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排序方式: 共有101条查询结果,搜索用时 15 毫秒
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Mathieu Albini Catherine Taillier Vincent Dalla Jérôme Blanchet Jacques Rouden 《Tetrahedron letters》2014
A dramatic improvement of our previous methodology based on a Suzuki–Miyaura cross-coupling to access 3,3′-disubstituted H8-BINOLs using microwave heating is reported herein. These new conditions represent a large gain in term of atom-economy, reaction time, catalyst loading, and excess of reagents employed. 相似文献
4.
We study the long-time asymptotics of the doubly nonlinear diffusion equation ${\rho_t={\rm div}(|\nabla\rho^m |^{p-2} \nabla\left(\rho^m\right))}We study the long-time asymptotics of the doubly nonlinear diffusion equation rt=div(|?rm |p-2 ?(rm)){\rho_t={\rm div}(|\nabla\rho^m |^{p-2} \nabla\left(\rho^m\right))} in
\mathbbRn{\mathbb{R}^n}, in the range
\fracn-pn(p-1) < m < \fracn-p+1n(p-1){\frac{n-p}{n(p-1)} < m < \frac{n-p+1}{n(p-1)}} and 1 < p < ∞ where the mass of the solution is conserved, but the associated energy functional is not displacement convex. Using a
linearisation of the equation, we prove an L
1-algebraic decay of the non-negative solution to a Barenblatt-type solution, and we estimate its rate of convergence. We then
derive the nonlinear stability of the solution by means of some comparison method between the nonlinear equation and its linearisation.
Our results cover the exponent interval
\frac2nn+1 < p < \frac2n+1n+1{\frac{2n}{n+1} < p < \frac{2n+1}{n+1}} where a rate of convergence towards self-similarity was still unknown for the p-Laplacian equation. 相似文献
5.
In a recent paper, Nguyen et al. (2018) built a distributionally robust estimator for the precision matrix of the Gaussian distribution. The distributional uncertainty size is a key ingredient in the construction of this estimator. We develop a statistical theory which shows how to optimally choose the uncertainty size to minimize the associated Stein loss. Surprisingly, rather than the expected canonical square-root scaling rate, the optimal uncertainty size scales linearly with the sample size. 相似文献
6.
Thiré N Cireasa R Staedter D Blanchet V Pratt ST 《Physical chemistry chemical physics : PCCP》2011,13(41):18485-18496
The predissociation dynamics of the vibrationless level of the first Rydberg 6s (B (1)E) state of CH(3)I has been studied by femtosecond-resolved velocity map imaging of both the CH(3) and I photofragments. The kinetic energy distributions of the two fragments have been recorded as a function of the pump-probe delay, and as a function of excitation within the umbrella and stretching vibrational modes of the CH(3) fragment. These observations are made by using (2 + 1) Resonant Enhanced MultiPhoton Ionization (REMPI) via the state of CH(3) to detect specific vibrational levels of CH(3). The vibrational branching fractions of the CH(3) are recovered by using the individual vibrationally state-selected CH(3) distributions to fit the kinetic energy distribution obtained by using nonresonant multiphoton ionization of either the I or the CH(3) fragment. The angular distributions and rise times of the two fragments differ significantly. These observations can be rationalized through a consideration of the alignment of the CH(3) fragment and the effect of this alignment on its detection efficiency. Two additional dissociation channels are detected: one associated with Rydberg states near 9.2 eV that were observed previously in photoelectron studies, and one associated with photodissociation of the parent cation around 15 eV. 相似文献
7.
Threshold photoelectron spectra (TPESs) were obtained for naphthalene, anthracene, pyrene, 1,2-dihydronaphthalene, and 9,10-dihydroanthracene using imaging photoelectron photoion coincidence spectroscopy, from threshold to a photon energy of ~20 eV. Outer valence Green's function calculations at the OVGF∕cc-pVTZ level of theory were used to assign molecular orbitals to the observed TPES features. There is generally good agreement between the predicted and observed bands. Threshold regions for each molecule exhibit vibrational structure which is readily assigned based on previous PES studies. While the measured adiabatic ionization energies (IE(a)) for naphthalene, anthracene, and pyrene are in good agreement with previous works, new values are reported for the two dihydro species (1,2-dihydronaphthalene, 8.010 ± 0.010 eV and 9,10-dihydroanthracene, 8.335 ± 0.010 eV). A comparison is also made with the G3∕∕B3LYP composite method, which consistently overestimates the IE values by 0.06-0.09 eV. The double ionization energies for anthracene and pyrene have been measured to be 19.3 ± 0.2 and 19.8 ± 0.2 eV, respectively. 相似文献
8.
Tharwat Mohy El Dine David Evans Prof. Jacques Rouden Dr. Jérôme Blanchet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5894-5898
A highly efficient and mild transamidation of amides with amines co‐catalysed by borinic acid and acetic acid has been reported. A wide range of functionalised formamides was synthesized in excellent yields, including important chiral α‐amino acid derivatives, with minor racemisation being observed. Experiments suggested that the reaction rely on a cooperative catalysis involving an enhanced boron‐derived Lewis acidity rather than an improved Brønsted acidity of acetic acid. 相似文献
9.
J.?M.?L’HermiteEmail author V.?Blanchet A.?Le?Padellec B.?Lamory P.?Labastie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,28(3):361-366
This paper describes the spectroscopy of Na3F both in the frequency and time domains. The photoionization efficiency curve shows two thresholds, associated to two isomers. The excited electronic states of the C2v isomer have been probed by photodepletion spectroscopy, and the results are used to analyze a time-resolved study of photoexcited Na3F, probed by photoionization. The pump-probe signal clearly shows damped oscillations, the period of which is fitted to
fs, close to twice the previously measured bending mode of Na2F [1], while the relaxation time is
fs.Received: 31 October 2003, Published online: 6 January 2004PACS:
36.40.Qv Stability and fragmentation of clusters - 33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion) 相似文献
10.
Dr. William Erb Akila Hellal Mathieu Albini Prof. Jacques Rouden Dr. Jérôme Blanchet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6608-6612
An unprecedented spontaneous reactivity between diazonium salts and diboronic acid has been unveiled, leading to a versatile arylboronic acid synthesis directly from (hetero)arylamines. This fast reaction (35 min overall) tolerates a wide range of functional groups and is carried out under very mild conditions. The radical nature of the reaction mechanism has been investigated. 相似文献