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排序方式: 共有886条查询结果,搜索用时 15 毫秒
81.
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Dr. Oscar Tutusaus Dr. Rana Mohtadi Dr. Timothy S. Arthur Dr. Fuminori Mizuno Dr. Emily G. Nelson Prof. Yulia V. Sevryugina 《Angewandte Chemie (International ed. in English)》2015,54(27):7900-7904
Unlocking the full potential of rechargeable magnesium batteries has been partially hindered by the reliance on chloride‐based complex systems. Despite the high anodic stability of these electrolytes, they are corrosive toward metallic battery components, which reduce their practical electrochemical window. Following on our new design concept involving boron cluster anions, monocarborane CB11H12? produced the first halogen‐free, simple‐type Mg salt that is compatible with Mg metal and displays an oxidative stability surpassing that of ether solvents. Owing to its inertness and non‐corrosive nature, the Mg(CB11H12)2/tetraglyme (MMC/G4) electrolyte system permits standardized methods of high‐voltage cathode testing that uses a typical coin cell. This achievement is a turning point in the research and development of Mg electrolytes that has deep implications on realizing practical rechargeable Mg batteries. 相似文献
83.
C‐Selective and Diastereoselective Alkyl Addition to β,γ‐Alkynyl‐α‐imino Esters with Zinc(II)ate Complexes
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Dr. Manabu Hatano Kenji Yamashita Mai Mizuno Orie Ito Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2015,54(9):2707-2711
Since umpolung α‐imino esters contain three electrophilic centers, regioselective alkyl addition with traditional organometallic reagents has been a serious problem in the practical synthesis of versatile chiral α‐amino acid derivatives. An unusual C‐alkyl addition to α‐imino esters using a Grignard reagent (RMgX)‐derived zinc(II)ate was developed. Zinc(II)ate complexes consist of a Lewis acidic [MgX]+ moiety, a nucleophilic [R3Zn]? moiety, and 2 [MgX2]. Therefore, the ionically separated [R3Zn]? selectively attacks the imino carbon atom ,which is most strongly activated by chelation of [MgX]+. In particular, chiral β,γ‐alkynyl‐α‐imino esters can strongly promote highly regio‐ and diastereoselective C‐alkylation because of structural considerations, and the corresponding optically active α‐quaternary amino acid derivatives are obtained within 5 minutes in high to excellent yields. 相似文献
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Takahiro Takayama Toshiki Mochizuki Kenichiro Todoroki Jun Zhe Min Hajime Mizuno Koichi Inoue Hiroyasu Akatsu Ichiro Noge Toshimasa Toyo'oka 《Analytica chimica acta》2015
Chiral metabolites are found in a wide variety of living organisms and some of them are understood to be physiologically active compounds and biomarkers. However, the overall analysis of chiral metabolomics is quite difficult due to the high number of metabolites, the significant diversity in their physicochemical properties, and concentration range from metabolite-to-metabolite. To solve this difficulty, we developed a novel approach for chiral metabolomics fingerprinting and chiral metabolomics extraction, which is based on the labeling of a pair of enantiomers of chiral derivatization reagents (i.e., DMT-(S,R)-Pro-OSu and DMT-3(S,R)-Apy) and precursor ion scan chromatography of the derivatives. The multivariate statistics is also required for this strategy. The proposed procedures were evaluated by the detection of a diagnostic marker (i.e., d-lactic acid) using the saliva of diabetic patients. This method was used for the determination of biomarker candidates of chiral amines and carboxyls in Alzheimer's disease (AD) brain homogenates. As the results, l-phenylalanine (L-Phe) and l-lactic acid (L-LA) were identified as the decreased and increased biomarker candidates in the AD brain, respectively. Therefore, the proposed approach seems to be helpful for the determination of non-target chiral metabolomics possessing amines and carboxyls. 相似文献
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This review article summarizes our recent researches for molecular design of polyoxometalates (POMs) and their related compounds
for environmentally-friendly functional group transformations. The divacant POM [γ-SiW10O34(H2O)2]4− exhibits high catalytic performance for mono-oxygenation-type reactions including epoxidation of olefins and allylic alcohols,
sulfoxidation, and hydroxylation of organosilanes with H2O2. We have successfully synthesized several POM-based molecular catalysts (metal-substituted POMs) with controlled active sites
by the introduction of metal species into the divacant POM as a “structural motif”. These molecular catalysts can efficiently
activate H2O2 (vanadium-substituted POM for epoxidation) and alkynes (copper-substituted POM for click reaction and oxidative homocoupling
of alkynes). The aluminum-substituted POM exhibits Lewis acidic catalysis for diastereoselective cyclization of (+)-citronellal
to (−)-isopulegol. In addition, we have developed POM-based “molecular heterogeneous catalysts” by the “solidification” and
“immobilization” of catalytically active POMs. 相似文献
88.
Two polyoxometalate assemblies, TBA(9)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)] (1; TBA = tetra-n-butylammonium) and TBA(6)Li(3)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)]·18H(2)O (2), were synthesized by trimerization of a dialuminum-substituted silicotungstate monomer. Both 1 and 2 possessed a layered structure composed of a basal sheet unit [TBA(3){γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)](6-) and interlayer cations. The interconversion between 1 and 2 reversibly took place through interlayer cation exchange. 相似文献
89.
Imoto M Matsui Y Takeda M Tamaki A Taniguchi H Mizuno K Ikeda H 《The Journal of organic chemistry》2011,76(15):6356-6361
Observations show that nitroanilines exhibit an unusually high S(N)Ar reactivity with OH(-) in aqueous media in reactions that produce nitrophenols. S(N)Ar reaction of 4-nitroaniline (2a) in aqueous NaOH for 16 h yields 4-nitrophenol (4a) quantitatively, whereas a similar reaction of 4-nitrochlorobenzene (1a) gave 4a in 2% yield together with recovered 1a in 97%, suggesting that the leaving ability of the NH(2) group far surpasses that of Cl under these conditions. An essential feature of S(N)Ar reactions of nitroanilines is probably that the NH(2) leaving group participates in a hydrogen-bonding interaction with H(2)O. Density functional theory (DFT) calculations for a set of 4-nitroaniline, OH(-), and H(2)O suggest a possible formation of a Meisenheimer complex stabilized by hydrogen-bonding interactions and a six-membered ring structure. The results obtained here contrast with conventional S(N)Ar reactivity profiles in which nitroanilines are nearly unreactive with nucleophiles in organic solvents. 相似文献
90.