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排序方式: 共有138条查询结果,搜索用时 31 毫秒
61.
Lilia Sghaier Christophe B. Y. Cordella Douglas N. Rutledge Mickaël Watiez Sylvie Breton Patrick Sassiat Didier Thiebaut Jrme Vial 《Journal of separation science》2016,39(9):1675-1683
Due to lipid oxidation, off‐flavors, characterized by a fishy odor, are emitted during the heating of rapeseed oil in a fryer and affect the flavor of rapeseed oil even at low concentrations. Thus, there is a need for analytical methods to identify and quantify these products. To study the headspace composition of degraded rapeseed oil, and more specifically the compounds responsible for the fishy odor, a headspace trap gas chromatography with mass spectrometry method was developed and validated. Six volatile compounds formed during the degradation of rapeseed oil were quantified: 1‐penten‐3‐one, (Z)‐4‐heptenal, hexanal, nonanal, (E,E)‐heptadienal, and (E)‐2‐heptenal. Validation using accuracy profiles allowed us to determine the valid ranges of concentrations for each compound, with acceptance limits of 40% and tolerance limits of 80%. This method was then successfully applied to real samples of degraded oils. 相似文献
62.
Gorokhovsky Alexander Saunina Svetlana Maximova Lilia Tretyachenko Elena Goffman Vladimir Escalante-Garcia José Iván Vikulova María 《Research on Chemical Intermediates》2022,48(3):1227-1248
Research on Chemical Intermediates - Potassium polytitanates powders were modified by treatment in aqueous solutions of manganese sulfate at different pH, the obtained intermediates (PPT/Mn) were... 相似文献
63.
Fuentes L Osorio U Quintero L Höpfl H Vázquez-Cabrera N Sartillo-Piscil F 《The Journal of organic chemistry》2012,77(13):5515-5524
A direct method for preparing 2,3-epoxyamides from tertiary allylamines via a tandem C-H oxidation/double bond epoxidation using sodium chlorite is reported. Apparently, the reaction course consists of two steps: (i) allylic oxidation of the starting allylamine to corresponding unsaturated allylamide with sodium chlorite followed by (ii) epoxidation of the allylamide to the 2,3-epoxyamide mediated by hypochlorite ion, which is formed in situ by reduction of sodium chlorite. The reaction conditions tolerate the presence of free hydroxyl groups and typical functional groups such as TBS, aryl, alkyl, allyl, acetyl, and benzyl groups; however, when an activated aromatic ring (e.g., sesamol) is present in the substrate, the use of a scavenger is necessary. 相似文献
64.
Aleksandr A. Bessonov Tamara V. Basova Vitaly G. Kiselev Lilia A. Sheludyakova Natalia B. Morozova Igor K. Igumenov 《Vibrational Spectroscopy》2009,51(2):283-288
The far-infrared and Raman spectra of binuclear molecules [Me2AuX]2 (X = Cl, Br, I) and [Me2Au(OOCR)]2 (R = Me, CF3, But, Ph) in the 600–70 cm−1 region are reported. The experimentally measured vibrational frequencies of [Me2AuX]2 are in a good agreement with density functional theory predictions. The Au…Au vibrational interactions predicted to be in the 270–60 cm−1 region of [Me2AuX]2 far-IR and Raman spectra have been observed. The Raman-active Au…Au vibrations of the [Me2Au(OOCR)]2 molecules were found to be in the same region as those of [Me2AuX]2. The Au–X stretching modes were observed between 100 and 250 cm−1 in accordance with the DFT predictions. Their frequencies in the IR spectra of [Me2AuX]2 increase in the sequence I < Br < Cl while the AuC2 stretching frequencies decrease in the same order. This fact might be an evidence of the decreasing covalent character of the gold-halogen bridges. The Au–O stretching bands of dimethylgold(III) carboxylates have been observed in the 500–250 cm−1 region, and Au–C stretching frequencies of both [Me2AuX]2 and [Me2Au(OOCR)]2 compounds have been found between 600 and 500 cm−1. 相似文献
65.
The histamine H(3) receptor (H(3)R) is a promising target in the development of new compounds for the treatment of mainly centrally occurring diseases. However, emerging novel therapeutic concepts have been introduced and some indications in the H(3)R field, e.g. migraine, pain or allergic rhinitis, might take advantage of peripherally acting ligands. In this work, kojic acid-derived structural elements were inserted into a well established H(3)R antagonist/inverse agonist scaffold to investigate the bioisosteric potential of γ-pyranones with respect to the different moieties of the H(3)R pharmacophore. The most affine compounds showed receptor binding in the low nanomolar concentration range. Evaluation and comparison of kojic acid-containing ligands and their corresponding phenyl analogues (3-7) revealed that the newly integrated scaffold greatly influences chemical properties (S Log P, topological polar surface area (tPSA)) and hence, potentially modifies the pharmacokinetic profile of the different derivatives. Benzyl-1-(4-(3-(piperidin-1-yl)propoxy)phenyl)methanamine ligands 3 and 4 belong to the centrally acting diamine-based class of H(3)R antagonist/inverse agonist, whereas kojic acid analogues 6 and 7 might act peripherally. The latter compounds state promising lead structures in the development of H(3)R ligands with a modified profile of action. 相似文献
66.
