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排序方式: 共有194条查询结果,搜索用时 62 毫秒
31.
Alan R. Kennedy Dr. Prokopis C. Andrikopoulos Dr. Jean‐Baptiste Arlin David R. Armstrong Dr. Neil Duxbury David V. Graham Jennifer B. A. Kirkhouse Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(37):9494-9504
The first solid‐state structures of ortho‐sulfonated monoazo dyestuffs are reported and compared to those of their para‐ and meta‐sulfonated analogues. The structures of the 16 Na, K, Cs, Mg, Ca, Sr, and Ba ortho‐sulfonated salts are found to have fewer M? O3S bonds than their isomeric equivalents and this in turn means that the metal type is no longer the prime indicator of which structural type will be adopted. M? O3S bonds are replaced by M? OH2, M? HOR and M–π interactions, apparently for steric reasons. As well as new bonding motifs, the changed dye shape also leads to new packing motifs. The simple organic/inorganic layering ubiquitous to the para‐ and meta‐sulfonated dye salt structures is replaced by variations (organic bilayers, inorganic channels), each of which correlates with a different degree of molecular planarity in the sulfonated azo dye anion. 相似文献
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Jean‐Baptiste Arlin Alan R. Kennedy 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(8):m213-m218
The structures of the Mg, Ca, Sr and Ba salts of 1‐naphthoic acid are examined and compared with analogous structures of salts of benzoate derivatives. It is shown that catena‐poly[[[diaquabis(1‐naphthoato‐κO)magnesium(II)]‐μ‐aqua] dihydrate], {[Mg(C11H7O2)2(H2O)3]·2H2O}n, exists as a one‐dimensional coordination polymer that propagates only through Mg—OH2—Mg interactions along the crystallographic b direction. In contrast with related benzoate salts, the naphthalene systems are large enough to prevent inorganic chain‐to‐chain interactions, and thus species with inorganic channels rather than layers are formed. The Ca, Sr and Ba salts all have metal centres that lie on a twofold axis (Z′ = ) and all have the common name catena‐poly[[diaquametal(II)]‐bis(μ‐1‐naphthoato)‐κ3O,O′:O;κ3O:O,O′], [M(C11H7O2)2(H2O)2]n, where M = Ca, Sr or Ba. The Ca and Sr salts are essentially isostructural, and all three species form one‐dimensional coordination polymers through a carboxylate group that forms three M—O bonds. The polymeric chains propagate via c‐glide planes and through MOMO four‐membered rings. Again, inorganic channel structures are formed rather than layered structures, and the three structures are similar to those found for Ca and Sr salicylates and other substituted benzoates. 相似文献
35.
Cord M Sirjean B Fournet R Tomlin A Ruiz-Lopez M Battin-Leclerc F 《The journal of physical chemistry. A》2012,116(24):6142-6158
This paper revisits the primary reactions involved in the oxidation of n-butane from low to intermediate temperatures (550-800 K) including the negative temperature coefficient (NTC) zone. A model that was automatically generated is used as a starting point and a large number of thermochemical and kinetic data are then re-estimated. The kinetic data of the isomerization of alkylperoxy radicals giving (?)QOOH radicals and the subsequent decomposition to give cyclic ethers has been calculated at the CBS-QB3 level of theory. The newly obtained model allows a satisfactory prediction of experimental data recently obtained in a jet-stirred reactor and in rapid compression machines. A considerable improvement of the prediction of the selectivity of cyclic ethers is especially obtained compared to previous models. Linear and global sensitivity analyses have been performed to better understand which reactions are of influence in the NTC zone. 相似文献
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We present a rigorous mathematical treatment of the zero-field orbital magnetic susceptibility of a non-interacting Bloch
electron gas, at fixed temperature and density, for both metals and semiconductors/insulators. In particular, we obtain the
Landau-Peierls formula in the low temperature and density limit as conjectured by Kjeldaas and Kohn (Phys Rev 105:806–813,
1957). 相似文献
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Dr. Baptiste Joalland Nuwandi M. Ariyasingha Dr. Sören Lehmkuhl Prof. Thomas Theis Prof. Stephan Appelt Prof. Eduard Y. Chekmenev 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(22):8732-8738
Radio amplification by stimulated emission of radiation (RASER) was recently discovered in a low-field NMR spectrometer incorporating a highly specialized radio-frequency resonator, where a high degree of proton-spin polarization was achieved by reversible parahydrogen exchange. RASER activity, which results from the coherent coupling between the nuclear spins and the inductive detector, can overcome the limits of frequency resolution in NMR. Here we show that this phenomenon is not limited to low magnetic fields or the use of resonators with high-quality factors. We use a commercial bench-top 1.4 T NMR spectrometer in conjunction with pairwise parahydrogen addition producing proton-hyperpolarized molecules in the Earth's magnetic field (ALTADENA condition) or in a high magnetic field (PASADENA condition) to induce RASER without any radio-frequency excitation pulses. The results demonstrate that RASER activity can be observed on virtually any NMR spectrometer and measures most of the important NMR parameters with high precision. 相似文献
40.
Yanling Li Amina Benchohra Buqin Xu Benoît Baptiste Keevin Bneut Paraskevas Parisiades Ludovic Delbes Alain Soyer Kamel Boukheddaden Rodrigue Lescouëzec 《Angewandte Chemie (International ed. in English)》2020,59(39):17272-17276
A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic FeIII2CoII2 square complex into a molecular switch exhibiting a full dia‐ to paramagnetic transition: FeIICoIII ? FeIIICoII. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure‐enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising‐like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors. 相似文献