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排序方式: 共有214条查询结果,搜索用时 390 毫秒
81.
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83.
Malval JP Suzuki S Morlet-Savary F Allonas X Fouassier JP Takahara S Yamaoka T 《The journal of physical chemistry. A》2008,112(17):3879-3885
The photophysical properties of a series of 1,8-naphthalimide photoacid generators were studied by steady state fluorescence and phosphorescence spectroscopy. Emission and excitation anisotropies, triplet quantum yields in polar and nonpolar solvent and photoacid generation were evaluated. The singlet excited state exhibits a low polarity and is strongly deactivated by an efficient intersystem crossing process. In protic solvent, a homolytic singlet cleavage of the N-O bond occurs and leads to the acid production. The existence of a triplet state close to the singlet state was clearly evidenced. The presence of close singlet excited states is supported by fluorescence anisotropy and picosecond laser spectroscopy experiments. Results of DFT calculations well confirm the experimental contentions and yield important information about the cleavage process involved in such compounds. 相似文献
84.
Yousuke Yamaoka Motoki Ueda Tohru Yamashita Kazuma Shimoda Ken-ichi Yamada Kiyosei Takasu 《Tetrahedron letters》2017,58(30):2944-2947
Cyclic ketene silyl acetals were utilized for [2 + 2] cycloaddition with propiolates to prevent an undesired electrocyclic ring opening reaction. Trimethylaluminum catalyzed this cycloaddition to afford the cyclobutene derivatives in high yields. The advantage of this reaction was highlighted by the successful application of β-substituted propiolates to afford the multi-substituted cyclobutenes. Furthermore, we applied this methodology to the late stage functionalization of natural product artemisinin. 相似文献
85.
Yue Wang Koki Ogasahara Daisuke Tomihama Dr. Radomir Mysliborski Dr. Masatoshi Ishida Yongseok Hong Yusuke Notsuka Prof. Dr. Yoshihisa Yamaoka Tomotaka Murayama Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Dr. Shigeki Mori Dr. Yuhsuke Yasutake Prof. Dr. Susumu Fukatsu Prof. Dr. Dongho Kim Prof. Dr. Hiroyuki Furuta 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16295-16300
The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-PdII and bis-PtII complexes of hexaphyrin via N-confusion modification led to substantial metal dπ–pπ interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long-wavelength shift of the lowest S0→S1 absorption beyond 1700 nm was achieved with the bis-PtII complex, t -Pt2-3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t -Pt2-3 potentially useful as a NIR-III PA contrast agent. The rigid bis-PdII complexes, t -Pd2-3 and c -Pd2-3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR-III-emissive and photoacoustic-response capabilities. 相似文献
86.
Masato Yamaoka Masakazu Sugishima Masato Noguchi Keiichi Fukuyama Yasuhisa Mizutani 《Journal of Raman spectroscopy : JRS》2011,42(5):910-916
Structural changes of heme‐heme oxygenase‐1 complex following carbon monoxide (CO) dissociation were studied by time‐resolved resonance Raman spectroscopy. We observed temporal changes for resonance Raman bands of the Fe–His stretch and the heme propionate bends in the subnanosecond and microsecond time regimes. These changes suggest structural rearrangements in the Fe–His linkage and the salt bridges of the heme propionates following CO dissociation. The present data supports the model proposed by an X‐ray crystallographic study. The Fe–His stretching mode exhibited an upshift until 30 µs after dissociation as the delay time increased. This is the first example of a CO‐dissociation‐induced strengthening of the Fe‐His linkage in hemeproteins. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
87.
Herein, we describe the first total synthesis of fomitellic acid B (2), a potent inhibitor of DNA polymerases α and β. There are two key features in this synthesis: (i) the AB ring system, with all requisite chiral centers, is stereoselectively constructed by means of titanium(III)-mediated radical cascade cyclization of epoxypolyene; and (ii) an enone moiety in the B-ring is generated by isomerization of an olefin followed by allylic oxidation. 相似文献
88.
Efficient Photocarrier Transfer and Effective Photoluminescence Enhancement in Type I Monolayer MoTe2/WSe2 Heterostructure
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Takao Yamaoka Hong En Lim Sandhaya Koirala Xiaofan Wang Keisuke Shinokita Mina Maruyama Susumu Okada Yuhei Miyauchi Kazunari Matsuda 《Advanced functional materials》2018,28(35)
Artificial van der Waals heterostructures of 2D layered materials are attractive from the viewpoint of the possible discovery of new physics together with improved functionalities. Stacking various combinations of atomically thin semiconducting transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se, Te) with a hexagonal crystal structure, typically leads to the formation of a staggered Type II band alignment in the heterostructure, where electrons and holes are confined in different layers. Here, the comprehensive studies are performed on heterostructures prepared from monolayers of WSe2 and MoTe2 using differential reflectance, photoluminescence (PL), and PL excitation spectroscopy. The MoTe2/WSe2 heterostructure shows strong PL from the MoTe2 layer at ≈1.1 eV, which is different from the quenched PL from the WSe2 layer. Moreover, enhancement of PL intensity from the MoTe2 layer is observed because of the near‐unity highly efficient photocarrier transfer from WSe2 to MoTe2. These experimental results suggest that the MoTe2/WSe2 heterostructure has a Type I band alignment where electrons and holes are confined in the MoTe2 layer. The findings extend the diversity and usefulness of ultrathin layered heterostructures based on transition metal dichalcogenides, leading to possibilities toward future optoelectronic applications. 相似文献
89.
A series of crosslinked microgels with quaternary ammonium ions on the surface was prepared by quaternization with N,N-dimethylbenzylamine in the presence of microgel particles prepared by emulsion copolymerization of styrene (St), chloromethylstyrene (CMS) and divinylbenzene (DVB). Microgels with diameters in the range of 15–100 nm were successfully dispersed in organic solvents such as 2-methoxyethanol and 2-ethoxyethanol without an emulsifier. A photosensitive layer was formed by coating a photosensitive solution on a grained aluminum plate. The solution was comprised of the microgels, the multifunctional monomer and standard ultraviolet (UV) photoinitiators, such as 2,4-diethyl thioxanthone (DETX)/ethyl p-di-ethylaminobenzoate (EPA). This gave a heterogeneous photosensitive layer which produced good polymer patterns after exposure to UV light followed by development in tap water. A typical polymer layer, consisting of the microgels (poly(styrene-co-N,N-dimethylbenzylvinyl-benzylammonium chloride-co-divinylbenzene)), DETX/EPA, and the multifunctional acrylate monomers, exhibited photosensitivity of 0.06 mJ/cm2 for UV light. This sensitivity is much higher than the homogeneous photopolymerization system with an analogous composition. 相似文献
90.