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21.
Cezary Pietraszuk Bogdan Marciniec Szymon Rogalski Helmut Fischer 《Journal of molecular catalysis. A, Chemical》2005,240(1-2):67-71
Effective homo-metathesis of a series of dichloro-substituted vinylsilanes H2C = C(H)SiCl2R (where R = Me, OSiMe3, C6H5, C6H4–Me-4, C6H4–CF3-4) in the presence of second generation Grubbs catalyst [Cl2(PCy3)(IMesH2)Ru(=CHPh)] (I) and Hoveyda–Grubbs catalyst (II) leads to selective formation of E-1,2-bis(silyl)ethenes and ethene. On the basis of the results of experiments with deuterium-labelled reagents, a metallacarbene mechanism has been suggested for these reactions. 相似文献
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The effect of increase of polarity of the solvent binary mixture methanol-benzene and acetonitrile-chloroform on the selectivity and the rate of metalloene reaction of different allyltin compounds with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), diethyl azodicarboxylate (DEAD) and singlet oxygen was studied. The more polar solvent favored the production of the M-ene product. Analogous comparative studies were carried out in Et2O and 4 mol dm−3 solutions of LiClO4 in diethyl ether. All studied reactions were strongly catalysed by LiClO4. Physicochemical studies were carried out in purpose to explain the catalytic effect of LiClO4 on the aforementioned reactions. In case of singlet oxygen and diethyl azodicarboxylate it was presumably a result of facilitation of the formation of the polar intermediate by the ionic medium. Whereas, in case of PTAD the mentioned previously effect could be associated with lowering its LUMO by association with lithium. The analogous catalytic effect of LiClO4 was also observed for reactions of organotin phenoxides with DEAD and bis(trichloroethyl) azodicarboxylate leading to corresponding ring-aminated phenols in excellent yield, and with diethyl acetylenedicarboxylate giving a mixture of corresponding vinyl ethers and ring ethenylated phenols. Organotin phenoxides were distinctly more active than the corresponding phenols. 相似文献
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Marcin Sobczak Cezary Dębek Ewa Olędzka Grzegorz Nałęcz‐Jawecki Wacław L. Kołodziejski Maria Rajkiewicz 《Journal of polymer science. Part A, Polymer chemistry》2012,50(18):3904-3913
A series of biomedical polyurethane elastomers (PURs) based on poly(ester‐carbonate)s (PECs) and polycarbonates (PCs) were synthesized and spectrally characterized fully. PEC or PC diols were synthesized by the ring‐opening polymerization of ε‐caprolactone, trimethylene carbonate, and neopentyl carbonate catalyzed by lipase from Candida antarctica. PURs were prepared by free‐metal method from PEC or PC diols and 4,4′‐methylenebis(phenyl isocyanate), with 1,4‐butanediol as a chain extender. The physical and mechanical properties as well as hydrolytic stability of the obtained PURs were determined. The toxicity of the received polymers was evaluated using bacterial luminescence test and two protozoans assays. The presented preliminary studies suggest that PEC or PC diols prepared in this way might be applied for the synthesis of biomedical PURs with improved hydrolytic stability. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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1-(Trimethylsilyl)-1-alkenes of general formula CH3(CH2)nCH?CHSi(CH3)3, where n = 3–15, have been prepared by a novel method, viz. by an effective cross-metathesis of vinyltrimethylsilane with 1-alkenes catalyzed by RuCl2(PPh3)3. Excess of 1-alkene in the reaction mixture gave 1-(trimethylsilyl)-1-alkenes in good yields of up to 60% (in terms of vinylsilane). The products were identified by NMR spectroscopic (1H, 13C NMR) and GC MS methods. 相似文献
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Glen P. Junor Jan Lorkowski Dr. Cory M. Weinstein Dr. Rodolphe Jazzar Prof. Dr. Cezary Pietraszuk Prof. Dr. Guy Bertrand 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22212-22217
Selenium NMR has become a standard tool for scaling the π-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene–selenium 77Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale. 相似文献