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81.
Ramos CI Santana-Marques MG Ferrer-Correia AJ Barata JF Tomé AC Neves MG Cavaleiro JA Abreu PE Pereira MM Pais AA 《Journal of mass spectrometry : JMS》2012,47(4):516-522
Two new isomeric aminomethyl corrole derivatives of [5,10,15-tris(pentafluorophenyl)corrolato]gallium(III) were synthesized with pyridine (py) molecules as axial ligands. When investigated by electrospray ionization mass spectrometry, in the positive and the negative ion modes, these compounds showed an unusual gas-phase behavior that could be used for their differentiation. In the positive ion mode, the differentiation was achieved through the formation of diagnostic fragment ions formed from [M-py?+?H](+) precursors, by (CH(3) )(2) NH and HF losses. An unusual addition of water to the main fragment ions provides an alternative route for isomer identification. Semi-empirical calculations were performed to elucidate the structures and stabilities of the main ionic species formed in the positive ion mode. In the negative ion mode isomer discrimination is accomplished via the fragmentation of the methoxide adduct ions [M-py?+?CH(3) O](-) through (CH(3) )(2) N(.) and HF losses. 相似文献
82.
Catarina I. V. Ramos M. Graça Santana‐Marques A. J. Ferrer‐Correia Joana F. B. Barata Augusto C. Tomé M. Graça P. M. S. Neves J. A. S. Cavaleiro Paulo E. Abreu Mariette M. Pereira Alberto A. C. C. Pais 《Journal of mass spectrometry : JMS》2012,47(4):516-522
Two new isomeric aminomethyl corrole derivatives of [5,10,15‐tris(pentafluorophenyl)corrolato]gallium(III) were synthesized with pyridine (py) molecules as axial ligands. When investigated by electrospray ionization mass spectrometry, in the positive and the negative ion modes, these compounds showed an unusual gas‐phase behavior that could be used for their differentiation. In the positive ion mode, the differentiation was achieved through the formation of diagnostic fragment ions formed from [M‐py + H]+ precursors, by (CH3)2NH and HF losses. An unusual addition of water to the main fragment ions provides an alternative route for isomer identification. Semi‐empirical calculations were performed to elucidate the structures and stabilities of the main ionic species formed in the positive ion mode. In the negative ion mode isomer discrimination is accomplished via the fragmentation of the methoxide adduct ions [M‐py + CH3O]‐ through (CH3)2 N. and HF losses. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
83.
L.M.GrafiaDrummond A.N.Iusem B.F.Svaiter 《应用数学学报(英文版)》2003,19(3):371-386
We develop first order optimality conditions for constrained vector optimization. The partial orders for the objective and the constraints are induced by closed and convex cones with nonempty interior. After presenting some well known existence results for these problems, based on a scalarization approach, we establish necessity of the optimality conditions under a Slater-like constraint qualification, and then sufficiency for the K-convex case. We present two alternative sets of optimality conditions, with the same properties in connection with necessity and sufficiency, but which are different with respect to the dimension of the spaces to which the dual multipliers belong. We introduce a duality scheme, with a point-to-set dual objective, for which strong duality holds. Some examples and open problems for future research are also presented, 相似文献
84.
A procedure for the determination of phenolic pesticides, i.e. the hydroxybenzonitriles bromoxynil and ioxynil and the 2,4-dinitrophenol-derivatives
dinoseb, dinosebacetate, dinoterb, dinoterbacetate, dinobuton, binapacryl and DNOC is presented. The herbicides with a free
phenolic OH-group as well as the corresponding esters are very strongly adsorbed on Carbopack B, a special graphitized carbon
black. In contrast to the esters, which can be removed almost quantitatively, the substances with a free phenolic OH-group
cannot be eluted in any significant amount. This effect was used for the derivatization of the herbicides directly on Carbopack
B, using diazomethane or TMSH as reagents. The derivatives were eluted with ethylacetate and identified and quantified by
GC/MS.
For recovery studies, water samples were spiked with the pesticides in concentrations within the range tolerated by the European
Drinking Water Guideline.
Received: 25 March 1996/Revised: 12 June 1996/Accepted: 17 June 1996 相似文献
85.
Alves Lourdes A. Vitolo Michele Felipe Maria das Graças A. de Almeida e Silva João Batista 《Applied biochemistry and biotechnology》2002,98(1-9):403-413
The sugarcane bagasse hydrolysate, which is rich in xylose, can be used as culture medium for Candida guilliermondii in xylitol production. However, the hydrolysate obtained from bagasse by acid hydrolysis at 120°C for 20 min has by-products
(acetic acid and furfural, among others), which are toxic to the yeast over certain concentrations. So, the hydrolysate must
be pretreated before using in fermentation. The pretreatment variables considered were: adsorption time (15,37.5, and 60 min),
type of acid used (H2So4 and H3Po4), hydrolysate concentration (original, twofold, and fourfold. concentrated), and active
charcoal (0.5, 1.75 and 3.0%). The suitability of the pretreatment was followed by measuring the xylose reductase (XR) and
xylitol dehydrogenase (XD) activity of yeast grown in each treated hydrolysate. The response surface methodology (24 full factorial design with a centered face) indicated that the hydrolysate might be concentrated fourfold and the pH adjusted
to 7.0 with CaO, followed by reduction to 5.5 with H3PO4. After that it was treated with active charcoal (3.0%) by 60 min. This pretreated hydrolysate attained the high XR/XD ratio
of 4.5. 相似文献
86.
