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排序方式: 共有496条查询结果,搜索用时 15 毫秒
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2.
Charles Romain Charlotte K. Williams 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(6):1633-1636
A novel chemoselective polymerization control yields predictable (co)polymer compositions from a mixture of monomers. Using a dizinc catalyst and a mixture of caprolactone, cyclohexene oxide, and carbon dioxide enables the selective preparation of either polyesters or polycarbonates or copoly(ester‐carbonates). The selectivity depends on the nature of the zinc–oxygen functionality at the growing polymer chain end, and can be controlled by the addition of exogeneous switch reagents. 相似文献
3.
Dr. Romain Ramozzi Dr. Nicolas Chéron Dr. Laurent El Kaïm Dr. Laurence Grimaud Dr. Paul Fleurat‐Lessard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):9094-9099
Following our previous mechanistic studies of multicomponent Ugi‐type reactions, theoretical calculations have been performed to predict the efficiency of new substrates in Ugi–Smiles couplings. First, as predicted, 2,4,6‐trichlorophenol experimentally gave the corresponding aryl‐imidate. Theoretical predictions of nitrosophenols as good acidic partners were then successfully confirmed by experiments. In the latter case, the reaction offers a new access to benzimidazoles. 相似文献
4.
Maria Laura Di Lorenzo Paolo Rubino Romain Luijkx Marion Hélou 《Colloid and polymer science》2014,292(2):399-409
The influence of chain structure on crystal polymorphism of poly(lactic acid) (PLA) with high l-lactic acid content (97.8–100 %) is detailed in this contribution. Upon usual processing conditions of PLA, only α and α′ crystals grow, which makes these two polymorphs of major interest for research. The two crystal modifications have similar chain packing, which complicates their quantitative analysis by diffraction methods. The two crystal modifications are instead easily identified by analysis of the crystallization kinetics, which varies not only with temperature, but also with crystal polymorphism. The dependence of the rate of ordering on temperature shows two distinct maxima around 105–110 and 120–125 °C, which are related to growth of α′ and α crystals, respectively. Addition of d-lactic acid co-units leads to a decrease of the overall crystallization rate of PLA, as well as of the rate of spherulite growth (G) of both the crystal modifications. The relative crystallization rates of α and α′ forms are highly affected by stereoregularity, especially in the PLA grades that have a high crystallization rate. A high d-lactic acid content results not only in an overall slower crystal growth, but also in a varied temperature range where each of the two crystal modifications prevail, with a shift to lower temperatures of both the maxima of the G vs. temperature plots, indicating that inclusion of d-lactic acid units in the PLA chain affects crystallization rate of both α and α′ crystal modifications. 相似文献
5.
The Al45Cr7 compound is considered to exhibit an approximant structure of the icosahedral Al4Cr phase. Its (010) surface has been investigated in detail using density functional calculations. Surface energy calculations show that the stable terminations result from a cleavage of the crystal between adjacent atomic planes, in agreement with the layered structure of the compound. The integrity of the icosahedral atomic arrangements (icosahedral clusters) found in the bulk structure, is predicted to be removed at the surface. This result is in contrast to what has been previously concluded for the (010) surface of the Al13Fe4 quasicrystal approximant. Our findings are discussed in relation to the bonding network in the compound, calculated using the Crystal Orbital Hamiltonian Population approach, as possible reasons for such contrasted behavior. 相似文献
6.
The Raman and infrared spectra of (NH4)3H(SO4)2 crystal were investigated in the range 20–300 K. An assignment of bands due to internal and external vibrations is given. The crystalline phases designated II, III, V and VII were identified and characterized spectroscopically. Hydrogen bonding, the nature and degree of structural (dis)order and the mechanisms of the phase transitions are discussed. The NH4+ ions show an important orientational disorder and become fully ordered in phase VII only. They are involved in all transitions and seem the main cause of the ferroelectricity at low temperature. 相似文献
7.
Romain Tessera 《Journal of Functional Analysis》2010,259(11):2793-2813
It is known that the algebra of Schur operators on ?2 (namely operators bounded on both ?1 and ?∞) is not inverse-closed. When ?2=?2(X) where X is a metric space, one can consider elements of the Schur algebra with certain decay at infinity. For instance if X has the doubling property, then Q. Sun has proved that the weighted Schur algebra Aω(X) for a strictly polynomial weight ω is inverse-closed. In this paper, we prove a sharp result on left-invertibility of the these operators. Namely, if an operator A∈Aω(X) satisfies ‖Afp‖?‖fp‖, for some 1?p?∞, then it admits a left-inverse in Aω(X). The main difficulty here is to obtain the above inequality in ?2. The author was both motivated and inspired by a previous work of Aldroubi, Baskarov and Krishtal (2008) [1], where similar results were obtained through different methods for X=Zd, under additional conditions on the decay. 相似文献
8.
9.
Dr. Samuel Oger Damien Schapman Dr. Romain Mougeot Dr. Stéphane Leleu Dr. Noëlle Lascoux Dr. Patrice Baldeck Dr. Magalie Bénard Dr. Thibault Gallavardin Dr. Ludovic Galas Dr. Xavier Franck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10954-10964
Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus. 相似文献
10.
Romain Tessier Raj Kumar Nandi Brendan G. Dwyer Daniel Abegg Charlotte Sornay Javier Ceballos Stphane Erb Sarah Cianfrani Alain Wagner Guilhem Chaubet Alexander Adibekian Jerome Waser 《Angewandte Chemie (International ed. in English)》2020,59(27):10961-10970
Current approaches to introduce terminal alkynes for bioorthogonal reactions into biomolecules still present limitations in terms of either reactivity, selectivity, or adduct stability. We present a method for the ethynylation of cysteine residues based on the use of ethynylbenziodoxolone (EBX) reagents. The acetylene group is directly introduced onto the thiol group of cysteine and can be used for copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) without further processing. Labeling proceeded with reaction rates comparable to or higher than the most often used iodoacetamide on peptides or maleimide on the antibody trastuzumab, and high cysteine selectivity was observed. The reagents were also used in living cells for cysteine proteomic profiling and displayed improved coverage of the cysteinome compared to previously reported iodoacetamide or hypervalent iodine reagents. Fine‐tuning of the EBX reagents allows optimization of their reactivity and physical properties. 相似文献