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131.
132.
133.
The Steven’s method of molecular orbitals for octahedral complexes containing transition metal ions has been used for estimating
the binding parameters and interpreting theg factors of VO
2
+
ion in single crystals. The expressions forg factors have been given in terms ofK
‖ andK
⊥ taking into account the tetragonal crystalline field and covalent binding effects. Computations show thatK
⊥ should be less than 0.066 in order to fit the experimentalg values. The ground state wave function (GSWF) of VO
2
+
ion doped in different single crystals has been estimated using crystal field theory. The GSWF is found to be ind
xy state with slight admixture of the excited states
,d
xz andd
yz. The hyperfine interaction parameterP and Fermi contact termX have also been estimated. 相似文献
134.
135.
Zheng T Narayan RS Schomaker JM Borhan B 《Journal of the American Chemical Society》2005,127(19):6946-6947
A simple and efficient process to cyclize triols containing a 1,2-diol functionality with a pendant hydroxyl group is presented. The one-pot procedure converts the 1,2-diol into an ortho ester in situ, which upon treatment with a Lewis acid generates a cyclic acetoxonium intermediate. This intermediate is subsequently trapped by the pendant hydroxyl group to generate a cyclic ether. The stereochemistry of the 1,2-diol is transferred to the product with complete fidelity (inversion at the site of cyclization), and the reaction proceeds with high regioselectivity. The process is akin to the Lewis acid-catalyzed intramolecular ring-opening of epoxides with hydroxyl groups yielding cyclic ethers of various sizes with regio- and stereochemical control. 相似文献
136.
Jianhui Wang Yinghuai Zhu Shoujian Li Chong Zheng John A. Maguire Narayan S. Hosmane 《Journal of organometallic chemistry》2003,680(1-2):173-181
The reactions of RNHSi(Me)2Cl (1, R=t-Bu; 2, R=2,6-(Me2CH)2C6H3) with the carborane ligands, nido-1-Na(C4H8O)-2,3-(SiMe3)2-2,3-C2B4H5 (3) and Li[closo-1-R′-1,2-C2B10H10] (4), produced two kinds of neutral ligand precursors, nido-5-[Si(Me)2N(H)R]-2,3-(SiMe3)2-2,3-C2B4H5, (5, R=t-Bu) and closo-1-R′-2-[Si(Me)2N(H)R]-1,2-C2B10H10 (6, R=t-Bu, R′=Ph; 7, R=2,6-(Me2CH)2C6H3, R′=H), in 85, 92, and 95% yields, respectively. Treatment of closo-2-[Si(Me)2NH(2,6-(Me2CH)2C6H3)]-1,2-C2B10H11 (7) with three equivalents of freshly cut sodium metal in the presence of naphthalene produced the corresponding cage-opened sodium salt of the “carbons apart” carborane trianion, [nido-3-{Si(Me)2N(2,6-(Me2CH)2C6H3)}-1,3-C2B10H11]3− (8) in almost quantitative yield. The reaction of the trianion, 8, with anhydrous MCl4 (M=Ti and Zr) in 1:1 molar ratio in dry tetrahydrofuran (THF) at −78 °C, resulted in the formation of the corresponding half-sandwich neutral d0-metallacarborane, closo-1-M[(Cl)(THF)n]-2-[1′-η1σ-N(2,6-(Me2CH)2C6H3)(Me)2Si]-2,4-η6-C2B10H11 (M=Ti (9), n=0; M=Zr (10), n=1) in 47 and 36% yields, respectively. All compounds were characterized by elemental analysis, 1H-, 11B-, and 13C-NMR spectra and IR spectra. The carborane ligand, 7, was also characterized by single crystal X-ray diffraction. Compound 7 crystallizes in the monoclinic space group P21/c with a=8.2357(19) Å, b=28.686(7) Å, c=9.921(2) Å; β=93.482(4)°; V=2339.5(9) Å3, and Z=4. The final refinements of 7 converged at R=0.0736; wR=0.1494; GOF=1.372 for observed reflections. 相似文献
137.
Sunil K. Maity Narayan C. Pradhan Anand V. Patwardhan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):114-121
The reaction between benzyl chloride and aqueous ammonium sulfide was carried out in an organic solvent – toluene, using tetrabutylammonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction. 相似文献
138.
139.
140.
Megumi Kayanuma Narayan Bera Martina Sandroni Yann Pellegrin Errol Blart Fabrice Odobel Chantal Daniel 《Comptes Rendus Chimie》2012,15(2-3):255-266
The structures and electronic absorption spectra of newly synthesized heteroleptic copper (I) complexes [CuL1L2]+ (L1 = phen-imidazole and/or L2 = dipyrido [3,2-a:2’,3’-c] phenazine derivatives) are analyzed under the light of density functional theory (DFT) and time-dependent DFT (TD-DFT). The ground states geometries, characterized by π-stacking interactions, have been optimized using PBE-D functional taking into account dispersion correction. The UV-visible theoretical absorption spectra have been calculated using B3LYP functional in vacuum and taking into account solvent corrections by means of the polarized continuum model (PCM). Whereas the PBE-D functional is well adapted to the determination of the structures, it does underestimate drastically the transition energies. The spectra are characterized by high density of states, mainly metal-to-ligand-charge-transfer (MLCT) and intra-ligand (IL), between 600 nm and 250 nm. Most of the complexes show an intense band in the near-UV energy domain (~320 nm) corresponding to an IL transition. The lowest part of the absorption spectra, starting at 600 nm, corresponds to MLCT transitions leading to a shoulder observed experimentally between 400 and 500 nm. The upper part of the spectra, beyond 300 nm, puts in evidence strong mixing between ligand-to-ligand-charge-transfer (LLCT), IL and MLCT states. 相似文献