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281.
Radiative decay of lithium-like ions following charge exchange collisions of 60 keV O6+ ions with H2
R. Baptist S. Bliman J.-J. Bonnet G. Chauvet S. Dousson D. Hitz B. Jacquot E.J. Knystautas 《Physics letters. A》1983,93(4):185-188
The distribution of captured electrons in the 60 keV collision is studied by detection of the subsequent far UV radiation. Strong lines corresponding to the 4f → 3d → 2p cascade have been observed. Assuming that capture to the n = 4 manifold dominates at this energy, a relative population of the l sublevels which increases with l-value is obtained. 相似文献
282.
The continuous-wave oscillation of a tunnel ring fiber laser is demonstrated. The high losses encountered in tunneling systems are compensated for by a high-gain amplifying medium from barrier widths for 0 to lambda/2. The experimental observations are in good agreement with a simple theoretical model. This near-field probe system allows one to detect small displacements in the picometer range. 相似文献
283.
The calibration of inclined hot wires used with constant temperature anemometers is performed for Mach numbers 2 and 3. The determination of the three relevant sensitivity coefficients is made for overheat ratios from 0.3 to 0.8. A strong unexpected influence of the overheat is observed independent of the apparatus used. Some particular behaviour of the angular sensitivity coefficient is observed for small-size wires; the origin of the two kinds of behaviour observed is not explained but is thought to be due to geometrical characteristics. Careful calibrations should be performed for each wire prior to any measurements. The study of turbulent stresses in a symmetrical wake at Mach 3.3 is then performed. It allows a check on the validity of the method using characteristic properties of such a flow. 相似文献
284.
Hubertus Ahlbrecht Gerhard Bonnet Dieter Enders Gerd Zimmermann 《Tetrahedron letters》1980,21(33):3175-3178
Metalated chiral allylamines of type 2 (M = Li, K) are used as chiral homoenolate equivalents and allow after alkylation and acidic hydrolysis asymmetric CC bond formations to β-substituted aldehydes in enantiomeric excesses up to 67%. 相似文献
285.
Pierre Bonnet 《Journal of Functional Analysis》1984,55(2):220-246
Call a locally compact group G, C1-unique, if L1(G) has exactly one (separating) C1-norm. It is easy to see that a 1-regular group G is C1-unique and that a C1-unique group is amenable. For connected groups G it is proved that G is C1-unique, if the interior R(G)0 of a certain part R(G) of Prim(G), called the regular part of Prim(G), is dense in Prim(G), and that C1-uniqueness of G implies the density of R(G) in Prim(G). From this it is derived that a connected group of type I is C1-unique if and only if R(G)0 is dense in Prim(G). For exponential G, a quite explicit version of this result in terms of the Lie algebra of G is given. As an easy consequence, examples of amenable groups, which are not C1-unique, and C1-unique groups, which are not 1-regular are obtained. Furthermore it is shown that a connected locally compact group G is amenable if and only if L1(G) has exactly one C1-norm, which is invariant under the isometric 1-automorphisms of L1(G). 相似文献
286.
A low angle twist boundary formed by bonding an ultrathin (001) silicon film onto a (001) silicon wafer is investigated using two-beam transmission electron microscopy to identify positively zigzag lines which separate large interfacial regions formed by square networks of 1/2? 110 ? screw misfit dislocations. An approach to the elastic field of a zigzag line is proposed from the repetitive use of angular dislocations added to a ribbon-like uniform distribution of infinitesimal dislocations parallel to a family of pure screw misfit dislocations. Theoretical and experimental images of successive triple nodes are compared to derive the unique set of Burgers vectors attached to a zigzag line. In principle, this approach can be applied to any elongated hexagonal mesh of a dislocation network. 相似文献
287.
