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81.
Li[B(OCH2CF3)4]: Synthesis,Characterization and Electrochemical Application as a Conducting Salt for LiSB Batteries
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Dr. Michael Rohde Dr. Philipp Eiden Verena Leppert Dr. Michael Schmidt Dr. Arnd Garsuch Dr. Guenter Semrau Prof. Dr. Ingo Krossing 《Chemphyschem》2015,16(3):666-675
A new Li salt with views to success in electrolytes is synthesized in excellent yields from lithium borohydride with excess 2,2,2‐trifluorethanol (HOTfe) in toluene and at least two equivalents of 1,2‐dimethoxyethane (DME). The salt Li[B(OTfe)4] is obtained in multigram scale without impurities, as long as DME is present during the reaction. It is characterized by heteronuclear magnetic resonance and vibrational spectroscopy (IR and Raman), has high thermal stability (Tdecomposition>271 °C, DSC) and shows long‐term stability in water. The concentration‐dependent electrical conductivity of Li[B(OTfe)4] is measured in water, acetone, EC/DMC, EC/DMC/DME, ethyl acetate and THF at RT In DME (0.8 mol L ?1) it is 3.9 mS cm?1, which is satisfactory for the use in lithium‐sulfur batteries (LiSB). Cyclic voltammetry confirms the electrochemical stability of Li[B(OTfe)4] in a potential range of 0 to 4.8 V vs. Li/Li+. The performance of Li[B(OTfe)4] as conducting salt in a 0.2 mol L ?1 solution in 1:1 wt % DME/DOL is investigated in LiSB test cells. After the 40th cycle, 86 % of the capacity remains, with a coulombic efficiency of around 97 % for each cycle. This indicates a considerable performance improvement for LiSB, if compared to the standard Li[NTf2]/DOL/DME electrolyte system. 相似文献
82.
83.
Pseudotetrahedral nickel(II) phenolate complexes Tp(R,Me)Ni-OAr (Tp(R,Me) = hydrotris(3-R-5-methylpyrazol-1-yl)borate; R = Ph {1a}, Me {1b}; OAr = O-2,6-(i)Pr(2)C(6)H(3)) were synthesized as models for nickel-substituted copper amine oxidase apoenzyme, which utilizes an N(3)O (i.e., His(3)Tyr) donor set to activate O(2) within its active site for oxidative modification of the tyrosine residue. The bioinspired synthetic complexes 1a,b are stable in dilute CH(2)Cl(2) solutions under dry anaerobic conditions, but they decompose readily upon exposure to O(2) and H(2)O. Aerobic decomposition of 1a yields a range of organic products consistent with formation of phenoxyl radical, including 2,6-diisopropyl-1,4-benzoquinone, 3,5,3',5'-tetraisopropyl-4,4'-diphenodihydroquinone, and 3,5,3',5'-tetraisopropyl-4,4'-diphenoquinone, which requires concurrent O(2) reduction. The dimeric product complex di[hydro{bis(3-phenyl-5-methylpyrazol-1-yl)(3-ortho-phenolato-5-methylpyrazol-1-yl)borato}nickel(II)] (2) was obtained by ortho C-H bond hydroxylation of a 3-phenyl ligand substituent on 1a. In contrast, aerobic decomposition of 1b yields a dimeric complex [Tp(Me,Me)Ni](2)(μ-CO(3)) (3) with unmodified ligands. However, a unique organic product was recovered, assigned as 3,4-dihydro-3,4-dihydroxy-2,6-diisopropylcyclohex-5-enone on the basis of (1)H NMR spectroscopy, which is consistent with dihydroxylation (i.e., addition of H(2)O(2)) across the meta and para positions of the phenol ring. Initial hydrolysis of 1b yields free phenol and the known complex [Tp(Me,Me)Ni(μ-OH)](2), while hydrolysis of 1a yields an uncharacterized intermediate, which subsequently rearranges to the new sandwich complex [(Tp(Ph,Me))(2)Ni] (4). Autoxidation of the released phenol under O(2) was observed, but the reaction was slow and incomplete. However, both 4 and the in situ hydrolysis intermediate derived from 1a react with added H(2)O(2) to form 2. A mechanistic scheme is proposed to account for the observed product formation by convergent oxygenation and hydrolytic autoxidation pathways, and hypothetical complex intermediates along the former were modeled by DFT calculations. All new complexes (i.e., 1a,b and 2-4) were fully characterized by FTIR, (1)H NMR, and UV-vis-NIR spectroscopy and by X-ray crystallography. 相似文献
84.
