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31.
The problem of steady laminar mixed convection boundary layer flow of an incompressible viscous fluid along vertical moving
thin needles with variable heat flux for both assisting and opposing flow cases is theoretically considered in this paper.
The governing boundary layer equations are first transformed into non-dimensional forms. The curvature effects are incorporated
into the analysis whereas the pressure variation in the axial direction has been neglected. These equations are then transformed
into similarity equations using the similarity variables, which are solved numerically using an implicit finite-difference
scheme known as the Keller-box method. The solutions are obtained for a blunt-nosed needle (m = 0). Numerical calculations are carried out for various values of the dimensionless parameters of the problem, which include
the mixed convection parameter λ, the Prandtl number Pr and the parameter a representing the needle size. It is shown from the numerical results that the skin friction coefficient, the surface (wall)
temperature and the velocity and temperature profiles are significantly influenced by these parameters. The results are presented
in graphical form and are discussed in detail. 相似文献
32.
Dr. Quan Pang Xiao Liang Ivan R. Kochetkov Dr. Pascal Hartmann Prof. Dr. Linda F. Nazar 《Angewandte Chemie (International ed. in English)》2018,57(31):9795-9798
The dendritic growth of Li metal leads to electrode degradation and safety concerns, impeding its application in building high energy density batteries. Forming a protective layer on the Li surface that is electron‐insulating, ion‐conducting, and maintains an intimate interface is critical. We herein demonstrate that Li plating is stabilized by a biphasic surface layer composed of a lithium‐indium alloy and a lithium halide, formed in situ by the reaction of an electrolyte additive with Li metal. This stabilization is attributed to the fast lithium migration though the alloy bulk and lithium halide surface, which is enabled by the electric field across the layer that is established owing to the electron‐insulating halide phase. A greatly stabilized Li‐electrolyte interface and dendrite‐free plating over 400 hours in Li|Li symmetric cells using an alkyl carbonate electrolyte is demonstrated. High energy efficiency operation of the Li4Ti5O12 (LTO)|Li cell over 1000 cycles is achieved. 相似文献
33.
Urszula Kosikowska Monika Wujec Nazar Trotsko Wojciech Ponka Piotr Paneth Agata Paneth 《Molecules (Basel, Switzerland)》2021,26(1)
The development of drug-resistant bacteria is currently one of the major challenges in medicine. Therefore, the discovery of novel lead structures for the design of antibacterial drugs is urgently needed. In this structure–activity relationship study, a library of ortho-, meta-, and para-fluorobenzoylthiosemicarbazides, and their cyclic analogues with 1,2,4-triazole scaffold, was created and tested for antibacterial activity against Gram-positive bacteria strains. While all tested 1,2,4-triazoles were devoid of potent activity, the antibacterial response of the thiosemicarbazides was highly dependent on substitution pattern at the N4 aryl position. The optimum activity for these compounds was found for trifluoromethyl derivatives such as 15a, 15b, and 16b, which were active against both the reference strains panel, and pathogenic methicillin-sensitive and methicillin-resistant Staphylococcus aureus clinical isolates at minimal inhibitory concentrations (MICs) ranging from 7.82 to 31.25 μg/mL. Based on the binding affinities obtained from docking, the conclusion can be reached that fluorobenzoylthiosemicarbazides can be considered as potential allosteric d-alanyl-d-alanine ligase inhibitors. 相似文献
34.
Reaction of phenylpropiolic ester (I) with α- and β-tetralones in the presence of sodium ethoxide yielded 5,6-dihydro-7,8-benzflavones and ethyl β-(2-tetralon-1-yl)cinnamates, as a result of Claisen and Michael reactions, respectively. The reaction of I with 3-ethoxy-2-cyclohexen-l-one and acetylcyclopropane in the presence of sodium ethoxide yielded acetylenic β-diketones and 2-aryl-6-cyclopropylpyran-4-ones, respectively. These products were identified on the basis of spectral and analytical data. 相似文献
35.
R. U. Amanov M. Yu. Antipin E. I. Matrosov A. A. Khodak Kh. T. Sharipov Yu. T. Struchkov M. I. Kabachnik 《Russian Chemical Bulletin》1992,41(3):495-499
X-ray diffraction analysis has been used to determine the crystal structures of the 1:1-composition products of protonation by perchloric acid of isomeric triphenyl-N-(4-methylpyridyl-2)phosphinimine (1) and triphenyl-N-(3-methylpyridyl-2)phosphinimine (2). The structures were refined toR=0.048 andR=0.052, respectively, using 2274 (1) and 2647 (2) reflections. The protonation centers are located at the sites of N atoms of the pyridine ring (1) and the phosphinimino group (2). The distribution of the bond lengths in the cations suggests that a significant contribution is made by a phosphonic structure with positive charges localized on the P atoms. N-H...O hydrogen bonds, with lengths of 2.890(4) and 3.020(3) Å, connect cations and anions in both structures.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 629–635, March, 1992. 相似文献
36.