Philippe Bonnet 《Comptes Rendus Mathematique》2004,338(11):863-868
Let C be an affine curve, and denote by H1(C) its first troncated De Rham cohomology group, i.e. the quotient of regular differential 1-forms on C by exact 1-forms. First we introduce a nonnegative invariant μ′(C,x) that measures the complexity of the singularity of C at the point x, and we establish the following formula: where H1(C) is the first singular homology group of C with complex coefficients. Second we consider a family of curves given by the fibres of a morphism , where X is an affine reduced surface. We analyse the behaviour of the function y?dimH1(f?1(y)). More precisely we show that it is constant over a Zariski open set, and that it is lower semi-continuous is general. To cite this article: P. Bonnet, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
288.
Mora G Piechaczyk O Houdard R Mézailles N Le Goff XF le Floch P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(32):10047-10057
The platinum-catalyzed allylation of amines with allyl alcohols was studied experimentally and theoretically. The complexes [Pt(eta(3)-allyl)(dppe)]OTf (2) and [Pt(eta(3)-allyl)(DPP-Xantphos)]PF(6) (5) were synthesized and structurally characterized, and their reactivity toward amines was explored. The bicyclic aminopropyl complex [Pt(CH(2)CH(2)CH(2)NHBn-kappa-C,N)(dppe)]OTf (3) was obtained from the reaction of complex 2 with an excess of benzylamine, and this complex was shown to be a deactivated form of catalyst 2. On the other hand, reaction of complex 5 with benzylamine and allyl alcohol led to formation of the 16-VE platinum(0) complex [Pt(eta(2)-C(3)H(5)OH)(DPP-Xantphos)] (7), which was structurally characterized and appears to be a catalytic intermediate. A DFT study showed that the mechanism of the platinum-catalyzed allylation of amines with allyl alcohols differs from the palladium-catalyzed process, since it involves an associative ligand-exchange step involving formation of a tetracoordinate 18-VE complex. This DFT study also revealed that ligands with large bite angles disfavor the formation of platinum hydride complexes and therefore the formation of a bicyclic aminopropyl complex, which is a thermodynamic sink. Finally, a combination of 5 and a proton source was shown to efficiently catalyze the allylation of a broad variety of amines with allyl alcohols under mild conditions. 相似文献
289.
Bonnet CS Fries PH Gadelle A Gambarelli S Delangle P 《Journal of the American Chemical Society》2008,130(31):10401-10413
We present a general theoretical framework suitable for an economical, but rigorous, analysis of the relaxivity and EPR data of paramagnetic metal complexes. This framework is based on the so-called Grenoble method that properly accounts for the fluctuations of the "static" zero-field splitting Hamiltonian and avoids the misinterpretation of experimental data, which occurs with the Solomon, Bloembergen, and Morgan (SBM) formalism and may lead to erroneous conclusions. The applicability of the SBM approximation is discussed. Our approach is implemented in the case of a new Gd(3+) chelate with a cyclodextrin derivative ligand hexakis(2-O-carboxymethyl-3,6-anhydro)-alpha-cyclodextrin (ACX), designed to obtain lanthanide complexes of enhanced stability in comparison to natural cyclodextrins. The introduction of carboxymethyl units on the six residual hydroxyl groups of an alpha-per-3,6-anhydro cyclodextrin leads to mono- and binuclear Ln(3+) complexes with log beta(110) approximately = 7.5. The GdACX complex induces large water proton relaxivity in 0.1 M KCl aqueous solution. The molecular parameters governing the longitudinal (r1) and transverse (r2) relaxivities above 1 T are obtained through simple SBM-like theoretical expressions and complementary experimental techniques. The metal hydration state, the translational diffusion coefficient of the complex, and its rotational correlation time are derived from luminescence lifetime studies, pulse-field gradient NMR, and deuteron quadrupolar relaxation, respectively. The high relaxivity induced by the GdACX complex is attributed to its high hydration state in the presence of potassium ions and to a rotational correlation time lengthened by the hydrophilic character of the ACX scaffold. 相似文献
290.
Bargueño P González-Lezana T Larrégaray P Bonnet L Rayez JC Hankel M Smith SC Meijer AJ 《The Journal of chemical physics》2008,128(24):244308
The possible existence of a complex-forming pathway for the H+O(2) reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6 eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O(2)(v=0,j=1)-->OH(v(')=1,j('))+O process reasonably well. 相似文献