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451.
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Jiaxi Guo Yanjun Liu Ricardo Prada‐Silvy Yongqiang Tan Samina Azad Beate Krause Petra Pötschke Brian P. Grady 《Journal of Polymer Science.Polymer Physics》2014,52(1):73-83
Two multi‐walled carbon nanotubes (MWCNTs) having relatively high aspect ratios of 313 and 474 with approximately the same diameter were melt mixed with polycarbonate (PC) in a twin‐screw conical micro compounder. The effects of aspect ratio on the electrical, mechanical, and thermal properties of the PC/MWCNT composites were investigated. Electrical conductivities and storage moduli of the filled samples are found to be independent of the starting aspect ratio for these high aspect ratio tubes; although the conductivities and storage moduli are still significantly higher than values of composites made with nanotubes having more commercially common aspect ratios of ~100. Transmission electron microscopy results suggest that melt‐mixing reduces these longer nanotubes to the same length, but still approximately two times longer than the length of commercially common aspect ratio tubes after melt‐mixing. Molecular weight measurements show that during melt‐mixing the longer nanotubes significantly degrade the molecular weight of the polymer as compared to very similar nanotubes with aspect ratio ~100. Because of the molecular weight reduction glass transition temperatures predictably show a large decrease with increasing nanotube concentration. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 73–83 相似文献
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Dr. Mahendra K. Sharma Timo Glodde Beate Neumann Dr. Hans-Georg Stammler Priv.-Doz. Dr. Rajendra S. Ghadwal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11113-11118
Crystalline 1,4-distannabarrelene compounds [(ADCAr)3Sn2]SnCl3 ( 3 - Ar ) (ADCAr={ArC(NDipp)2CC}; Dipp=2,6-iPr2C6H3, Ar=Ph or DMP; DMP=4-Me2NC6H4) derived from anionic dicarbenes Li(ADCAr) ( 2 - Ar ) (Ar=Ph or DMP) have been reported. The cationic moiety of 3 - Ar features a barrelene framework with three coordinated SnII atoms at the 1,4-positions, whereas the anionic unit SnCl3 is formally derived from SnCl2 and chloride ion. The all carbon substituted bis-stannylenes 3 - Ar have been characterized by NMR spectroscopy and X-ray diffraction. DFT calculations reveal that the HOMO of 3 - Ph (ϵ=−6.40 eV) is mainly the lone-pair orbital at the SnII atoms of the barrelene unit. 3 - Ar readily react with sulfur and selenium to afford the mixed-valence SnII/SnIV compounds [(ADCAr)3SnSn(E)](SnCl6)0.5 (E=S 4 - Ar , Ar=Ph or DMP; E=Se 5 - Ph ). 相似文献
455.
Jan-Henrik Weddeling Dr. Yury V. Vishnevskiy Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):16111-16121
Several ethylenedioxy-bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non-covalent dispersion-driven inter- and intramolecular aryl–aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid–centroid distance. Single-molecule structures generally adopt folded conformations with short intramolecular aryl–aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1-(pentafluorophenoxy)-2-(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl–aryl distances in the gas phase. Solid-state structures are dominated by stretched structures without intramolecular aryl–aryl interactions but interactions with neighboring molecules. 相似文献
456.
The molecular cobalt fluorides CoF2, CoF3 and CoF4 are studied and compared by employing different basis sets as well as Quantum Information Theory (QIT) to investigate their correlation effects. These prototypical monomers may be systematically extended in size yielding a novel quasi 1-dimensional, strongly correlated model system consisting of cobalt atoms bridged by oxygen atoms and fluorine termination on both ends. Accurate correlation energies are obtained using Full Configuration Interaction (FCI) and Full Configuration Interaction Quantum Monte Carlo (FCIQMC) calculations and the results are compared to Coupled Cluster and Density Matrix Renormalization Group (DMRG) energies. The analysis indicates the cobalt atom requires a larger number of one-electron basis functions than fluorine and the use of localized molecular orbitals may facilitate calculations for the extended systems. 相似文献
457.
M. Sc. Dorian J. Mikolajczak Dr. Allison A. Berger Prof. Dr. Beate Koksch 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8858-8867
The self-assembly of peptides onto the surface of gold nanoparticles has emerged as a promising strategy towards the creation of artificial enzymes. The resulting high local peptide density surrounding the nanoparticle leads to cooperative and synergistic effects, which result in rate accelerations and distinct catalytic properties compared to the unconjugated peptide. This Minireview summarizes contributions to and progress made in the field of catalytically active peptide–gold nanoparticle conjugates. The origin of distinct properties, as well as potential applications, are also discussed. 相似文献
458.
Dennis Rottschäfer Nga Kim T. Ho Beate Neumann Dr. Hans‐Georg Stammler Dr. Maurice van Gastel Dr. Diego M. Andrada Priv.‐Doz.Dr. Rajendra S. Ghadwal 《Angewandte Chemie (International ed. in English)》2018,57(20):5838-5842
Stable N‐heterocyclic carbene analogues of Thiele and Chichibabin hydrocarbons, [(IPr)(C6H4)(IPr)] and [(IPr)(C6H4)2(IPr)] ( 4 and 5 , respectively; IPr=C{N(2,6‐iPr2C6H3)}2CHCH), are reported. In a nickel‐catalyzed double carbenylation of 1,4‐Br2C6H4 and 4,4′‐Br2(C6H4)2 with IPr ( 1 ), [(IPr)(C6H4)(IPr)](Br)2 ( 2 ) and [(IPr)(C6H4)2(IPr)](Br)2 ( 3 ) were generated, which respectively afforded 4 and 5 as crystalline solids upon reduction with KC8. Experimental and computational studies support the semiquinoidal nature of 5 with a small singlet?triplet energy gap ΔES?T of 10.7 kcal mol?1, whereas 4 features more quinoidal character with a rather large ΔES?T of 25.6 kcal mol?1. In view of the low ΔES?T, 4 and 5 may be described as biradicaloids. Moreover, 5 has considerable (41 %) diradical character. 相似文献
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460.