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71.
Visinoni R Giorgianni S Stoppa P Ghersetti S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(10):1887-1899
The diode laser spectrum of cis-1,2-CHF=CHF has been measured and analyzed in the nu4 fundamental region near 1016 cm(-1). This vibration of symmetry species A1 corresponds to the C-F symmetric stretching motion and gives rise to a strong b-type band. The rovibrational analysis, extended to the P, Q, and R branches, led to the identification of 2800 lines with J < or = 62, Ka < or = 18, Kc < or = 62. The assigned transitions free of major resonance contributions, fitted using Watson's A-reduction Hamiltonian in the Ir representation, yielded a set of spectroscopic parameters up to the quartic coefficients for the V4 = 1 state. Several perturbation effects occur throughout the band, mainly caused by the first-order c-type Coriolis interaction with the nu5 + nu11, vibrational state. Even though no transitions to the perturbing level were observed, the band orign and the rotational constants for the perturber were determined from a dyad model which includes the Coriolis interaction term. 相似文献
72.
S. Cesca P. V. Duranti A. Roggero G. Santi M. Bruzzone 《Journal of polymer science. Part A, Polymer chemistry》1974,12(6):1209-1232
The terpolymerization of ethylene, propylene, and methylcyclopentadienyl-5-endonorborn-2-enylmethane (III) by means of different vanadium-based coordination catalysts was investigated. The structure of III and its isomeric composition was studied by using vapor-phase chromatography, mass spectrometry, and NMR, infrared, and ultraviolet spectroscopy. The catalyst system V Acac3–Et2AlCl was used under different conditions, and the influence of several variables regulating the terpolymerization process were related to the properties of the resulting terpolymers (EPTM). The insertion of III into EPTM chains takes place randomly and does not influence the random distribution of comonomers. The selective opening of the norbornene double bond of III has been demonstrated by use of 2,3-dihydro-III as model compound. Tritiated III gave a radiochemical titer of unsaturation in excellent agreement with the value deduced from ultraviolet measurements. The influence of Lewis bases added to VAcac3–Et2AlCl catalyst is discussed. 相似文献
73.
S. Croft L.G. Evans A. Favalli D.K. Hauck D. Henzlova P. Santi 《Radiation measurements》2012,47(7):467-474
A standard nondestructive assay technique for determining the mass of plutonium in an item is passive neutron coincidence counting. In passive neutron coincidence counting, the dead time or rate loss corrections for the singles and doubles neutron counting rates are routinely made using empirical relationships that are based on the design and performance of the individual counter used to make the measurements. The empirical methods were developed ahead of any supporting theory for dead time losses and have worked well to date for the majority of safeguards measurement scenarios. Modern applications using highly efficient systems with short neutron lifetimes together with the challenges posed by highly multiplying items mean dead time corrections of higher fidelity are needed. While many attempts have been made to develop dead time corrections that are based on the physical principles of the measurements being performed, these corrections have often been found to be difficult to implement in a real system. For instance, Matthes and Haas developed an approach in 1985 which did not gain favor largely because the form of the doubles correction apparently required numerical integration which was difficult to implement with the computer technology of that time. A recent review into the approach that was developed by Matthes and Haas has determined that a straightforward analytical expression can be derived for the doubles correction that is similar to the singles rate correction that was developed in their original work. An analysis of the expressions is presented here to show how they relate to the traditional empirical methods. Further, we illustrate their implications and limitations. For instance the empirical methods do not address within burst losses i.e. rate related losses due to the correlated neutron bursts from fission, whereas the Matthes and Hass expression for singles counting does exhibit such an effect. 相似文献
74.
Marcello Tiecco Lorenzo Testaferri Andrea Temperini Luana Bagnoli Francesca Marini Claudio Santi 《合成通讯》2013,43(12):2167-2179
Simple alkenes react with PhSeOTf and NaN3 in MeCN to afford β-phenylseleno azides as the result of a stereospecific trans addition. The regioselectivity of the process is determined by the structure of the alkene. 相似文献
75.
