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31.
32.
Linda Feketeová Jan Žabka Fabio Zappa Verena Grill Paul Scheier Tilmann D. Märk Zdenek Herman 《Journal of the American Society for Mass Spectrometry》2009,20(6):927-938
Surface-induced interactions of the projectile ion C2D4+ with room-temperature (hydrocarbon covered) stainless steel, carbon highly oriented pyrolytic graphite (HOPG), and two different
types of diamond surfaces (O-terminated and H-terminated) were investigated over the range of incident energies from a few
eV up to 50 eV. The relative abundance of the product ions in dependence on the incident energy of the projectile ion [collision-energy
resolved mass spectra, (CERMS) curves] was determined. The product ion mass spectra contained ions resulting from direct dissociation
of the projectile ions, from chemical reactions with the hydrocarbons on the surface, and (to a small extent) from sputtering
of the surface material. Sputtering of the surface layer by low-energy Ar+ ions (5–400 eV) indicated the presence of hydrocarbons on all studied surfaces. The CERMS curves of the product ions were
analyzed to obtain both CERMS curves for the products of direct surface-induced dissociation of the projectile ion and CERMS
curves of products of surface reactions. From the former, the fraction of energy converted in the surface collision into the
internal excitation of the projectile ion was estimated as 10% of the incident energy. The internal energy of the surface-excited
projectile ions was very similar for all studied surfaces. The H-terminated room-temperature diamond surface differed from
the other surfaces only in the fraction of product ions formed in H-atom transfer surface reactions (45% of all product ions
formed versus 70% on the other surfaces). 相似文献
33.
Fei Z Ang WH Geldbach TJ Scopelliti R Dyson PJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(15):4014-4020
A series of imidazolium dicarboxylic acids have been prepared from the reaction of the 1,3‐bis(carboxymethyl)imidazolium zwitterion with the Brønsted acids HX (X=F, Br, Cl, ClO4). The structures of these acids have been established in the solid state by single‐crystal X‐ray diffraction, which revealed that the cations and anions form strong hydrogen bonds through O? H???X interactions, leading to the formation of dimeric and polymeric networks. These acids react with elemental zinc and cobalt to form stable polymeric coordination complexes, some of which have also been characterised by X‐ray diffraction. 相似文献
34.
Georg Ramer Jürgen Kasberger Markus Brandstetter Ahmed Saeed Bernhard Jakoby Bernhard Lendl 《Applied physics. B, Lasers and optics》2014,116(2):325-332
We present the design and fabrication of a single-mode slab waveguide structure for mid-infrared spectroscopy optimized for broadband coupling. The sensor uses grating couplers for robust off-axis coupling and a silicon nitride guiding layer for mechanical robustness. An external cavity quantum cascade laser-based transmission method is introduced for characterizing the structure’s broadband coupling behavior. Light from an external cavity quantum cascade laser with a spectral range of 0.5 μm around 6 μm was coupled into the waveguide without the need for moving parts. First spectra taken with this sensor are presented. 相似文献
35.
Yifang Ouyang Xiaofeng Tong Chang Li Hongmei Chen Xiaoma Tao Tilmann Hickel Yong Du 《Physica B: Condensed Matter》2012,407(23):4530-4536
With this work we present a newly developed potential for the Fe–Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D03-Fe3Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D03-Fe3Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe–Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe–Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe–Al system. 相似文献
36.
S Jürschik B Agarwal T Kassebacher P Sulzer CA Mayhew TD Märk 《Journal of mass spectrometry : JMS》2012,47(9):1092-1097
In this work, we illustrate the application of proton transfer reaction mass spectrometry (PTR-MS) in the field of food and drink safety. We present proof-of-principle measurements of four different drinks (water, tea, red wine and white wine) each spiked separately with four different date rape drugs (chloral hydrate, tricholorethanol, γ-butyrolactone and butanediol). At first, the ideal PTR-MS operating conditions (reduced electric field strength and monitoring the most abundant [fragment] ion) for detection of the drugs were determined utilizing a time-of-flight-based PTR-MS instrument. We then dissolved small quantities of the drugs (below the activation threshold for effects on humans) into the various types of drinks and detected them using a quadrupole-based PTR-MS instrument via two different sampling methods: (1) dynamic headspace sampling and (2) direct liquid injection. Both methods have their advantages and drawbacks. Only with dynamic headspace sampling can rape drug contaminations be detected within a timeframe of seconds, and therefore, this method is the most promising use of PTR-MS as a fast, sensitive and selective monitor for the detection of food and drink contamination. Copyright ? 2012 John Wiley & Sons, Ltd. 相似文献
37.
