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91.
Visart de Bocarmé T Chau TD Tielens F Andrés J Gaspard P Wang RL Kreuzer HJ Kruse N 《The Journal of chemical physics》2006,125(5):054703
We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures (p < 10(-4) m/bar) and temperatures (T = 300-350 K). Steady electric fields of 6 V/nm do not allow dissociating the oxygen molecule. The measured O2+ intensities rather reflect ionization of O2 molecules at critical distances above the Au tip surface. Certain amounts of Au-O2 complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with Au10 clusters (Delta E = 0.023 eV) and comparatively stronger interaction with Au1/Au(100) model surfaces (Delta E = 0.25 eV). No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra. 相似文献
92.
Four exchange properties, including the usual one, are discussed. Assuming the finiteness condition or a weaker condition (called minimal condition), all four are equivalent. But examples show that in general no two of the four properties are equivalent. Furthermore it is shown that all four properties and the minimal condition follow from the Existence Theorem for a basis. 相似文献
93.
Control of an Adaptive Refinement Technique of Generalized Cell Mapping by System Dynamics 总被引:1,自引:0,他引:1
Generalized cell mapping is an efficient and powerful numerical tool for the prediction of the long-term behavior and global analysis of nonlinear dynamic systems. The only drawback of this method is the enormous computational effort it requires for high-dimensional systems. We overcome this problem by adaptively refining a very rough starting cell grid, where the adaptation is controlled by the long-term dynamics of the system. We illustrate the efficiency of our approach by examples. 相似文献
94.
95.
Wieslaw Wojnowski Karl Peters Eva-Maria Peters Hans Georg von Schnering 《无机化学与普通化学杂志》1985,531(12):147-152
Contributions to the Chemistry of Silicon-Sulfur Compounds. XXXV. The Dimeric Thallium(I)-tri-tert-butoxysilanethiolate Thallium(I)-tri-tert-butoxysilanethiolate is formed as a dimer by reaction of tri-tert-butoxysilanethiol with TlNO3. The compound crystallizes as colourless triclinic plates. F.I. mass spectra show only the mass of the dimeric species (m/e = 968), in the E.I. mass spectra, however, also the peak for the monomeric unit (m/e = 484) is observed. The molecule is of 1 /Ci symmetry. The central four-membered ring is plane, the bond distances and angles therein are d (Tl? S) = 289 pm and S/Tl/S = 91.5°. The Tl atoms are additionally coordinated by an oxygen atom of the tri-tert-butoxysilyl group (d(Tl? O) = 280 pm). The mean bond angle at the threebonded sulfur atom was found to be 90° (d(S? Si) = 207.8 pm). Related details of the structure are discussed (space group P1 ; a = 927.5 pm, b = 1395.1 pm, c = 882.1 pm; α = 108.43°, β = 116.77°, γ = 90.98°; Z = 2; R = 0.032; 2887 reflections hkl). 相似文献
96.
Waldemar Adam Hector Rebollo Heinz Dürr Karl-Heinz Pauly Karl Peters Eva-Maria Peters Hans-Georg von Schnering 《Tetrahedron letters》1982,23(9):923-926
4-Methyl-1,2,4-triazoline-3,5-dione (MTAD) gives with 7-spiro-fluorenyl-1,3,5-cycloheptatriene () initially he norcaradine-type urazole () which at ambient temperatures rearranges into (), while 102 gives the tropilidene-type endoperoxide (). 相似文献
97.
98.
Klaus Bieger Gernot Heckmann Ekkehard Fluck Frank Weller Karl Peters Eva-Maria Peters 《无机化学与普通化学杂志》1995,621(12):1981-1988
1,4-Dihydro-1λ5,4λ5-[1,4]diphosphinines and a 1,4-Dihydro-1λ3,4λ3-[1,4]diphosphinine Reaction of thio- or dithiocarbonic acids with ethinyl amino phosphanes leads to 1,4-dihydro-1λ5,4λ5-[1,4]diphosphinine-1,4-disulfides. By this route compounds 4, 7 , and 8 have been prepared. Desulfurization of 4 with tri-n-butylphosphane results in 1,2,4,5-tetraphenyl-1,4-dihydro-1λ3,4λ3-[1,4]-diphosphinine 5 , which can be oxidized with tert-butyl-peroxide to the corresponding dioxide, 6 . From the reaction mixture of phenyl-phenylethinyl diethylamino phosphane and thioacetamide compound 4 and the unsymmetrical 1,4-dihydro-1λ5,4λ5-[1,4]diphosphinine 9 were isolated. Properties, nmr, ir and mass spectra of all new products are reported. A mechanism for the formation of 9 is suggested. The results of the X-ray structure determination of 8 and 9 are described. 相似文献
99.
Bringmann G Menche D Kraus J Mühlbacher J Peters K Peters EM Brun R Bezabih M Abegaz BM 《The Journal of organic chemistry》2002,67(16):5595-5610
The "lactone concept" has been efficiently employed for the first atropo-enantioselective synthesis of knipholone and related natural phenylanthraquinones. Besides the regio- and stereoselective construction of the biaryl axis, another important step was the "synthetically late" introduction of the C-acetyl group, either by a Friedel-Crafts type acetylation or by an ortho-selective Fries rearrangement first tested on simplified model systems and subsequently applied to the highly atroposelective preparation of the natural products and of simplified analogs thereof for biotesting. The synthetic availability of these natural biaryls, their precursors, and their unnatural analogs permitted a broader investigation of the antiplasmodial activities of these interesting biaryls. 相似文献
100.