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101.
Relative stabilities (ΔGc) of ammonium-bound monomers and dimers of anomeric β-
-pentofuranosyl 1α- and 1β-azide derivates are determinate using the kinetic method by measuring relative rates of competitive collision-induced dissociations of dimeric [ANH4B]+ and trimeric [A2NH4B]+ or [ANH4B2]+ cluster ions. Comparison between calculated ammonium affinities (AAs) and relative stabilities (ΔGc) of ammonium-bound monomers shows qualitative correlations between both thermochemical quantities, but in two examples the activation barrier differences of competitive fragmentation channels cause a large disparity between both thermochemical data. Therefore, the most stable ammonium-bound monomers of the anomeric lα- and lβ-2,3,5-tri-O-benzyl-β-
-arabino-pento-furanosyl azides possess the lowest ammonium affinities and the highest relative stabilities. Two different relative stabilities measured for the same ammonium-bound homo- or hetero-dimers indicate dissimilar activated barriers of trimers transition states for dimer formations. The activated barriers of trimers depend on the relative stabilities of ammonium-bound monomer within the trimeric cluster ions. 相似文献
102.
103.
A method based on ion chromatography (IC) and inductively coupled plasma MS (ICP-MS) was developed for the speciation of arsenic in water and soil extracts. An anion-exchange column (G3154A/101) was used to separate As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) with excellent resolution. Various ammonium salts, including NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4HCO3, were examined as eluents to reduce matrix interference from chloride and to solve clogging problems. The best arsenic speciation was obtained within 9 min with excellent resolution and without interference from high chloride concentrations using an eluent containing 7.5 mM (NH4)2HPO4 at pH 7.9. The detection limits for the target arsenic species ranged from 0.1 to 0.4 microg/L with direct injection of sample without matrix elimination. The proposed method was effectively demonstrated by determining arsenic species in contaminated waters and soils of Bangladesh. 相似文献
104.
Three-dimensional (3D) architecture of TiO2 hollow sphere has many excellent and interesting performances that attract significant attention nowadays. In this paper, a simple surface erosion approach to the fabrication of TiO2 hollow spheres via the hydrothermal process has been developed. The morphologies and the phase were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The results indicate that the anatase-type TiO2 hollow spheres with a diameter of ∼1 μm are successfully synthesized. The shell thickness of TiO2 hollow spheres is ∼150 nm and the size of hollow cavity is ∼600 nm. By the control experiments, the influence of ammonium fluoride and hydrogen peroxide on the hollow spherical structures was studied. Hydrogen peroxide acts as both the oxidant and the bubble generator, ammonium fluoride is crucial for the erosion and dissolution of titanium, the detailed dissolution-crystallization mechanism for the formation of TiO2 hollow spheres was also proposed. 相似文献
105.
Masaki Matsui Yuya Tsuzuki Yasuhiro Kubota Kazumasa Funabiki Toshiyasu Inuzuka Kazuhiro Manseki Shinji Higashijima Hidetoshi Miura Hiroyasu Sato Tsukasa Yoshida 《Tetrahedron》2018,74(40):5867-5878
(2R,3aR,8bR)- and (2S,3aS,8bS)-2-Methyl indoline dye tetrabutylammonium carboxylates exhibited the highest conversion efficiency among four regio and stereo isomers. These indoline dyes also showed higher conversion efficiency than DN350. 相似文献
106.
Rasim Tanbug Kristin Kirschbaum A. Alan Pinkerton 《Journal of chemical crystallography》1999,29(1):45-55
Two energetic salts of the melaminium cation have been prepared and structurally characterized from room temperature X-ray single crystal diffraction data. Melaminium dinitramide (I), triclinic, P1¯, a = 6.6861(11), b = 6.9638(16), c = 10.447(2) Å , = 99.07(3), = 98.30(3), = 108.50(3)°, V = 445.6(2) Å3, and Z = 2. Melaminium nitrate (II), monoclinic, P21/c, a = 3.5789(7), b = 20.466(4), c = 10.060(2) Å, = 94.01(2)°, V = 735.0(3) Å3, and Z = 4. The crystal structures of both salts show distinct monoprotonated melaminium cations and dinitramide- or nitrate anions, respectively. Efficient packing in the solid state is achieved by extensive hydrogen bonding between two-dimensional zigzag ribbons of the melaminium cations and the respective anions resulting in high densities of the solid state structures of 1.74 (I) and 1.71 g/cm3 (II). 相似文献
107.