Transparent Boundary Conditions for Split-Step Padé Approximations of the One-Way Helmholtz Equation
In this paper, we generalize the nonlocal discrete transparent boundary condition introduced by F. Schmidt and P. Deuflhard (1995, Comput. Math. Appl.29, 53–76) and by F. Schmidt and D. Yevick (1997, J. Comput. Phys.134, 96–107) to propagation methods based on arbitrary Padé approximations of the two-dimensional one-way Helmholtz equation. Our approach leads to a recursive formula for the coefficients appearing in the nonlocal condition, which then yields an unconditionally stable propagation method. 相似文献
38.
39.
In contrast to Fe+/diol complexes, gas-phase dehydrogenation of the corresponding FeII alkoxides, [FeO(CH2)nCH2OH]+, is a highly specific process in the course of which oxidation of the terminal OH group takes place. Based on labeling studies, this is the exclusive mechanism for n = 2 and 3 (Scheme: path ); for higher homologues, as for example [FeOf(CH2)7CH2OH]+, the labeling data demonstrate that an additional mechanism is operative, involving the dehydrogenation of internal positions of the alkyl chain (path ). The Fe+-mediated oxidation –CH2OH → –CHO +H2: constitutes one of the rare examples of O-H bond activation by late cationic transition-metal ions. 相似文献
40.
Edgar Mark Erich Zbiral Hannelore H. Brandstetter 《Monatshefte für Chemie / Chemical Monthly》1980,111(1):289-307
Reaction of methyl -D-galactopyranoside (1) with two equivalents oft-butyldimethylchlorosilane yields methyl 2,6-bis-O-(tBDMSi)--D-galactopyranoside (1 b), methyl 3,6-bis-O-(tBDMSi)--D-galactopyranoside (1 c) and methyl 4,6-bis-O-(tBDMSi)--D-galactopyranoside (1 d). Likewise methyl -D-mannopyranoside (6) affords methyl 2,6-bis-O-(tBDMSi)--D-mannopyranoside (6 d) and methyl 3,6-bis-O-(tBDMSi)--D-mannopyranoside (6 b), which can be isomerised withTPP/DEAD to methyl 4,6-bis-O-(tBDMSi)--D-mannopyranoside (6 f). Methyl 6-O-(tBDMSi)--D-galactopyranoside (1 a) and methyl 6-O-(tBDMSi)--D-mannopyranoside (6 a) can be prepared from1 or6 with one equivalent oft-butyldimethylchlorosilane.Without an external nucleophile the sugar derivatives1 a and1 b react withTPP/DEAD to form the 3,4-carbonato--D-galactopyranosides1 h and1 i and the 3,4-carbonato-2-O-ethoxycarbonyl--D-galactoside (1 j). In contrast to the formation of the compound1 i by means ofTPP/DEAD the reaction of1 a withTPP and Di-t-butyl-azodicarboxylate (DTBAD) yields the 2,3-anhydro--D-taloside (4 b) and only a small amount of1 i. The epoxide4 b can be cleaved withp-nitrobenzoylchloride/pyridine to the 3-chloro-3-deoxy-2,6-di-O-p-nitrobenzoyl--D-idoside (5). Reaction of1 c and1 d withTPP/DEAD yields the 2,3-anhydro--D-gulopyranoside (2), which can be transformed with NaN3/NH4Cl to the 2-azido-2-deoxy--D-idopyranoside (3).Likewise6 a and6 d can be converted to the 3,4-anhydro--D-talosides (7 a and7 b). Reaction of7 b or6 d withTPP/DEAD/NH3 leads to 3,4-anhydro-2-azido-2-deoxy--D-galactopyranoside (8) and 3-azido-3-deoxy--D-altropyranoside (10), resp.The epoxide7 b is opened with NaN3/NH4Cl to the 4-azido-4-deoxymannosides (11 a and11 c) and the 3-azido-3-deoxy--D-idopyranoside (12), while the epoxide8 affords the 2,4-di-azido-2,4-dideoxy--D-glucopyranoside (9).Structures were elucidated by1H-NMR-analysis of the corresponding acetates.
H. H. Brandstetter undE. Zbiral, Helv., im Druck. 相似文献