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981.
Abstract Aromatic polyesters were obtained in relatively good yields (~ 70%) from reactions of 3- and 4-bromomethylbenzoic acids with tri-ethylamine in chlorobenzene. A copolymer was prepared in 58% yield by reaction of a 1:1 mixture of the two acids under similar conditions. The polyesters were characterized by IR, 1H- and 133C-NMR spectra, x-ray powder diffraction, DSC behavior, solution viscosity, and hydrolysis to the corresponding hydroxymethylbenzoic acids. Molecular weights were determined by 1H-NMR endgroup analysis. Possible mechanisms for the reactions are discussed. 相似文献
982.
Prashant K. Sharma Manvendra Kumar Avinash C. Pandey 《Journal of nanoparticle research》2011,13(4):1629-1637
Copper doped ZnO nanoparticles were synthesized by a chemical technique based on a hydrothermal method. The crystallite sizes,
estimated by XRD and TEM/SEM for different doping percentage of Cu2+ (1–10%), were found to be in the range of ~10–15 nm. TEM/SEM images showed formation of uniform nanorods, the aspect ratio
of which varied with doping percentage. Photoluminescence (PL) measurement showed strong green visible emission and PL intensity
was found enhanced with increase in doping percentage. The increase in the PL intensity was mainly due to Cu incorporation
in ZnO lattice. Currently, light-emitting diodes (LEDs) giving ultraviolet emission have been combined with broad-band visible
green phosphors to make white-light LEDs. Thus, green luminescent ZnO:Cu2+ nanoparticles are seen as necessary and condemnatory constituent for white-light generation from UV LEDs, underlying the
importance of the current work. 相似文献
983.
Location coverage models with demand originating from nodes and paths: Application to cellular network design 总被引:3,自引:0,他引:3
Elif Tokar Erdemir Rajan Batta Seth Spielman Peter A. Rogerson Alan Blatt Marie Flanigan 《European Journal of Operational Research》2008,190(3):610-632
Location covering problems, though well studied in the literature, typically consider only nodal (i.e. point) demand coverage. In contrast, we assume that demand occurs from both nodes and paths. We develop two separate models – one that handles the situation explicitly and one which handles it implicitly. The explicit model is formulated as a Quadratic Maximal Covering Location Problem – a greedy heuristic supported by simulated annealing (SA) that locates facilities in a paired fashion at each stage is developed for its solution. The implicit model focuses on systems with network structure – a heuristic algorithm based on geometrical concepts is developed. A set of computational experiments analyzes the performance of the algorithms, for both models. We show, through a case study for locating cellular base stations in Erie County, New York State, USA, how the model can be used for capturing demand from both stationary cell phone users as well as cell phone users who are in moving vehicles. 相似文献
984.
Jyoti Pandey 《Tetrahedron》2009,65(45):9350-84
An organocatalytic multicomponent reaction involving 3,4-dihydro-(2H)-pyran, aromatic aldehydes, and urea/thiourea as substrates and l-proline/TFA as catalyst afforded hexahydropyrano pyrimidinones (thiones) in good yields. The method is simple, economical, and ecofriendly to generate hexahydropyrano pyrimidinones as precursors for many biologically active molecules and fused oxazines (PA-824), the lead molecules for tuberculosis chemotherapy. 相似文献
985.
Journal of Thermal Analysis and Calorimetry - The detonation combustion phenomenon is supersonic combustion process and follows on thermal explosion in combustor. Deflagration to detonation... 相似文献
986.
The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new class of bis(thiosemicarbazones) (H2L), derived by condensing isatin with different N(4)‐substituted thiosemicarbazides, have been studied both by a conventional stirring method and also using microwave technology. Binuclear products of type [{(η5‐C5H5)2TiCl} 2(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon analysis, electrical conductance, magnetic moment and spectral (UV‐visible, IR, 1H NMR and 13C NMR) data. FAB mass spectra of these compounds were also recorded to confirm the binuclear structures. Studies were conducted to assess the growth inhibiting potential of the ligands and complexes against various fungal, viral and bacterial strains. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
987.
Vinay S. Pandey Awadhesh Kr. Singh A.S. Achalkumar C.V. Yelamaggad 《Phase Transitions》2013,86(12):1049-1058
The investigated optically active dimeric compound, 4-n-dodecyloxy-4′-(cholesteryloxycarbonyl-1-butyloxy) chalcone, shows wide temperature ranges of two twisted grain boundary (TGB) phases, namely TGBA and TGBC*. The dielectric spectroscopy has been carried out for this compound in the frequency range of 1?Hz to 35?MHz for two different conditions of molecular anchoring. A relaxation mode has been detected in the TGBA and TGBC* phases for the planar anchoring of the molecules. This mode lies in the MHz region and has the characteristics of amplitude fluctuation of directors (soft mode). Results are supportive of the theory developed for the soft modes of TGBA and TGBC* phases. Dielectric anisotropy shows an unusual but characteristic (of TGB phases) variation with temperature. 相似文献
988.
Benzimidazole fused chiral mono aza-15-crown-5 2, was obtained in a single step from (S)-(?)-2-(α-hydroxyethyl) benzimidazole 1. This new class of aza-crown has a unique structure with the chiral unit being held in a stable conformation due to adjacent benzimidazole ring contributing to its stereodiscrimination ability. The interactions between the host aza-crown and enantiomerically pure amine guests in ionic and neutral forms exhibited the enantio-discrimination ability. The preliminary evaluation of the chiral sensing was monitored using 1H NMR and circular dichroism (CD) analysis of the complexes at their molar equivalence. The binding parameters were determined using electronic absorption spectroscopy. 相似文献
989.
990.
S. D. Rajan 《基于设计的结构力学与机械力学》2013,41(4):455-474
ABSTRACT Solutions to engineering design problems formulated as nonlinear programming (NLP) problems usually require the use of more than one optimization technique. Moreover, the interaction between the user (analysis/synthesis) program and the NLP system can lead to interface, scaling, or convergence problems. An NLP solution system is presented that seeks to solve these problems by providing a programming system to ease the user-system interface. A simple set of rules is used to select an optimization technique or to switch from one technique to another in an attempt to detect, diagnose, and solve some potential problems. Numerical examples involving finite element based optimal design of space trusses and rotor bearing systems are used to illustrate the applicability of the proposed methodology. 相似文献