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排序方式: 共有139条查询结果,搜索用时 15 毫秒
91.
Marko Stojkovic Narasimha R. Uda Peter Brodmann Milica Popovic Peter C. Hauser 《Journal of separation science》2012,35(24):3509-3513
The use of CE with contactless conductivity detection for the determination of PCR products is demonstrated for the first time. The separation of specific length PCR products according to their size could be achieved using 5% PVP as a sieving medium in a separation buffer consisting of 20 mM Tris and 20 mM 2‐(cyclohexylamino)ethansulphonic acid (pH 8.5). A fused silica capillary of 60 cm length and 50 μm id and an applied separation voltage of –15 kV were employed and separations could be completed within 20–50 min. PCR amplified DNA fragments of different sizes obtained from different bacterial plasmid templates as well as a fragment from genomic DNA of genetically modified soybeans could be successfully identified. 相似文献
92.
Milica Kosović Željko Jaćimović Živadin D. Bugarčić Biljana V. Petrović 《Transition Metal Chemistry》2016,41(2):161-168
Substitution reactions of three Pd(II) complexes, [Pd(cbdca)Cl2]2? (cbdca = cyclobutane-1,1-dicarboxylato), [Pd(ox)Cl2]2? (ox = oxalato) and [Pd(mal)Cl2]2? (mal = malonato), with different five- and six-membered N-heterocycles, such as pyrazole, 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazine, imidazole, pyridazine and pyrimidine, were investigated in aqueous 0.10 M NaClO4 with the presence of 20 mM NaCl using variable-temperature stopped-flow spectrophotometry. Substitution of these complexes occurs in two consecutive reversible steps, and their reactivity decreases in order [Pd(cbdca)Cl2]2? > [Pd(mal)Cl2]2? > [Pd(ox)Cl2]2?. The most reactive nucleophile among the five-membered heterocycles is imidazole, while pyridazine is the most reactive among the six-membered heterocycles. Activation parameters were determined for all reactions, and negative values for entropy of activation, ΔS≠, support an associative mode of substitution. The reaction between [Pd(mal)Cl2]2? complex and pzBr was investigated by 1H NMR, and the obtained results confirm that substitution with nitrogen-donor nucleophile does not lead to decomposition of the complex. 相似文献
93.
Milica Kosović Željko Jaćimović Živadin D Bugarčić 《Journal of Coordination Chemistry》2015,68(17-18):3003-3012
Substitution reactions of five monofunctional Pd(II) complexes, [Pd(terpy)Cl]+ (terpy = 2,2′;6′,2″-terpyridine), [Pd(bpma)Cl]+ (bpma = bis(2-pyridylmethyl)amine), [Pd(dien)Cl]+ (dien = diethylenetriamine or 1,5-diamino-3-azapentane), [Pd(Me4dien)Cl]+ (Me4dien = 1,1,7,7-tetramethyldiethylenetriamine), and [Pd(Et4dien)Cl]+ (Et4dien = 1,1,7,7-tetraethyldiethylenetriamine), with unsaturated N-heterocycles such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazole, pyrazine, and imidazole were investigated in aqueous 0.10 M NaClO4 in the presence of 10 mM NaCl using variable-temperature stopped-flow spectrophotometry. The second-order rate constants k2 indicate that the reactivity of the Pd(II) complexes decrease in the order [Pd(terpy)Cl]+ > [Pd(bpma)Cl]+ > [Pd(dien)Cl]+ > [Pd(Me4dien)Cl]+ > [Pd(Et4dien)Cl]+. The most reactive nucleophile of the heterocycles is pyrazine, while the slowest reactivity is with pyrazole. Activation parameters were determined for all reactions and negative entropies of activation, ΔS≠, supporting an associative mode of substitution. The reactions between [Pd(bpma)Cl]+ and 1,2,4-triazole, pzI, and pzBr were also investigated by 1H NMR to define the manner of coordination. These results could be useful for better explanation of structure-reactivity relationships of Pd(II) complexes as well as for the prediction of potential targets of Pd(II) complexes toward common N-heterocycles, constituents of biomolecules and different N-bonding pharmaceutical agents. 相似文献
94.
Plouffe BD Njoka DN Harris J Liao J Horick NK Radisic M Murthy SK 《Langmuir : the ACS journal of surfaces and colloids》2007,23(9):5050-5055
Microfluidic devices have recently emerged as effective tools for cell separation compared to traditional techniques. These devices offer the advantages of small sample volumes, low cost, and high purity. Adhesion-based separation of cells from heterogeneous suspensions can be achieved by taking advantage of specific ligand-receptor interactions. The peptide sequences Arg-Glu-Asp-Val (REDV) and Val-Ala-Pro-Gly (VAPG) are known to bind preferentially to endothelial cells (ECs) and smooth muscle cells (SMCs), respectively. This article examines the roles of REDV and VAPG and fluid shear stress in achieving selective capture of ECs and SMCs in microfluidic devices. The adhesion of ECs in REDV-coated devices and SMCs in VAPG-coated devices increases significantly compared to that of the nontargeted cells with decreasing shear stress. Furthermore, the adhesion of these cells is shown to be independent of whether these cells flow through the devices as suspensions of only one cell type or as a heterogeneous suspension containing ECs, SMCs, and fibroblasts. Whereas the overall adhesion of cells in the devices is determined mainly by shear stress, the selectivity of adhesion depends on the type of peptide and on the device surface as well as on the shear stress. 相似文献
95.