Schickling T Gebhard F Bünemann J Boeri L Andersen OK Weber W 《Physical review letters》2012,108(3):036406
We use the Gutzwiller variational theory to calculate the ground-state phase diagram and quasiparticle bands of LaOFeAs. The Fe3d-As4p Wannier-orbital basis obtained from density-functional theory defines the band part of our eight-band Hubbard model. The full atomic interaction between the electrons in the iron orbitals is parametrized by the Hubbard interaction U and an average Hund's-rule interaction J. We reproduce the experimentally observed small ordered magnetic moment over a large region of (U,J) parameter space. The magnetically ordered phase is a stripe spin-density wave of quasiparticles. 相似文献
67.
Flávia?Rodrigues?de Oliveira Silva Maria?Helena?Bellini Vivian?Regina?Trist?o Nestor?Schor Nilson?Dias?VieiraJr. Lilia?Coronato?Courrol 《Journal of fluorescence》2010,20(6):1159-1165
Prostate cancer is one of the most common types of cancer in men, and unfortunately many prostate tumours remain asymptomatic
until they reach advanced stages. Diagnosis is typically performed through Prostate-Specific Antigen (PSA) quantification,
Digital Rectal Examination (DRE) and Transrectal Ultrasonography (TU). The antigen (PSA) is secreted by all prostatic epithelial
cells and not exclusively by cancerous ones, so its concentration also increases in the presence of other prostatic diseases.
DRE and TU are not reliable for early detection, when histological analysis of prostate tissue obtained from a biopsy is necessary.
In this context, fluorescence techniques are very important for the diagnosis of cancer. In this paper we explore the potential
of using endogenous phorphyrin blood fluorescence as tumour marker for prostate cancer. Substances such as porphyrin derivatives
accumulate substantially more in tumours than in normal tissues; thus, measuring blood porphyrin concentration by autofluorescence
intensity may provide a good parameter for determining tumour stage. In this study, the autofluorescence of blood porphyrin
was analyzed using fluorescence and excitation spectroscopy on healthy male NUDE mice and in those with prostate cancer induced
by inoculation of DU145 cells. A significant contrast between the blood of normal and cancer subjects could be established.
Blood porphyrin fluorophore showed an enhancement on the fluorescence band around 632 nm following tumour growth. Fluorescence
detection has advantages over other light-based investigation methods: high sensitivity, high speed and safety. However it
does carry the drawback of low specificity of detection. The extraction of blood porphyrin using acetone can solve this problem,
since optical excitation of further molecular species can be excluded, and light scattering from blood samples is negligible. 相似文献
68.
Lilia Krivodonova 《Journal of computational physics》2010,229(22):8537-8551
We develop an efficient local time-stepping algorithm for the method of lines approach to numerical solution of transient partial differential equations. The need for local time-stepping arises when adaptive mesh refinement results in a mesh containing cells of greatly different sizes. The global CFL number and, hence, the global time step, are defined by the smallest cell size. This can be inefficient as a few small cells may impose a restrictive time step on the whole mesh. A local time-stepping scheme allows us to use the local CFL number which reduces the total number of function evaluations. The algorithm is based on a second order Runge–Kutta time integration. Its important features are a small stencil and the second order accuracy in the L2 and L∞ norms. 相似文献
69.
DNA and Carbon nanotubes (CNTs) have unique physical, mechanical and electronic properties that make them revolutionary materials for advances in technology. In state-of-the-art applications, these physical properties can be exploited to design a type of bio-nanorobot. In this paper, we present the behavior of DNA-based nanotweezers and show the capabilities of controlling this robotic device. The theoretical calculations are based on the Peyrard-Bishop model for DNA dynamics. Furthermore, the influence of the van der Waals force between two CNTs on the opening and closing of nanotweezers is studied in comparison with the stretching forces of DNA. 相似文献
70.
We analyze the discretization errors of discontinuous Galerkin solutions of steady two-dimensional hyperbolic conservation laws on unstructured meshes. We show that the leading term of the error on each element is a linear combination of orthogonal polynomials of degrees p and p+1. We further show that there is a strong superconvergence property at the outflow edge(s) of each element where the average discretization error converges as O(h
2p+1) compared to a global rate of O(h
p+1). Our analyses apply to both linear and nonlinear conservation laws with smooth solutions. We show how to use our theory to construct efficient and asymptotically exact a posteriori discretization error estimates and we apply these to some examples. 相似文献