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131.
Phase transitions of tetra(isopropylammonium)decachlorotricadmate(II) [(CH3)2CHNH3]4Cd3Cl10 crystal have been studied by infrared, far infrared and Raman measurements in wide temperature range, between 11 K and 388 K. The temperature changes of wavenumber, center of gravity, width and intensity of the bands were analyzed to clarify cationic and anionic contributions to the phase transitions mechanism. The results of investigation showed earlier by differential scanning calorimetry (DSC), thermal expansion and dielectric measurements clearly confirmed the sequence of phase transitions at T1=353 K, T2=294 K and T3=260 K. The current results derived from DSC and infrared measurements revealed additional phase transition at T4=120 K. 相似文献
132.
Enrique J. Baran 《光谱学快报》2013,46(2-3):151-155
Recently, Braunstein and Clark1 described the synthesis and vibrational spectra of complexes containing the AuCl2, AuBr2 and AuI2 ions. In order to obtain a deeper insight into the vibrational properties of these anions it seems interesting to calculate, using the available spectroscopic data, values for the mean amplitudes of vibration and some related quantities. 相似文献
133.
I. P. Vorona N. P. Baran S. S. Ishchenko V. V. Rudko L. S. Chumakova V. Yu. Povarchuk 《Physics of the Solid State》2008,50(10):1852-1856
Powders of the B-type synthetic apatite exposed to gamma or ultraviolet irradiation were investigated using EPR spectroscopy. It was shown that ultraviolet irradiation leads to the appearance of the EPR spectrum near g = 2, which is similar to the spectrum observed upon gamma irradiation. The decomposition of the EPR spectra into components and the simulation of the shape of the experimental EPR signals revealed that these signals are associated primarily with two types of CO 2 ? radicals, namely, the axial CO 2 ? radicals and the orthorhombic CO 2 ? radicals. The differences in the shapes of the EPR spectra of the samples exposed to gamma and ultraviolet irradiation were explained by different ratios between the axial and orthorhombic CO 2 ? radicals. It was established that thermal annealing results in an increase in the relative contribution to the total EPR spectrum. This increase was explained by the transformation of the orthorhombic radicals into the axial radicals. 相似文献
134.
Patricia A.M. Williams Evelina G. Ferrer María J. Correa Enrique J. Baran Eduardo E. Castellano Oscar E. Piro 《Journal of chemical crystallography》2004,34(4):285-290
The crystal structure of the complexes [Zn(sac)2(im)2] (1) and [Zn(sac)2(bzim)2]22Et-OHH2O (2) (sac = saccharinate anion; im = imidazole; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X-ray diffractometry. Complex 1 crystallizes in the monoclinic P2
1/n space group with a = 9.1585(5), b = 16.4409(6), c = 15.0249(5) Å, = 94.079(1)°, and Z = 4, whereas complex 2 belongs to the triclinic space group P1 with a = 10.8500(2), b = 12.4860(2), c = 13.5640(3) Å, = 115,696(1), = 100.086(1), = 102.169(1)°, and Z = 1. In both complexes, the Zn(II) cations are in a slightly distorted tetrahedral ZnN4 environment, coordinated to two saccharinate anions and to two imidazole (1) and to two benzimidazole (2) molecules. The complexes were also characterized by means of infrared spectroscopy and their thermal behavior investigated by means of thermogravimetric and differential thermal analytical techniques. 相似文献
135.
136.
Chatterjee PB Bhattacharya S Audhya A Choi KY Endo A Chaudhury M 《Inorganic chemistry》2008,47(11):4891-4902
A general protocol for the synthesis of micro-oxo divanadium(V) compounds [LOV(micro-O)VO(Salen)] (1-5) incorporating coordination asymmetry has been developed for the first time. One of the vanadium centers in these compounds has an octahedral environment, completed by tetradentate Salen ligand, while the remaining center has square pyramidal geometry, made up of tridentate biprotic Schiff-base ligands (L2-) with ONO (1-3) and ONS (4, 5) type donor combinations. Single crystal X-ray diffraction analysis, ESI-MS, and NMR (both 1H and 51V) spectroscopy have been used extensively to establish their identities. The V(1)-O(6)-V(2) bridge angle in these compounds, save 3, lie in a narrow range (166.20(9)-157.79(16) degrees) with the V2O3 core having a rare type of twist-angular structure, somewhat intermediate between the regular anti-linear and the syn-angular modes. For 3, however, the bridge angle is sufficiently smaller 117.92(8) degrees that it forces the V2O3 core to adopt an anti-angular geometry. The V(1)...V(2) separations in these molecules (3.7921(7)-3.3084(6) A) are by far the largest compared to their peers containing a V2O3 core. The molecules retain the binuclear structures also in solution as confirmed by NMR spectroscopy. Their redox behaviors appear quite interesting, each undergoing a one-electron reduction in the positive potential range (E1/2, 0.42-0.45 V vs Ag/AgCl) to generate a trapped-valence mixed-oxidation products [LVVO-(micro-O)-OVIV(salen)]1-, confirmed by combined coulometry-EPR experiments. The bent V-O-V bridge in these molecules probably prevents the symmetry-constrained vanadium d xy orbitals, containing the unpaired electron, to overlap effectively via the ppi orbitals of the bridging oxygen atom, thus accounting for the trapped-valence situation in this case. 相似文献
137.
138.
Philippe Teyssi Janusz Baran Philippe Dubois Robert Jr
me Jin-Shan Wang Jianming Yu Yisong Yu Thomas Zundel 《Macromolecular Symposia》1998,132(1):303-307
As an illustration of the frantic development of (meth)acrylic esters anionic polymerization during the last decade, three significant breakthroughs will be presented and analyzed:— extension of the LAP (ligated anionic polymerization) concept to the practical synthesis of both high iso- or syndio high MW PMMA; — the production of “perfect” hydrocarbon gels from tailored PMMA-polybutadiene-PMMA triblock copolymers; — the use of reactivity “boosters” allowing to climb back up the nucleophilic reactivity scale, i.e. initiating styrene, dienes and (meth)acrylates polymerization with alcoholates and silanolates. 相似文献
139.
O. V. Quinzani S. H. Tarulli S. Garcia‐Granda C. Marcos E. J. Baran 《Crystal Research and Technology》2002,37(12):1338-1343
The crystal structure of the title complex has been determined by single X‐ray diffraction methods and refined to an R‐value of 0.0543. It crystallizes in the monoclinic P21/a space group with a = 21.1231(9), b = 9.4523(4), c = 16.1874(7) Å, β = 107.3706(3)° and Z = 4. The compound represents only the second known example of a simple mononuclear metal complex containing simultaneously N‐ and O‐bonded saccharinato ligands. Its infrared spectrum and thermal behavior are also briefly discussed. 相似文献
140.