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排序方式: 共有353条查询结果,搜索用时 15 毫秒
341.
Rocco G Toledo C Ahumada I Sepúlveda B Cañete A Richter P 《Journal of chromatography. A》2008,1193(1-2):32-36
An efficient continuous pressurized solvent extraction (PSE) method assisted by ultrasound energy was developed for the extraction of polychlorinated biphenyls (PCBs) from biosolids. Analytes were determined in the extracts by gas chromatography-mass spectrometry in selected ion monitoring (SIM) mode. A screening-type experimental design pointing to dynamic extraction time as the only significant variable in the extraction process was carried out to optimize PCB extraction from the biosolids. Final selected conditions for PSE were extraction temperature, 50 degrees C; static extraction time, 0 min; and dynamic extraction time, 30 min. Recovery of the PSE method was 73%, which was significantly improved (103%) when PSE was assisted with 30-min ultrasound (US-PSE). Precision of the overall method, expressed as relative standard deviation, was 3.6% and the detection limit was 0.037 mg/kg. The method was applied to the determination of PCBs in biosolids from different water treatment plants from central Chile. 相似文献
342.
Prof. Arturo Arduini Dr. Rocco Bussolati Prof. Alberto Credi Simone Monaco Prof. Andrea Secchi Dr. Serena Silvi Prof. Margherita Venturi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(50):16203-16213
The development of a pseudorotaxane motif capable of performing unidirectional threading and dethreading processes under control of external stimuli is particularly important for the construction of processive linear motors based on rotaxanes and, at least in principle, it discloses the possibility to access to rotary motors based on catenanes. Here, we report a strategy to obtain the solvent‐controlled unidirectional transit of a molecular axle through a molecular wheel. It is based on the use of appropriately designed molecular components, the essential feature of which is their non‐symmetric structure. Specifically they are an axle containing a central electron‐acceptor 4,4′‐bipyridinium core functionalized with a hexanol chain at one side, and a stilbene unit connected through a C6 chain at the other side, and a heteroditopic tris(phenylureido)‐calix[6]arene wheel. In apolar solvents the axle threads into the wheel from its upper rim and with the end carrying the OH group, giving an oriented pseudorotaxane structure. After a stoppering reaction, which replaces the small hydroxy group with a bulky diphenylacetyl moiety, and replacement of the apolar solvent with a polar one, dethreading occurs through the slippage of the stilbene unit from the lower rim of the wheel, that is, in the same direction of the threading process. The essential role played by the stilbene unit to achieve the unidirectional transit of the axle through the wheel, and to tune the dethreading rate by light is also demonstrated. 相似文献
343.
Antonio RanieriGianantonio Battistuzzi Marco Borsari Carlo Augusto BortolottiGiulia Di Rocco Stefano MonariMarco Sola 《Electrochemistry communications》2012,14(1):29-31
Urea-unfolded yeast iso-1-cytochrome c electrostatically adsorbed on a gold electrode coated with an anionic self-assembled monolayer yields a heme-mediated electrocatalytic reduction of H2O2 (pseudo-peroxidase activity). Under the same conditions, native cytochrome c is inactive. In the unfolded protein, the Met80 heme iron ligand is replaced by a histidine residue yielding a bis-His-ligated form. H2O2 electrocatalysis occurs with an efficient mechanism likely involving direct H2O2 interaction with the iron(II) center and formation of a transient ferryl group. Comparison of the catalytic activity of a few urea-unfolded single and double Lys-to-Ala variants shows that the kinetic affinity of H2O2 for the heme iron and kcat of the bis-His-ligated form are strongly affected by the geometry of protein adsorption, controlled by specific surface lysine residues. 相似文献
344.
Francesco Sansone Alessandro Casnati Rocco Ungaro Mohamed Saadioui Jean-François Dozol 《Tetrahedron》2006,62(29):6749-6753
Three calix[6]arene derivatives (1a-c) and two calix[8]arene derivatives (2a,b), with six and eight CMPO residues, respectively, attached to the narrow/lower rim via ether links, were synthesised. Preliminary liquid-liquid extraction studies for Eu(III) and Am(III) from aqueous nitric acid to o-nitrophenylhexyl ether reveal remarkable properties with respect to efficiency and selectivity, especially for the tert-butylcalix[6]arene derivative with a -(CH2)3- spacer. 相似文献
345.
Sansone F Dudic M Donofrio G Rivetti C Baldini L Casnati A Cellai S Ungaro R 《Journal of the American Chemical Society》2006,128(45):14528-14536
Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lower rim bind to DNA, condense it, and in some cases, promote cell transfection depending on their structure and lipophilicity. Atomic force microscopy (AFM) studies indicate that upon DNA binding the hydrophobic association of the lipophilic chains of cone guanidinium calix[4]arenes drives the formation of intramolecular DNA condensates, characterized by DNA loops emerging from a dense core. Furthermore, hexyl and octyl chains confer to these calixarenes cell transfection capabilities. Conversely, larger and conformationally mobile calix[6]- and calix[8]arene methoxy derivatives form intermolecular aggregates characterized by "gorgonlike" structures composed of multiple plectomenes. These adducts, in which interstrand connections are dominated by electrostatic interactions, fail to promote cell transfection. Finally, calix[4]arenes in a 1,3-alternate conformation show an intermediate behavior because they condense DNA, but the process is driven by charge-charge interactions. 相似文献
346.