High-resolution infrared spectrum of CHD279Br: ro-vibrational analysis of the ν5 and ν9 fundamentals
ABSTRACTThe high-resolution infrared spectrum of CHD279Br has been investigated by Fourier transform spectroscopy in the range 700–900?cm?1 at an unapodized resolution of 0.0035?cm?1. This spectral region is characterised by the absorptions of the ν5 (814.5185?cm?1) and ν9 (716.9649?cm?1) fundamental bands, corresponding to H–C–Br deformation and CD2 rocking modes, respectively. The ν5 vibration of symmetry species A′ gives rise to an a-/c-hybrid band with a predominant a-type component, while the ν9 mode of A′′ symmetry produces a b-type envelope. The spectral analysis resulted in the identification of 5290 (J′?≤?63 and Ka′?≤?13) and 1657 (J′?≤?53 and Ka′?≤?12) transitions for ν5 and ν9 bands, respectively. The assigned data were fitted using the Watson’s S-reduced Hamiltonian in the Ir representation and the v5?=?1 and v9?=?1 state parameters up to the quartic centrifugal distortion terms have been obtained. From spectral simulations the dipole moment ratio |Δμa/Δμc| of the ν5 band has been determined to be 1.4?±?0.1 while the intensity ratio between ν5 and ν9 fundamentals has been estimated to have a value of 4.3?±?0.5. 相似文献
76.
77.
Dr. Haibo Mei Dr. Jianlin Han Dr. Santos Fustero Mercedes Medio-Simon Daniel M. Sedgwick Dr. Claudio Santi Dr. Renzo Ruzziconi Dr. Vadim A. Soloshonok 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11797-11819
Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain fluorine atoms. In this review, we profile 17 fluorine-containing drugs approved by the food and drug administration (FDA) in 2018. The newly approved pharmaceuticals feature several types of aromatic F and CF3, as well as aliphatic (CF2) substitution, offering advances in the treatment of various diseases, including cancer, HIV, malarial and smallpox infections. 相似文献
78.
Anna Demurtas Silvia Pescina Sara Nicoli Patrizia Santi Cristina Padula 《Biomedical chromatography : BMC》2019,33(11)
Crisaborole is a boron compound recently approved by the US Food and Drug Administration as a 2% ointment for the treatment of mild to moderate atopic dermatitis. This work describes a simple method for the quantification of the drug in the skin layers at the end of in‐vitro permeation experiments. Chromatographic separation was carried out on a reverse‐phase C18 column using a mixture of trifluoroacetic acid 0.05%–acetonitrile (55:45, v/v) as mobile phase, pumped at 1 ml/min. Column temperature was 35°C and UV detection was performed at 250 nm. The method was linear in the range of concentration from 0.06 to 6 μg/ml (R2 = 1) and was selective, precise and accurate. Depending on the solvent used, the LOQ ranged from 0.014 to 0.030 μg/ml and the LOD from 0.005 to 0.010 μg/ml. The extraction from all the skin layers was quantitative. The developed method was successfully tested in an in‐vitro permeation study, proving to be an effective tool in the development of new formulations containing crisaborole. 相似文献
79.
Our aim is to investigate spaces with σ-discrete and meager dense sets, as well as selective versions of these properties. We construct numerous examples to point out the differences between these classes while answering questions of Tkachuk [22], Hutchison [13] and the authors of [7]. 相似文献
80.
Yindee Suttisawat Pramoch Rangsunvigit Boonyarach Kitiyanan Santi Kulprathipanja 《Journal of Solid State Electrochemistry》2010,14(10):1813-1819
Sodium aluminum hydride or sodium alanate (NaAlH4) has been considered as a potential material for hydrogen storage. Although its theoretical hydrogen storage capacity is
5.5 wt.% at 250 °C, the material still has its drawback in the regeneration issue. With the use of certain catalysts, the
regeneration problem can somewhat be alleviated with added benefits in the decrease in the hydrogen decomposition temperature
and the increase in the decomposition rate. This work summarizes what we have learned from the decomposition of NaAlH4 with/without catalysts and co-dopants. The decomposition was carried out using a thermovolumetric apparatus. For the tested
catalysts—HfCl4, VCl3, TiO2, TiCl3, and Ti—the decomposition temperature of the hydride decreases; however, they affect the temperature in the subsequent cycles
differently and TiO2 appears to have the most positive effect on the temperature. Sample segregation and the morphological change are postulated
to hinder the reversibility of the hydride. To prevent the problems, co-dopants—activated carbon, graphite, and MCM-41—were
loaded. Results show that the hydrogen reabsorption capacity of HfCl4- and TiO2-doped NaAlH4 added with the co-dopants increases 10–50% compared with that without a co-dopant, and graphite is the best co-dopant in
terms of reabsorption capacity. In addition, the decomposition temperature in the subsequent cycles of the co-dopant doped
samples decreases about 10–15 °C as compared to the sample without a co-dopant. Porosity and large surface area of the co-dopant
may decrease the segregation of bulk aluminum after the desorption and improve hydrogen diffusion in/out bulk of desorbed/reabsorbed
samples. 相似文献