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排序方式: 共有226条查询结果,搜索用时 15 毫秒
51.
Wen Hua LENG* Zhao ZHANG Shao An CHENG Jian Qing ZHANG Chu Nan CAO Department of Chemistry Yuquan Campus Zhejiang University Hangzhou 《中国化学快报》2001,(11)
Over the last few decades, there has been a growing interest in the application of photocatalysis towards the treatment of polluted water1-4. It was well demonstrated that the anodic bias potential exerted on photoanode could prevent significantly the recombination rate of photogenerated carriers, consequently, it can improve the efficiency of photocatalytic degradation of organics2-4. For this, the study of photoelectrocatalytic degradation of pollutants has been of particular interest to r… 相似文献
52.
Dr. Morten Jensen Dr. Rikke Kristensen Dr. Sissel S. Andersen Dan Bendixen Prof. Dr. Jan O. Jeppesen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6165-6175
A tetra-stable donor–acceptor [2]rotaxane 1 ⋅4PF6 has been synthesized. The dumbbell component is comprised of an oxyphenylene (OP), a tetrathiafulvalene (TTF), a monopyrrolo-TTF (MPTTF), and a hydroquinone (HQ) unit, which can act as recognition sites (stations) for the tetra-cationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+). The TTF and the MPTTF stations are located in the middle of the dumbbell component and are connected by a triethylene glycol (TEG) chain in such a way that the pyrrole moiety of the MPTTF station points toward the TTF station, while the TTF and MPTTF stations are flanked by the OP and HQ stations on their left hand side and right hand side, respectively. The [2]rotaxane was characterized in solution by 1H NMR spectroscopy and cyclic voltammetry. The spectroscopic data revealed that the majority (77 %) of the tetra-stable [2]rotaxane 1 4+ exist as the translational isomer 1 ⋅MPTTF4+ in which the CBPQT4+ ring encircles the MPTTF station. The electrochemical studies showed that CBPQT4+ in 1 ⋅MPTTF4+ undergoes ring translation as result of electrostatic repulsion from the oxidized MPTTF unit. Following tetra-oxidation of 1 ⋅MPTTF4+, a high-energy state of 1 8+ was obtained (i.e., 1 ⋅TEG8+) in which the CBPQT4+ ring was located on the TEG linker connecting the di-oxidized TTF2+ and MPTTF2+ units. 1H NMR spectroscopy carried out in CD3CN at 298 K on a chemically oxidized sample of 1 ⋅MPTTF4+ revealed that the metastable state 1 ⋅TEG8+ is only short-lived with a lifetime of a few minutes and it was found that 70 % of the positively charged CBPQT4+ ring moved from 1 ⋅TEG8+ to the HQ station, while 30 % moved to the much weaker OP station. These results clearly demonstrate that the CBPQT4+ ring can cross both an MPTTF2+ and a TTF2+ electrostatic barrier and that the free energy of activation required to cross MPTTF2+ is ca. 0.5 kcal mol−1 smaller as compared to TTF2+. 相似文献
53.
Kouhei Ookuma Tomoyuki Amako Hiyori Aoyama Tomohiro Sato Nobuo Tajima Reiko Kuroda 《Molecular Crystals and Liquid Crystals》2014,592(1):209-217
Charge-transfer (CT) complexes were prepared using racemic (rac)-10,10′-dihydroxy-9,9′-biphenanthryl, which has a large and highly π-conjugated phenanthrene ring, as the electron donor and p-benzoquinone as the electron acceptor. This CT system showed a polymorphism. 相似文献
54.
