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61.
Dietrich Döpp Alaa A HassanAboul-Fetouh E Mourad Ahmed M Nour El-DinKlaus Angermund Carl KrügerChristian W Lehmann Jörg Rust 《Tetrahedron》2003,59(27):5073-5081
N-Arylisoindolines 1a-i react with ethenetetracarbonitrile 2 in aerated benzene by formation of [3-(2-aryl-3-dicyanomethylene-2,3-dihydro-1H-isoindol-1-ylidene)-2-aryl-2,3-dihydro-1H-isoindol-1-ylidene]propanedinitriles 8a-i (20-36%), N-aryl-3-dicyanomethylene-isoindol-2-ones 9a-i (15-21%) and N-arylphthalimides 10a-i (4-9%) as well as 1,1,2,2-tetracyanoethane 11 (35-55%). The structure of 8d has been unambiguously confirmed by a single crystal X-ray structure analysis. A rationale for the formation of products 8-11 is presented. 相似文献
62.
Two alternative approaches for the calibration of the intramolecular nitrogen isotope distribution in nitrous oxide using isotope ratio mass spectrometry have yielded a difference in the 15N site preference (defined as the difference between the delta15N of the central and end position nitrogen in NNO) of tropospheric N2O of almost 30 per thousand. One approach is based on adding small amounts of labeled 15N2O to the N2O reference gas and tracking the subsequent changes in m/z 30, 31, 44, 45 and 46, and this yields a 15N site preference of 46.3 +/- 1.4 per thousand for tropospheric N2O. The other involves the synthesis of N2O by thermal decomposition of isotopically characterized ammonium nitrate and yields a 15N site preference of 18.7 +/- 2.2 per thousand for tropospheric N2O. Both approaches neglect to fully account for isotope effects associated with the formation of NO+ fragment ions from the different isotopic species of N2O in the ion source of a mass spectrometer. These effects vary with conditions in the ion source and make it impossible to reproduce a calibration based on the addition of isotopically enriched N2O on mass spectrometers with different ion source configurations. These effects have a much smaller impact on the comparison of a laboratory reference gas with N2O synthesized from isotopically characterized ammonium nitrate. This second approach was successfully replicated and leads us to advocate the acceptance of the site preference value 18.7 +/- 2.2 per thousand for tropospheric N2O as the provisional community standard until further independent calibrations are developed and validated. We present a technique for evaluating the isotope effects associated with fragment ion formation and revised equations for converting ion signal ratios into isotopomer ratios. 相似文献
63.
J. J. Buitendag W. J. Naudé R. Saayman N. J. A. Rust J. W. Koen 《Zeitschrift für Physik A Hadrons and Nuclei》1980,295(2):107-119
The spins and electromagnetic properties of levels in45Sc up to 2,352 keV were studied by means of inelastic proton scattering using a 3-parameter coincidence arrangement and Coulomb excitation with3He and4He beams. Relevant experimental results are discussed in terms of the Thankappen-True core-plus-particle model. 相似文献
64.
Control of the charge state of metal atoms on thin MgO films 总被引:1,自引:0,他引:1
Sterrer M Risse T Martinez Pozzoni U Giordano L Heyde M Rust HP Pacchioni G Freund HJ 《Physical review letters》2007,98(9):096107
The arrangement of single gold and palladium atoms deposited on the surface of a 3 monolayer thin film of MgO was investigated using low-temperature scanning tunneling microscopy. While Pd atoms are arranged in a random fashion, Au forms an ordered array on the surface. The long-range ordering as well as the scanning tunneling microscopy appearance of single Au atoms on a 3 monolayer thin MgO film can be explained by partial charge transfer from the substrate to Au atoms as predicted recently by density functional theory calculations [Phys. Rev. Lett. 94, 226104 (2005)10.1103/PhysRevLett.94.226104]. In contrast with that, Au atoms on a thick film were found to be essentially neutral. 相似文献
65.
66.
TV image intensifiers with storage devices can be utilized for the read-out and processing in real-time of electron microscopic images. By means of the single electron response and the detection quantum efficiency (DQE) the dimensioning principles for the design of such devices are explained and studied for various special systems. Whereas at high final image current densities a DQE decay depending on the dynamic range of the camera tube must be accepted, with sufficient optoelectronic preamplification at medium current densities values of about 0.80 are obtained. The ideal detector (DQE = 1) is realized at small current densities with digital processing and storage. 相似文献
67.
Jrg Saßmannshausen Jrg Rust Richard Goddard 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):e236-e237
The title compound, [Zr(C7H7)3(C15H17)], (I), crystallizes from light petroleum with two independent molecules in the asymmetric unit. Whereas in the parent molecule, Zr(η5‐C5H5)(CH2Ph)3, all three Zr—CH2Ph angles are equal, in (I), they differ significantly. In spite of their different environments, both independent molecules in (I) exhibit a small, an expected, and a large Zr—CH2Ph angle. The angles are similar to those of the closely related tribenzyl[η5‐(benzyldimethylsilyl)cyclopentadienyl]zirconium complex. The smallest Zr—CH2Ph angle and the consequently relatively short Zr?Cipso distance are indicative of η2‐bonding of the benzyl group. 相似文献
68.
On the Reactivity of Tetrakis(trifluoromethyl)cyclopentadienone towards Carbon‐Based Lewis Bases 下载免费PDF全文
Sigrid Holle Dr. Daniel Escudero Dr. Blanca Inés Jörg Rust Prof. Walter Thiel Dr. Manuel Alcarazo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2744-2749
The reactivitiy of tetrakis(trifluoromethyl)cyclopentadienone towards different C‐based Lewis bases, such as N‐heterocyclic carbenes (NHC), ylides and isonitriles, are reported. While sterically not hindered carbenes were found to yield kinetic adducts by regiospecific nucleophilic attack at the position adjacent to the carbonyl group of the ketone, bulkier nucleophiles afforded the thermodynamically more stable O‐bridged zwitterions. Interestingly, isonitriles were found to dimerize and trimerize under the same reaction conditions, forming bicyclic products that evolve differently depending on the nature of the substituents. 相似文献
69.
70.
Sterrer M Fischbach E Heyde M Nilius N Rust HP Risse T Freund HJ 《The journal of physical chemistry. B》2006,110(17):8665-8669
The formation of surface color centers (F(S) centers) by electron bombardment of thin MgO(001) films is investigated using electron paramagnetic resonance and low-temperature scanning tunneling microscopy. At low electron doses both techniques indicate the formation of singly occupied color centers (F(S)(+)), whereas at high electron doses the doubly occupied type (F(S)(0)) is dominant. It is suggested that with increasing electron dose F(S)(+) centers are transformed into F(S)(0). Tunneling spectra of individual F(S)(0) centers reveal a large distribution of energetic positions of occupied and unoccupied states, which is caused by local variations of the coordination number of the defects and explains the broad signals usually detected with integrating spectroscopic techniques. 相似文献