In previous work we have postulated that highly rotationally-excited hydrides, AH, can relax by way of “cascading”, i.e., rapid vibrational exchange in which AH is vibrationally deactivated with retention of rotational quantum number (ΔvAH = ?1, ΔJAH ≈ 0). Infrared chemiluminescence studies reported here provide evidence of cascading in OH2 and HCl2 (2 symbolises vibrational excitation in the ground electronic state). The collision partners, BC, responsible for the cascading are thought to be (i) OH2 + NO2, (ii) HCl2 + NOCl and (iii) HCl2 + ICl. Extremely rapid vibrational exchange is indicative of a resonant process. Resonance must occur for a wide range of vAH and JAH, and a variety of collision partners BC. A plausible basis for such a process involves multiquantum vibrational and rotational transitions in the recipient molecule, BC, which “tune” the energy-exchange to resonance. 相似文献
37.
Nazar Savytskyy 《Physics letters. A》2008,372(11):1851-1855
We show that using the concept of the two-dimensional level number N⊥ one can experimentally study of the nodal domains in a three-dimensional (3D) microwave chaotic rough billiard with the translational symmetry. Nodal domains are regions where a wave function has a definite sign. We found the dependence of the number of nodal domains ℵN⊥ lying on the cross-sectional planes of the cavity on the two-dimensional level number N⊥. We demonstrate that in the limit N⊥→∞ the least squares fit of the experimental data reveals the asymptotic ratio ℵN⊥/N⊥?0.059±0.029 that is close to the theoretical prediction ℵN⊥/N⊥?0.062. This result is in good agreement with the predictions of percolation theory. 相似文献
38.
Yin SC Grondey H Strobel P Anne M Nazar LF 《Journal of the American Chemical Society》2003,125(34):10402-10411
Monoclinic lithium vanadium phosphate, alpha-Li(3)V(2)(PO(4))(3), is a highly promising material proposed as a cathode for lithium-ion batteries. It possesses both good ion mobility and high lithium capacity because of its ability to reversibly extract all three lithium ions from the lattice. Here, using a combination of neutron diffraction and (7)Li MAS NMR studies, we are able to correlate the structural features in the series of single-phase materials Li(3-y)V(2)(PO(4))(3) with the electrochemical voltage-composition profile. A combination of charge ordering on the vanadium sites and lithium ordering/disordering among lattice sites is responsible for the features in the electrochemical curve, including the observed hysteresis. Importantly, this work highlights the importance of ion-ion interactions in determining phase transitions in these materials. 相似文献
39.
C. Shobha Devi Penumaka Nagababu M. Shilpa Y. Praveen Kumar M. Rajender Reddy Nazar Md Gabra S. Satyanarayana 《Journal of the Iranian Chemical Society》2012,9(5):671-680
A series of four polypyridyl Ru(II) complexes such as [Ru(L)4(PIP)]2+ and [Ru(L)4PPIP]2+ where L is 4-amino pyridine and Pyridine (PIP?=?2-phenylimidazo[4,5-f] [1, 10] phenanthroline), (PPIP?=?2-(4??-phenoxy-phenyl) imidazo[4,5-][1, 10]phenanthroline) have been synthesized and characterized by elemental analysis, physicochemical methods such as UV?Cvis, IR and NMR spectroscopic techniques. The DNA-binding behavior of these complexes was investigated by electronic absorption titrations, fluorescence spectroscopy, viscosity measurements and salt-dependent studies. The experimental results indicate that all these complexes can bind to DNA through an intercalation mode, the DNA-binding affinities of these complexes follow the order [Ru(4-APy)4(PPIP)]2+(1)?>?[Ru(Py)4PPIP]2+(2)?>?[Ru(4-APy)4(PIP)]2+(3)?>?[Ru(Py)4PIP]2+(4). Noticeably, these complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA. Further, all four complexes screened for their antimicrobial activity indicate that the complexes show appreciable activity against Escherichia coli and Neurospora Crassa. In addition, in the presence of Co2+, the emission of DNA-[Ru(L4)PPIP/PIP]2+ can be quenched and recovered by the addition of EDTA, which exhibited the DNA ??light switch?? properties. 相似文献
40.
This paper investigates the effect of non-uniform temperature gradient and magnetic field on Marangoni convection in a horizontal fluid layer heated from below and cooled from above with a constant heat flux. A linear stability analysis is performed. The influence of various parameters on the convection onset is analyzed. Six non-uniform basic temperature profiles are considered, and some general conclusions about their desta- bilizing effects are presented. 相似文献