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排序方式: 共有210条查询结果,搜索用时 15 毫秒
31.
Anne-Lise Marie Elena Dominguez-Vega François Saller Jean-Luc Plantier Rémi Urbain Delphine Borgel N. Thuy Tran Govert W. Somsen Myriam Taverna 《Analytica chimica acta》2016
Antithrombin (AT) is a plasma glycoprotein which possesses anticoagulant and anti-inflammatory properties. AT exhibits various forms, among which are native, latent and heterodimeric ones. We studied the potential of capillary electrophoresis-mass spectrometry (CE-MS) using a sheath liquid interface, electrospray ionization (ESI), and a quadrupole-time-of-flight (Q-TOF) mass spectrometer to separate and quantify the different AT forms. For CE separation, a neutral polyvinyl alcohol (PVA) coated capillary was employed. The protein conformation was preserved by using a background electrolyte (BGE) at physiological pH. A sheath liquid of isopropanol-water 50:50 (v/v) with 14 mM ammonium acetate delivered at a flow rate of 120 μL h−1 resulted in optimal signal intensities. Each AT form exhibited a specific mass spectrum, allowing unambiguous distinction. Several co-injection experiments proved that latent AT had a higher electrophoretic mobility (μep) than native AT, and that these conformers could associate to form a heterodimer during the CE analysis. The developed CE-MS method enabled the detection and quantitation of latent and heterodimeric forms in a commercial AT preparation stored at room temperature for three weeks. 相似文献
32.
Dry Reforming of Methane on a Highly‐Active Ni‐CeO2 Catalyst: Effects of Metal‐Support Interactions on C−H Bond Breaking
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B. Sc. Zongyuan Liu Dr. David C. Grinter Dr. Pablo G. Lustemberg Dr. Thuy‐Duong Nguyen‐Phan Dr. Yinghui Zhou B. Sc. Si Luo Dr. Iradwikanari Waluyo Dr. Ethan J. Crumlin Dr. Dario J. Stacchiola Prof. Jing Zhou Dr. Javier Carrasco Prof. H. Fabio Busnengo Dr. M. Verónica Ganduglia‐Pirovano Dr. Sanjaya D. Senanayake Prof. José A. Rodriguez 《Angewandte Chemie (International ed. in English)》2016,55(26):7455-7459
Ni‐CeO2 is a highly efficient, stable and non‐expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density‐functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2?x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way. 相似文献
33.
The potential of a series of newly synthesized poly(N,N-dimethylacrylamide) (PDMA) grafted polyacrylamide (PAM) copolymers (P(AM-PDMA)) as a replaceable separation medium for protein analysis was studied. A comparative study with and without copolymers was performed; the separation efficiency, analysis reproducibility and protein recovery proved that the P(AM-PDMA) copolymers were efficient in suppressing the adsorption of basic proteins onto the silica capillary wall. Furthermore, the size-dependent retardation of native proteins in a representative P(AM-PDMA) copolymer was demonstrated by Ferguson analysis. The results showed that the P(AM-PDMA) copolymers combine the good coating property of PDMA and the sieving property of PAM and could be applied as a sieving matrix for the analysis of native proteins. 相似文献
34.
Hong Van Nguyen Duong Thuy Tran Hung Khac Pham 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(2):37
Network structure as well as structural and compositional heterogeneities in aluminosilicate (Al2O3-2SiO2) under compression is investigated by analysis and visualization of simulation data. Structural and compositional heterogeneities are clarified through analysis of topology structure and size distribution of TO x -clusters (T = Si, Al; x = 3, 4, 5, 6) as well as OT y -clusters (y = 2, 3, 4). The TO x -cluster can be considered as TO x -grains. It appears that the structure of aluminosilicate is the mixture of TO x -grains with a different short-range order structure and this is the origin of structural heterogeneity. Regarding their composition, the OSi y - and OAl y -clusters can be considered as silica- and alumina-grains respectively, and the structure of aluminosilicate can thus be considered to be formed from silica- and alumina-grains. This results in compositional heterogeneity. Moreover, the degree of polymerization and polyamorphism as well as dynamic heterogeneity is also discussed in detail. 相似文献
35.
Rhodes CJ Tran TT Morris H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(6):1401-1410
Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of Vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs free energies, for the overall reactions. Within the linear free energy relationship (LFER) assumption, that the Gibbs free energy of activation is proportional to the overall Gibbs free energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants. A method is devised, involving a competitive reaction between *CH3 radicals and both the spin-trap PBN and the antioxidant, which enables the relatively rapid determination of a relative ordering of activities for a series of potential antioxidant compounds, and also of their rate constants for scavenging *CH3 radicals (relative to the rate constant for addition of *CH3 to PBN). 相似文献
36.
