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1.
Pentacoordinate complex cations of the general formula [(C6F5)2SbL3]3+ stabilized as solid salts in combination with tetraphenylborate (BPh4), tetrafluorobroate (BF4) anions, where L=DMSO, Ph3AsO, PyO, DMF, α-, β- and γ-picoline have been isolated. The newly formed complexes were characterized by elemental analysis, molar conductance measurements, solid-state IR and com/content/image/1-s2.0-S0022113903000940-si3.gif"> and com/content/image/1-s2.0-S0022113903000940-si4.gif"> NMR. From these results, a five-fold coordination around antimony was required. 相似文献
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Anna B. DenisovaVyacheslav Ya. Sosnovskikh Wim Dehaen Suzanne ToppetLuc Van Meervelt Vasiliy A. Bakulev 《Journal of fluorine chemistry》2002,115(2):183-192
Reaction of 2-hydrazinothiazoles 1 with 1-thienyl- and 1-furyl-1,3-butanediones 2a,b in methanol in the presence of hydrochloric acid mainly leads to a mixture of pyrazoles 3 and pyrazolines 4 or pyrazoles 3 and 5 in strong acidic conditions. Isomeric hydrazones 6 and pyrazolines 4 were formed and isolated in these reactions in the absence of hydrochloric acid. It has been shown that the regioselectivity in the reaction of diketones 2 with hydrazine 1 is governed by both the concentration of acid and the nature of substituents in the 1,3-diketones 2. Cyclization of hydrazones 6 is shown to occur under milder conditions than dehydration for pyrazolines 4. The new heterocyclic compounds were prepared and fully characterized by NMR spectra and by X-ray analysis for 3c. 相似文献
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Akira Ando 《Journal of fluorine chemistry》2005,126(5):765-770
Treatment of 2-chloro-3,3-difluoroprop-2-en-1-ol derivatives (2) with methanesulfonyl chloride in the presence of a base did not give the expected esters but 2-chloro-1,1-difluoroprop-2-enyl methanesulfonates (4) through a novel [3,3] sigmatropic rearrangement. Reaction of 4 with diethylzinc in the presence of tetrakis(triphenylphosphine) palladium gave 1-alkyl- or 1-aryl-2-chloro-3-fluoropenta-1,3-dienes in moderate to good yields through a Ccom/sd/entities/sbnd" class="glyphImg">C bond formation followed by dehydrofluorination. 相似文献
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Herbert W. Roesky 《Journal of fluorine chemistry》2004,125(11):1765-1769
The synthesis of carbaalanes of composition [(AlF)6(AlNMe3)2(CR)6] containing terminal fluorine atoms is described. The clusters have in common that the central core consists of eight aluminum and six carbon atoms. Six of the eight aluminum atoms are bearing six terminal fluorine atoms. The fluorination of (t-BuNCH2AlH)4 results in the formation of the aggregate (t-BuNCH2AlF)4. In group 14, the fluorine containing unsaturated compounds LGeF, LGecom/sd/entities/dbnd" class="glyphImg">S(F), LGecom/sd/entities/dbnd" class="glyphImg">Se(F), and LGecom/sd/entities/dbnd" class="glyphImg">NSiMe3(F) were prepared (Lcom/sd/entities/dbnd" class="glyphImg">HC(CMeNAr)2), Ar = 2,6-iPr2C6H3 and Ar = 2,6-Me2(C6H3)). 相似文献
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The molecular structure and absorption spectra of monothio- and dithio-naphthalimides were compared to their naphthalimide analogues using AM1, PM3 and ZINDO/S semiempirical quantum chemical methods. The substitution of the 4R-naphthalimide oxygen atoms by sulphur atoms resulted in a red-shift of the absorption spectra by Δλmax60-65 and 100-140 nm, respectively. The thionated naphthalimide derivatives do not show observable fluorescence due to intersystem crossing to the triplet com/content/image/1-s2.0-S0022286003003181-si8.gif">-states localised at the CS groups. The com/content/image/1-s2.0-S0022286003003181-si9.gif">-absorption bands of monothioimides are located at 525-580 nm (ε=60-80) and those for dithioimides at 535-560 nm (ε=140-390) and 628-686 nm (ε=34-68). None of these transitions are solvent sensitive. The com/content/image/1-s2.0-S0022286003003181-si10.gif">-transitions of N-phenylthioimides have also a small contribution from com/content/image/1-s2.0-S0022286003003181-si11.gif">-states due to a partial conjugation between CS group and π-electronic system of the N-phenyl ring. As a result, the com/content/image/1-s2.0-S0022286003003181-si12.gif"> bands of aromatic substituted N-phenylthioimides are red-shifted as compared to those of the aliphatic N-methyl-thioimides. 相似文献
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Birgit Hischenhuber Hans Havlicek Jelena Todoric Sonja Höllrigl‐Binder Wolfgang Schreiner Bernhard Knapp 《Journal of computational chemistry》2013,34(21):1862-1879
Antigen presenting cells present processed peptides via their major histocompatibility (MH) complex to the T cell receptors (TRs) of T cells. If a peptide is immunogenic, a signaling cascade can be triggered within the T cell. However, the binding of different peptides and/or different TRs to MH is also known to influence the spatial arrangement of the MH α‐helices which could itself be an additional level of T cell regulation. In this study, we introduce a new methodology based on differential geometric parameters to describe MH deformations in a detailed and comparable way. For this purpose, we represent MH α‐helices by curves. On the basis of these curves, we calculate in a first step the curvature and torsion to describe each α‐helix independently. In a second step, we calculate the distribution parameter and the conical curvature of the ruled surface to describe the relative orientation of the two α‐helices. On the basis of four different test sets, we show how these differential geometric parameters can be used to describe changes in the spatial arrangement of the MH α‐helices for different biological challenges. In the first test set, we illustrate on the basis of all available crystal structures for (TR)/pMH complexes how the binding of TRs influences the MH helices. In the second test set, we show a cross evaluation of different MH alleles with the same peptide and the same MH allele with different peptides. In the third test set, we present the spatial effects of different TRs on the same peptide/MH complex. In the fourth test set, we illustrate how a severe conformational change in an α‐helix can be described quantitatively. Taken together, we provide a novel structural methodology to numerically describe subtle and severe alterations in MH α‐helices for a broad range of applications. © 2013 Wiley Periodicals, Inc. 相似文献
8.
A new simple receptor 1 based on aminosalicylimine was prepared. It exhibited an ‘off–on fluorescence type’ mode with high sensitivity in the presence of Zn2+. In particular, this chemosensor could clearly distinguish Zn2+ from Cd2+. Also, it could be a reusable chemosensor because the addition of EDTA quenched the fluorescence of the Zn2+-2·1 complex. Furthermore, receptor 1 had a sufficiently low detection limit (68 nM) in aqueous solutions, which implies that 1 could sense the nanomolar concentration of Zn2+. Therefore, this sensor has the ability to be a practical system for the monitoring of Zn2+ concentrations in aqueous samples. 相似文献
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