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排序方式: 共有74条查询结果,搜索用时 78 毫秒
1.
Summary Flow injection analysis associated with a gradient mixing technique can be used for the determination of free acidity and total acidity (sum of free and bonded hydrogen ions) in a few microliters by reaction with suitable acid/base indicators and UV/VIS-detection. A rapid analysis of the two parameters in single raindrops in dependence on their size is possible [1]. 相似文献
2.
Gas Phase Intercalation of Graphite by SbCl4F Gas Phase Intercalation of Graphite by SbCl4F using a two-zone technique is a method to prepare intercalation compounds of different stage index n in temperature range between 120 and 140°C. The reaction is a process of successive decrease of stage index. Increasing the reaction time, i. e. concentration, regions of pure stages alternate with two-phase regions. Intercalation compounds were characterized by X-ray technique, EPMA, and chemical methods. The compounds are stable in ordinary air, with aqueous HCl as well as KOH only pentavalent but not any trivalent antimony can be removed. The identity periods along c-axis in pure stages are Ic = 9.33 Å (n = 1), 12.72 Å (n = 2), 16.06 Å (n = 3) and 19.40 Å (n = 4). A (√7 × √ 7) 19.1° in-plane structure of intercalants was found. The uptake curve of mass with time reveals a discontinuity connected with formation of stage 2. Concave shape of curve during starting period at 120 and 125°C will be interpreted as a consequence of an induction time. From X-ray and EPMA studies it may be concluded that nucleation at the prismatic crystal edges controls the kinetics of reaction. Assuming a first order kinetics of filling the vacant sites, the same activation energy in case of formation of stage 1 and stage 2 have been determined approximately (97 and 102 kJ/mol). 相似文献
3.
Tanja M. Wrodnigg Walter Gaderbauer Peter Greimel Herwig H?usler Friedrich K. Sprenger Arnold E. Stütz 《Journal of carbohydrate chemistry》2013,32(8):975-990
ABSTRACT By an Amadori rearrangement of easily available 5-azido-5-deoxy-D-glucofuranose with dibenzylamine and subsequent catalytic hydrogenation of the resulting 5-azido-1-(N,N-dibenzyl)amino-1,5-dideoxy-D-fructopyranose, 1-amino-1,2,5-trideoxy-2,5-imino-D-mannitol was obtained in only two steps and in excellent overall yield. Likewise, other amines were employed to introduce extended side chains ultimately suitable for attachment of the inhibitor to solid supports. The reported rearrangement reaction is a high yielding, convenient and apparently general entry to 1-aminodeoxyketopyranoses modified at C-5, facilitated by the ring enlargement of the aldofuranose to the ketopyranose as an additional driving force. A range of selected chain extended analogues was prepared by acylation of N-1. Inhibitors obtained exhibit K i-values with D-glucosidases in the micromolar range. Interestingly, 1-N-acylation resulted in superior inhibitory activities, as did the addition of a hexyl chain. 相似文献
4.
Kreckel H Motsch M Mikosch J Glosík J Plasil R Altevogt S Andrianarijaona V Buhr H Hoffmann J Lammich L Lestinsky M Nevo I Novotny S Orlov DA Pedersen HB Sprenger F Terekhov AS Toker J Wester R Gerlich D Schwalm D Wolf A Zajfman D 《Physical review letters》2005,95(26):263201
The energy-resolved rate coefficient for the dissociative recombination (DR) of H(3)(+) with slow electrons has been measured by the storage-ring method using an ion beam produced from a radiofrequency multipole ion trap, employing buffer-gas cooling at 13 K. The electron energy spread of the merged-beams measurement is reduced to 500 microeV by using a cryogenic GaAs photocathode. This and a previous cold- measurement jointly confirm the capability of ion storage rings, with suitable ion sources, to store and investigate H(3)(+) in the two lowest, (J,G) = (1,1) and (1,0) rotational states prevailing also in cold interstellar matter. The use of para-H(2) in the ion source, expected to enhance para-H(3)(+) in the stored ion beam, is found to increase the DR rate coefficient at meV electron energies. 相似文献
5.
Møller C Sprenger RR Stürup S Højrup P 《Analytical and bioanalytical chemistry》2011,401(5):1623-1633
Using insulin as a model protein for binding of oxaliplatin to proteins, various mass spectrometric approaches and techniques
were compared. Several different platinum adducts were observed, e.g. addition of one or two diaminocyclohexane platinum(II)
(Pt(dach)) molecules. By top-down analysis and fragmentation of the intact insulin–oxaliplatin adduct using nano-electrospray
ionisation quadrupole time-of-flight mass spectrometry (nESI-Q-ToF-MS), the major binding site was assigned to histidine5
on the insulin B chain. In order to simplify the interpretation of the mass spectrum, the disulphide bridges were reduced.
This led to the additional identification of cysteine6 on the A chain as a binding site along with histidine5 on the B chain.
Digestion of insulin–oxaliplatin with endoproteinase Glu-C (GluC) followed by reduction led to the formation of five peptides
with Pt(dach) attached. Identification of several of the binding sites was obtained using matrix-assisted laser desorption/ionization
(MALDI)-ToF-ToF-MS and liquid chromatography-nESI-Q-ToF-MS. Upon comparing the top-down and bottom-up approaches, the suitability
of the bottom-up approach for determining binding sites was questioned, as the release and possible re-association of Pt(dach)
were demonstrated upon enzymatic digestion. The associated advantages and disadvantages of ESI and MALDI were also pointed
out. 相似文献
6.
7.
A new class of resonant dispersive shock waves was recently identified as solutions of the Kawahara equation— a Korteweg–de Vries (KdV) type nonlinear wave equation with third‐ and fifth‐order spatial derivatives— in the regime of nonconvex, linear dispersion. Linear resonance resulting from the third‐ and fifth‐order terms in the Kawahara equation was identified as the key ingredient for nonclassical dispersive shock wave solutions. Here, nonlinear wave (Whitham) modulation theory is used to construct approximate nonclassical traveling dispersive shock wave (TDSW) solutions of the fifth‐ order KdV equation without the third derivative term, hence without any linear resonance. A self‐similar, simple wave modulation solution of the fifth order, weakly nonlinear KdV–Whitham equations is obtained that matches a constant to a heteroclinic traveling wave via a partial dispersive shock wave so that the TDSW is interpreted as a nonlinear resonance. The modulation solution is compared with full numerical solutions, exhibiting excellent agreement. The TDSW is shown to be modulationally stable in the presence of sufficiently small third‐order dispersion. The Kawahara–Whitham modulation equations transition from hyperbolic to elliptic type for sufficiently large third‐order dispersion, which provides a possible route for the TDSW to exhibit modulational instability. 相似文献
8.
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10.
Difluorobromophosphine reacts readily with bis(trifluoromethylthio)- mercury to yield the fluorophosphine CF3SPF2 in excellent yields. The resulting new phosphine is readily oxidized under very moderate conditions by ClF, Cl2 and O2 to give new chlorofluorophosphorane and fluorophosphoryl compounds which contain the CF3S moiety. CF3SPF2Cl2 and CF3SPF2Cl were not characterized because of their tendency to disproportionate. CF3SP(O)F2 has, however, been isolated and characterized. All the new compounds are relatively unstable and decompose with a fluoride shift from the methyl group to the phosphorus atom. A new synthetic route to the known difluorophosphoryl compounds OPF2Cl, OPF2Br, OPF2NCS and OPF2(CH3)2, by the direct oxidation of the respective difluorophosphine with oxygen, has been found. 相似文献