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71.
Competitive coordination by the nitrone and the dipolarophile to the Lewis acid catalysts like metal triflates controls the acceleration and deceleration of the catalyzed 1,3-dipolar cycloaddition reactions as compared to the uncatalyzed one. This fact has been established through variation in steady state fluorescence of the substrates in presence of catalyst. Li+ found to catalyze both the cycloaddition between α-p-chlorophenyl-N-phenyl nitrone (N1) and Benzylidene acetophenone (D1) as well as between N1 and 3-Phenyl-1-pyridin-2-yl-propenone (D2) efficiently. While Yb3+ can catalyze only the cycloaddition between N1 and D2. The experimental findings have been rationalized on the basis of DFT calculations and analysis based on the frontier molecular orbital energies and relative electrophilicity of the reactants. 相似文献
72.
Tandrima Chaudhuri Prashant Sukla Moumita Mahapatra Bipin Rooj Sandip K. Nayak Subrata Chattopadhyay Manas Banerjee 《Journal of solution chemistry》2012,41(1):143-155
Absorption and emission spectroscopic studies of (dibenzoylmethanato)boron difluoride (1bf) in various polar and non-polar, protic and aprotic solvents are reported. The solvatochromic shifts of the spectral bands
were examined in terms of solvent properties, including donor and acceptor numbers, followed by multilinear regression in
which several solvent parameters were simultaneously analyzed. This π-conjugated positively charged system exhibits excellent solvatochromism. Variations in the electronic absorption spectral
characteristics of 1bf were studied in solution in the presence of zinc perchlorate. Absorption spectral studies indicate stable complex formation
between the zinc ion and 1bf in the ground state in aprotic dipolar benzonitrile rather than in protic polar solvent methanol. Zinc ion binding of 1bf was theoretically rationalized through frontier molecular orbital interaction. 相似文献
73.
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76.
Manas Banerjee Sankar Prasad Bhattacharyya 《International journal of quantum chemistry》1982,21(5):905-915
The performance of a recently proposed scaled one-electron Hamiltonian (SOEH ) model is tested against parallel sets of restricted open-shell calculations by the method of Roothaan. It is found that the energy calculated by SOEH model, in general, lies slightly higher than the energy computed by the restricted open-shell method of Roothaan lending credibility to the application of variational argument to the scaled pseudoenergy functional (Eav) for deriving the SOEH model. The numerical stability of the converged SOEH energy with respect to changes in trial vectors indicates the reliability of the method. The SOEH model is shown to perform well in the calculation of geometries of radicals and ions. The convergence behavior of the SOEH model is compared with that of the restricted open-shell method of Roothaan. 相似文献
77.
The performance of the VN—1 potential model at the INDO/2 level of approximation in the calculation of transition energy, singlet—triplet splitting, change in molecular structure, inversion barrier and electron-density distribution in the excited electronic states of a few simple carbonyls is analysed. The method turns out to be reasonably successful in many ways. 相似文献
78.
The 3-aminocarbazoles 1a-e were condensed with phenyl and benzyl isothiocyanates on montmorillonite K10 clay or TLC-grade silica gel at room temperature to furnish efficiently the N-phenyl and N-benzylthioureidocarbazoles, 2a-e and 2f, respectively, within minutes. When adsorbed on montmorillonite K10 clay impregnated with para-toluene sulfonic acid (1:1, w/w) and heated at 60-70 °C, 2a-e and 2f furnished the 2-anilino and 2-benzylaminothiazolo[4,5-c]carbazoles, 3a-e and 3f, respectively, regioselectively in high yields. The cyclisation was also effective for the N-methylthioureidocarbazoles 2g-i. 相似文献
79.
Bhattacharya S Chattopadhyay S Nayak SK Banerjee M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):729-735
Supramolecular complexation of [60]- and [70]fullerenes with 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert butyl)calix[6]arene (I) has been studied in CCl(4) medium by NMR spectrometric method. All of the complexes are found to be stable with 1:1 stoichiometry. Formation constants (K) of the above supramolecular complexes have been determined from systematic variation of NMR chemical shifts of specific protons of I in the presence of [60]- and [70]fullerenes. Trends in the K value suggest that [70]fullerene binds more strongly with I relative to [60]fullerene. Both PM3 and ab initio calculations reveal that the intermolecular interaction in the [70]fullerene/I complex proceeds through quite deep energy minima. 相似文献
80.
Satish D Joglekar 《Pramana》1989,32(3):195-207
We discuss the general theory of renormalization of unbroken gauge theories in the nonlinear gauges in which the gauge-fixing
term is of the form
We show that higher loop renormalization modifiesfα [A] to contain ghost terms of the form
and show how the corresponding ghost terms are deduced fromfα [A, c, c] uniquely. We show that the theory can be renormalized while preserving a modified form of BRS invariance by multiplicative
and independent renormalizations onA, c, g, η, ζ, τ. We briefly discuss the independence of the renormalized S-matrix from η,ζ, τ. 相似文献