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601.
Kenneth M. Doxsee Nicholas P. Wood Erin M. Hanawalt Timothy J. R. Weakley 《Heteroatom Chemistry》1996,7(5):383-389
Treatment of titanacyclobutenes with two equivalents of dichlorophenylphosphine affords diphosphacyclopentenes, two examples of which were structurally characterized by single-crystal X-ray diffraction analysis. The analogous reaction of a titanacyclobutene with dichlorophenylstibine affords the corresponding distibacyclopentene as well as a stibacyclobutene. © 1996 John Wiley & Sons, Inc. 相似文献
602.
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604.
Dr. David O. Guarin Sameer M. Joshi Anna Samoilenko Mohammad S. H. Kabir Erin E. Hardy Dr. Atsush M. Takahashi Prof. Jan H. Ardenkjaer-Larsen Prof. Eduard Y. Chekmenev Dr. Yi-Fen Yen 《Angewandte Chemie (International ed. in English)》2023,62(31):e202219181
We report dissolution Dynamic Nuclear Polarization (d-DNP) of [15N3]metronidazole ([15N3]MNZ) for the first time. Metronidazole is a clinically approved antibiotic, which can be potentially employed as a hypoxia-sensing molecular probe using 15N hyperpolarized (HP) nucleus. The DNP process is very efficient for [15N3]MNZ with an exponential build-up constant of 13.8 min using trityl radical. After dissolution and sample transfer to a nearby 4.7 T Magnetic Resonance Imaging scanner, HP [15N3]MNZ lasted remarkably long with T1 values up to 343 s and 15N polarizations up to 6.4 %. A time series of HP [15N3]MNZ images was acquired in vitro using a steady state free precession sequence on the 15NO2 peak. The signal lasted over 13 min with notably long T2 of 20.5 s. HP [15N3]MNZ was injected in the tail vein of a healthy rat, and dynamic spectroscopy was performed over the rat brain. The in vivo HP 15N signals persisted over 70 s, demonstrating an unprecedented opportunity for in vivo studies. 相似文献
605.
Alaa S. Abd-El-Aziz Rawda M. Okasha Erin K. Todd Tarek H. Afifi Patrick O. Shipman K. Michelle D. Copping 《Macromolecular Symposia》2004,209(1):185-194
The synthesis of cationic cyclopentadienyliron-containing polymers with pendent azobenzene chromophores was accomplished via metal-mediated nucleophilic aromatic substitution reactions. All of the desired polymers were isolated as vibrantly coloured materials and displayed excellent solubility in polar aprotic solvents. Cationic and neutral cyclopentadienyliron polymers incorporating azo dyes in the backbone were also prepared. Reactions of azo dyes with dichlorobenzene complexes allowed for the isolation of cationic cyclopentdienyliron (CpFe+) complexes with azo dye chromophores. These complexes were then reacted with 1,1′-ferrocenedicarbonyl chloride to produce the trimetallic monomers with terminal chloro groups. These monomers contained two pendent CpFe+ cations and a neutral iron moiety in the backbone. Nucleophilic substitution reactions of these monomers with oxygen and sulfur containing dinucleophiles gave rise to a new class of polymeric materials. The pendent CpFe+ moieties could also be cleaved from the polymer backbones using photolysis to afford novel ferrocene based polymers. The UV-vis spectra of the organoiron monomers and polymers display similar wavelength maxima however incorporating azobenzene chromophores with electron-withdrawing substituent into the polymer chains resulted in bathochromic shifts of the λmax values. 相似文献
606.
Alaa S. Abd-El-Aziz Nelson M. Pereira Waleed Boraie Shaune L. McFarlane Erin K. Todd 《Macromolecular Symposia》2004,209(1):207-216
The synthesis of sulfone-containing monomers with pendent cationic cyclopentadienyliron (CpFe+) moieties has been accomplished via nucleophilic aromatic substitution of dichloroarene complexes with a number aliphatic dithiols. These complexes were further oxidized using m-CPBA to give the sulfone-based monomers. Polymerization of the sulfone-based monomers with O-containing nucleophiles produced the sulfone-based polymers. Direct nucleophilic aromatic substitution of dichloroarene complexes with dinucleophiles allowed for the formation of organoiron sulfide-based polymers. Oxidation of these polymers led to the formation of sulfone polymers with the pendent iron moieties. The organometallic monomers and polymers were found to be more soluble in polar solvents in comparison to their organic analogues. 相似文献
607.
Erin M. Hanada Patrick J. McShea Prof. Suzanne A. Blum 《Angewandte Chemie (International ed. in English)》2023,62(43):e202307787
Trimethylsilyl chloride (TMSCl) is commonly used to “activate” metal(0) powders toward oxidative addition of organohalides, but knowledge of its mechanism remains limited by the inability to characterize chemical intermediates under reaction conditions. Here, fluorescence lifetime imaging microscopy (FLIM) overcomes these prior limitations and shows that TMSCl aids in solubilization of the organozinc intermediate from zinc(0) metal after oxidative addition, a previously unknown mechanistic role. This mechanistic role is in contrast to previously known roles for TMSCl before the oxidative addition step. To achieve this understanding, FLIM, a tool traditionally used in biology, is developed to characterize intermediates during a chemical reaction—thus revealing mechanistic steps that are unobservable without fluorescence lifetime data. These findings impact organometallic reagent synthesis and catalysis by providing a previously uncharacterized mechanistic role for a widely used activating agent, an understanding of which is suitable for revising activation models and for developing strategies to activate currently unreactive metals. 相似文献
608.
Dr. Mengting Liu Dr. Masao Ohashi Qingyang Zhou Dr. Jacob N. Sanders Prof. Erin P. McCauley Prof. Phillip Crews Prof. K. N. Houk Prof. Yi Tang 《Angewandte Chemie (International ed. in English)》2023,62(40):e202311266
We uncovered and reconstituted a concise biosynthetic pathway of the strained dipeptide (+)-azonazine A from marine-derived Aspergillus insulicola. Formation of the hexacyclic benzofuranoindoline ring system from cyclo-(l -Trp-N-methyl-l -Tyr) is catalyzed by a P450 enzyme through an oxidative cyclization. Supplementing the producing strain with various indole-substituted tryptophan derivatives resulted in the generation of a series of azonazine A analogs. 相似文献