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51.
Katalin Zih-Perényi Péter Jankovics Éva Sugár Alexandra Lásztity 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
A separation procedure for antimony(III) and antimony(V) was developed with the use of chelating celluloses. Sb(III) was separately pre-concentrated on imino diacetic acid–ethyl cellulose in the acidic pH range, in which the uptake of Sb(V) was negligible in the μg L− 1 concentration range. On the other hand, both Sb species Sb(V) and Sb(III) were pre-concentrated on a chloride form of 2,2′-diaminodiethylamine-cellulose. These solid phase extraction procedures were combined with graphite furnace atomic absorption spectrometry (SPE–GFAAS) for Sb detection. Pharmaceutical compounds of organic and inorganic types (ten compounds), as well as mineral water samples (twelve types) were analyzed. Detection limits of 0.18 µg L− 1 Sb(III) and 0.25 µg L− 1 Sb(V) were found in aqueous sample solutions and water samples, respectively, considering a 25-fold pre-concentration. The total Sb, mostly in the form of Sb(V), could be determined in phosphate-containing pharmaceuticals, while in phosphoric acid, Sb(III) was the dominant form. In all other types of samples the Sb content was below the detection threshold, and therefore, the potential suitability of the SPE–GFAAS method for the determination of Sb(III) species was proven by recovery tests of spiked samples. This method ensures the required detection power with regard to the allowable Sb limits established by international organizations. 相似文献
52.
Dávid Ádám Zoltán Mincsovics Emil Pápai Katalin Ludányi Krisztina Antal István Klebovich Imre 《平面色谱法杂志一现代薄层色谱法》2008,21(2):119-123
JPC – Journal of Planar Chromatography – Modern TLC - A new, simplified open-vessel microwave extraction (OVME) method has been used to prepare aqueous extracts of Sennae folium and... 相似文献
53.
Mincsovics Emil Pápai Katalin Ludányi Krisztina Dávid Ádám Zoltán Budai Marianna Antal István Klebovich Imre 《平面色谱法杂志一现代薄层色谱法》2008,21(5):361-366
JPC – Journal of Planar Chromatography – Modern TLC - The newly developed experimental OPLC separation unit 100 (OSU 100) has been used for fully on-line multiple hyphenation using the... 相似文献
54.
55.
Tamba M Dajka K Ferreri C Asmus KD Chatgilialoglu C 《Journal of the American Chemical Society》2007,129(28):8716-8723
The one-electron reduction of methanesulfonyl chloride (MeSO2Cl) leads, in the first instance, to an electron adduct MeSO2Cl(.)(-) which lives long enough for direct detection and decays into sulfonyl radicals MeSO2(.) and Cl(-), with k = 1.5 x 10(6) s(-1). Both, MeSO2Cl(.)(-) and MeSO2(.) showed a similar absorption in the UV with lambdamax of 320 nm. In the presence of oxygen, MeSO2Cl(.)(-) transfers an electron to O(2) and establishes an equilibrium with superoxide. The rate constant for the forward reaction was measured to 4.1 x 10(9) M(-1) s(-1), while for the back reaction only an interval of 1.7 x 10(5) to 1.7 x 10(6) M(-1) s(-1) could be estimated, with a somewhat higher degree of confidence for the lower value. This corresponds to an equilibrium constant in the range of 2.4 x 10(3) to 2.4 x 10(4). With reference to E degrees (O2/O2(.)(-)) = -155 mV, the redox potential of the sulfonyl chloride couple, E degrees (MeSO2Cl/MeSO2Cl(.)(-)), thus results between being equal to -355 and -414 mV (vs NHE). MeSO2Cl(.)(-) reduces (besides O2) 4-nitroacetophenone. The underlying electron transfer took place with k = 1.5 x 10(9) M(-1) s(-1), corroborating an E degrees for the sulfonyl chloride couple significantly exceeding the above listed lower value. The MeSO2(.) radical added to oxygen with a rate constant of 1.1 x 10(9) M(-1) s(-1). Re-dissociation of O2 from MeSO2OO(.) occurred only very slowly, if at all, that is, with k < 10(5) s(-1). MeSO2(.) radicals can act as the catalyst for the cis-trans isomerization of several Z- and E-mono-unsaturated fatty acid methyl esters in homogeneous solution. The effectiveness of the isomerization processes has been addressed, and in the presence of oxygen the isomerization is completely suppressed. 相似文献
56.
