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排序方式: 共有414条查询结果,搜索用时 93 毫秒
191.
Nicola Ferrari Cecilia Ada Maestri Paolo Bettotti Mario Grassi Michela Abrami Marina Scarpa 《Molecules (Basel, Switzerland)》2021,26(9)
The influence of the physical, rheological, and process parameters on the cellulose nanocrystal (CNC) drops before and after external gelation in a CaCl2 solution was investigated. The dominant role of the CNC’s colloidal suspension properties, such as the viscous force, inertial, and surface tension forces in the fluid dynamics was quantitatively evaluated in the formation of drops and jellified beads. The similarity and difference between the behavior of carbohydrate polymers and rod-like crystallites such as CNC were enlightened. Pump-driven and centrifugally-driven external gelation approaches were followed to obtain CNC hydrogel beads with tunable size and regular shape. A superior morphological control—that is, a more regular shape and smaller dimension of the beads—were obtained by centrifugal force-driven gelation. These results suggest that even by using a simple set-up and a low-speed centrifuge device, the extrusion of a colloidal solution through a small nozzle under a centrifugal field is an efficient approach for the production of CNC hydrogel beads with good reproducibility, control over the bead morphology and size monodispersion. 相似文献
192.
Lorenza Gardella Michela Calabrese Orietta Monticelli 《Colloid and polymer science》2014,292(9):2391-2398
In this study, maleic-anhydride-grafted polylactide (PLA-g-MA) was investigated as a potential compatibilizing agent for the polylactide (PLA)/poly(ε-caprolactone) (PCL) system, with the aim of enhancing the final properties of the two polymer blends. Indeed, PLA-g-MA was prepared via reactive blending through a free radical process and characterized by means of 1H-NMR and titration measurements, which demonstrated that the employed procedure allows grafting 0.7 wt% of MA onto the polymer backbone, while avoiding a dramatic reduction of PLA molecular mass. The specific effect of the MA-grafted PLA on the features of the PLA/PCL system was highlighted by adding different amounts of PLA-g-MA to 70:30 (w/w) PLA/PCL blends, where the 70 % PLA component was progressively substituted by its maleated modification. The efficiency of PLA-g-MA as a compatibilizer for the PLA/PCL blends was assessed through SEM analysis, which showed that the dimensions of PCL domains decrease and their adhesion to PLA improves by increasing the amount of PLA-g-MA in the blends. The peculiar microstructure promoted by the presence of PLA-g-MA was found to enhance the mechanical properties of the blend, improving the elongation at break without decreasing its Young’s modulus. Our study demonstrated that not only the microstructure but also the thermal properties of the blends were significantly affected by the replacement of PLA with PLA-g-MA. 相似文献
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195.
Dickson Maria Michela Espa Giuseppe Giuliani Diego Santi Flavio Savadori Lucia 《Nonlinear dynamics》2020,101(3):1833-1846
Nonlinear Dynamics - This paper aims at investigating empirically whether and to what extent the containment measures adopted in Italy had an impact in reducing the diffusion of the COVID-19... 相似文献
196.
Michela Maione Jgor Arduini Giovanna Mangani Annalisa Geniali 《International journal of environmental analytical chemistry》2013,93(4):241-253
Continuous monitoring of the atmospheric volatile halogenated hydrocarbons is needed in light of the role played by these compounds in global climate change phenomena. The analytical methodology described in the following implies the use of a gas chromatographic–mass spectrometric system equipped with a sampling/pre-concentration unit, for the simultaneous and continuous analysis of a number of halogenated hydrocarbons present in the atmosphere at concentration levels ranging from a few to hundreds of part per trillion by volume. The optimization of the analytical procedure in terms of efficiency, linearity, and reproducibility is reported together with some of the results obtained in the frame of a monitoring activity carried out on a remote mountain station in central Italy. 相似文献
197.
Michela Serresi Ranieri Bizzarri Francesco Cardarelli Fabio Beltram 《Analytical and bioanalytical chemistry》2009,393(4):1123-1133
Genetically encoded fluorescent proteins are optimal reporters when used to monitor cellular processes as they can be targeted
to any subcellular region by fusion to a protein of interest. Here, we present the pH-sensitive fluorescent protein E1GFP which is ideally suited to monitor pH changes in dynamic intracellular structures in real time with high spatio temporal
resolution. E1GFP is a ratiometric pH indicator by emission with a pK close to 6.0. We describe an application of this novel pH reporter
in the measurement of pH changes along the endo-lysosomal pathway. By fusing E1GFP to the HIV-Tat protein which is endowed with cell-penetrating properties, we were able to monitor multi-step endocytosis
from the initial cell-surface binding through to the intracellular endocytic network in real time. This represents a framework
for the application of E1GFP to the in situ detection of pH changes involved in dynamic biological phenomena.
