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81.
Roland A. Fischer Dana Weiß Iris Müller Nikolaus Fröhlich Gernot Frenking 《Journal of organometallic chemistry》2004,689(24):4611-4623
The reactions of the sterically demanding group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER2)(R)] (3: E = Ga, R = CH2SiMe3; 5: E = In, R = CH2t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct σ(Pt-E) bonds were obtained by oxidative addition of an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt] produced in situ by thermolysis of the starting complex [(dcpe)Pt(CH2t-Bu)(H)]. The single crystal structure determination reveals a Pt-Ga bond length of 2.376(2) Å and a Pt-In bond length of 2.608(1) Å. All new compounds were characterised by elemental analysis, 31P and 195Pt NMR spectroscopy. Interestingly, the Pt-Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(μ2-H)[CH2Si(CH3)2 CH2Ga(CH2SiMe3)2]} (4) during crystallization from solution at room temperature. The X-ray single crystal structure analysis revealed both complexes 3 and 4 coexisting in the unit cell in a 1:1 relation. The inaccessibility of analytically pure samples of the Pt-Al complex {(dcpe)Pt[Al(CH2t-Bu)2](CH2t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH2t-Bu)] with Al(CH2t-Bu) on the basis of 31P and 195Pt NMR data, is attributed to an enhanced tendency to isomerisation into the alkyl/hydride Pt/Al congener of 4. A brief DFT analysis of the bonding situation of the model complex [(dhpe)Pt(GaMe2)(Me)] (1M) revealed, that the contribution of π(Pt-Ga) back-bonding is negligible. 相似文献
82.
Eighteen amino acids; proline, alanine, valine, leucine, isoleucine, hydroxyproline, phenylalanine, ornithine, glycine, serine, aspartic acid, glutamic acid, threonine, asparagine, lysine, tyrosine, tryptophan, and arginine were identified by polyamide layer chromatography via DNP (dinitrophenly) derivatives in Angelica acutiloba Kitagawa (Tang-Kwei) 相似文献
83.
Müller IM Spillmann S Franck H Pietschnig R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2207-2213
The rational synthesis of an octahedral coordination capsule in which the triangular faces are covered by single ligands is described herein. Starting with tris(2-hydroxybenzylidene)triaminoguanidinium chloride [H(6)L]Cl, we observed an oxidative cyclization of this ligand in the presence of PPh(4) (+) ions resulting in the complex [Pd(H(2)L')(PPh(3))] (1). The use of 5,5-diethylbarbiturate (bar(2-)) as a bridging ligand in the presence of [Co(en)(3)](3+) (en=ethylenediamine) leads to the formation of a rectangular box with the formula (Et(4)N)(6)[[Co[(PdCl)(Pd)L](2)(mu-bar)](2)] (2). The analysis of the architecture of compounds 1 and 2 enables the development of a self-assembly strategy for the synthesis of an octahedral coordination cage 3 with the formula Na(4)(Et(3)NH)(12)[(Pd(3)L)(8)[mu-(bar)](12)].x H(2)O. Compound 3 was characterized by (13)C-MAS-NMR spectroscopy and single-crystal structure analysis. 相似文献
84.
Treatment of cycloalkanone dimethyl acetals 3 – 6 with sorbyl alcohol (=(2E,4E)‐hexa‐2,4‐dien‐1‐ol; 1 ) in the presence of acids afforded the novel cycloalkenones 8, 9, 11 , and 13 via a domino reaction (Claisen rearrangement with intramolecular ene reaction and retro‐ene reaction). Cyclopentenone 8 was readily transformed into 14 and 15 , methyl homologues of racemic methyl jasmonate ( 16 ) and methyl dihydrojasmonate (=Hedione®; 17 ), respectively. The organoleptic properties of 14 and 15 are also discussed. 相似文献
85.
Robert S. Klein Federico G. De Las Heras Steve Y-K. Tam Iris Wempen Jack J. Fox 《Journal of heterocyclic chemistry》1976,13(3):589-592
The synthesis of 3-methyl-7-oxo-5-thioxo-4H,6H-1,2,3-triazolo[1,5-a]-1,3,5- triazine (a new bicyclic system) is described. The key step involves reaction of 4-amino-5-methyl-1,2,3-triazole with carbethoxyisothiocyanate followed by cyclization with alkali. 相似文献
86.
87.
88.
Paolo Costa Iris Trosien Miguel Fernandez‐Oliva Elsa Sanchez‐Garcia Wolfram Sander 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(9):2694-2698
The fluorenyl cation is a textbook example for a 4π antiaromatic cation. However, contrasting results have been published on how the annelated benzene rings compensate the destabilizing effect of the 4π antiaromatic five‐membered ring in its core. Whereas previous attempts to synthesize this cation in superacidic media resulted in undefined polymeric material only, we herein report that it can be generated and isolated in amorphous water ice at temperatures below 30 K by photolysis of diazofluorene. Under these conditions, the fluorenylidene is protonated by water to give the fluorenyl cation, which could be characterized spectroscopically. Its absorption in the visible‐light range matches that previously obtained by ultrafast absorption spectroscopy, and furthermore, its IR spectrum could be recorded. The IR bands in amorphous ice very nicely match predictions from DFT and DFT/MM calculations, suggesting the absence of strong interactions between the cation and surrounding water molecules. 相似文献
89.
90.