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51.
Thomas Andre´s Wolcan Ezequiel Fe´liz Mario R. Capparelli Alberto L. 《Transition Metal Chemistry》1997,22(6):541-544
The kinetics of the complexation of NiII by pteroylglutamic acid have been studied in the 545 ∘C range, the ionic strength
(0.6 M) being regulated with KNO3, in the 5.5–7.0pH range, using the stopped-flow method. Under the experimental conditions
two processes were observed. The faster process was detected in the millisecond range and is associated with the reaction
between NiII and the ligand. The slower is observed within a few seconds. Complementary equilibrium studies were made at 25
∘C. The results are consistent with the formation of a 1:1 complex between the reactants, and a mechanism is proposed to account
for the observed behaviour. Equilibrium constants for the NiII plus pteroylglutamic acid system, as well as activation parameters,
are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
52.
53.
Anne Tscheliessnig Danny Ong Jeremy Lee Siqi Pan Gernalia Satianegara Kornelia Schriebl Andre Choo Alois Jungbauer 《Journal of chromatography. A》2009,1216(45):7851-7864
A two-step purification strategy comprising of polyethylene glycol (PEG) precipitation and anion-exchange chromatography was developed for a panel of monoclonal immunoglobulin M (IgM) (pI 5.5–7.7) produced from hybridoma cultures. PEG precipitation was optimized with regards to concentration, pH and mixing. For anion-exchange chromatography, different resins were screened of which Fractogel EMD, a polymer grafted porous resin had the highest capacity. Despite its significantly slower mass transfer, the binding capacity was still higher compared to a convection driven resin (monolith). This purification strategy was successfully demonstrated for all 9 IgMs in the panel. In small scale most antibodies could be purified to >95% purity with the exception of two which gave a lower final purity (46% and 85%). The yield was dependent on the different antibodies ranging from 28% to 84%. Further improvement of recovery and purity was obtained by the digestion of DNA present in the hybridoma supernatant using an endonuclease, benzonase. So far this strategy has been applied for the purification of up to 2 l hybridoma supernatants. 相似文献
54.
This paper presents techniques for solving the problem of minimizing investment costs on an existing gas transportation network. The goal of this program is to find, first, the optimal location of pipeline segments to be reinforced and, second, the optimal sizes (among a discrete commercial list of diameters) under the constraint of satisfaction of demands with high enough pressure for all users. 相似文献
55.
Starting from Smoluchowski's hypothesis, a simple algorithm is developed in order to obtain the apparent rate constant at large values of time, t, with some physical and chemical processes, as in the case of diffusion controlled reactions. Some practical examples are illustrated, assuming nonuniform distribution function, space-dependent diffusion coefficient or short-range interaction leading to an asymptotic analytical expression of the form α + β/√t, where α and β are constants function of the system of interest. 相似文献
56.
Andre Silva Pimentel Geoffrey S. Tyndall John J. Orlando Michale D. Hurley Timothy J. Wallington Mads P. Sulbaek Andersen Paul Marshall Theodore S. Dibble 《国际化学动力学杂志》2010,42(8):479-498
Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH3)2, and tert‐butyl formate, HC(O)OC(CH3)3. Product distributions are reported from both Cl‐ and OH‐initiated oxidation, and reaction mechanisms are proposed to account for the observed products. The proposed mechanisms include examples of the α‐ester rearrangement reaction, novel isomerization pathways, and chemically activated intermediates. The atmospheric oxidation of isopropyl formate by OH radicals gives the following products (molar yields): acetic formic anhydride (43%), acetone (43%), and HCOOH (15–20%). The OH radical initiated oxidation of tert‐butyl formate gives acetone, formaldehyde, and CO2 as major products. IR absorption cross sections were derived for two acylperoxy nitrates derived from the title compounds. Rate coefficients are derived for the kinetics of the reactions of isopropyl formate with OH (2.4 ± 0.6) × 10?12, and with Cl (1.75 ± 0.35) × 10?11, and for tert‐butyl formate with Cl (1.45 ± 0.30) × 10?11 cm3 molecule?1 s?1. Simple group additivity rules fail to explain the observed distribution of sites of H‐atom abstraction for simple formates. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 479–498, 2010 相似文献
57.
58.
The sorption kinetics for the removal aldehydes from aqueous solutions with Amberlite XAD-16 and MPP particles impregnated
with Primene JM-T was investigated. A model, accounting for the simultaneous mass transfer and chemical reaction, is developed
to describe the process. It is based on the analogy to the diffusion and reaction in a stagnant liquid sphere, but corrected
for the porosity and particle properties influencing the diffusion. The developed model describes the kinetic behavior of
the process in the low concentration region rather well. However, in the high concentration region, larger discrepancies are
observed. Initially, the influence of the flow rate was investigated to eliminate the effect of the external mass transfer.
The influence of the particle morphology was investigated for both physical and reactive sorption. Physical sorption experiments
were used to determine the factor τ that takes the particle properties influencing the diffusion into account. It was shown that the diffusion is faster in XAD-16
than in MPP impregnated systems. Reaction rate constant k
x
was determined by fitting the model to the experimental data. Sorption of benzaldehyde appears to be significantly slower
(k
x
∼10−4 l/mol s) than the sorption of pentanal (k
x
∼10−3 l/mol s) due to the slower chemical reaction. The influence of the particle size was investigated for the sorption of pentanal
with XAD-16. It was observed that the particle size does influence the diffusion term, but does not have an effect on the
reaction rate. On the other hand, the extractant loading influences the reaction rate slightly in the low concentration region,
whereas the initial concentration of the solute has more pronounced effect. 相似文献
59.
J. -C. Andre M. L. Viriot 《Journal of photochemistry and photobiology. A, Chemistry》1990,50(3):343-360
The principle of the use of a fluorescent relay is described. Its aims is to transform undesirable wavelengths into active photons for a specific photoreaction and to improve the use of commercial mercury vapour lamps in photochemistry. The light profile in the photoreactor in the presence of a fluorescent relay has been established, using a sensor made of an optical fibre with a small integrating sphere; the experimental values are compared with the model (the lamp is assumed to be a quasi-linear source). The determination of a semi-empirical model for the light distribution, which considers the partial transmission of fluorescent light through the lamp (shadow effect), leads to the calculation of the extinction coefficient μO of the fluorescent solution corresponding to the best efficiency of the fluorescent relay. 相似文献
60.
Crystal structures based on powder XRD and hydrogenation properties of 24 Pd‐rich intermetallics are presented. 相似文献