Enhanced Photostability and Red-NIR Photosensitivity of Conjugated Polymer Charge-Transfer Complexes
Anastasiya E. Ozimova Vladimir V. Bruevich Thomas Dittrich Dmitry Yu. Paraschuk 《Macromolecular Symposia》2010,296(1):138-143
A promising route to photostable and low-bandgap polymer materials for optoelectronic and photonic applications could be utilization of donor-acceptor ground-state charge-transfer complexes (CTCs) of wide-bandgap conjugated polymers. In this work, we report our results on photostability and photoelectric studies of CTC between an archetypical conjugated polymer MEH-PPV and low-molecular-weight acceptor 2,4,7-trinitrofluorenone (TNF). By using the pump-probe laser photobleaching technique, we show that the photodegradation rate of MEH-PPV:TNF blend films decreases up to four orders of magnitude as compared with pristine MEH-PPV. By using photocurrent and surface photovoltage spectroscopies, we demonstrate that the photoelectric sensitivity of the MEH-PPV:TNF CTC can be deeply extended in the polymer optical gap down to 1 µm. However, the main drawback of the CTC studied is their low charge collection efficiency, and an approach to increasing it is discussed. 相似文献
55.
T. Yamase 《Catalysis Surveys from Asia》2003,7(4):203-217
The photocatalytic action of polyoxometalates (PMs), which is initiated by the photoexcitation of the oxygen-to-metal charge-transfer (O M LMCT) bands of PM, is based on the electron–hole pair separation followed by reductive and oxidative reactions with surrounding molecules. It is shown that the O M LMCT triplet states are involved in the photoredox reactions in which the significance of the highly negative oxidation potential for the photoreduced PMs can be considered in connection with the photocatalytic H2 formation from a great variety of organic substrates with their dehydrated oxidation. When the reaction of the photoreduced PMs with the electron acceptor hardly occurs kinetically or thermodynamically, they undergo self-assembled organization to nanosized supramolecules (as a result of photoencapsulation of small molecules and ring cluster formation). Some typical examples for the electron–hole pair separation and the photoredox reactions developed in our laboratory are discussed. 相似文献
56.
The apparent stability constants for porphyrin and metalloporphyrin complexes with an electron acceptor have been determined in mixed solvents. The variation of the apparent stability with solvent composition is evaluated in terms of solvation of the complex and reactant species and in terms of the exclusion of the solvent from the solvation sheath of the reactants, according to the equilibrium AS
a
+DS
b
=CS
x
+yS. 相似文献
57.
Massimiliano Arca Francesco A. Devillanova Alessandra Garau Francesco Isaia Vito Lippolis Gaetano Verani Francesco Demartin 《无机化学与普通化学杂志》1998,624(4):745-749
The reactions between triphenylphosphine sulfide (Ph3PS) and ICl in CCl4 and IBr in CH2Cl2 in 1 : 1 molar ratio give the solid adducts Ph3PS · ICl ( I ) and Ph3PS · IBr ( II ) whose structures have been solved by X-ray diffraction. Compounds I and II consist of discrete molecule units and feature the S–I–Cl or S–I–Br linear group. The S–I bond distances in I , II (2.641(1), 2.665(1) Å respectively) and in compound 2 Ph3PS · 3 I2 ( III ) (2.729(2) Å) are correlable to the net increase in the I–X (X = Cl, Br, I) bond distance. The structural features of I , II and III are in accordance with 31P CP–MAS NMR, FT-Raman and FT-IR spectral data, and elucidate the nature of the donor (Ph3PS)-acceptor (ICl, IBr, I2) interaction. 相似文献
58.
59.
The electron paramagnetic resonance (EPR) parameters (zero-field splitting D and g factors g||,
g⊥)
of Cr4+ ions in
Ca2GeO4 crystals have been calculated from the complete high-order perturbation formulas of EPR parameters for a 3d2 ion in trigonal MX4 clusters. In these formulas, in addition
to the contributions to EPR parameters from the widely used crystal-field
(CF) mechanism, the contributions from the charge-transfer (CT) mechanism
(which are often neglected) are included. From the calculations, it is found that for the high valence state 3dn ions in crystals, the reasonable explanation of EPR parameters (in particular, the g factors) should take both the CF and CT mechanisms into account. 相似文献
60.
合成了由六次甲基四胺与H 相似文献