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51.
José Luis Martínez Vidal Antonia Garrido Frenich María M. Aguilera-Luiz Roberto Romero-González 《Analytical and bioanalytical chemistry》2010,397(7):2777-2790
Two rapid multi-residue screening methods for the determination of 21 veterinary drugs in milk by ultra-high-performance liquid
chromatography-tandem mass spectrometry (UHPLC-MS/MS) have been developed and compared. For both methods, veterinary drugs
were extracted from milk samples using a rapid extraction procedure based on the modification of the well-known QuEChERS (Quick,
Easy, Cheap, Effective, Rugged, and Safe) method, and no further clean-up steps were necessary. One screening method was based
on the selection of a characteristic neutral loss or product ion of the various families of compounds, whereas another one
was based on the choice of a selected reaction monitoring (SRM) for each compound. These methods were compared with regards
to false negatives, cut-off values and the unreliability region. The total run time for both methods was 3 min, allowing quick
selection of samples that contained veterinary drugs. Non-negative samples were re-analyzed by the UHPLC-MS/MS confirmation/quantification
method, which consisted in the monitoring of two SRM for each compound. The methods were validated according to international
guides. The proposed analytical methods allow for the identification and confirmation of the target veterinary drugs at trace
levels employing quick analysis time. 相似文献
52.
Mercedes Gallego-Gallegos María Liva Garrido Riansares Muñoz Olivas Patricia Baravalle Claudio Baggiani Carmen Cámara 《Journal of chromatography. A》2010,1217(20):3400-3407
Molecular imprinting technology has been employed for the first time to prepare a specifically affinity chromatographic stationary phase for speciation purposes. Tributyltin has been chosen as the template molecule and the non-covalent approach has been applied. Three different polymerization methods have been evaluated: (i) a composite material, (ii) a polymer prepared via-Iniferter grafting; (iii) an emulsion polymer. Columns packed with different polymers have been evaluated by liquid chromatography (LC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). The chromatographic conditions as well as the analytical characteristics of the developed method are discussed in this paper. Our findings have shown formation of specific cavities in the grafted Iniferter as well as in the emulsion polymers with the latter achieving resolution of four organotin compounds. Detection limits are similar to those obtained with commercial, but not specific, stationary phases (6 pg for monobutyltin, MBT; 10 pg for both tributyltin, TBT, and triphenyltin, TPhT; and 20 pg for dibutyltin, DBT). The main advantage of this proposed stationary phase is that good recovery is obtained for all species, including MBT. Baseline resolution for TBT and TPhT has also been obtained. The high selectivity of this column prevents matrix interferences. The method has been validated by analyzing two biota reference materials (ERM-CE477 mussel tissue and T-38 oyster tissue). 相似文献
53.
Jurado-Navas A Balsells JM Paris JF Castillo-Vázquez M Puerta-Notario A 《Optics letters》2011,36(20):4095-4097
General analytical expressions are derived for the average bit error rate of an intensity modulation and direct detection link using unbounded optical wavefront with on-off keying signalling technique propagating under all possible irradiance fluctuation conditions. These expressions include in a single equation the link performance of most of the proposed statistical models derived until now. 相似文献
54.
The formalism to describe electron scattering reactions on two-neutron halo nuclei is developed. The halo nucleus is described as a three-body system (core +n + n), and the wave function is obtained by solving the Faddeev equations in coordinate space. We discuss elastic and quasielastic scattering using the impulse approximation to describe the reaction mechanism. We apply the method to investigate the case of electron scattering on 6He. Spectral functions, response functions, and differential cross sections are calculated for both neutron knockout and knockout by the electron. 相似文献
55.
A Garrido Frenich J R Torres-Lapasió K De Braekeleer D L Massart J L Martínez Vidal M Martínez Galera 《Journal of chromatography. A》1999,855(2):487-499
Simple to use interactive self-modelling mixture analysis (SIMPLISMA), orthogonal projection (OPA) and Needle Search (NS) approaches have been applied to the determination of a number of compounds present in a complex multicomponent system. None of these three approaches succeeded completely when they were tested using the whole data matrix. When OPA and NS were applied to three simpler submatrices, obtained by dividing the total data matrix, and where a smaller number of compounds were present, better performance was achieved. 相似文献
56.
57.
Remedios Fernández-Fernández Juan Carlos López-Martínez Roberto Romero-González José Luis Martínez-Vidal María Isabel Alarcón Flores Antonia Garrido Frenich 《Chromatographia》2010,72(1-2):55-62
A rapid, reliable and sensitive method has been developed to determine malic and citric acid in fruits and vegetables. The methodology is based on simple extraction with an aqueous solution of ethanol (80% v/v) and subsequent chromatographic analysis by liquid chromatography coupled to mass spectrometry. Electrospray ionization in negative mode was used. The best response for citric and malic acid was provided by molecular ions [M?H]? at m/z 191 and 133 respectively. These ions were used for quantification, whereas other fragments were used as confirmation ions. Different variables involved in the separation and detection process, such as mobile phase, gradient profile and flow rate have been optimised. Linearity, repeatability, recovery and limits of quantification were evaluated. Good linearity was obtained up to 5,000 mg kg?1. Recovery ranged from 90.0 to 104.6%, repeatability (expressed as RSD) was <8% for tested matrices, and limits of quantification were equal or lower than 65 mg kg?1. Finally, the method was applied to the analysis of samples of orange, tomato and pepper. 相似文献
58.
59.
Alvarez-Rodríguez R Jensen AS Fedorov DV Fynbo HO Garrido E 《Physical review letters》2007,99(7):072503
We compute energy distributions of three particles emerging from decaying many-body resonances. We reproduce the measured energy distributions from decays of two archetypal states chosen as the lowest 0+ and 1+ resonances in 12C populated in beta decays. These states are dominated by sequential, through the 8Be ground state, and direct decays, respectively. These decay mechanisms are reflected in the "dynamic" evolution from small, cluster or shell-model states, to large distances, where the coordinate or momentum space continuum wave functions are accurately computed. 相似文献
60.
J. M. Martinez C. Volzone L. B. Garrido 《Journal of Thermal Analysis and Calorimetry》2017,128(1):61-69
Aluminum-pillared montmorillonites are useful materials for their application as catalysts, adsorbents and ceramic composites. The precursor is a pillared montmorillonite that is not thermally stabilized. The precursor preparation methods, textural properties and catalytic activity have been extensively investigated, but comparatively, studies concerning their thermal transformations at high temperature are limited. In this work, precursors were prepared using two types of montmorillonites, Cheto (Ch) and Wyoming (W), and using two different OH–Al polymer sources: hydrolyzed (H) and commercial (C) solutions. Structural and thermal transformations of the precursors with heating up to 1200 °C were determined by X-ray diffraction and thermogravimetric analysis. Thermal analysis of these precursors below 600 °C revealed the influence of OH–Al polymers from the two solutions. The major phases developed at 1200 °C from the original montmorillonites were mullite for W and cordierite for Ch. The content of these phases depended on the aluminum in the octahedral sheet of the pristine montmorillonites. Amorphous phase, cristobalite, spinel, sapphirine and others phases were also found. The intercalation of OH–Al polymers in montmorillonites caused an increase in amorphous content after treatment at 1030 °C; however, it favored mullite development above 1100 °C. Although total aluminum content of both W and Ch precursors was similar, the transformation to mullite was directly related to the octahedral aluminum/magnesium ratio. The phase composition of the products at 1200 °C was not dependent on the type of intercalated OH–Al polymers. The increase in mullite content of the thermally treated precursors contributes to its possible application as advanced ceramic products. 相似文献