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101.
Enhanced π‐Backdonation from Gold(I): Isolation of Original Carbonyl and Carbene Complexes
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Dr. Maximilian Joost Dr. Laura Estévez Sonia Mallet‐Ladeira Dr. Karinne Miqueu Dr. Abderrahmane Amgoune Dr. Didier Bourissou 《Angewandte Chemie (International ed. in English)》2014,53(52):14512-14516
The specific electronic properties of bent o‐carborane diphosphine gold(I) fragments were exploited to obtain the first classical carbonyl complex of gold [(DPCb)AuCO]+ (ν(CO)=2143 cm?1) and the diphenylcarbene complex [(DPCb)Au(CPh2)]+, which is stabilized by the gold fragment rather than the carbene substituents. These two complexes were characterized by spectroscopic and crystallographic means. The [(DPCb)Au]+ fragment plays a major role in their stability, as substantiated by DFT calculations. The bending induced by the diphosphine ligand substantially enhances π‐backdonation and thereby allows the isolation of carbonyl and carbene complexes featuring significant π‐bond character. 相似文献
102.
Photocatalytic Water Oxidation by a Pyrochlore Oxide upon Irradiation with Visible Light: Rhodium Substitution Into Yttrium Titanate
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Borbala Kiss Dr. Christophe Didier Timothy Johnson Dr. Troy D. Manning Dr. Matthew S. Dyer Dr. Alexander J. Cowan Dr. John B. Claridge Prof. James R. Darwent Prof. Matthew J. Rosseinsky 《Angewandte Chemie (International ed. in English)》2014,53(52):14480-14484
A stable visible‐light‐driven photocatalyst (λ≥450 nm) for water oxidation is reported. Rhodium substitution into the pyrochlore Y2Ti2O7 is demonstrated by monitoring Vegard′s law evolution of the unit‐cell parameters with changing rhodium content, to a maximum content of 3 % dopant. Substitution renders the solid solutions visible‐light active. The overall rate of oxygen evolution is comparable to WO3 but with superior light‐harvesting and surface‐area‐normalized turnover rates, making Y2Ti1.94Rh0.06O7 an excellent candidate for use in a Z‐scheme water‐splitting system. 相似文献
103.
Dr. Antoine Tardy Noémie Gil Dr. Christopher M. Plummer Prof. Didier Siri Dr. Didier Gigmes Dr. Catherine Lefay Dr. Yohann Guillaneuf 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14625-14634
Radical ring-opening polymerization (rROP) of cyclic ketene acetals (CKAs) combines the advantages of both ring-opening polymerization and radical polymerization thereby allowing the robust production of polyesters coupled with the mild polymerization conditions of a radical process. rROP was recently rejuvenated by the possibility to copolymerize CKAs with classic vinyl monomers leading to the insertion of cleavable functionality into a vinyl-based copolymer backbone and thus imparting (bio)degradability. Such materials are suitable for a large scope of applications, particularly within the biomedical field. The competition between the ring-opening and ring-retaining propagation routes is a major complication in the development of efficient CKA monomers, ultimately leading to the use of only four monomers that are known to completely ring-open under all experimental conditions. In this article we investigate the radical ring-opening polymerization of model CKA monomers and demonstrate by the combination of DFT calculations and kinetic modeling using PREDICI software that we are now able to predict in silico the ring-opening ability of CKA monomers. 相似文献
104.
Dr. Jessica Rodriguez Dr. György Szalóki Dr. E. Daiann Sosa Carrizo Dr. Nathalie Saffon-Merceron Dr. Karinne Miqueu Dr. Didier Bourissou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1527-1531
Gold(III) π-complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of PdII π-allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π-allyl complexes, which have remained elusive so far. The (P,C)AuIII(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air-stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi-symmetric η3-coordination of the allyl moiety. The π-allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β-diketo enolates. 相似文献
105.
Maxime Boudjelel Richard Declercq Sonia Mallet-Ladeira Ghenwa Bouhadir Didier Bourissou 《无机化学与普通化学杂志》2020,646(13):561-564
The vinyl carbenoid H2C=CBr(Li) has been used as key precursor to prepare a geminal C(sp2)-bridged phosphine-borane. Starting from bromoethene, two sequences of lithiation/electrophilic trapping, with ClPiPr2 and FBMes2 respectively, affords iPr2P–C(=CH2)–BMes2 3 [Mes = 2,4,6-(H3C)3C6H2]. This new phosphine-borane 3 was characterized by multi-nuclear NMR and mass spectroscopy. It adopts a monomeric open structure without P→B interaction. A few crystals of a secondary product 4 were analyzed by X-ray diffraction, revealing an unusual dimeric structure. 相似文献
106.