The crystal structures of two hexammonium polymorphs, 1 and 2, and the ethane-1,2-diammonium, 3, salts of dinitramide have been determined. 1 crystallizes in the triclinic space group
with cell dimensions a = 6.391(2), b = 7.5826(9), c = 10.828(1) Å, a = 77.58(1), = 88.18 (2), = 87.54(2)°, 2 crystallizes in the monoclinic space group P21/c with cell dimensions a = 6.4893(3), b = 14.5149(8), c = 10.6557(4) Å, = 94.300(4)°, and 3 crystallizes in the triclinic space group
with cell dimensions a = 5.614(1), b = 6.867(2), c = 7.371(2) Å, = 68.89(2), = 89.00(2), = 78.90(2)°. The three structures all contain protonated amine cations which are involved in hydrogen bonding interactions with dinitramide anions. 相似文献
108.
The crystal structures of cubane-1,4-diammonium dinitramide, 1, and cubane-1,2,4,7-tetraammonium dinitramide, 2, have been determined. 1 crystallizes in the space group P21/c with cell dimensions a = 6.018(2), b = 11.642(3), c = 9.754(3) Å, = 107.24(2), while 2 crystallizes in the space group P21/c with cell dimensions a = 9.401(4), b = 9.603(3), c = 12.603(4) Å, 111.08(3). In these structures the ammonium substituents are symmetrically attached with respect to the cubane skeleton and have neither low lying empty orbitals nor available lone pairs of electrons thus they have a minimal effect on the metrical parameters of the cubane skeleton. All C–C bond lengths are close to the overall average C–C bond length for all reported cubanes of 1.559 Å. The conformations adopted by the dinitramide ions in both structures are quite different, with the bend, twist, and torsion angles for the dinitramide ion in 1 being significantly larger than those found for the dinitramide ions in 2, due to the different types of hydrogen bonding found in the two structures. In 2, the conformation adopted by the adjacent ammonium ions allows two of the three protons from each ammonium cation to form hydrogen bonds in such a manner that they span either the syn or the anti oxygen atoms of a single dinitramide anion. The dinitramide anion is thus constrained by these interactions and is less free to twist and bend. These results provide further confirmation that the metrical parameters of both the cubane and dinitramide moieties are flexible and reflect their local environment. 相似文献
109.
The crystal structures of the hexaaquomagnesium (1), hexaaquomanganese (2), and hexaaquozinc (3) dihydrate salts of dinitramide have been determined. 1 crystallizes in the monoclinic space group P21/n with cell dimensions a = 9.589(2), b = 7.420(1), c = 11.116(2) Å, = 108.25(3)°, 2 crystallizes in the monoclinic space group P21/n with cell dimensions a = 9.623(4), b = 7.477(2), c = 11.274(3) Å, = 108.38(3)°, and 3 crystallizes in the monoclinic space group P21/n with cell dimensions a = 9.513(1), b = 7.4270(8), c = 11.164(1) Å, = 108.806(6)°. The three structures are isostructural, consisting of hexaaquo cations, dinitramide anions and water molecules interlinked by an extensive three dimensional hydrogen bonding interactions. All oxygen atoms as well as the central nitrogen atom of the dinitramide anion are involved in acceptor hydrogen bonds with neighboring water protons. As a consequence of the constraints imposed by these hydrogen bonds the dinitramide ions are almost planar with average deviations of 0.01 Å for 1, 0.03 Å for 2 and 0.03 Å for 3. 相似文献
110.
Colomba Di Blasi Carmen Branca Antonio Galgano 《Polymer Degradation and Stability》2008,93(2):335-346
The decomposition of fir wood, impregnated with diammonium sulfate and diammonium phosphate, has been investigated with a laboratory scale reactor together with gas-chromatographic analysis of gas and condensable organics. The dependence of products and other process variables on the salt concentration in the wood (from 0 to about 20% on a dry wood basis) and the heating temperature (650-900 K) is qualitatively similar for the two cases. Given heating temperatures of about 650-750 K and using as a reference water-extracted wood, diammonium sulfate and diammonium phosphate concentrations of about 1% are apt to cause a small increase (factors of 1.2-2) in the yields of levoglucosan, 5-methyl-2-furaldehyde and 2-acetylfuran, whereas values in the range 2-5% highly augment the yields of levoglucosenone and 2-furaldehyde (factors of 14-16 and 3-2, respectively). Salt concentrations above 10% confer excellent fire retardance properties of wood with total yields of water and char up to about 70 and 85% and ratio values of non-combustible to combustible volatile products up to 3.5 and 6.5, respectively. The displacement of the reaction process at lower temperatures, the higher exothermicity associated with the enhanced char formation, the reduced convective cooling and the endothermicity of salt decomposition also highly affect the conversion times and the overall rates of volatile species release. 相似文献