We consider scalar hyperbolic conservation laws with a nonconvex flux, in one space dimension. Then, weak solutions of the associated initial value problems can contain undercompressive shock waves. We regularize the hyperbolic equation by a parabolic–elliptic system that produces undercompressive waves in the hyperbolic limit regime. Moreover we show that in another limit regime, called capillarity limit, we recover solutions of a diffusive–dispersive regularization, which is the standard regularization used to approximate undercompressive waves. In fact the new parabolic–elliptic system can be understood as a low-order approximation of the third-order diffusive–dispersive regularization, thus sharing some similarities with the relaxation approximations. A study of the traveling waves for the parabolic–elliptic system completes the paper. 相似文献
85.
We consider shape, size and regularity of the hulls K
t
of the chordal Schramm–Loewner evolution driven by a symmetric α-stable process. We obtain derivative estimates, show that
the domains are H?lder domains, prove that K
t
has Hausdorff dimension 1, and show that the trace is right-continuous with left limits almost surely.
Research supported in part by NSF Grant DMS-0600206.
Research supported in part by NSF Grants DMS-0501726 and DMS-0244408. 相似文献
86.
Tobias Frank Johannes CM Schlachetzki Bettina G?ricke Katrin Meuer Gundula Rohde Gunnar PH Dietz Mathias B?hr Armin Schneider Jochen H Weishaupt 《BMC neuroscience》2009,10(1):49-10
Background
The hematopoietic Granulocyte-Colony Stimulating Factor (G-CSF) plays a crucial role in controlling the number of neutrophil progenitor cells. Its function is mediated via the G-CSF receptor, which was recently found to be expressed also in the central nervous system. In addition, G-CSF provided neuroprotection in models of neuronal cell death. Here we used the retinal ganglion cell (RGC) axotomy model to compare effects of local and systemic application of neuroprotective molecules. 相似文献87.
We consider the problem of detection and estimation of chaotic signals in the presence of white Gaussian noise. Traditionally this has been a difficult problem since generalized likelihood ratio tests are difficult to implement due to the chaotic nature of the signals of interest. Based on Poincare's recurrence theorem we derive an algorithm for approximating a chaotic time series with unknown initial conditions. The algorithm approximates signals using elements carefully chosen from a dictionary constructed based on the chaotic signal's attractor. We derive a detection approach based on the signal estimation algorithm and show, with simulated data, that the new approach can outperform other methods for chaotic signal detection. Finally, we describe how the attractor based detection scheme can be used in a secure binary digital communications protocol. 相似文献
88.
Christian Rohde 《Numerische Mathematik》1998,81(1):85-123
Summary. Systems of nonlinear hyperbolic conservation laws in two space dimensions are considered which are characterized by the fact
that the coupling of the equations is only due to source terms. To solve these weakly coupled systems numerically a class
of explicit and implicit upwind finite volume methods on unstructured grids is presented. Provided an unique entropy solution
of the system of conservation laws exists we prove that the approximations obtained by these schemes converge for vanishing
discretization parameter to this entropy solution. These results are applied to examples from combustion theory and hydrology
where the existence of entropy solutions can be shown. The proofs rely on an extension of a result due to DiPerna concerning
measure valued solutions to the case of weakly coupled hyperbolic systems.
Received April 29, 1997 相似文献
89.
The 6.2-keV Mössbauer transition of181Ta was used to study both the Isomer-Shift (IS) and the quadrupole interaction in Re-single crystal host in the temperature range of 77 K to 517 K. Spectra were obtained for the181W diffused into Re-single crystal source using a single line Ta-metal absorber. The temperature change for the IS, δS/δT, is 55(1)×10?4 mm/s·deg, which is of the order of ?24 times the second-order Doppler shift. The temperature change of the electric field gradient follows the T3/2 relation. The relative smaller change of the EFG with respect to the IS change with temperature, reflects the strong role of the change of the s-electron density (s-d electron transfer) with temperature over other parameters. 相似文献
90.