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151.
H.?S.?Barud C.?A.?RibeiroEmail author Marisa?S.?Crespi M.?A.?U.?Martines J.?Dexpert-Ghys R.?F.?C.?Marques Y.?Messaddeq S.?J.?L.?Ribeiro 《Journal of Thermal Analysis and Calorimetry》2007,87(3):815-818
Cellulose–phosphate composite
membranes have been prepared from bacterial cellulose membranes (BC) and sodium
polyphosphate solution. The structure and thermal behavior of the new composites
were evaluated by X-ray diffraction (XRD), 31P-nuclear
magnetic resonance (NMR), scanning electron microscopy (SEM), differential
scanning calorimetry (DSC), thermogravimetry (TG) and thermomechanical analysis
(TMA). From XRD analyses the Iα and Iβ cellulose crystalline phases
were identified together with crystalline sodium phosphate that covers the
cellulose microfibrils as revealed by SEM. 31P
NMR spectra show peaks assigned to Q0 and Q1
phosphate structures to be compared to the Q2 units
that characterize the precursor polyphosphate. Glass transition temperature, T
g, obtained from TMA curves
and thermal stability obtained from TG and DSC measurements, were observed
to be dependent on the phosphate content. 相似文献
152.
Evaneide Nascimento Lima Marisa Spirandeli Crespi C. A. Ribeiro Sonia de Almeida 《Journal of Thermal Analysis and Calorimetry》2007,90(3):823-826
Leachate samples from a sanitary landfill of Araraquara city and composting usine of Vila Leopoldina, São Paulo, Brazil were lyophilized to remove the water content. TG/DTG curves at different heating rates were recorded. The second step of the thermal decomposition of leachate from the Araraquara landfill (CB1), from the composting usine from Vila Leopoldina (CB2) from the organic phase extracted (FO) and aqueous phase (FA) were all kinetically evaluated using the non-isothermal method.By Flynn-Wall isoconversional method the following values were obtained: E=234±3.65 kJ mol?1 and logA=29.7±0.58 min?1 for CB1; E=129±1.66 kJ mol?1 and logA=11.8±0.10 min?1 for CB2; E=51.6±1.35 kJ mol?1 and logA=6.09±0.09 min?1 for FO and E=76.91±6.33 kJ mol?1 and logA=8.88±0.7 min?1 for FA with 95% confidence level. Applying the procedures of Málek and Koga, SB kinetic model (?esták-Berggren) is the most appropriate to describe the decomposition of CB1, CB2, FO and FA. 相似文献
153.
Dr. Marisa Rico‐Santacruz Dr. Elena Serrano Dr. Giuseppe Marcì Dr. Elisa I. García‐López Dr. Javier García‐Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18338-18344
Mesoporous titania–organosilica nanoparticles comprised of anatase nanocrystals crosslinked with organosilica moieties have been prepared by direct co‐condensation of a titania precursor, tetrabuthylortotitanate (TBOT), with two organosilica precursors, 1,4‐bis(triethoxysilyl) benzene (BTEB) and 1,2‐bis(triethoxysilyl) ethane (BTEE), in mild conditions and in the absence of surfactant. These hybrid materials show both high surface areas (200–360 m2 g?1) and pore volumes (0.3 cm3 g?1) even after calcination, and excellent photoactivity in the degradation of rhodamine 6G and in the partial oxidation of propene under UV irradiation, especially after the calcination of the samples. During calcination, there is a change in the TiIV coordination and an increase in the content of Si?O?Ti moieties in comparison with the uncalcined materials, which seems to be responsible for the enhanced photocatalytic activity of hybrid titania–silica materials as compared to both uncalcined samples and the control TiO2. 相似文献
154.
Canzoneri M Bruno M Rosselli S Russo A Cardile V Formisano C Rigano D Senatore F 《Natural product communications》2011,6(7):1023-1026
Salvia verbenaca L. (syn. S. minore) is a perennial herb known in the traditional medicine of Sicily as "spaccapetri" and is used to resolve cases of kidney stones, chewing the fresh leaves or in decoction. The chemical composition of the essential oil obtained from aerial parts of S. verbenaca collected in Piano Battaglia (Sicily) on July 2009, was analyzed by GC and GC-MS. The oil was strongly characterized by fatty acids (39.5%) and carbonylic compounds (21.2%), with hexadecanoic acid (23.1%), (Z)-9-octadecenoic acid (11.1%) and benzaldehyde (7.3%) as the main constituents. The in vitro activity of the essential oil against some microorganisms in comparison with chloramphenicol by the broth dilution method was determined. The oil exhibited a good activity as inhibitor of growth of Gram + bacteria. 相似文献
155.
Liu L Yang J Li J Dong J Sišak D Luzzatto M McCusker LB 《Angewandte Chemie (International ed. in English)》2011,50(35):8139-8142
Less is more: an open-framework zirconium phosphate with unusual 7-ring channels was synthesized ionothermally from a deep-eutectic solvent. This small-pore material displays a CO(2)/CH(4) adsorption ratio (17.3 at 1 bar) that is significantly higher than that of typical 8-ring materials, making it highly attractive for CO(2)/CH(4) separations. 相似文献
156.
