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201.
The present paper reports a comprehensive and complementary study on structural, electronic and phonon properties of face centered cubic fluorites, namely CaF2, BaF2 and SrF2, using first principles density functional calculations within the generalized gradient approximation. The calculated lattice constants and bulk modulus are in good agreement with available experimental data. The analysis of band structure and density of states confirms the ionic character for all the three fluorides. The phonon dispersion curves and corresponding phonon density of states obtained in the present work are consistent with the available experimental and other theoretical data. The LO-TO splitting is maximum for CaF2, which confirms that the ionicity is maximum in the case of CaF2. The phonon properties for SrF2 have been calculated for the first time. 相似文献
202.
High field electrical switching on blown films of MoO3(60%)–P2O5(40%), MoO3(50%)–WO3(10%)–P2O5(40%), and MoO3(45%)–WO3(15%)–P2O5(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage
characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but
N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses
was observed. The important observation was that with the addition of WO3 to binary MoO3–P2O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation
between MoO3 content and density which decreased with the increase of MoO3 content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that
the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show
any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate
glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was
explained by thermal (formation of crystalline filaments) and electronic models. 相似文献
203.
204.
205.
利用粘度碰撞积分方程的直接反演方法计算了两个二元气体混合体系即苯-甲醇和甲烷-四氟甲烷的低密度势能.另外利用动力学理论以及对应态原理计算了两种体系不同温度和不同比例的粘度系数和扩散系数.计算结果和实验数据具有较好的一致性. 相似文献
206.
207.
A novel debromination of vic-dibromides to alkenes with InCl3(cat.)/Sm system in aqueous media has been developed. The reaction gives the E-isomers with excellent yields. 相似文献
208.
A high-quality mass-analyzed threshold ionization (MATI) spectrum of 2-chloropropene, 2-C3H5Cl, is reported. Its ionization energy determined for the first time from the 0-0 band position was 9.5395+/-0.0006 eV. Almost all the peaks in the MATI spectrum could be vibrationally assigned utilizing the frequencies calculated at the B3LYP6-311++G(3df,3pd) level and the Franck-Condon factors calculated with the molecular parameters obtained at the same level. In particular, the observed methyl torsional progression could be reproduced very well through quantum-mechanical calculations using the molecular parameters obtained at this level. Dramatic lowering of the torsional barrier inferred from the experimental data was entirely compatible with the B3LYP6-311++G(3df,3pd) results. The torsional barrier and the internal rotational constant determined by fits to six torsional peaks were 53.6 and 5.20 cm(-1), respectively. A brief discussion at the level of molecular orbital is presented to account for the dramatic lowering of the torsional barrier upon ionization. 相似文献
209.
One-photon mass-analyzed threshold ionization (MATI) spectra for the X (2)E(3/2) states of CH(3)I(+) and CD(3)I(+) were measured using vacuum ultraviolet radiation generated by four-wave mixing in Kr. Spin-orbit density functional theory calculations at the B3LYP/aug-cc-pVTZ level and spin-orbit/Jahn-Teller calculations were made to aid vibrational assignment. Each vibrational band consisted of several peaks due to different DeltaK transitions, which could be assigned by using molecular parameters determined in the previous high resolution photodissociation spectroscopic study. Possibility of generating mass-selected, vibronically selected and K-selected ion beam with decent intensity by one-photon MATI was demonstrated. The ionization energies to the X (2)E(3/2) states of CH(3)I(+) and CD(3)I(+) corrected for the rotational contribution were 9.5386+/-0.0006 and 9.5415+/-0.0006 eV, respectively. 相似文献
210.
Thiel OR Bernard C King T Dilmeghani-Seran M Bostick T Larsen RD Faul MM 《The Journal of organic chemistry》2008,73(9):3508-3515
Small molecule TRPV1 antagonists have been a recent focus in the search for pain treatment agents. We herein describe a practical and scalable synthesis of AMG 628 (1), a bis-substituted pyrimidine derivative that was identified as a highly efficacious agent, suitable for clinical development. Highlights of our approach include a practical route to a substituted benzothiazole, a scalable synthesis of an enantiopure piperazine fragment, and identification of conditions for selective coupling reactions on 2,6-dichloropyrimidine, to access the active pharmaceutical ingredient in high purity and overall yield. 相似文献