Paulius Mikulskis Daniela Cioloboc Milica Andrejić Sakshi Khare Joakim Brorsson Samuel Genheden Ricardo A. Mata Pär Söderhjelm Ulf Ryde 《Journal of computer-aided molecular design》2014,28(4):375-400
We have estimated free energies for the binding of nine cyclic carboxylate guest molecules to the octa-acid host in the SAMPL4 blind-test challenge with four different approaches. First, we used standard free-energy perturbation calculations of relative binding affinities, performed at the molecular-mechanics (MM) level with TIP3P waters, the GAFF force field, and two different sets of charges for the host and the guest, obtained either with the restrained electrostatic potential or AM1-BCC methods. Both charge sets give good and nearly identical results, with a mean absolute deviation (MAD) of 4 kJ/mol and a correlation coefficient (R 2) of 0.8 compared to experimental results. Second, we tried to improve these predictions with 28,800 density-functional theory (DFT) calculations for selected snapshots and the non-Boltzmann Bennett acceptance-ratio method, but this led to much worse results, probably because of a too large difference between the MM and DFT potential-energy functions. Third, we tried to calculate absolute affinities using minimised DFT structures. This gave intermediate-quality results with MADs of 5–9 kJ/mol and R 2 = 0.6–0.8, depending on how the structures were obtained. Finally, we tried to improve these results using local coupled-cluster calculations with single and double excitations, and non-iterative perturbative treatment of triple excitations (LCCSD(T0)), employing the polarisable multipole interactions with supermolecular pairs approach. Unfortunately, this only degraded the predictions, probably because of a mismatch between the solvation energies obtained at the DFT and LCCSD(T0) levels. 相似文献
96.
Milica Ilić Menka Petkovska Andreas Seidel-Morgenstern 《Journal of chromatography. A》2009,1216(33):6098-6107
In this work adsorption equilibria of binary mixtures are quantified analyzing the nonlinear frequency response of a chromatographic column. Local partial derivatives of an isotherm model can be estimated for certain steady-states from the low frequency asymptotes of the corresponding frequency response functions (FRFs). The required FRFs correspond to two different compounds and the type of the imposed inlet concentration changes, e.g. periodical inlet concentration changes of only one compound or of both of them. For an accurate determination of isotherm parameters, it is necessary to approach as close as possible the low frequency asymptotic behaviour of these functions. Based on principles valid for the FRFs corresponding to the adsorption of a single solute, frequencies needed to reach the low frequency asymptotes of the functions of interest for estimating competitive isotherms are defined in this paper. The relation between the accuracy of the isotherm parameters determined and numbers and types of periodical inlet concentration changes and steady-states analyzed is also evaluated. 相似文献
97.
Milica Stojanović 《Periodica Mathematica Hungarica》2013,67(1):115-131
There are investigated supergroups of some hyperbolic space groups with simplicial fundamental domain. Six simplices considered here from [9] are collected in families F9 (T 23, T 64), F10 (T 21, T 49, T 61), F29 (T 34). All of them have the same symmetry by half-turn h, with axis through the midpoints of edges A 0 A 1 and A 2 A 3. Since that isometry identifies pairs of points, if a supergroup with such smaller fundamental domain exists, it is of index 2. At the side pairings of T 34 this half-turn implies additional reflections, equal parameters 2a = 6b, and leads to Family 2, considered in [9]. Other possibility to find supergroups is when the simplices have vertices out of the absolute. In that case we can truncate them by polar planes of the vertices and the new polyhedra are fundamental domains of richer groups. 相似文献
98.
Milton J. Kiefel Robin J. Thomson Milica Radovanovic Mark von Itzstein 《Journal of carbohydrate chemistry》2013,32(8):937-959
ABSTRACT The synthesis of thioglycosides for use as metabolically stable biological probes is an area of continued interest. This paper describes the synthesis of functionalised carbohydrates which contain an anomeric thio group. During the course of this work we have examined the most viable route into compounds such as the specifically functionalised carbohydrates 36 and 37, and have also investigated the usefulness of disulfides as protecting groups for anomeric thiols. 相似文献
99.
100.
The modified imbedded disc retraction method for measurement of interfacial tension in polymer melts
The imbedded disc retraction method is used to estimate interfacial tension in LLDPE/PS system with PS as the imbedded disc.
Shape evolution of a disc of one material (PS) imbedded into the matrix of another material is observed (LLDPE). Three to
five repetitions at three different temperature levels are observed. The Newtonian model of Rundqvist et al. (1996) for the
imbedded disc retraction is modified to include elastic effects. The modified model is derived assuming uniaxial extension,
starting with the lower convected Maxwell model. Both the original model and modified imbedded disc retraction model are used
in data analysis. The mean values of interfacial tension at 190 °C, 200 °C, and 210 °C are 6.8 ± 0.7 mN/m, 3.9 ± 0.3 mN/m,
and 3.7 ± 0.2 mN/m, respectively. A method of estimating whether elastic effects will significantly affect the estimated interfacial
tension value during retraction for the given polymer pair is provided.
Received: 6 August 1999 Accepted: 2 January 2001 相似文献