikowska T. Haupt P. Girtler D. Kuhn K. W. J. Barnham J. Wells P. R. S. Wright J. Macnaughton F. Mandl F. Shabaan M. Bardadin-Otwinowska M. Szczekowski 《Zeitschrift fur Physik C Particles and Fields》1986,31(3):401-408
Results on inclusive ? production inK ? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ? state around 2.1 GeV/c2 as suggested byK + experiments, but there is some excess of events in the region 1.94?1.98 GeV/c2 consistent with theF-meson mass as observed ine + e ? experiments. 相似文献
15.
The apparent molar volumes, V,2, of glycine, L-alanine, DL--amino-n-butyric acid, L-valine, and L-leucine have been determined in aqueous 0.25, 0.75, 1.0, and 1.5 mol-dm–3 tetraethylammonium bromide (TEAB) solutions by density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volumes, V2,m, for the amino acids in aqueous tetraethylammonium bromide and the standard partial molar volumes of transfer (tr V2,m) of the amino acids from water to the aqueous salt solutions. The linear correlation of V2,m for a homologous series of amino acids has been utilized to calculate the contribution of the charged end groups (NH3+, COO–), CH2 group, and other alkyl chains of the amino acids to V2,m. The results of the standard partial molar volumes of transfer from water to aqueous tetraethylammonium bromide have been interpreted in terms of ion–ion, ion–polar, and hydrophobic–hydrophobic group interactions. The volume of transfer data suggest that ion–ion or ion–hydrophilic interactions are predominant in the case of glycine and alanine, and hydrophobic–hydrophobic group interactions are predominant in the case of DL--amino butyric acid, L-valine, and L-leucine. 相似文献
16.
Banerjee D Mitra S Mukherjee S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(6):1271-1278
Proton transfer processes of 4-hydroxy-3-formyl benzoic acid (HFBA) have been studied in a number of different protic solvents by means of absorption, emission and nanosecond transient spectroscopy at room temperature and 77K. Intermolecular interaction occurs in polar protic solvents only in presence of a base in the ground state whereas in the excited state, intermolecular complex formation and proton transfer occurs even in pure protic solvents. The dianion is detected in water, methanol, ethanol and TFE in presence of base. HFBA shows phosphorescence in pure ethanol at 77K. The occurrence of phosphorescence is due to rupture of the intramolecular bond and rotation of the formyl group. We have calculated quantum yields of fluorescence and also estimated decay rates from nanosecond measurements. The energetics of the ground and excited state proton transfer in HFBA have been investigated at the AM1 level of approximation. The ground singlet is predicted to have a large activation barrier on the proton transfer path, while the barrier height is much lower on the corresponding excited singlet surface. 相似文献
17.
Summary The kinetics of reduction of [MnIII(cydta)]– (where H4cydta=trans-cyclohexane-1,2-diamine-N N N' N'-tetraacetic acid) by some thiourea reductants have been studied in aqueous solution by stopped-flow techniques in the pH ranges 2.5–4.5 and 9.2–10.2. An initial increase in absorbance followed by a steady decrease indicated the formation of a precursor complex prior to the electron transfer step. The reactions are first order in both oxidant and reductant. The observed increase in rate in going from low to high pH is attributed to the difference in reactivities of the aqua and hydroxo species of the MnIII complex; the higher reactivity of the latter is consistent with the formation of a ligand-bridged activated species prior to electron transfer. The reactivity order for the thiourea derivatives follows the order of their reported substituent effects. 相似文献
18.
Mukul Biswas Madhusudan Banerjee Mrinal M. Maiti 《Journal of polymer science. Part A, Polymer chemistry》1984,22(9):1997-2004
Copper(II)-exchanged-13X molecular sieves, prepared from four copper(II) salts, namely, sulfate, nitrate, chloride, and acetate, and their activities in the polymerization of N-vinylcarbazole at a fixed copper ion exchange level were studied. From the kinetic characteristics of polymerization it was established that the variation in activities of the Cu-exchanged sieves is due primarily to the difference in the pH of the original salt solution, which is responsible for the varying degree of proton exchange with the zeolite during copper ion exchange. A first-order dependence of the rate of polymerization was observed with respect to H+ ion concentration of the original copper-salt solution. It was further established that the rate of polymerization of exchanged copper ion, at a hypothetical zero proton concentration, is low. A mechanism of polymerization of NVC on copper-exchanged-13X zeolite was suggested on the basis of the results obtained. 相似文献
19.
Arijit BanerjeeSamir Kumar Maji Michael G.B. DrewDebasish Haldar Arindam Banerjee 《Tetrahedron letters》2003,44(4):699-702
A single-crystal X-ray diffraction study of the terminally protected tetrapeptide Boc-β-Ala-Aib-Leu-Aib-OMe 1 (Aib: α-aminoisobutyric acid; β-Ala: β-Alanine) reveals that it adopts a new type of double turn structure which self-associates to form a unique supramolecular helix through intermolecular hydrogen bonds. Scanning electron microscopic studies show that peptide 1 exhibits amyloid-like fibrillar morphology in the solid state. 相似文献
20.
Rupendranath Banerjee 《Transition Metal Chemistry》1985,10(4):147-148
Summary In low acid (0.02 M HClO4) media, Pb2+ ion strongly catalyses the aquation of Cr(ox)
3
3–
to givecis-Cr(ox)2(OH2)
2
–
ion. The catalytic efficiency of Pb2+ as represented by the second order rate constant, kpb (3.76 × 10–4 M–1 s–1 at 25 °C; I, 1.0 M perchlorate), for the Pb2+ catalysed path is remarkably higher than might be expected on the basis of Kpb-ox, the first formation constant for the lead-oxalate complex. This catalytic superiority of Pb2+ has been found to result mainly from a comparatively much lower H (65.2 ±0.8 kJ mol–1) value which more than compensates for the relatively unfavourable S value (–93.2 ±2.4 JK–1mol–1) for this catalysed path. This low S value is, however, in line with the entropy of hydration of Pb2+ ion. These facts, together with the different LFER plots, have been utilised to propose a plausible mechanism for such catalysed reactions. 相似文献