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排序方式: 共有106条查询结果,搜索用时 625 毫秒
41.
Sebastian Ani?a 《Nonlinear Analysis: Real World Applications》2012,13(2):725-735
A two-component reaction-diffusion system modelling a class of spatially structured epidemic systems is considered. The system describes the spatial spread of infectious diseases mediated by environmental pollution. A relevant problem, related to the possible eradication of the epidemic, is the so called zero stabilization. In a series of papers, necessary conditions, and sufficient conditions of stabilizability have been obtained. It has been proved that it is possible to diminish exponentially the epidemic process in the whole habitat, just by reducing the concentration of the pollutant in a nonempty and sufficiently large subset of the spatial domain. The stabilizability with a feedback control of the harvesting type is related to the magnitude of the principal eigenvalue of a certain operator which is not selfadjoint. In this paper, we have proposed an approximating method for this principal eigenvalue. Further, we have faced the problem of finding the optimal position (by translation) of the support of the feedback stabilizing control in order to minimize both the infected population and the pollutant at a certain finite time. 相似文献
42.
A mild and efficient protocol for the synthesis of vicinal tricarbonyl compounds from β-dicarbonyls in a single step using cerium(IV) ammonium nitrate as a catalytic oxidant is described. Ease of execution, wide substrate scope and the suitability for the synthesis of commercially important compounds like ninhydrin, alloxan and oxoline make this reaction particularly noteworthy. 相似文献
43.
44.
Combined spectroscopic studies on post-functionalized Au25 cluster as an ATR-FTIR sensor for cations
Ani Baghdasaryan Elodie Brun Yuming Wang Giovanni Salassa Jrme Lacour Thomas Bürgi 《Chemical science》2021,12(21):7419
Recently, significant research activity has been devoted to thiolate-protected gold clusters due to their attractive optical and electronic properties. These properties as well as solubility and stability can be controlled by post-synthetic modification strategies. Herein, the ligand exchange reaction between Au25(2-PET)18 cluster (where 2-PET is 2-phenylethanethiol) and di-thiolated crown ether (t-CE) ligands bearing two chromophores was studied. The post-functionalization aimed to endow the cluster with ion binding properties. The exchange reaction was followed in situ by UV-vis, 1H NMR and HPLC. MALDI mass analysis revealed the incorporation of up to 5 t-CE ligands into the ligand shell. Once functionalized MALDI furthermore showed complexation of sodium ions to the cluster. ATR-FTIR spectroscopic studies using aqueous solutions of K+, Ba2+, Gd3+ and Eu3+ showed noticeable spectral shifts of the C–O stretching band around 1100 cm−1 upon complexation. Further spectral changes point towards a conformational change of the two chromophores that are attached to the crown ether. Density functional theory calculations indicate that the di-thiol ligand bridges two staple units on the cluster. The calculations furthermore reproduce the spectral shift of the C–O stretching vibrations upon complex formation and reveal a conformational change that involves the two chromophores attached to the crown ether. The functionalized clusters have therefore attractive ion sensing properties due to the combination of binding properties, mainly due to the crown ether, and the possibility for signal transduction via an induced conformational change involving chromophore units.Using ligand exchange reactions an atomically precise gold cluster was functionalized with a di-thiolated crown ether. Using in situ infrared spectroscopy films of the resulting composite were shown to incorporate metal cations. 相似文献
45.
Pseudo almost periodic solutions for a model of hematopoiesis with an oscillating circulation loss rate 下载免费PDF全文
Ani Jiang 《Mathematical Methods in the Applied Sciences》2016,39(12):3215-3225
In this paper, a model of hematopoiesis with an oscillating circulation loss rate is investigated. By applying the exponential dichotomy theory, contraction mapping fixed‐point theorem, and differential inequality techniques, a set of sufficient conditions are obtained for the existence and exponential stability of positive pseudo almost periodic solutions of the model. Some numerical simulations are carried out to support the theoretical findings. Our results improve and generalize those of the previous studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
46.