Jean Roncali Francis Garnier Robert Garreau Didier Delabouglise Marc Lemaire 《Macromolecular Symposia》1989,24(1):77-90
The mechanism of the electropolymerization of thiophene derivatives has been investigated by varying the electrosynthesis conditions and the monomer structure. The results of these analyses led to the definition of optimized electrosynthesis conditions allowing the control of the electrical and electrochemical properties of poly(thiophenes). On the basis of these results, the properties of these polymers have been modified by means of a new one-step electrosynthesis of conducting composite materials and by the direct electropolymerization of tailor-made functionalized monomers. For this purpose, the steric conditions associated to the various possibilities of covalent derivatization have been analyzed, leading to the definition of a “functionalization space”, compatible with the preservation of high conductivity and electrochemical reversibility in the resulting polymers. This concept has been applied to the synthesis of highly conducting chiral poly(thiophenes) on which an effect of enantioselective molecular recognition has been demonstrated for the first time. 相似文献
107.
Piotr Kurcok Andrzej Matuszowicz Zbigniew Jedliski Hans R. Kricheldorf Philippe Dubois Robert Jrme 《Macromolecular rapid communications》1995,16(7):513-519
The influence of methyl substituent on the mechanism of the ring-opening polymerization of β-lactones initiated by alkali metal alkoxides is discussed. Attention has been paid to the effect of the substituent position in the monomer molecule on the ring-opening mechanism, the 3,3-dimethyl-2-oxetanone (pivalolactone), 4-methyl-2-oxetanone (β-butyrolactone) and 2-oxetanone (β-propiolactone) being chosen as model monomers. Moreover, it was found unexpectedly that in the case of pivalolactone polymerization, besides open-chain polymers, cyclic oligomers are produced. 相似文献
108.
A combination of energy filtered transmission electron microscopic (EF-TEM) procedures is proposed for the non-perturbing physico-chemical characterization of submicron mineral and organic colloids in aquatic systems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine the optimum EF-TEM analysis conditions. In this paper, it is demonstrated that (i) our model colloids are morphologically representative of naturally occurring mineral/organic associations, (ii) EF-TEM allows the detection of fine xanthan ultrastructures without artefacts of conventional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM within a hematite/xanthan mixture. This EF-TEM procedure appears to be appropriate for the characterization of real aquatic samples. 相似文献
109.
Catherine Bessada Aydar Rakhmatullin Anne-Laure Rollet Didier Zanghi 《Journal of fluorine chemistry》2009,130(1):45-52
In situ high temperature nuclear magnetic resonance in molten fluoride mixtures gives some structural picture of the complexes existing in the melt, i.e. of their nature and relative proportion. Thanks to the development of a laser heating system associated with a close crucible in boron nitride, we can describe experimentally the evolution of these complexes from the anions and the cations point of view. By 19F NMR, we have shown the existence of three kinds of fluorine atoms depending on the composition: free fluorine like in pure LiF (non-bonded), bridging fluorine in melts rich in LnF3 in addition with terminal fluorine singly bonded to one rare earth. Data obtained by NMR spectroscopy are also combined with EXAFS measurements, again thanks to a specific development of the sample holder adapted with molten fluorides and high temperature. This study is a part of our systematic investigation of the different Alk-LnF3 systems by NMR and EXAFS spectroscopy. 相似文献
110.
Daniel L. Obrzut Prakash M. Adekkanattu Jyothi Thundimadathil Jing Liu Delphine R. Dubois James A. Guin 《Reaction Kinetics and Catalysis Letters》2003,80(1):113-121
SAPO-34 silicoaluminophosphate molecular sieve produces large amounts of methane at elevated temperatures in the methanol
to olefins (MTO) process. This significantly reduces the lower olefins selectivity a key factor in determining the commercial
viability of this catalyst. Impregnation of the SAPO-34 molecular sieve with metal ions such as K, Cs, Pt, Ag and Ce was found
to reduce the amount of methane significantly at higher temperatures thereby increasing the lower olefins selectivity. This
observed effect is less apparent at lower temperatures where the amount of methane formed is generally low.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献