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21.
Constrained‐Geometry Bisphosphazides Derived from 1,8‐Diazidonaphthalene: Synthesis,Spectroscopic Characteristics,Structural Features,and Theoretical Investigations
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Julius F. Kögel Nuri C. Abacılar Felicia Weber Dr. Benjamin Oelkers Dr. Klaus Harms Dr. Borislav Kovačević Prof. Dr. Jörg Sundermeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):5994-6009
Investigations on the Staudinger reaction between 1,8‐diazidonaphthalene and phosphorous(III) building blocks, a key step in the synthesis of superbasic bisphosphazene proton sponges, yielded a set of bisphosphazides with a constrained geometry 1,8‐disubstituted naphthalene backbone. This compound class has attracted our interest not only due to their surprisingly high stability, but in particular because of their theoretically predicted basicity in the range of their bisphosphazene analogues that can be referred to the constrained geometry interaction of two highly basic nitrogen atoms. Eleven new bisphosphazides bearing simple P‐amino groups as well as P‐guanidino substituents, azaphosphatrane moieties, P2 building blocks, or chiral P‐amino substituents derived from L ‐proline are presented. They were studied concerning their spectroscopic properties and partly also their chromophoric and structural features. In the case of the pyrrolidino‐substituted TPPN(2N2) (TPPN=1,8‐bis(trispyrrolidinophosphazenyl)naphthalene), the stepwise nitrogen elimination is investigated theoretically and experimentally, which led to the isolation and structural characterization of TPPN(1N2) bearing a phosphazide and a phosphazene functionality in one molecule. Attempts to protonate the obtained bisphosphazides and to prove the computationally predicted pKBH+ values through NMR titration reactions resulted in their decay, which again was rationalized by theoretical calculations. Altogether we present the so far most extensive spectroscopic, structural and theoretical investigation of constrained geometry bisphosphazides and their Brønsted and Lewis basic properties. 相似文献
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Julius F. Kögel Sebastian Ullrich Borislav Kovačević Sebastian Wagner Jörg Sundermeyer 《无机化学与普通化学杂志》2020,646(13):923-932
We present a convenient three-step synthesis of amino substituted phosphazenyl phosphines of the general formula (R2N)3P=N–P(NR2)2 [NR2 = N(CH2)4, N(CH2)5, N(CH2)6]. These easily accessible mixed valent compounds display a surprisingly high proton affinity and basicity in the same range as the corresponding Schwesinger diphosphazene (Me2N)3P=N–P=NEt(NMe2)2 (Et-P2) and Verkade's proazaphosphatrane superbases. Within the central [PIII–N=PV] scaffold, the phosphine PIII and not the phosphazene NIII atom is the center of highest proton affinity, basicity and donor strength. As P-bases, the title compounds display calculated proton affinities between 265.8 (NR2 = NMe2) and 274.7 kcal · mol–1 [NR2 = N(CH2)4] and pKBH+ values between 26.4 (NR2 = NMe2) and 31.5 [NR2 = N(CH2)4] on the acetonitrile scale. As P-nucleophiles, they are key intermediates in the synthesis of hyperbasic bis(diphosphazene) proton sponges, chiral bis(diphosphazene) proton pincers, bisphosphazides, and superbasic P2-bisylides. Their Staudinger reactions as nucleophile towards 1,8-diazidonaphthalene leading to 1,8-naphthalene-bisphosphazides is described in detail. The donor strength of the title compounds towards fragments [Se] and [Ni(CO)3] is in the same range as that of N-heterocyclic carbenes. 相似文献
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Lidia Angeleri-Hü gel Jan Trlifaj 《Transactions of the American Mathematical Society》2002,354(11):4345-4358
Let be a right noetherian ring and let be the class of all finitely presented modules of finite projective dimension. We prove that findim iff there is an (infinitely generated) tilting module such that pd and . If is an artin algebra, then can be taken to be finitely generated iff is contravariantly finite. We also obtain a sufficient condition for validity of the First Finitistic Dimension Conjecture that extends the well-known result of Huisgen-Zimmermann and Smalø.
25.
Kovalchuk VI Krägel J Makievski AV Loglio G Ravera F Liggieri L Miller R 《Journal of colloid and interface science》2002,252(2):433-442
The amplitude- and phase-frequency characteristics of oscillating bubble systems with a closed measuring cell are analyzed. The shape of the frequency characteristics is qualitatively different for bubbles smaller or larger than a hemisphere, respectively, and also for diluted and concentrated surfactant solutions. Moreover, the presence of a surfactant in the solution strongly influences the characteristic frequencies of the system. The experiments performed under ground and microgravity conditions show a good qualitative agreement with theoretically predicted amplitude- and phase-frequency characteristics and confirm the adequacy of the proposed theory. The comparison of high-frequency limits of the surface dilatational elasticity with the theoretical Gibbs elasticities calculated according to the respective adsorption isotherm shows good agreement for small surfactant concentrations. At higher concentrations large discrepancies are observed which can possibly be explained by the violation of the linearity condition for the surface layer. 相似文献
26.
Antons A Schroeder K Voigtländer B Cherepanov V Berger R Blügel S 《Physical review letters》2002,89(23):236101
The early stages of surfactant- (As, Sb) mediated homoepitaxial growth on Si (111) are examined by scanning tunneling microscopy and extensive ab initio calculations of Si(n) clusters (n=12). The results reveal the different microscopic behavior of the two surfactants: On As-covered Si (111), one exclusively finds two-dimensional islands with double-layer height which show the (1 x 1) terrace structure. On Sb-covered Si (111), the islands show two different reconstructions: at the rim of the islands a (1 x 1) structure appears, while in the center the (square root 3 x square root 3) terrace structure is observed. 相似文献
27.
Hirnet A Schroeder K Blügel S Torrelles X Albrecht M Jenichen B Gierer M Moritz W 《Physical review letters》2002,88(22):226102
Sb induces on Ge(113) a c(2 x 2) reconstruction in which Sb breaks one Ge-Ge bond and occupies an interstitial site, in contrast to Sb adsorption on other Si or Ge surfaces. Sb saturates the three dangling bonds per unit cell of the (113) surface inducing a large strain which is released by occupation of the interstitial site. Two neighboring Sb at interstitial sites form a dimer. The structure has been determined by x-ray diffraction, applying direct methods, and ab initio density-functional-theory calculations. The adsorption geometry and the high binding energy lead one to expect that Sb cannot be used as a surfactant for the growth of Si/Ge layers on the (113) surface. 相似文献
28.
W. Brügel 《Fresenius' Journal of Analytical Chemistry》1973,263(4):272-282
Zusammenfassung Nache einer allgemeinen Besprechung der Möglichkeiten der Röntgen-Photoelektronen-Spektroskopie werden einige charakteristische Beispiele aus dem Gebiet der organischen und anorganischen Chemie, der Katalysatoren und der Oberflächenanalyse diskutiert.Vortrag anläßlich der Tagung Euroanalysis I, 28. 8. bis 1. 9. 1972 in Heidelberg. 相似文献
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