Riva E Rencurosi A Gagliardi S Passarella D Martinelli M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(22):6221-6226
An efficient total synthesis of the natural alkaloid (+)-dumetorine by using flow technology is described. The process entailed five separate steps starting from the enantiopure (S)-2-(piperidin-2-yl)ethanol 4 with 29% overall yield. Most of the reactions were carried out by exploiting solvent superheating and by using packed columns of immobilized reagents or scavengers to minimize handling. New protocols for performing classical reactions under continuous flow are disclosed: the ring-closing metathesis reaction with a novel polyethylene glycol-supported Hoveyda catalyst and the unprecedented flow deprotection/Eschweiler-Clarke methylation sequence. The new protocols developed for the synthesis of (+)-dumetorine were applied to the synthesis of its simplified natural congeners (-)-sedamine and (+)-sedridine. 相似文献
157.
Marisa Di Sabatino Anne L. Dons Joachim Hinrichs Lars Arnberg 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(2):144-148
A commercially available Element GD, the latest generation of glow discharge mass spectrometry (GDMS), has been used for quantitative analysis of impurities in silicon for photovoltaic applications (PV silicon). In order to be able to accurately measure impurities in silicon, relative sensitivity factors (RSFs) need to be determined. These factors are, currently, given only for steel matrices. In this study, standard silicon materials with known levels of impurities have been produced and independent analytical methods have been used for determining the RSFs for silicon matrices. It has been found that the tuning parameters of the Element GD, mainly the discharge gas flow rate, influence the RSF values. In addition, it has been found that RSF values are matrix specific; RSFs for a silicon matrix differ significantly from those for metallic conductor matrices even under identical instrumental parameters. A study of the relative reproducibility in the quantitative analysis of impurities in solar cells silicon has shown variations between 5% and 12%. 相似文献
158.
Marcelo Kobelnik Douglas Lopes Cassimiro Clóvis. A. Ribeiro Jorge M. V. Capela Diogines S. Dias Marisa S. Crespi 《Journal of Thermal Analysis and Calorimetry》2012,108(1):213-218
The thermal behaviour of Mg-diclofenac compound was evaluated by simultaneous TG-DTA and DSC. The profile of the DSC curves
showed that this compound possesses two transition phases: endothermic and exothermic between 170–180 °C and 185–195 °C, respectively.
The endothermic reaction is reversible (enantiotropic). Thus, different experimental conditions, i.e. masses sample, open
and crimped lids crucible, static and dynamic atmospheres were utilized for DSC analysis for evaluation of this transition
phase. In a static atmosphere the enantiotropic reaction was not observed. The obtained data were utilized to obtain the kinetic
parameters, which were calculated by the Capela and Ribeiro method. The results show that the activation energy for the transition
phase depends on the different experimental conditions. 相似文献
159.
Gustavo Martínez-Sierra Marisa Miranda-Tirado 《International Journal of Mathematical Education in Science & Technology》2013,44(5):700-720
This paper reports a qualitative research that identifies Mexican high school students’ social representations of mathematics. For this purpose, the social representations of ‘mathematics’, ‘learning mathematics’ and ‘teaching mathematics’ were identified in a group of 50 students. Focus group interviews were carried out in order to obtain the data. The constant comparative style was the strategy used for the data analysis because it allowed the categories to emerge from the data. The students’ social representations are: (A) Mathematics is…(1) important for daily life, (2) important for careers and for life, (3) important because it is in everything that surrounds us, (4) a way to solve problems of daily life, (5) calculations and operations with numbers, (6) complex and difficult, (7) exact and (6) a subject that develops thinking skills; (B) To learn mathematics is…(1) to possess knowledge to solve problems, (2) to be able to solve everyday problems, (3) to be able to make calculations and operations, and (4) to think logically to be able to solve problems; and (C) To teach mathematics is…(1) to transmit knowledge, (2) to know to share it, (3) to transmit the reasoning ability, and (4) to show how to solve problems. 相似文献
160.
The gills and the respiratory swim bladders of juvenile specimens (mean body mass 100 g) of the basal teleost Arapaima gigas (Cuvier 1829) were evaluated using stereological methods in vertical sections. The surface areas, harmonic mean barrier thicknesses and morphometric diffusing capacities for oxygen and carbon dioxide were estimated. The average respiratory surface area of the swim bladder (2173 cm2 kg?1) exceeded that of the gills (780 cm2 kg?1) by a factor of 2.79. Due to the extremely thin air–blood barrier in the swim bladder (harmonic mean 0.22 μm) and the much thicker water–blood barrier of the gills (9.61 μm), the morphometric diffusing capacity for oxygen and carbon dioxide was 88 times greater in the swim bladder than in the gills. These data clearly indicate the importance of the swim bladder, even in juvenile A. gigas that still engage in aquatic respiration. Because of the much greater diffusion constant of CO2 than O2 in water, the gills also remain important for CO2 release. 相似文献