Figure The green fluorecent protein variant, E1GFP, is a ratiometric pH-indicator by emission with a pK close to 6.0 and is therefore
particularly suitable for pH detection below neutrality. Upon excitation of the neutral state of the chromophore (~400-410
nm), E1GFP emission properties are strongly dependent on the environmental pH. We describe an application of this novel pH-reporter
in the measurement of pH changes along the endo-lysosomal pathway. By fusing E1GFP to the HIV-Tat protein, which is endowed
with cell-penetrating properties, we were able to monitor in real-time multi-step endocytosis from the initial cell-surface
binding through to the intracellular endocytic network.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
198.
Casetta B Vecchione G Tomaiuolo M Margaglione M Grandone E 《Journal of mass spectrometry : JMS》2009,44(3):346-352
6-oxo-PGF(1alpha) and TXB(2) are the metabolites of the prostanglandin PGI(2) and of the thromboxane TXA(2), respectively. PGI(2) and TXA(2) are arachidonic acid-derived compounds which regulate the blood hemostasis. Their quick metabolism leads to the 6-oxo-PGF(1alpha) and TXB(2) metabolites in plasma. In order to study on a large base the external factors influencing the hemostatic conditions, there is a need for a fast and reliable assay for quantitating these metabolites. Some methods have been published for the analysis of the arachidonic acid-derived compounds and some are dealing with mass spectrometry but nonspecifically centered on these specific compounds with a fast and cheap protocol, amenable for large-scale studies. Here we describe an analytical strategy that incorporates a two-dimensional chromatography running coupled to tandem mass spectrometry that minimizes the sample preparation and addresses the presence of the TXB(2) anomers for a robust quantitation measurement. After a protein precipitation, 100 microl of the supernatant (corresponding to 50 microl of the original plasma) was injected in a two-dimensional chromatographic system which operates an on-line clean-up and a subsequent chromatographic separation of the targeted analytes with a limit of quantitation (LOQ) of 22 pg/ml for 6-oxo-PGF(1alpha), and and a LOQ of 25 pg/ml for TXB(2). 相似文献
199.
Ottaviani MF Leonardis I Cappiello A Cangiotti M Mazzeo R Trufelli H Palma P 《Journal of colloid and interface science》2010,352(2):512-519
The structure of the octadecyl (C18) chain layer attached to a silica surface in the presence of binary solvents (acetonitrile/water; methanol/water) was investigated by electron paramagnetic resonance (EPR) and reverse-phase high-performance liquid chromatography (RP-HPLC), using 4-hydroxy-2,2,6,6 tetramethylpiperidine-N-oxyl (Tempol) to mimic the behavior of pollutants with medium-low polarity. The computer-aided analysis of the EPR spectra provided structural and dynamical information of the probe and its environments which clarified the modifications of the chain conformations that occur at different solvent compositions. Capacity factors, k', were calculated as a function of the percentage of water/organic solvent (mobile phase), and the retention behavior of the C18-functionalized silica surface (stationary phase) was compared with the results obtained with EPR analysis under static conditions. In particular, EPR analysis showed that, at percentages of ACN equal or higher than 50%, the chain layer assume a quite ordered structure, whereas at percentages lower than 50% the chains tend to collapse and fold on the silica surface. In this latter situation, the hydrophobic net of the C18 chains strongly limits Tempol mobility. In methanol/water mixtures, both EPR and RP-HPLC analysis showed that the probe was adsorbed into a poorly ordered interphase. If the residual silanols at the silica surface were bonded to a sililating agent (endcapping), both EPR and RP-HPLC analysis showed a decreased adsorption of the probe with respect to the non-endcapped silica at the same mobile phase composition. 相似文献
200.
Quaranta M Gehring T Odell B Brown JM Blackmond DG 《Journal of the American Chemical Society》2010,132(43):15104-15107
Observations of an intriguing inverse temperature dependence on reaction rate and a profound induction period in the Soai autocatalytic reaction are reported along with detailed kinetic and NMR investigations of the product alkoxide at low temperatures, leading to the suggestion that the active catalyst is derived in situ from the tetrameric ground state. 相似文献