Katalin F. Medzihradszky Gregory W. Adams Alma L. Burlingame Robert H. Bateman Martin R. Green 《Journal of the American Society for Mass Spectrometry》1996,7(1):1-10
This report describes the fragmentation processes for peptides induced by collisional activation of the 12C isobar of matrix-assisted laser desorption ionization (MALDI)-generated pseudomolecular ions employing an EBE orthogonal acceleration time-of-flight mass spectrometer and using xenon as the collision gas at a laboratory collision energy of 800 eV. These MALDI-collision-induced dissociation (CID) spectra are shown to provide sequence information of comparable quality to those obtained by using high energy CID conditions with liquid secondary ionization mass spectrometry on a four-sector tandem instrument. Peptide sequencing via MALDI-CID is demonstrated on three tryptic peptides obtained from a bacterial protein (P450 isozyme) of unknown sequence. Sensitivity is shown to be at the 1 pmol level for standard peptides. 相似文献
57.
Péter Baracskay Viola Kiglics Katalin A Kékesi Gábor Juhász András Czurkó 《BMC neuroscience》2009,10(1):133
Background
The impairment of the pontine reticular formation (PRF) has recently been revealed to be histopathologically connected with focal-cortical seizure induced generalized convulsive status epilepticus. To elucidate whether the impairment of the PRF is a general phenomenon during status epilepticus, the focal-cortical 4-aminopyridine (4-AP) application was compared with other epilepsy models. The presence of "dark" neurons in the PRF was investigated by the sensitive silver method of Gallyas in rats sacrificed at 3 h after focal 4-AP crystal or systemic 4-AP, pilocarpine, or kainic acid application. The behavioral signs of the developing epileptic seizures were scored in all rats. The EEG activity was recorded in eight rats. 相似文献58.
Kövér KE Batta G Fehér K 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,181(1):89-97
Here, we present a modified CPMG-HSQMBC experiment which is capable to reduce the detrimental phase twists in the "long-range" connectivity multiplets caused by proton-proton couplings. We demonstrate that concerted CPMG pulse trains applied on both nuclei in the starting CPMG-INEPT transfer step can considerably be improved by composite pi pulses that compensate for pulse imperfections and off-resonance effects. Experimental optimization of the interpulse delay within the CPMG cycle was found to be crucial in order to achieve the best possible "decoupling" of homonuclear coupling modulation. 相似文献
59.
Dr. Mihály Herczeg Dr. László Lázár Dr. Zsuzsanna Bereczky Prof. Dr. Katalin E. Kövér István Timári Prof. Dr. János Kappelmayer Prof. Dr. András Lipták Prof. Dr. Sándor Antus Dr. Anikó Borbás 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(34):10643-10652
Two pentasaccharide sulfonic acids that were related to the antithrombin‐binding domain of heparin were prepared, in which two or three primary sulfate esters were replaced by sodium‐sulfonatomethyl moieties. The sulfonic‐acid groups were formed on a monosaccharide level and the obtained carbohydrate sulfonic‐acid esters were found to be excellent donors and acceptors in the glycosylation reactions. Throughout the synthesis, the hydroxy groups to be methylated were masked in the form of acetates and the hydroxy groups to be sulfated were masked with benzyl groups. The disulfonic‐acid analogue was prepared in a [2+3] block synthesis by using a trisaccharide disulfonic acid as an acceptor and a glucuronide disaccharide as a donor. For the synthesis of the pentasaccharide trisulfonic acid, a more‐efficient approach, which involved elongation of the trisaccharide acceptor with a non‐oxidized precursor of the glucuronic acid followed by post‐glycosidation oxidation at the tetrasaccharide level and a subsequent [1+4] coupling reaction, was elaborated. In vitro evaluation of the anticoagulant activity of these new sulfonic‐acid derivatives revealed that the disulfonate analogue inhibited the blood‐coagulation‐proteinase factor Xa with outstanding efficacy; however, the introduction of the third sulfonic‐acid moiety resulted in a notable decrease in the anti‐Xa activity. The difference in the biological activity of the disulfonic‐ and trisulfonic‐acid counterparts could be explained by the different conformation of their L ‐iduronic‐acid residues. 相似文献
60.
McGouran JF Kramer HB Mackeen MM di Gleria K Altun M Kessler BM 《Organic & biomolecular chemistry》2012,10(17):3379-3383
Novel ubiquitin-based active site probes including a fluorescent tag have been developed and evaluated. A new, functionalizable electrophilic trap is utilized allowing for late stage diversification of the probe. Attachment of fluorescent dyes allowed direct detection of endogenous deubiquitinating enzyme (DUB) activities in cell extracts by in-gel fluorescence imaging. 相似文献