M. Rosario M. Domingues Olga V. Nemirovskiy M. Graço O. S. Marques M. Graça Neves J. A. S. Cavaleiro A. J. Ferrer-Correia Michael L. Gross 《Journal of the American Society for Mass Spectrometry》1998,9(8):767-774
High-energy (HE) and low-energy (LE) collisionally activated decompositions of octaethylporphyrin (OEP) and its metal complexes (ZnOEP and CuOEP) depend on whether the precursor is produced by electrospray ionization as protonated molecules or by fast atom bombardment as radical cations or protonated molecules. LE activation leads to such simple product-ion spectra that a complete picture of fragmentation emerges only after nine stages of tandem mass spectrometry (MS9). HE activation, on the other hand, gives product-ion spectra that afford an integrated view of all the decomposition channels in a single MS/MS experiment. These results are the basis of a recommendation that OEP is an appropriate model compound for investigating energy effects in the collisional activation of organic and bioorganic molecule ions. 相似文献
87.
H. Bretschneider K. Hohenlohe-Oehringen K. Graßmayr 《Monatshefte für Chemie / Chemical Monthly》1972,103(6):1523-1530
Ohne Zusammenfassung
Arylsulfonylureido- and Arylsulfonylamidoacyl Derivatives of Hydroxy cycloalkanes as potential antidiabetica (V): (1R)-, (1S)-, and (1RS)-3-endo-tosylureido borneol and (1R)-3-endo-tosylureido isoborneol相似文献
88.
Oxidation of 2-pyridinemethanol (2-pyol), 2,6-pyridinedimethanol (2,6-pydol) and 2-pyridinecarboxaldehyde (2-pyal) by CrVI was studied under pseudo-first-order conditions in the presence of a large excess of reductant and at various H+
aq concentrations; [CrVI] = 8 × 10–4 M, [reductant] = 0.025–0.20 M, [HClO4] = 1.0 and 2.0 M (I = 1.2 and 2.1 M) or 0.5–2.0 (I = 2.1 M). A parabolic dependence of the pseudo-first-order rate constant (k
obs) versus [H+] was observed for all the reductants. A linear dependence of k
obs on [2,6-pydol] and, unusually, higher than first-order dependence on [2-pyol] and [pyal] was established. The apparent activation parameters for reactions studied at constant [H+] at I = 1.2 and 2.1 M were determined. The presence of chromium species at the intermediate oxidation states: CrV, CrIV and CrII, was deduced based on e.s.r. measurements and the kinetic effects of MnII or O2 (Ar), respectively. Comparison of the available second-order rate constants for aromatic alcohols and aldehydes demonstrated that chelating abilities of the reductant facilitates the redox process, whereas the electron-withdrawing effect caused by protonating the pyridine nitrogen atom acts in the opposite direction. The unusual low reactivity of 2-pyol was ascribed to intramolecular hydrogen bond formation. 相似文献
89.
Marcelo R. L. Oliveira José E. J. C. Graúdo Nivaldo L. Speziali Vito M. De Bellis 《Structural chemistry》1999,10(1):41-45
Potassium N-4-methylphenylsulfonyldithiocarbimate, K2(4-CH3C6H4SO2N=CS2), reacted with nickel(II) chloride hexahydrate and tetrabutylammonium bromide to form the bis(N-4-methylphenylsulfonyldithiocarbimate)nickelate(II) tetrabutylammonium salt (Bu4N)2[Ni(4-CH3C6H4S2C=NSO2)2]. The elemental analyses, IR and UV-Vis data obtained were consistent with the formation of a
diamagnetic planar complex. The 1H NMR and the 13C NMR spectra showed the expected signals for the dithiocarbimate moiety and the tetrabutylammonium cation. The single-crystal structure analysis showed that this substance crystallizes in the triclinic
space group with a = 10.474(3) Å, b = 10.767(3) Å, c = 13.657(3) Å and = 81.54(2)°, = 80.44(2)°, = 67.63(2)°, V = 1398.5(8) Å3, and Z = 2. The nickel atom is coordinated to four sulfur atoms. 相似文献
90.
Summary The 1,3-dipolar cycloaddition reactions of 4,6-diazaphenanthrene 6-phenacylide formed in situ from the appropriate quaternary bromide in basic medium were investigated; as dipolarophiles acrylonitrile, ethyl acrylate,n-butyl acrylate and diethyl maleate were used.
1,3-Dipolare Cycloadditionsreaktionen von 4,6-Diazaphenanthren-6-phenacylid
Zusammenfassung Es wurden die 1,3-dipolaren Cycloadditionen von 4,6-Diazaphenanthren-6-phenacylid untersucht, welches in situ aus dem entsprechenden quaternären Bromid in Gegenwart von Alkali dargestellt wurde. Als Dipolarophile wurden Acrylnitril, Ethylacrylat,n-Buthylacrylat und Diethylmaleat eingesetzt.相似文献