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101.
Stephan Enthaler Bernhard Hagemann Giulia Erre Kathrin Junge Matthias Beller 《化学:亚洲杂志》2006,1(4):598-604
Iron complexes generated in situ catalyze homogeneously the transfer hydrogenation of aliphatic and aromatic ketones by utilizing 2‐propanol as a hydrogen donor in the presence of base. The influence of different reaction parameters on the catalytic activity is investigated in detail by applying a three‐component catalyst system composed of an iron salt, 2,2′:6′,2′′‐terpyridine, and PPh3. The scope and limitations of the described catalyst is shown in the reduction of 11 different ketones. In most cases, high conversion and excellent chemoselectivity are obtained. Mechanistic studies indicate a monohydride reaction pathway for the homogeneous iron catalyst. 相似文献
102.
A.A. Pasternak J. Srebrny A.D. Efimov V.M. Mikhajlov E.O. Podsvirova Ch. Droste T. Morek S. Juutinen G.B. Hagemann M. Piiparinen S. Törmänen A. Virtanen 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):435-448
Lifetimes of excited states in 118Te have been measured using the Doppler Shift Attenuation (DSA) and Recoil Distance (RD) methods in the 109Ag(13C, p3n) reaction at a beam energy of 54 MeV. Lifetime values of the ground-state band levels with spins I
π = 2+-16+ have been obtained. The excitation energies and B(E2) values are interpreted in the framework of a version of IBFM ( IBM + 2qp) with the maximum boson number exceeding its standard
value. A satisfactory agreement with experimental level scheme and B(E2) values for the ground-state band is achieved.
Received: 7 June 2001 / Accepted: 7 February 2002 相似文献
103.
Elisabeth Hagemann 《Mathematische Annalen》1937,114(1):126-143
Ohne ZusammenfassungDiese Arbeit ist von der philosophischen Fakultät der Universität Bonn als Dissertation angenommen worden. Den Herren O. Toeplitz und G. Köthe bin ich für mannigfache Anregungen und Ratschläge zu größtem Dank verpflichtet. 相似文献
104.
Matching-based preprocessing algorithms to the solution of saddle-point problems in large-scale nonconvex interior-point optimization 总被引:1,自引:0,他引:1
Olaf Schenk Andreas Wächter Michael Hagemann 《Computational Optimization and Applications》2007,36(2-3):321-341
Interior-point methods are among the most efficient approaches for solving large-scale nonlinear programming problems. At
the core of these methods, highly ill-conditioned symmetric saddle-point problems have to be solved. We present combinatorial
methods to preprocess these matrices in order to establish more favorable numerical properties for the subsequent factorization.
Our approach is based on symmetric weighted matchings and is used in a sparse direct LDL
T factorization method where the pivoting is restricted to static supernode data structures. In addition, we will dynamically
expand the supernode data structure in cases where additional fill-in helps to select better numerical pivot elements. This
technique can be seen as an alternative to the more traditional threshold pivoting techniques. We demonstrate the competitiveness
of this approach within an interior-point method on a large set of test problems from the CUTE and COPS sets, as well as large
optimal control problems based on partial differential equations. The largest nonlinear optimization problem solved has more
than 12 million variables and 6 million constraints. 相似文献
105.
The odd-proton nuclei 123I and 125I have been studied in the reactions 121Sb(α, 2n)123I and 123Sb(α, 2n)125I, respectively. The level schemes, spin and parity assignments are based on results obtained from singles γ-ray spectra (Eα = 27 MeV) and excitation functions, from measurements of delayed γ-rays, γ-γ coincidences, internal conversion electrons and γ-ray angular distributions. High-spin positive- and negative-parity bands with energies up to 2948 keV and spins up to in 123I and with energies up to 3775 keV and spins up to have been established. In the decay schemes of both nuclei two separated structures of levels have been observed. One group of levels shows a strong ΔJ = 2 quasirotational pattern predicted by the particle-vibration coupling model. The ΔJ = 1 sequence on a + state is assigned as a rotational structure built on the axially symmetric deformed state . In 123I a 28 ns isomer at 2660.0 keV has been found. 相似文献
106.
107.
D.L. Hillis O. Christensen B. Fernandez A.J. Ferguson J.D. Garrett G.B. Hagemann B. Herskind B.B. Back F. Folkmann 《Physics letters. [Part B]》1978,78(4):405-409
Multiplicity distributions and 〈Eγ〉 have been measured for the reaction at E(Ar) = 161, 182, 189, 209, and 236 MeV. The data at E(Ar) = 236 MeV indicate that pre-equilibrium neutrons are emitted. These data, together with other reactions leading to Er final systems, are discussed in terms of pre-equilibrium mechanisms. 相似文献
108.
109.
The band structures of the odd-A isotopes 101Pd, 103Pd and 105Pd are discussed in the framework of a core plus particle coupling model. The pairing factor (uj2 ? vj2) contained in the effective coiupling strength is found to be responsible for the change of the band structure observed in 101Pd into a structure observed in the 103,105Pd nuclei. 相似文献
110.
Efficient and easily reproducible synthesis of sterically hindered multibrominated corroles is achieved via dipyrromethane-aldehyde condensation reaction in good yields.Boron trifluoride dietherate(BF_3-Et_2O) is found to be the effective catalyst for cyclization reaction,giving corrole as the major product. 相似文献