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71.
Amer?Baniodeh Abhishake?Mondal Ravil?GaleevEmail authorView authors OrcID profile Andrei?Sukhanov Rushana?Eremina Violeta?Voronkova Christopher?E.?Anson Annie?K.?Powell 《Applied magnetic resonance》2017,48(1):101-113
The DyIII ions in the dimer [Dy2(H2tea)2(O2CPh)4]·2H2O (1) (H3tea = triethanolamine) have the 9-coordinate monocapped square-antiprismatic ligand field environment. Compound 1 shows slow relaxation of magnetization which is observable only with applied magnetic fields. This is consistent with the idea that low-symmetry ligand fields allow for the quantum tunneling of magnetization. This is reflected by the fact that there are no observable maxima in the out-of-phase ac susceptibility above 1.8 K. The {g}-tensor of the DyIII ions {g x = 11, g y = 8.2, g z = 1} further underlying the reduced uniaxiality in this system was determined in electron paramagnetic resonance (X- and Q-band) studies of 1 at temperatures down to 4 K. 相似文献
72.
We report the manipulation of a Kondo resonance originating from the spin-electron interactions between a two-dimensional molecular assembly of TBrPP-Co molecules and a Cu(111) surface at 4.6 K. By manipulating nearest-neighbor molecules with a scanning tunneling microscope tip we are able to tune the spin-electron coupling of the center molecule inside a hexagonal molecular assembly in a controlled step-by-step manner. The Kondo temperature increases from 105 to 170 K with decreasing the number of nearest neighbor molecules from six to zero. The scattering of surface electrons by the molecules located at edges of the molecular layer reduces the spin-electron coupling strength for the molecules inside the layer. Investigations of different molecular arrangements indicate that the observed Kondo resonance is independent on the molecular lattice. 相似文献
73.
Raminta Skipitytė Agnė Mašalaitė Andrius Garbaras Rūta Mickienė Ona Ragažinskienė Violeta Baliukonienė 《Isotopes in environmental and health studies》2017,53(3):243-260
Stable isotope analysis was applied to describe the poultry house environment. The poultry house indoor environment was selected for this study due to the relevant health problems in animals and their caretakers. Air quality parameters including temperature, relative humidity, airflow rate, NH3, CO2 and total suspended particles, as well as mean levels of total airborne bacteria and fungi count, were measured. Carbon isotope ratios (13C/12C) were obtained in size-segregated aerosol particles. The carbon (13C/12C) and nitrogen (15N/14N) isotope ratios were measured in feed, litter, scrapings from the ventilation system, feathers and eggs. Additionally, the distribution of δ13C and δ15N values in different tissues of the chicken was examined. The airborne bacteria and fungi extracted from the air filters collected from poultry farms were grown in the laboratory in media with known isotope values and measured for stable isotope ratios. Analysis of isotope fractionation between microorganisms and their media indicated the applicability of stable isotope analysis in bulk samples for the identification of source material. The analysed examples imply that stable isotope analysis can be used to examine the indoor environment along with its biology and ecology, and serve as an informative bioanalytical tool. 相似文献
74.
Block parallel iterative methods for the solution of mildly nonlinear systems of equations of the form are studied. Two-stage methods, where the solution of each block is approximated by an inner iteration, are treated. Both
synchronous and asynchronous versions are analyzed, and both pointwise and blockwise convergence theorems provided. The case
where there are overlapping blocks is also considered. The analysis of the asynchronous method when applied to linear systems
includes cases not treated before in the literature.
Received June 5, 1997 / Revised version received December 29, 1997 相似文献
75.
tefan Ailer Silvia Jakabov Lucia Beneov Violeta Ivanova-Petropulos 《Molecules (Basel, Switzerland)》2022,27(11)
The review summarizes the latest scientific findings and recommendations for the prevention of three very common wine faults of non-microbial origin. The first group, presented by the reductive aromas, is caused mainly by excessive H2S and other volatile sulfur compounds with a negative impact on wine quality. The most efficient prevention of undesirable reductive aromas in wine lies in creating optimal conditions for yeast and controlling the chemistry of sulfur compounds, and the pros and cons of correction methods are discussed. The second is browning which is associated especially with the enzymatic and non-enzymatic reaction of polyphenols and the prevention of this fault is connected with decreasing the polyphenol content in must, lowering oxygen access during handling, the use of antioxidants, and correction stands for the use of fining agents. The third fault, atypical aging, mostly occurs in the agrotechnics of the entire green land cover in the vineyard and the associated stress from lack of nutrients and moisture. Typical fox tones, naphthalene, or wet towel off-odors, especially in white wines are possible to prevent by proper moisture and grassland cover and alternating greenery combined with harmonious nutrition, while the correction is possible only partially with an application of fresh yeast. With the current knowledge, the mistakes in wines of non-microbial origin can be reliably prevented. Prevention is essential because corrective solutions for the faults are difficult and never perfect. 相似文献
76.
