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71.
closo-Undecaborates were synthesized by the deprotonation of B11H13(SMe2) with LitBu in thp or K[BHEt3] in thf, [Li(thp)3]2[B11H11] and K2[B11H11] being obtained in 83 and 93% yield, respectively. K2[B11H11] can be transformed into A2[B11H11] with the corresponding ammonium chlorides in aqueous solution (A = [NMe3Ph], [NBzlEt3], [N(PPh3)2]). The crystal structure analysis of [Li(thp)3]2[B11H11] (space group P21/c) reveals a rather distorted octadecahedron for the [B11H11]2– anion, whereas the corresponding octadecahedron in [NBzlEt3]2[B11H11] (space group P212121) exhibits a structure close to C2v symmetry, expected for the free anion. The protonation of [B11H11]2– at low temperature gives [B11H12]–, whose structure could be elucidated by NMR methods; it is formed, apparently, by the opening of the B1–B4 edge of [B11H11]2– in the course of its known degenerate skeletal rearrangement, followed by the protonation of the B2–B4 edge. The reaction of [B11H12]– with a second molecule of the acid HX (X = CF3COO) gives nido-[B11H13X]–. The addition of BH3 to [B11H11]2– yields closo-[B12H12]2– under loss of H2. Two [B11H11]2– units are fused by the aid of FeCl3, with the known anion [B22H22]2– as the product, whose 11B-NMR signals could completely be assigned on the basis of Cs symmetry. The compound [NBzlEt3][N(PPh3)2][B22H22] crystallizes in the space group Pna21. 相似文献
72.
Lars Müller-Meskamp Rainer Waser Melanie Homberger Ulli Englert 《Surface science》2009,603(4):716-8968
The self-assembly of ω-ferrocenylalkanethiols (FcCnSH) with different alkyl-spacer lengths on Au(1 1 1) substrates has been studied by scanning tunneling microscopy (STM). Upon deposition at room temperature FcCnSH molecules tend to form multilayers, while by thermal treatment monolayer formation, a rearrangement of the molecules and the formation of ordered domains is achieved. The surface structure of the resulting full coverage self-assembled monolayers is resolved with molecular resolution by STM. The ordered monolayer structure of ω-ferrocenylpropanethiol is discussed in comparison with its bulk crystal structure, derived from single crystal X-ray analysis. Based on these results a monolayer structure of ω-ferrocenylalkanethiols with longer alkyl chains closely related to the bulk crystal structure of the shorter alkyl-spacer derivates is suggested. Our results provide detailed insight into the self-assembly of FcCnSH on gold substrates. 相似文献
73.
Tushar S. Basu Baul Archana Mizar Eleonora Rivarola Michal Hol?apek Ulli Englert 《Journal of organometallic chemistry》2006,691(16):3416-3425
A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L6H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph2Sn(L1)2 · (CH3)2CO (1), Ph2Sn(L4)2 (4) and Ph2Sn(L5)2 (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl - (L1H); 4′-methylphenyl - (L4H) and 4′-bromophenyl - (L5H)) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by 119Sn NMR spectroscopic results. The in vitro cytotoxicity of 1 is reported and compared with Ph2Sn(Ox)2 (Ox = deprotonated quinolin-8-ol) against seven well characterized human tumor cell lines. 相似文献
74.
Tim Hammerer Laurent Weisgerber Stefan Schenk Othmar Stelzer Ulli Englert Walter Leitner Giancarlo Franciò 《Tetrahedron: Asymmetry》2012,23(1):53-59
New diphosphinite ligands based on atropoisomeric diol backbones and (R,R)-2,5-dimethylphospholane moieties have been prepared and fully characterised. For each ligand structure, both diastereomers have been synthesised. These ligands are available through a straightforward procedure in good yields. The solid state structures of two diastereomeric ligands are reported. These ligands have been applied to Rh-catalysed asymmetric hydrogenations and hydroformylations of CC bonds as well as in Ir-catalysed asymmetric hydrogenations of CN bonds. Turnover frequencies in the range of 10,000 h?1 and enantioselectivities of up to 98% ee have been achieved. The different chirality elements within the ligands led to marked cooperative effect in catalysis. Interestingly, there is no general privileged diastereomeric structure but rather a matched diastereomer for each application. 相似文献
75.
Both ATLAS and CMS have reported a discovery of a Standard Model-like Higgs boson H of mass around 125 GeV. Consistency with the Standard Model implies the non-observation of non-SM-like decay modes of the newly discovered particle. Sensitivity to such decay modes, especially when they involve partially invisible final states is currently beyond scrutiny of the LHC. We systematically study such decay channels in the form of H→AA→jets+missing energy, with A a light scalar or pseudo-scalar, and analyze to what extent these exotic branching fractions can be constrained by direct measurements at the LHC. While the analysis is challenging, constraints as good as BR?10% can be obtained. 相似文献
76.
Christoph Englert Tilman PlehnMichael Rauch Dirk ZerwasPeter M. Zerwas 《Physics letters. [Part B]》2012,707(5):512-516
Interpretations of Higgs searches critically involve production cross sections and decay probabilities for different analysis channels. Mixing effects can reduce production rates, while invisible decays can reduce decay probabilities. Both effects may transparently be quantified in Higgs systems where a visible Higgs boson is mixed with a hidden sector Higgs boson. Recent experimental exclusion bounds can be re-interpreted in this context as a sign for non-standard Higgs properties. Should a light Higgs boson be discovered, then our analysis will quantify how closely it may coincide with the Standard Model. 相似文献
77.
Zoltan Homonnay Peter Buszlai Judit Nádor Virender K. Sharma Erno Kuzmann Attila Vértes 《Hyperfine Interactions》2012,205(1-3):17-21
The reaction of the μ-oxo-diiron(III)-L complex (L = EDTA, ethylene diamine tetraacetate, HEDTA, hydroxyethyl ethylene diamine triacetate, and CyDTA, cyclohexane diamine tetraacetate) with peroxynitrite in alkaline solution was studied by M?ssbauer spectroscopy using rapid-freezing technique. These complexes yield an (L)FeIII(η 2-O $_{2})^{3-}$ complex ion when they react with hydrogen peroxide and the formation of the peroxide adduct results in a deep purple coloration of the solution. The same color appears when the reaction occurs with peroxinitrite. Although spectrophotometry indicated some difference between the molar extinction coefficients of the peroxo and the peroxinitrito adducts, the M?ssbauer parameters proved to be the same within experimental error. It is concluded that the peroxynitrite ion decomposes when reacting with FeIII(L) and the peroxo adduct forms. 相似文献
78.
Light is used to 'gate' the Diels-Alder reaction using a photoresponsive dithienylfuran backbone and turn the reversibility of the Diels-Alder reaction 'off' and 'on' at 100 °C. These features make the reported system an excellent candidate for developing the next generation of self-healing polymers and photothermal drug delivery vehicles. 相似文献
79.