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541.
Christian Balischewski Dr. Karsten Behrens Dr. Kerstin Zehbe Dr. Christina Günter Stefan Mies Dr. Eric Sperlich Alexandra Kelling Prof. Dr. Andreas Taubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17504-17513
Thirteen N-butylpyridinium salts, including three monometallic [C4Py]2[MCl4], nine bimetallic [C4Py]2[M1−xaMxbCl4] and one trimetallic compound [C4Py]2[M1−y-zaMybMzcCl4] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 °C. X-ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10−4 and 10−8 S cm−1. Some Cu-based ILs reach conductivities of 10−2 S cm−1, which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47×10−1 S cm−1 at 70 °C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V. 相似文献
542.
Kerstin Schulze‐Matthi Jürgen Bendig Petra Neubauer Burkhard Ziemer 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):e257-e258
The bonding geometry of sulfur in the cations of the title compounds, C8H11S+·CF3SO3? and C13H13S+·CF3SO3?, respectively, is similar and is independent of the ratio of the Me/Ph substituents. As expected, in both cations, the S—Ph bonds are somewhat shorter than the S—Me bonds. In both crystal structures, the interaction between cations and anions is similar. 相似文献
543.
Heine KB Clegg JK Heine A Gloe K Gloe K Henle T Bernhard G Cai ZL Reimers JR Lindoy LF Lach J Kersting B 《Inorganic chemistry》2011,50(4):1498-1505
The metal complexation properties of the naturally occurring Maillard reaction product isomaltol HL(2) are investigated by measurement of its stability constants with copper(II), zinc(II), and iron(III) using potentiometric pH titrations in water, by structural and magnetic characterization of its crystalline complex, [Cu(L(2))(2)]·8H(2)O, and by density functional theory calculations. Strong complexation is observed to form the bis(isomaltolato)copper(II) complex incorporating copper in a typical (pseudo-)square-planar geometry. In the solid state, extensive intra- and intermolecular hydrogen bonding involving all three oxygen functions per ligand assembles the complexes into ribbons that interact to form two-dimensional arrays; further hydrogen bonds and π interactions between the furan moiety of the anionic ligands and adjacent copper(II) centers connect the complexes in the third dimension, leading to a compact polymeric three-dimensional (3D) arrangement. The latter interactions involving copper(II), which represent an underappreciated aspect of copper(II) chemistry, are compared to similar interactions present in other copper(II) 3D structures showing interactions with benzene molecules; the results indicate that dispersion forces dominate in the π system to chelated copper(II) ion interactions. 相似文献
544.
Dr. Timo Bollermann Mariusz Molon Dr. Christian Gemel Kerstin Freitag Dr. Rüdiger W. Seidel Dr. Moritz von Hopffgarten Paul Jerabek Prof. Dr. Gernot Frenking Prof. Dr. Roland A. Fischer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4909-4915
The synthesis, characterization, and theoretical investigation by means of quantum‐chemical calculations of an oligonuclear metal‐rich compound are presented. The reaction of homoleptic dinuclear palladium compound [Pd2(μ‐GaCp*)3(GaCp*)2] with ZnMe2 resulted in the formation of unprecedented ternary Pd/Ga/Zn compound [Pd2Zn6Ga2(Cp*)5(CH3)3] ( 1 ), which was analyzed by 1H and 13C NMR spectroscopy, MS, elemental analysis, and single‐crystal X‐ray diffraction. Compound 1 consisted of two Cs‐symmetric molecular isomers, as revealed by NMR spectroscopy, at which distinct site‐preferences related to the Ga and Zn positions were observed by quantum‐chemical calculations. Structural characterization of compound 1 showed significantly different coordination environments for both palladium centers. Whilst one Pd atom sat in the central of a bi‐capped trigonal prism, thereby resulting in a formal 18‐valence electron fragment, {Pd(ZnMe)2(ZnCp*)4(GaMe)}, the other Pd atom occupied one capping unit, thereby resulting in a highly unsaturated 12‐valence electron fragment, {Pd(GaCp*)}. The bonding situation, as determined by atoms‐in‐molecules analysis (AIM), NBO partial charges, and molecular orbital (MO) analysis, pointed out that significant Pd? Pd interactions had a large stake in the stabilization of this unusual molecule. The characterization and quantum‐chemical calculations of compound 1 revealed distinct similarities to related M/Zn/Ga Hume–Rothery intermetallic solid‐state compounds, such as Ga/Zn‐exchange reactions, the site‐preferences of the Zn/Ga positions, and direct M? M bonding, which contributes to the overall stability of the metal‐rich compound. 相似文献
545.
This paper presents rules for numerical integration over spherical caps and discusses their properties. For a spherical cap
on the unit sphere
\mathbbS2\mathbb{S}^2, we discuss tensor product rules with n
2/2 + O(n) nodes in the cap, positive weights, which are exact for all spherical polynomials of degree ≤ n, and can be easily and inexpensively implemented. Numerical tests illustrate the performance of these rules. A similar derivation
establishes the existence of equal weight rules with degree of polynomial exactness n and O(n
3) nodes for numerical integration over spherical caps on
\mathbbS2\mathbb{S}^2. For arbitrary d ≥ 2, this strategy is extended to provide rules for numerical integration over spherical caps on
\mathbbSd\mathbb{S}^d that have O(n
d
) nodes in the cap, positive weights, and are exact for all spherical polynomials of degree ≤ n. We also show that positive weight rules for numerical integration over spherical caps on
\mathbbSd\mathbb{S}^d that are exact for all spherical polynomials of degree ≤ n have at least O(n
d
) nodes and possess a certain regularity property. 相似文献
546.