Ralitsa Chimshirova Milena Popova Amina Chakir Violeta Valcheva Simeon Dimitrov Boryana Trusheva Abderrahmane Romane Vassya Bankova 《Molecules (Basel, Switzerland)》2022,27(7)
The chemical composition and antimicrobial activity of propolis from a semi-arid region of Morocco were investigated. Fifteen compounds, including triterpenoids (1, 2, 7–12), macrocyclic diterpenes of ingol type (3–6) and aromatic derivatives (13–15), were isolated by various chromatographic methods. Their structures were elucidated by a combination of spectroscopic and chiroptical methods. Compounds 1 and 3 are new natural compounds, and 2, 4–6, and 9–11 are newly isolated from propolis. Moreover, the full nuclear magnetic resonance (NMR) assignments of three of the known compounds (2, 4 and 5) were reported for the first time. Most of the compounds tested, especially the diterpenes 3, 4, and 6, exhibited very good activity against different strains of bacteria and fungi. Compound 3 showed the strongest activity with minimum inhibitory concentrations (MICs) in the range of 4–64 µg/mL. The combination of isolated triterpenoids and ingol diterpenes was found to be characteristic for Euphorbia spp., and Euphorbia officinarum subsp. echinus could be suggested as a probable and new plant source of propolis. 相似文献
77.
Preparation of photocrosslinked sol‐gel composites based on urethane‐acrylic matrix,silsesquioxane sequences,TiO2, and Ag/Au Nanoparticles for use in photocatalytic applications
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Andreea L. Chibac Violeta Melinte Tinca Buruiana Ionel Mangalagiu Emil C. Buruiana 《Journal of polymer science. Part A, Polymer chemistry》2015,53(10):1189-1204
An acid urethane oligodimethacrylate based on poly(ethylene glycol) was synthesized and used in the preparation of hybrid composites containing silsesquioxane sequences and titania domains formed through sol‐gel reactions along with silver/gold nanoparticles (Ag/Au NPs) in situ photogenerated during the UV‐curing process. The photopolymerization kinetics studied by Fourier transform infrared spectroscopy and photoDSC showed that the photoreactivity of the investigated formulations depends on the amount of titanium butoxide (5–20 wt %) added in the system subjected to UV irradiation. The introduction of 1 wt % AgNO3/AuBr3 in formulations slightly improved the degree of conversion but diminished the polymerization rates. The formation of hybrid materials comprising predominantly amorphous TiO2/SiO2 NPs, with or without Ag/Au NPs, was confirmed through specific analyses. The evaluation of photocatalytic activity demonstrated that the synthesized hybrid films are suitable for the complete removal of organic pollutants (phenolic compounds) from water under UV irradiation (200–350 min) at low intensity (found in the solar radiation). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1189–1204 相似文献
78.
Andreea L. Chibac Violeta Melinte Tinca Buruiana Emil C. Buruiana 《Journal of polymer science. Part A, Polymer chemistry》2014,52(5):728-738
Urethane–urea dimethacrylates were synthesized and used in the preparation of nanocomposites containing gold nanoparticles (Au NPs) in situ photogenerated during the UV‐curing process in the absence of reducing agent. A study of the photopolymerization kinetics showed that the photoreactivity of the monomers alone or in combination with a dual urethane benzophenone (BP) macromer is dependent on the nature of photoinitiator (Irgacure819, BP/amine) and the formulation composition. It was found that the addition of 1 wt % AuBr3 in monomers slightly improved the polymerization rate and the degree of conversion. The formation of Au NPs into the network was confirmed through UV–vis, XRD, EDX, SAXS, and TEM analyses, the last indicating the existence of NPs with size around 8.5 nm and spherical/triangle shapes. On addition of 10 wt % 2[N‐methacryloyloxyethyl‐(N'‐2‐thioethyl)] (urea) in formulation, the Au NPs (200 nm) became predominantly cubic/hexagonal in shape. The composite films emit fluorescence at 575 nm, and this property could be exploited in the field of fluorescent bio/sensors. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 728–738 相似文献
79.
80.
By reacting [Pd(
)(μ-Cl)]2 with AgClO4 in NCMe, the corresponding cationic complexes [Pd(
)(NCMe)2]ClO4 (
= phenylazophenyl-C2,N1; dimethylbenzylamine-C2,N; 8-methylquinoline-C8,N) can be obtained. Solutions containing the cations [Pd(
)(S)2]+ are obtained when the reaction is carried out in tetrahydrofuran or acetone (S). The treatment of these solutions with bidentate ligands (L—L) (Ph2PCH2PPh2,Ph2PNHPPh2 or Ph2PCH2PPh2CHC(O)Ph) gives the mononuclear [Pd(
)(L3l)]ClO4 complexes, with L3l acting as a chelate ligand. On the other hand [Pd(
(μ-Cl)]2 reacts with L3l (Ph2PCH2PPh2, Ph2PNHPPh2) yielding [Pd(
)Cl(L3l)] with L3l acting as monodentate. The reactions between [Pd(
)(NCMe)2]ClO4 and 2,2′-bipyrimidyl give rise to the formation of the mononuclear [Pd(
) (bipym)]ClO4 or binuclear [Pd2(
)2(μ-bipym)](ClO4)2, [(
)Pd(μ-bipym)Pd(
)](ClO4)2 derivatives. Finally [Pd(
)Cldppm] (dppm = Ph2PCH2PPh2) react with NaH producing the neutral complexes [Pd(
)(ddppm)] (ddppm = Ph2PCHPPh2) which by reaction with HCl lead again to the starting materials [Pd(
)Cl(dppm)]. 相似文献