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101.
Amoureux JP Morais C Trebosc J Rocha J Fernandez C 《Solid state nuclear magnetic resonance》2003,23(4):213-223
In complement to the previously proposed multiple-quantum magic-angle-spinning (MQMAS) and satellite transition MAS (STMAS) sequences, we describe a new two-dimensional high-resolution method, inverse-STMAS (I-STMAS) that allows second-order quadrupolar averaging. Like STMAS, I-STMAS correlates second-order quadrupole dephasing occurring on coherences related to the central transition (CT) and satellite transitions (STs), but does it in a reverse manner: CT evolves during the t1 period while STs are detected during t2. Although STMAS and I-STMAS are symmetric, there are some interesting and useful differences between the two methods. For example, we show that during the acquisition time t2, it is possible to over-sample the data and then to process them to suppress the CT–CT correlation resonance. 相似文献
102.
Iuga D Morais C Gan Z Neuville DR Cormier L Massiot D 《Journal of the American Chemical Society》2005,127(33):11540-11541
We show for the first time that it is possible to acquire high-resolution heteronuclear NMR correlation experiments in solid state between second-order-broadened half integer quadrupolar nuclei (i.e., 27Al and 17O) using the scalar J-coupling. The sensitivity of the experiment is dramatically improved at high fields (gain proportional to the fourth power of the principal field) with a combination of signal enhancement techniques. This turns a challenging experiment into a real tool. We apply this experiment to characterize a calcium aluminate glass in which we prove the presence of tricluster mu3 oxygen sites and describe the signature of their directly bonded aluminum sites. Applications involve a large range of possible pairs of quadrupolar nuclei in different materials, such as glasses, porous or mesoporous framework materials, zeolites, hybrid organic-inorganic, and bioinvolved materials. 相似文献
103.
A solid-state nuclear magnetic resonance (NMR) experiment, which provides high-resolution two-dimensional heteronuclear correlation (HETCOR) spectra between 27Al and 31P, is described. The first part of the experiment uses triple-quantum or quintuple-quantum magic-angle spinning (MQMAS) NMR of spin-5/2 nuclei (27Al) to produce an isotropic echo that is unaffected by the second-order quadrupolar broadening. The magnetization is then transferred to the spin-1/2 (31P) nuclei via cross-polarization (CP), resulting in isotropic resolution in both spectral dimensions. To illustrate its usefulness, this method (referred to as MQHETCOR) is applied to two important microporous framework aluminophosphates, hydrated VPI-5 and AIPO4-40. 相似文献
104.
Sara Silva Eduardo M. Costa Hlder Oliveira Vitor De Freitas Rui M. Morais Conceio Calhau Manuela Pintado 《Molecules (Basel, Switzerland)》2022,27(20)
Several arguments have been made to substantiate the need for natural antimicrobials for the food industry. With blueberry extracts, the most compelling are both their healthy connotation and the possibility of obtaining a multipurpose solution that can be an antioxidant, colorant, and antimicrobial. From an antimicrobial perspective, as blueberry/anthocyanin-rich extracts have been associated with a capacity to inhibit harmful bacteria while causing little to no inhibition on potential probiotic microorganisms, the study of potential benefits that come from synergies between the extract and probiotics may be of particular interest. Therefore, the present work aimed to evaluate the effect of an anthocyanin-rich extract on the adhesion of five different probiotics as well as their effect on the probiotics’ capacity to compete with or block pathogen adhesion to a mucin/BSA-treated surface. The results showed that, despite some loss of probiotic adhesion, the combined presence of extract and probiotic is more effective in reducing the overall amount of adhered viable pathogen cells than the PROBIOTIC alone, regardless of the probiotic/pathogen system considered. Furthermore, in some instances, the combination of the extract with Bifidobacterium animalis Bo allowed for almost complete inhibition of pathogen adhesion. 相似文献
105.
Frida Mariana Morais Friederike Buchholz Tom Hartmann Johannes Lerchner Thomas R. Neu Bärbel Kiesel Hauke Harms Thomas Maskow 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2203-2210
Bacteriophages or phage-derived biological structures are a promising alternative to the application of antibiotics to eradicate biofilms. These countermeasures are highly cell specific. For a better understanding of the sequence of the underlying processes (attachment, infection, multiplication, phage release), for optimization of phage applications, or simply for screening of suitable phages or phage-derived enzymes, real-time monitoring devices are urgently required. Calorimetry is promising because it is non-invasive and quantitatively connected to the metabolic fluxes. Chip-calorimetry provides real-time information about biofilm eradication by phages. This was confirmed by comparison with reference analyses (i.e., confocal laser scanning microscopy, colony plate counts, or phage titre determination). Furthermore, chip-calorimetry provides additional information which was not captured by the reference methods such as the enhanced cell-specific heat production caused by the infection process and a residual activity of seemingly persistent bacteria. 相似文献
106.
