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排序方式: 共有155条查询结果,搜索用时 31 毫秒
11.
Dr. Ludovic Fournier Dr. Isabelle Aujard Dr. Thomas Le Saux Sylvie Maurin Sandra Beaupierre Prof. Dr. Jean‐Bernard Baudin Prof. Dr. Ludovic Jullien 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17494-17507
The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron‐donating groups in the 7 position and electron‐withdrawing groups in the 2‐, and 2‐ and 3 positions. In particular, we showed that the diethylamino‐thiocoumarylmethyl and the diethylamino‐coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470–500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue‐cyan light sources, respectively. 相似文献
12.
Disassembly Kinetics of Quinone‐Methide‐Based Self‐Immolative Spacers that Contain Aromatic Nitrogen Heterocycles 下载免费PDF全文
Ahmed Alouane Dr. Raphaël Labruère Katherine J. Silvestre Dr. Thomas Le Saux Dr. Frédéric Schmidt Prof. Dr. Ludovic Jullien 《化学:亚洲杂志》2014,9(5):1334-1340
We prepared several pyridine‐ and pyrimidine‐based self‐immolative spacer groups to evaluate the significance of the resonance energy of the spacer aromatic ring on the kinetics of 1,4‐ and 1,6‐elimination reactions, which govern spacer disassembly. Subsequently, we relied on a photoactivation procedure to accurately analyze the disassembly kinetics. Beyond providing new results that are relevant for deriving quantitative structure–property relationships, herein, we demonstrate that pH value can be used as an efficient parameter to finely control the disassembly time of a self‐immolative spacer after an initial activation. 相似文献
13.
Stéphanie Gracia Cédric Marion Jullien Rey Florence Popowycz Stéphane Pellet-Rostaing Marc Lemaire 《Tetrahedron letters》2012,53(25):3165-3168
Horner-Wadsworth Emmons olefination followed by asymmetric hydrogenation allowed the first synthetic access to the chiral thiotryptophan with good enantiomeric excess. Oxazolidinone formation followed by a Pictet–Spengler condensation provided the benzothiophenic analog of Azatoxin. 相似文献
14.
A. Jullien X. Chen A. Ricci J.-P. Rousseau R. Lopez-Martens L. P. Ramirez D. Papadopoulos A. Pellegrina F. Druon P. Georges 《Applied physics. B, Lasers and optics》2011,102(4):769-774
A 80???J, 6?fs, CEP-stable high-contrast injector is demonstrated. The device relies on standard pulse post-compression in hollow-core fiber followed by a temporal filter based on cross-polarized wave generation. Pulses with a Gaussian spectrum over 350?nm, centered at 750?nm, are generated. Temporal measurements show that the contrast of the few-cycle pulses is enhanced on a femtosecond and picosecond time scale. The carrier-envelope phase stability is preserved (0.3?rad RMS). These performances make the system an ideal seed laser for high-power, high-contrast OPCPA systems. 相似文献
15.
The Silberstein models for computing the main polarizabilities of polyatomic molecules are discussed. They apparently constitute the simplest sufficient approach to account for experimental data and assimilate the atoms' electronic surroundings to mutually interacting conducting polarizable spheres. If it is supposed the spheres are centered on the nuclei of the corresponding atoms, interesting but poor results are obtained. More complicated calculations, modifying the center's localisation according to physicochemical evidences, show that a very good estimation of average polarizabilities and anisotropies can be achieved, assuming that in a given molecule the spheres associated to two bounding atoms are tangential and that their polarizabilities are the third power of their proper radius. This “geometrically improved” Silberstein model is compared to the quantum mechanical and “optic valence” models as well as to the other lately used Silberstein models: we put forward its interest and possibilities in relating structure and reactivity, or structure and stability. 相似文献
16.
Encouraged by experiments on 4He in aerogels, we confine planar spins in the pores of simulated aerogels (diffusion limited cluster-cluster aggregation) in order to study the effect of quenched disorder on the critical behavior of the three-dimensional XY model. Monte Carlo simulations and finite-size scaling are used to determine critical couplings K(c) and exponents. In agreement with experiments, clear evidence of change in the thermal critical exponents nu and alpha is found at nonzero volume fractions of impurities. These changes are explained in terms of hidden long-range correlations within disorder distributions. 相似文献
17.
Aujard I Baltaze JP Baudin JB Cogné E Ferrage F Jullien L Perez E Prévost V Qian LM Ruel O 《Journal of the American Chemical Society》2001,123(34):8177-8188
Pure organic molecules exhibiting a suitable concave rigid shape are expected to give porous glasses in the solid state. Such a feature opens new opportunities to avoid crystallization and to improve molecular solubility in relation to the high internal energy of these solid phases. To quantitatively explore the latter strategy, a series of rigid tetrahedral conjugated molecules nC and the corresponding models nR have been synthesized. Related to the present purpose, several properties have been investigated using UV absorption, steady-state fluorescence emission, differential scanning calorimetry, (1)H NMR translational self-diffusion, magic angle spinning (13)C NMR, and multiple-beam interferometry experiments. The present tetrahedral crosses are up to 8 orders of magnitude more soluble than the corresponding model compounds after normalization to the same molecular length. In addition, they give concentrated monomeric solutions that can be used to cover surfaces with homogeneous films whose thickness goes down to the nanometer range. Such attractive features make cross-like molecular architectures promising for many applications. 相似文献
18.
J.F. Sadoc R. Jullien N. Rivier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):355-363
An extension of the Voronoi tessellation, the Laguerre polyhedral decomposition, is introduced and applied to the analysis
of the packing geometry of amino-acids in folded proteins. This method considers an ensemble of points with different weights
and therefore it is well suited for a geometrical analysis of a set of objects with a wide size distribution. With this method
it is shown that the true volumes occupied by the amino-acids inside a protein is better described than with the standard
Voronoi procedure. This method allows defining unambiguously (without cut-off distance) the neighborhood for each amino-acid
in a given protein and contact matrices can be established which contain all topological informations on the internal structure.
Finally, a statistical analysis of the geometrical characteristics of the polyhedra attached to each amino-acid is done over
a collection of 35 proteins.
Received 20 November 2002 / Received in final form 26 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: sadoc@lps.u-psud.fr 相似文献
19.
We show that a standard hollow-core fiber (HCF) compressor device can be used to efficiently compress multi-mJ energy laser
pulses down to few-cycle duration, when seeded with linearly chirped, circularly polarized pulses. With this approach, we
routinely generate carrier-envelope phase (CEP)-locked, 1.6 mJ, 4.8 fs pulses using only 3 mJ, 25 fs pulses as the seed. 相似文献
20.
Eliminating the contribution of interfering compounds is a key step in chemical analysis. In complex media, one possible approach is to perform a preliminary separation. However purification is often demanding, long, and costly; it may also considerably alter the properties of interacting components of the mixture (e.g. in a living cell). Hence there is a strong interest for developing separation-free non-invasive analytical protocols. Using photoswitchable probes as labelling and titration contrast agents, we demonstrate that the association of a modulated monochromatic light excitation with a kinetic filtering of the overall observable is much more attractive than constant excitation to read-out the contribution from a target probe under adverse conditions. An extensive theoretical framework enabled us to optimize the out-of-phase concentration first-order response of a photoswitchable probe to modulated illumination by appropriately matching the average light intensity and the radial frequency of the light modulation to the probe dynamics. Thus, we can selectively and quantitatively extract from an overall signal the contribution from a target photoswitchable probe within a mixture of species, photoswitchable or not. This simple titration strategy is more specifically developed in the context of fluorescence imaging, which offers promising perspectives. 相似文献