Griffin K Montagne C Hoang CT Clarkson GJ Shipman M 《Organic & biomolecular chemistry》2012,10(5):1032-1039
2-Methyleneaziridines can be tethered to a variety of alkene or alkyne acceptors through the saturated carbon of the heterocyclic ring by application of a simple lithiation/alkylation sequence (8 examples, 31-59%). Treatment of the resultant alkene bearing substrates with BF(3)·OEt(2) leads to cis-octahydrocyclopenta[c]pyrroles in which up to four contiguous stereocentres are created in a diastereocontrolled manner after reductive work-up. Using an alkyne based substrate, a 2,4,5,6-tetrahydrocyclopenta[c]pyrrole is produced by rapid tautomerisation of the initially formed bisenamine. Evidence that these (3 + 2) 'cycloadditions' proceed in a stepwise manner via a 2-aminoallyl cation is presented. 相似文献
37.
Tam NM Ngan VT de Haeck J Bhattacharyya S Le HT Janssens E Lievens P Nguyen MT 《The Journal of chemical physics》2012,136(2):024301
The geometric structures of neutral and cationic Si(n)Li(m)(0/+) clusters with n = 2-11 and m = 1, 2 are investigated using combined experimental and computational methods. The adiabatic ionization energy and vertical ionization energy (VIE) of Si(n)Li(m) clusters are determined using quantum chemical methods (B3LYP/6-311+G(d), G3B3, and CCSD(T)/aug-cc-pVxZ with x = D,T), whereas experimental values are derived from threshold photoionization experiments in the 4.68-6.24 eV range. Among the investigated cluster sizes, only Si(6)Li(2), Si(7)Li, Si(10)Li, and Si(11)Li have ionization thresholds below 6.24 eV and could be measured accurately. The ionization threshold and VIE obtained from the experimental photoionization efficiency curves agree well with the computed values. The growth mechanism of the lithium doped silicon clusters follows some simple rules: (1) neutral singly doped Si(n)Li clusters favor the Li atom addition on an edge or a face of the structure of the corresponding Si(n)(-) anion, while the cationic Si(n)Li(+) binds with one Si atom of the bare Si(n) cluster or adds on one of its edges, and (2) for doubly doped Si(n)Li(2)(0/+) clusters, the neutrals have the shape of the Si(n+1) counterparts with an additional Li atom added on an edge or a face of it, while the cations have both Li atoms added on edges or faces of the Si(n)(-) clusters. 相似文献
38.
The capillary viscometer is used to measure the shear stress-shear rate relationship of a wide range of purely viscous fluids.
It is however not considered as an appropriate instrument for obtaining the yield stress and the post-yield behaviour of fluids
that have a yield stress. This is partly because conventional methods of processing the capillary viscometry data of purely
viscous fluids cannot be applied to similar data of fluids with yield stress. The unavoidable experimental noise in the capillary
data, particularly at low shear rates, also makes it difficult to obtain a reliable estimate of the yield stress from capillary
data. In this investigation the problem of converting the capillary viscometry data of yield stress fluids into a shear stress-shear
rate curve and a yield stress is formulated as a Volterra integral equation of the first kind. This is an ill-posed problem
i.e. noise in the data will be amplified by inappropriate methods of data processing. A method, based on Tikhonov regularisation
that takes into account the ill-posed nature of the problem, is then developed to solve this problem for fluids with yield
stress. The performance of this method is assessed by applying it to a set of “synthetic” capillary viscometry data with added
random noise and to a set of experimental data for a concentrated suspension of TiO2 taken from the literature. In both cases Tikhonov regularisation was able to extract the complete shear properties of these
fluids from capillary viscometry data alone.
Received: 22 November 1999/Accepted: 17 December 1999 相似文献
39.
Dung Nguyen Tien Thanh Do Minh Huong Nguyen Thi Thuy Phan Thi Hoan Nguyen Thi Thanh Dinh Thi Mai Van Trang Nguyen Son Ninh The 《Structural chemistry》2020,31(6):2435-2450
Structural Chemistry - Quinolone and isoquinolone alkaloids, which were found in the plant kingdom, are now potential antioxidants. In this case study, a quantum calculated procedure utilizing the... 相似文献
40.
The hydrolysis of dihydropyranyl acetals by sulfurie acid leads to cyelenones, but by the use of pyridinium ptoluenesulfonate, δ-ketoaldehydes may be isolated. Those compounds do not undergo aldol condensation under these conditions. 相似文献