Jacqueline Moreira de Morais Orlando David Henrique dos Santos Tatiani Delicato Pedro Alves da Rocha‐Filho 《Journal of Dispersion Science and Technology》2013,34(7):1009-1014
Emulsion stability is controlled by the physicochemical properties of the adsorbed layers formed on the surface of the droplets. Zeta potential and droplet size measured initially and during storage can estimate O/W emulsion stability. The aim of this study was to characterize and evaluate the effects of different hydrolyzable compounds employed in pharmaceutical and cosmetic preparations on the zeta potential and droplet size of canola O/W nano‐emulsions and, consequently, the emulsion stability. The samples containing additives demonstrated significant change in zeta potential, but in spite of that, no macroscopic instability was observed. Yet the droplet size values did not undergo significant change. 相似文献
107.
A turbidimetric flow-injection system was developed for the determination of sulfate in natural and residual water samples, with no previous treatment, using spectrophotometric detection. The precipitating agent, 7.0% (w/v) barium chloride solution prepared in 0.10% (w/v) polyvinyl alcohol, was added by using the merging-zones approach. A 100 mg/L sulfate solution in 0.07M nitric acid was mixed with the sample before it entered the injection loop to improve the detection limit, provide in-line pH adjustment, and prevent the interference of some anionic species. The relative standard deviations of the results were between 1.4 and 3.0% and were in agreement with results obtained by the reference method. Samples within a linear concentration range of 10-120 mg SO4(2-)/L can be analyzed at a rate of 40/h. The detection limit is 5 mg SO4(2-)/L. 相似文献
108.
M. Dalla Riva J. Morais P. Musolino 《Mathematical Methods in the Applied Sciences》2013,36(12):1569-1582
The purpose of this paper is to construct a family of fundamental solutions for elliptic partial differential operators with quaternion constant coefficients. The elements of such family are expressed by means of functions, which depend jointly real analytically on the coefficients of the operators and on the spatial variable. We show some regularity properties in the frame of Schauder spaces for the corresponding single layer potentials. Ultimately, we exploit our construction by showing a real analyticity result for perturbations of the layer potentials corresponding to complex elliptic partial differential operators of order two. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
109.
Effects of structure and reactivity of renewable origin alcohols in the conversion and selectivity of the SnCl2-catalyzed reactions in the presence and absence of urea were assessed. Convenient simple and suitable method for the synthesis of carbamates from renewable origin alcohols and urea in one-step are provided. We have assessed the activity of SnCl2 catalyst, a commercially affordable Lewis acid, in reactions of urea alcoholysis with different natural origin alcohols (geranyl, neryl, bornyl, cinnamyl, α-terpinyl and benzyl alcohols), aiming to synthesize carbamates, which are biologically active compounds, building blocks in organic synthesis and raw material to synthesize polyurethanes. The low cost of urea, the water tolerant catalyst and phosgene free reaction are positive aspects of this carbamates synthesis process. The different reaction pathways were assessed. A mechanism was proposed based on FT-IR experiments and experimental data. 相似文献
110.
M. A. González-Martínez S. Morais R. Puchades A. Maquieira M. P. Marco D. Barceló 《Fresenius' Journal of Analytical Chemistry》1998,361(2):179-184
Intensive agriculture associated with the use of large amounts of different pesticides, together with the growing concern
about the potential contamination of ground water, have brought about the need for developing fast screening methods. This
work presents the automation of an enzyme-linked immunosorbent assay for atrazine by means of a flow-through system. Three
different solid supports for antibody immobilization were compared in a direct competitive assay format. Sensitivity reached
in all cases was below the maximum level allowed in the EU (100 ng L–1). Cross-reactivity of atrazine-related compounds was also studied. The performance of the different supports is discussed
regarding sensitivity and immunosurface regeneration.
Received: 21 July 1997 / Revised: 7 November 1997 / Accepted: 11 November 1997 相似文献