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961.
962.
963.
964.
The solute-solvent interactions of hydrogen-bonded phenol-(H2O)n (n=3-5) clusters in electronic excited states were investigated by means of the time-dependent density functional theory (TDDFT) method. The geometric structures and IR spectra in ground state, S1 state, and T1 state of the clusters, were calculated using the density functional theory (DFT) and TDDFT methods. Only the ring form isomer, the most stable one of the cluster, was considered in this study. Four, five and six intermolecular hydrogen bonds were formed in phenol-(H2O)3, phenol-(H2O)4, and phenol-(H2O)5 clusters, respectively. Based on the analysis of IR spectra, it is revealed that the “window region” between unshifted and shifted absorption bands in both S1 and T1 state becomes broader compared with that in ground state for the corresponding clusters. Furthermore, two interesting phenomenon were observed: (1) with the anticlockwise order of the ring formed by the intermolecular hydrogen bonds in the H-bonded phenol-(H2O)n (n=3-5) clusters, the strengths of the intermolecular hydrogen bonds decrease in all the S0, S1 and T1 states; (2) upon electronic excitation, the smaller the distance between phenol and water is, the larger the change of intermolecular hydrogen bonds strength is. Moreover, the intermolecular hydrogen bond (phenolic OH is the H donor) is strengthened in excited state compared with that in ground state. But the intermolecular hydrogen bond (phenolic OH is the H acceptor) is weakened in excited state. 相似文献
965.
The interaction of La3+ to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by La3+ was a static quenching process and the binding constant is 1.75×104 L mol−1 and the number of binding sites is 1 at 289 K. The thermodynamic parameters (ΔH=−20.055 kJ mol−1, ΔG=−23.474 kJ mol−1, and ΔS=11.831 J mol−1 K−1) indicate that electrostatic effect between the protein and the La3+ is the main binding force. In addition, UV-vis, CD, and synchronous fluorescence results showed that the addition of La3+ changed the conformation of BSA. 相似文献
966.
The interaction between promethazine hydrochloride (PMT) and bovine serum albumin (BSA) in vitro was investigated by means of fluorescence spectroscopy and absorption spectroscopy. The fluorescence of BSA was quenched remarkably by PMT and the quenching mechanism was considered as static quenching by forming a complex. The association constants Ka and the number of binding sites n were calculated at different temperatures. The BSA-PMT binding distance was determined to be less than 8 nm, suggesting that energy transfer from BSA to PMT may occur. The thermodynamic parameters of the interaction between PMT and BSA were measured according to the van’t Hoff equation. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be −23.62 kJ mol−1 and −0.10 J mol−1 K−1, respectively, which indicated that the interaction of PMT with BSA was driven mainly by van der Waals forces and hydrogen bonds. The binding process was a spontaneous process in which Gibbs free energy change (ΔG) was negative. In addition, the results of synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that binding of PMT with BSA can induce conformational changes in BSA. 相似文献
967.
The structure of oxalyl bromide (COBr)2 in the ground and four lowest excited electronic states was theoretically investigated using the CASPT2/cc-pVTZ-DK method. Structural information obtained allowed the reassignment of the and vibronic absorption spectra. Generalization of oxalyl halide structural data for the ground and excited electronic states is presented. 相似文献
968.
A.V. Potapov L.A. Surin S. Schlemmer T.F. Giesen 《Journal of Molecular Spectroscopy》2011,270(2):116-119
The pure rotational spectrum of the Ne–CO van der Waals complex has been measured in the frequency range of 208–230 GHz by using the Cologne supersonic jet spectrometer for terahertz applications (SuJeSTA). Eleven new transitions were assigned as belonging to two R- and two Q-branches of the K = 2–1 subband detected for the first time in the ground vibrational state of CO (νCO = 0). Improved molecular parameters of the Ne–CO complex were obtained which allowed for a sensitive test of the available intermolecular potential energy surfaces of the Ne–CO system. 相似文献
969.
The gas-phase Raman spectra of 1,3-butadiene and its 2,3-d2, 1,1,4,4-d4, and d6 isotopologues have been recorded with high sensitivity and resolution of 0.7 cm−1. Hot band series of fundamentals and combinations involving the ν13 torsional vibration of the s-trans rotamer have been observed for each of the isotopologues. Modes studied were ν10 (CH wag), ν12 (CH2 twist), ν10 + ν12, ν15 (CH2 wag) + ν16 (CH2 twist), and ν23 (CH2 rock) + ν24 (CCC deformation). The spacings of the quantum states of the torsional contribution were found to decrease with additional excitation of this mode (ν13) in the upper vibrational states except for the ν23 + ν24 combination state. 相似文献
970.
K.R. Karim 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(6):1026-1034
X-ray and Auger transition rates, X-ray wavelengths, and fluorescence yields are calculated for variously ionized silicon atoms with configurations 1s2sm2pn, m=0-2, n=1-6. The calculation has been performed using the Hartree-Fock atomic model. Intermediate coupling and configuration interaction have been taken into account. The energies and widths are found to be strongly affected by configuration mixing. The results from the present calculation have been compared with those available in the literature. The theoretical Kα hypersatellite and satellite spectra fall into several well-separated regions, corresponding to each of the possible number of spectator electrons in the 2s and 2p shells. The dependence of radiative rates and fluorescence yields on the number of spectator electrons is also investigated. 相似文献