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31.
Souad Chaouche Rachid Ouarsal Brahim El Bali Mohammed Lachkar Michael Bolte Michal Dusek 《Journal of chemical crystallography》2010,40(6):526-530
Abstract
Crystal structure of Li2HPO3,H2O was determined by single-crystal X-Ray diffraction analysis at 173(2) K. It crystallizes in the monoclinic system (P21/c) with the parameters: a = 5.0322(9) ?, b = 8.9795(17) ?, c = 17.088(4) ?, β = 92.672(16)° and Z = 8. The structure was refined to R = 0.0237 and ωR = 0.0650 for 1449 reflexions. The framework of Li2HPO3, H2O can be described as layers perpendicular to the crystallographic c axis. The structure contains two types of Li-tetrahedrons. In one kind each O atom belongs to one HPO3 group, while in the second kind one apex is an O from water. A network of hydrogen bonds interactions insures the connection between the layers. 相似文献32.
Souad Chaouche Rachid Ouarsal Mohammed Lachkar Francesco Capitelli Brahim El Bali 《Journal of chemical crystallography》2010,40(6):486-490
Abstract
A new hybrid phosphate, (C6H5NH3)[ZnCl(HPO3)], has been synthesized and its structure characterized from single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Pbca (n. 61) with the unit-cell parameters: a = 9.8635(2) ?, b = 9.4516(10) ?, c = 22.2430(4) ?, Z = 8 and V = 2,073.62(6) ?3. The final R factors were R/ωR = 0.0361/0.0924. Its framework might be described as a layered structure with two (010)-parallel cationic and anionic layers. The IR spectrum of this phase shows characteristic bands of phosphite and anilinium groups. 相似文献33.
34.
The expansion of a plasma induced by laser ablation is investigated using a single-fluid model combined with Saha?s equation. The space coordinates x and time t are combined to a one self-similar variable ξ=x/(ct). To obtain ordinary differential equations, two different transformations for the density are used. The density profiles during the expansion are found to be completely different, one corresponds to the common results i.e., the density decreases monotonically with ξ, while with the second transformation, the profile shows a density increasing for certain interval of the self-similar variable. This effect is enhanced with higher initial ionization fraction. The role of the initial velocity which corresponds to the start of the expansion from an unperturbed plasma or from an expansion already going on is pointed out. 相似文献
35.
Rachid Touzani Michael HaibachAgnieszka J. Nawara-Hultzsch Sghir El KadiriThomas J. Emge Alan S. Goldman 《Polyhedron》2011,30(15):2530-2534
The complexation of the simple 1-hydroxymethyl-3,5-dimethylpyrazole (HL) ligand with Fe and Ni salts leads to interesting polynuclear complexes in good yield. X-ray diffraction reveals that the resulting complexes (μ4-L)4Ni4Cl4(H2O)4 and (μ2-L)4(μ3-L)2Fe8Cl16(μ4-O)6 adopt cubane-type and open-cubane-type structures in the solid state. 相似文献
36.
Kashinath D Tisserand S Puli N Falck JR Baati R 《European journal of organic chemistry》2010,2010(10):1869-1874
Nucleophilic mixed chromium(II) and chromium(III) acetylides are generated from the smooth reduction of primary 1,1,1-trichloroalkanes with chromium(II) chloride in the presence of an excess amount of triethylamine at room temperature. These species arise from chromium(III) vinylidene carbenoids. It has been demonstrated that uncommon low-valent Cr(II) acetylides are formed by C-H insertion of Cr(II)Cl(2) into terminal alkynes, formed in situ through the Fritsch- Buttenberg-Wiechell (FBW) rearrangement, whereas Cr(III) acetylides are concomitantly generated by HCl elimination from the chromium(III) vinylidene carbenoid. Both divergent pathways result, overall, in the formation of nucleophilic acetylides. In situ trapping with electrophilic aldehydes afforded propargyl alcohols. Furthermore, deuteration experiments and the use of deuterium labeled 1,1,1-trichloroalkane substrates demonstrated the prevalence of low-valent Cr(II) acetylides, potentially useful, yet highly elusive synthetic intermediates. 相似文献
37.
38.
We design and analyze an unconditionally convergent nonstandard finite-difference method to study transmission dynamics of a mathematical model of HIV-TB co-infection. The dynamics of this model are studied using the qualitative theory of dynamical systems. These qualitative features of the continuous model are preserved by the numerical method that we propose in this paper. This method also preserves positivity of the solution which is one of the essential requirements when modelling epidemic diseases. Furthermore, we show that the numerical method is unconditionally stable. Competitive numerical results confirming theoretical investigations are provided. Comparisons are also made with other conventional approaches that are routinely used to solve these types of problems. 相似文献
39.
Rachid Rahouadj Jean-Franois Ganghoffer Christian Cunat 《Mechanics Research Communications》2003,30(2):119-123
In the first part of this contribution, the Lie-symmetries of the principle of least action associated to the constitutive equations of the DNLR formalism of relaxation have been presented. We examine in this second part the continuous symmetries corresponding to the simple case of stress relaxation under isothermal conditions. The well-known principle of time/temperature equivalence is discussed in terms of variational symmetry for the Jacobi’s action functional, and connected to the Onsager’s relation near the thermodynamic equilibrium. 相似文献
40.
Enrique Alvarez-Manzaneda Rachid ChahbounEsteban Alvarez Ramón Alvarez-ManzanedaPedro E. Muñoz Fermín JiménezHanane Bouanou 《Tetrahedron letters》2011,52(31):4017-4020
The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon-carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds. 相似文献