Ivanović AZ Cupić ZD Janković MM Kolar-Anić LjZ Anić SR 《Physical chemistry chemical physics : PCCP》2008,10(38):5848-5858
Attractor reconstruction is done from the time series obtained by experimental investigation and by deterministic and stochastic simulation of the Bray-Liebhafsky oscillatory reaction. The appearance of deterministic chaos is confirmed and proven by both simulation and experiment, determining Lyapunov exponents for the sequences of flow rate values, as the control parameter. Moreover, unusual chaotic series were additionally recorded in the experiments, which cannot be found in deterministic numerical simulations. Therefore, an explanation of the difference between the dynamic behavior in the experiment and the deterministic simulation was sought and stochastic simulations based on the same reaction model were particularly useful. The fine structure of the chaotic windows, derived from the analysis of deterministic simulations in the range of flow rate values, made the system highly susceptible to noise induced effects, in general. 相似文献
47.
The UV irradiation effects on stability of polystyrene, poly(4-methoxystyrene), poly(4-methylstyrene), poly(α-methylstyrene), poly(4-tert-butylstyrene), poly(4-chlorostyrene), and poly(4-bromostyrene) in dichloromethane, dichloromethane, tetrahydrofuran, and N,N-dimethylformamide solutions were studied in the presence of oxygen at different intervals of irradiation time. The photodegradation was studied at 293 K using fluorescence spectroscopy. Solutions of these polymers were accompanied by quenching of monomer and excimer emissions during the exposure of their solutions to UV light, and by a change in the structure of the fluorescence spectrum. Irradiation of poly(4-methylstyrene) and poly(α-methylstyrene) at excitation wavelength of 265 nm showed an increase of fluorescence intensity of a broad band, at longer wavelength without clear maxima. This may indicate that photodestruction of these polymers by irradiation with light of frequency absorbed by the polymer, may start from a random chain scission, with the possibility of formation of polyene and carbonyl compounds. 相似文献
48.
Radical reactions have been a fascinating arena in organic chemistry for decades and the rapid progress in this field is the topic of this review. Generation of radicals through sustainable catalysis using photoredox catalysts and iron based catalysts have significantly expanded the scope of radical reactions for carbon–carbon and carbon-heteroatom bond formations in recent years. Selective transformations using silver salts and other single electron transfer oxidants have also played significant roles. Cascade reactions based on radical intermediates have even widened the potential of radical reactions for carbocyclic and heterocyclic constructions. The recent advances (2014–2017) in radical based methods for CC bond formations are discussed in this digest review. 相似文献
49.
Vijay Nair Rajeev S. Menon Ani Deepthi B. Rema Devi A.T. Biju 《Tetrahedron letters》2005,46(8):1337-1339
Isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones react in one-pot to afford novel spirocyclic compounds with double insertion of the isocyanide. 相似文献
50.
The catalytic cracking of heavy fuel oil was investigated over the equilibrium fluid catalytic cracking catalyst (E-Cat) as a base component with the mesoporous MCM-41 as an additive. The catalytic performance of the E-Cat/MCM-41 system was assessed in a fixed-bed MAT unit. The reaction was performed at temperatures of 500, 530, 550 and 600°C and the product distributions in both gaseous and liquid phases were studied. The yields of products including light olefins, liquefied petroleum gas (LPG), gasoline, dry gas, coke and also the conversions obtained over different temperatures were reported and some generalities discussed. The maximum yield of propylene (17.5%) was obtained at 550°C whereas the highest conversion and gasoline yield was gained at 530°C. An eight-lump kinetic model containing 11 kinetic parameters was considered. Those parameters were estimated based on experimental data at specific temperatures by fourth order Runge–Kutta algorithm and the least square method. In addition, Arrhenius equation was used to calculate apparent activation energies. The calculated data of the product yields were in a close agreement with the experimental data. 相似文献