Cubature over the sphere in Sobolev spaces of arbitrary order 总被引:1,自引:1,他引:1
This paper studies numerical integration (or cubature) over the unit sphere for functions in arbitrary Sobolev spaces Hs(S2), s>1. We discuss sequences of cubature rules, where (i) the rule Qm(n) uses m(n) points and is assumed to integrate exactly all (spherical) polynomials of degree ≤n and (ii) the sequence (Qm(n)) satisfies a certain local regularity property. This local regularity property is automatically satisfied if each Qm(n) has positive weights. It is shown that for functions in the unit ball of the Sobolev space Hs(S2), s>1, the worst-case cubature error has the order of convergence O(n-s), a result previously known only for the particular case . The crucial step in the extension to general s>1 is a novel representation of , where Pℓ is the Legendre polynomial of degree ℓ, in which the dominant term is a polynomial of degree n, which is therefore integrated exactly by the rule Qm(n). The order of convergence O(n-s) is optimal for sequences (Qm(n)) of cubature rules with properties (i) and (ii) if Qm(n) uses m(n)=O(n2) points. 相似文献
547.
548.
Manuel M. Bentlohner Laura‐Alice Jantke Thomas Henneberger Christina Fischer Kerstin Mayer Dr. Wilhelm Klein Prof. Dr. Thomas F. Fässler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13946-13952
The addition of Sn and Zn ions to [Ge9] clusters by reaction of [Ge9]4? with SnPh2Cl2, ZnCp*2 (Cp*=pentamethylcyclopentadienyl), or Zn2[HC(Ph2P=NPh)2]2 is reported. The resulting Sn‐ and Zn‐bridged clusters [(Ge9)M(Ge9)]q? (M=Sn, q=4; M=Zn, q=6) display various coordination modes. The M atoms that coordinate to the open square of a C4v‐symmetric [Ge9] cluster form strong covalent multicenter M?Ge bonds, in contrast to the M atoms coordinating to triangular cluster faces. Molecular orbital analyses show that the M atoms of the Ge9M fragments coordinate to a second [Ge9] cluster with similar orbitals but in different ways. The [Ge9Sn]2?unit donates two electrons to the triangular face of a second [Ge9]2? cluster with D3h symmetry, whereas [Ge9Zn]2?acts as an electron acceptor when interacting with the triangular face of a D3h‐symmetric [Ge9]4? unit. 相似文献
549.
Kerstin Mayer Lorenz J. Schiegerl Prof. Dr. Thomas F. Fässler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18794-18800
We report on the synthesis of new derivatives of silylated clusters of the type [Ge9(SiR3)3]? (R = SiMe3, Me = CH3; R = Ph, Ph = C6H5) as well as on their reactivity towards copper and zinc compounds. The silylated cluster compounds were synthesized by heterogeneous reactions starting from the Zintl phase K4Ge9. Reaction of K[Ge9{Si(SiMe3)3}3] with ZnCl2 leads to the already known dimeric compound [Zn(Ge9{Si(SiMe3)3}3)2] ( 1 ), whereas upon the reaction with [ZnCp*2] the coordination of [ZnCp*]+ to the cluster takes place (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) under the formation of [ZnCp*(Ge9{Si(SiMe3)3}3)] ( 2 ). A similar reaction leads to [CuPiPr3(Ge9{Si(SiMe3)3}3)] ( 3 ) from [CuPiPr3Cl] (iPr=isopropyl). Further we investigated the novel silylated cluster units [Ge9(SiPh3)3]? ( 4 ) and [Ge9(SiPh3)2]? ( 5 ), which could be identified by mass spectroscopy. Bis‐ and tris‐silylated species can be synthesized by the respective stoichiometric reactions, and the products were characterized by ESI‐MS and NMR experiments. These clusters show rather different reactivity. The reaction of the tris‐silylated anion 4 with [CuPiPr3Cl] leads to [(CuPiPr3)3Ge9(SiPh3)2]+ as shown from NMR experiments and to [(CuPiPr3)4{Ge9(SiPh3)2}2] ( 6 ), which was characterized by single‐crystal X‐ray diffraction. Compound 6 shows a new type of coordination of the Cu atoms to the silylated Zintl clusters. 相似文献
550.
The Influence of the Capping Agent on the Oxidation of Silver Nanoparticles: Nano‐impacts versus Stripping Voltammetry 下载免费PDF全文
Her Shuang Toh Dr. Kerstin Jurkschat Prof. Richard G. Compton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2998-3004
The influence of capping agents on the oxidation of silver nanoparticles was studied by using the electrochemical techniques of anodic stripping voltammetry and anodic particle coulometry (“nano‐impacts”). Five spherical silver nanoparticles each with a different capping agent (branched polyethylenimine (BPEI), citrate, lipoic acid, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP)) were used to perform comparative experiments. In all cases, regardless of the capping agent, complete oxidation of the single nanoparticles was seen in anodic particle coulometry. The successful quantitative detection of the silver nanoparticle size displays the potential application of anodic particle coulometry for nanoparticle characterisation. In contrast, for anodic stripping voltammetry using nanoparticles drop casting, it was observed that the capping agent has a very significant effect on the extent of silver oxidation. All five samples gave a low oxidative charge corresponding to partial oxidation. It is concluded that the use of anodic stripping voltammetry to quantify nanoparticles is unreliable, and this is attributed to nanoparticle aggregation. 相似文献