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排序方式: 共有204条查询结果,搜索用时 343 毫秒
51.
Dr. Keishiro Tahara Nazuna Terashita Dr. Ken Tokunaga Shiomi Yabumoto Prof. Jun-ichi Kikuchi Dr. Yoshiki Ozawa Prof. Masaaki Abe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13728-13738
Realization of molecular quantum cellular automata (QCA), a promising architecture for molecular computing through current-free processes, requires improved understanding and application of mixed-valence (MV) molecules. In this report, we present an electrostatic approach to creating MV subspecies through internalizing opposite charges in close proximity to MV ionic moieties. This approach is demonstrated by unsymmetrically attaching a charge-responsive boron substituent to a well-known organometallic MV complex, biferrocenium. Guest anions (CN− and F−) bind to the Lewis acidic boron center, leading to unusual blue-shifts of the intervalence charge-transfer (IVCT) bands. To the best of our knowledge, this is the first reported example of a zwitterionic MV series in which the degree of positive charge delocalization can be varied by changing the bound anions, and serves to clarify the interplay between IVCT parameters. The key underlying factor is the variable zero-level energy difference in the MV states. This work provides new insight into imbuing MV molecules with external charge-responsiveness, a prerequisite of molecular QCA techniques. 相似文献
52.
Peng Zhang Dr. Priyesh Jain Caroline Tsao Dr. Zhefan Yuan Dr. Wenchen Li Bowen Li Kan Wu Dr. Hsiang‐Chieh Hung Dr. Xiaojie Lin Prof. Shaoyi Jiang 《Angewandte Chemie (International ed. in English)》2018,57(26):7743-7747
The commonly used “stealth material” poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti‐PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high‐dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase–PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase–PEG conjugates. 相似文献
53.
Combining Fullerenes and Zwitterions in Non‐Conjugated Polymer Interlayers to Raise Solar Cell Efficiency
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Dr. Yao Liu Dr. Madhu Sheri Marcus D. Cole Prof. Todd Emrick Prof. Thomas P. Russell 《Angewandte Chemie (International ed. in English)》2018,57(31):9675-9678
Polymer zwitterions were synthesized by nucleophilic ring‐opening of 3,3′‐(but‐2‐ene‐1,4‐diyl)bis(1,2‐oxathiolane 2,2‐dioxide) (a bis‐sultone) with functional perylene diimide (PDI) or fullerene monomers. Integration of these polymers into solar cell devices as cathode interlayers boosted efficiencies of fullerene‐based organic photovoltaics (OPVs) from 2.75 % to 10.74 %, and of non‐fullerene‐based OPVs from 4.25 % to 10.10 %, demonstrating the versatility of these interlayer materials in OPVs. The fullerene‐containing polymer zwitterion ( C60‐PZ ) showed a higher interfacial dipole (Δ) value and electron mobility than its PDI counterpart ( PDI‐PZ ), affording solar cells with high efficiency. The power of PDI‐PZ and C60‐PZ to improve electron injection and extraction processes when positioned between metal electrodes and organic semiconductors highlights their promise to overcome energy barriers at the hard‐soft materials interface of organic electronics. 相似文献
54.
Markov Chain Monte Carlo (MCMC) Method for Studying Magnetic Behaviors in Trinuclear Cobalt(II) Compound
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Dr. Quan Wang Hang‐Xing Li Dr. Kun‐Miao Wang Dr. Xiao Wang Zhe Xue Lei Jia Dr. Lin Du Prof. Qi‐Hua Zhao 《化学:亚洲杂志》2018,13(11):1415-1418
A CoII coordination polymer built from a mixed azide and zwitterionic pyridinium ions and its temperature‐dependent magnetic properties are described. We used the Markov chain Monte Carlo (MCMC) method to fit the data, and found the following results: (1) there are strong correlations between the model parameters; (2) the data at above 28 K are well fitted by the magnetism model. 相似文献
55.