Stefano Vecchio Romolo Di Rocco Carla Ferragina 《Journal of Thermal Analysis and Calorimetry》2009,97(3):805-810
The thermal behaviour of the complexes formed in situ between the aromatic diamine 1,10-phenanthroline and the Co(II) and
Ni(II) ions intercalated between the layers of γ-zirconium phosphate was studied by simultaneous TG/DSC techniques. The obtained
materials show similar thermal behaviour: after a multi-step dehydration process they showed an oxidative decomposition in
only one step. The kinetic study of the decomposition process was performed using both the model-free methods of Ozawa-Flynn-Wall
and Kissinger. The former method provides a negligible dependence of activation energy on the degree of reaction α for both
materials. Activation energies derived by the Kissinger method show a good agreement with the mean values derived by the Ozawa-Flynn-Wall
method. The Arrhenius rate constants determined using also the pre-exponential factor values demonstrate that their thermal
stability can be considered comparable, within the experimental uncertainty. Finally, a reliable method was applied to determine
the model function from the best fit between the numerical dependence of the integral function g(α) vs. α and several theoretical model dependencies reported in literature for the most commonly used models. A Mampel first-order
reaction model was selected to describe the thermal decomposition in both the materials studied. 相似文献
347.
In this paper, we develop a theory of monotone operators in the framework of abstract convexity. First, we provide a surjectivity result for a broad class of abstract monotone operators. Then, by using an additivity constraint qualification, we prove a generalization of Fenchel??s duality theorem in the framework of abstract convexity and give some criteria for maximal abstract monotonicity. Finally, we present necessary and sufficient conditions for maximality of abstract monotone operators. 相似文献
348.
Edible Mushrooms as Source of Fibrin(ogen)olytic Enzymes: Comparison between Four Cultivated Species
Tania Petraglia Tiziana Latronico Grazia Maria Liuzzi Angela Fanigliulo Aniello Crescenzi Rocco Rossano 《Molecules (Basel, Switzerland)》2022,27(23)
Cardiovascular diseases represent the main cause of death. A common feature of cardiovascular disease is thrombosis resulting from intravascular accumulation of fibrin. In the last years, several fibrinolytic enzymes have been discovered in many medicinal or edible mushrooms as potential new antithrombotic agents. This study aimed to compare the fibrin(ogen)olytic activity of crude extracts from the fruiting bodies of four cultivated edible mushrooms: Lentinula edodes, Pleurotus ostreatus, Pleurotus eryngii, and Agrocybe aegerita. Fibrin(ogen)olytic activity was assessed by fibrin plate, spectrophotometric assay and electrophoretic analysis (SDS-PAGE and zymography). The highest activity was detected for P. ostreatus followed by P. eryngii, L. edodes and A. aegerita. Results indicated that enzymes exhibited maximum activity at pH 6–7 and 30–40 °C, respectively. Enzyme activity was inhibited by serine and metalloprotease inhibitors. We proposed a new index called the Specific Fibrin(ogen)olytic Index (SFI), which allows specification of the proportion of the total proteolytic capacity due to the fibrin(ogen)olytic activity. These data suggest that the extracts from fruiting bodies or powdered mushrooms can be used as functional ingredients for the development of new functional foods that may act as thrombolytic agents responding, at the same time, to the increasing demand for safe, healthy and sustainable food. 相似文献
349.
Giulia Di Rocco Antonio Ranieri Marco Borsari Marco Sola Carlo Augusto Bortolotti Gianantonio Battistuzzi 《Molecules (Basel, Switzerland)》2022,27(17)
The Met80Ala variant of yeast cytochrome c is known to possess electrocatalytic properties that are absent in the wild type form and that make it a promising candidate for biocatalysis and biosensing. The versatility of an enzyme is enhanced by the stability in mixed aqueous/organic solvents that would allow poorly water-soluble substrates to be targeted. In this work, we have evaluated the effect of dimethylsulfoxide (DMSO) on the functionality of the Met80Ala cytochrome c mutant, by investigating the thermodynamics and kinetics of electron transfer in mixed water/DMSO solutions up to 50% DMSO v/v. In parallel, we have monitored spectroscopically the retention of the main structural features in the same medium, focusing on both the overall protein structure and the heme center. We found that the organic solvent exerts only minor effects on the redox and structural properties of the mutant mostly as a result of the modification of the dielectric constant of the solvent. This would warrant proper functionality of this variant also under these potentially hostile experimental conditions, that differ from the physiological milieu of cytochrome c. 相似文献
350.
Dr. Rosarita D'Orsi Viviana Claudia Canale Dr. Rocco Cancelliere Dr. Omar Hassan Omar Prof. Claudia Mazzuca Prof. Laura Micheli Prof. Alessandra Operamolla 《European journal of organic chemistry》2023,26(11):e202201457
The surface functionalization of cellulose nanocrystals is presently considered a useful and straightforward tool for accessing very reliable biocompatible and biodegradable nanostructures with tailored physical and chemical properties. However, to date the fine characterization of the chemical appendages introduced onto cellulose nanocrystals remains a challenge, due to the low sensitivity displayed by the most common techniques towards surface functionalization. In this paper, we demonstrate the easy functionalization of cellulose nanocrystals with aliphatic and aromatic amines, demonstrating the tunability of their properties in dependence on the selected functionality. Then, we apply to colloidal suspensions of modified nanocrystals 1H NMR analysis to elucidate their surface structure. To the best of our knowledge, this is the first report where such investigation was performed on cellulose nanocrystals presenting both surface and reducing end modification. These results involve interesting implications for the fields of cultural heritage and of materials chemistry. 相似文献