Sunil Vibhute Dattatraya Jamale Santosh Undare Navanath Valekar Kirti Patil Govind Kolekar 《合成通讯》2017,47(19):1747-1757
An environmental friendly synthetic route has been investigated for the synthesis of quinazolin-8 (4H)-one derivatives in the presence of anthranilic acid as a catalyst. The zwitter ion formed in course of reaction may a play key role in the desired transformations leading good to excellent yields. Evaluation of the present protocol by green chemistry metrics demonstrated that it is highly efficient and eco-compatible. 相似文献
56.
57.
Piotr Przybylski Krystian Pyta Katarzyna Klich Wojciech Schilf Bohdan Kamieński 《Magnetic resonance in chemistry : MRC》2014,52(1-2):10-21
13C, 15N CP/MAS, including 1H–13C and 1H–15N short contact time CP/MAS experiments, and FTIR methods were applied for detailed structural characterization of ansa‐macrolides as 3‐formylrifamycin SV (1) and its derivatives (2–6) in crystal and in powder forms. Although HPLC chromatograms for 2/CH3OH and 2/CH3CCl3 were the same for rifampicin crystals dissolved in respective solvents, the UV–vis data recorded for them were different in 300–375 nm region. Detailed solid state 13C and 15N CP/MAS NMR and FTIR studies revealed that rifampicin (2), in contrast to 3‐formylrifamycin SV (1) and its amino derivatives (3–6), can occur in pure non‐ionic or zwitterionic forms in crystal and in pure these forms or a mixture of them in a powder. Multinuclear CP/MAS and FTIR studies demonstrated also that 3–6 derivatives were present exclusively in pure zwitterionic forms, both in powder and in crystal. On the basis of the solid state NMR and FTIR studies, two conformers of 3‐formylrifamycin SV were detected in powder form due to the different orientations of carbonyl group of amide moiety. The PM6 molecular modeling at the semi‐empirical level of theory, allowed visualization the most energetically favorable non‐ionic and zwitterionic forms of 1–6 antibiotics, strongly stabilized via intramolecular H‐bonds. FTIR studies indicated that the originally adopted forms of these type antibiotics in crystal or in powder are stable in standard laboratory conditions in time. The results presented point to the fact that because of a possible presence of two forms of rifampicin (compound 2), quantification of the content of this antibiotic in relevant pharmaceuticals needs caution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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59.
Huimin Liu QiongMei Zhang Limin Wang Prof. Dr. Xiaofeng Tong Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(6):1968-1972
A new PPh3‐catalyzed synthesis of alkyl 2‐[aryl(tosylimino)methyl]acrylates from propiolate and N‐tosylimine has been developed. Deuterium‐labelling experiments show that the reaction mechanism involves several hydrogen‐transfer processes, which are not the turnover‐limiting step and strongly rely on the nature of the reaction media. The stable phosphonium–enamine zwitterion, which was proven to play an important role in the catalytic cycle, has been isolated and characterised by X‐ray analysis. 相似文献
60.
Mark Stradiotto Prof. Dr. Kevin D. Hesp Rylan J. Lundgren 《Angewandte Chemie (International ed. in English)》2010,49(3):494-512
Zwitterionic platinum group metal complexes that feature formal charge separation between a cationic metal fragment and a negatively charged ancillary ligand combine the desirable reactivity profile of related cationic complexes with the broad solubility and solvent tolerance of neutral species. As such, zwitterionic complexes of this type have emerged as attractive candidates for a diversity of applications, most notably involving the breaking and/or forming of E? H and E? C σ bonds involving a main group element E. Important advances in ancillary ligand design are documented that have enabled the construction of platinum group metal zwitterions. Also summarized are the results of stoichiometric and catalytic investigations in which the reactivity of such zwitterions and their more traditionally employed cationic relatives in σ bond activation chemistry are compared and contrasted. 相似文献