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11.
The calculation of vibrational contributions to molecular properties using vibrational coupled cluster (VCC) response theory is discussed. General expressions are given for expectation values, linear response functions, and transition moments. It is shown how these expressions can be evaluated for arbitrary levels of excitation in the wave function parameterization as well as for arbitrary coupling levels in the potential and property surfaces. The convergence of the method is assessed by benchmark calculations on formaldehyde. Furthermore, excitation energies and infrared intensities are calculated for the fundamental vibrations of furan using VCC limited to up to two-mode and up to three-mode excitations, VCC[2] and VCC[3], as well as VCC with full two-mode and approximate three-mode couplings, VCC[2pt3]. 相似文献
12.
Williams MR True AB Izmaylov AF French TA Schroeck K Schmuttenmaer CA 《Physical chemistry chemical physics : PCCP》2011,13(24):11719-11730
Experimental and computational THz (or far-infrared) spectra of polycrystalline valine samples are reported. The experimental spectra have been measured using THz time-domain spectroscopy. Spectra of the pure enantiomers, both D and L, as well as the dl racemate have been taken at room temperature and low temperature (78 K). The spectra of the pure D and L enantiomers are essentially identical, and they are markedly different from the DL racemate. In addition, a temperature-dependent study of L-valine was undertaken in which the absorption maxima were found to red shift as a function of increasing temperature. The vibrational absorption spectra (frequencies and intensities) were calculated using the harmonic approximation with the Perdew-Burke-Ernzerhof (PBE) functional, localized atomic orbital basis sets, and periodic boundary conditions. The calculated and experimental spectra are in good qualitative agreement. A general method of quantifying the degree to which a calculated mode is intermolecular versus intramolecular is demonstrated, with the intermolecular motions further separated into translational versus rotational/librational motion. This allows straightforward comparison of spectra calculated using different basis sets or other constraints. 相似文献
13.
14.
The experimental technique of a new type of polarization measurement especially for use with low-energy polarized targets is described. It is possible to derive the nuclear polarization as well as the nuclear spin-lattice relaxation time from measurements of the internal field. 相似文献
15.
In a seminal 1994 paper Lusztig (1994) [26], Lusztig extended the theory of total positivity by introducing the totally non-negative part (G/P)?0 of an arbitrary (generalized, partial) flag variety G/P. He referred to this space as a “remarkable polyhedral subspace”, and conjectured a decomposition into cells, which was subsequently proven by the first author Rietsch (1998) [33]. In Williams (2007) [40] the second author made the concrete conjecture that this cell decomposed space is the next best thing to a polyhedron, by conjecturing it to be a regular CW complex that is homeomorphic to a closed ball. In this article we use discrete Morse theory to prove this conjecture up to homotopy-equivalence. Explicitly, we prove that the boundaries of the cells are homotopic to spheres, and the closures of cells are contractible. The latter part generalizes a result of Lusztig's (1998) [28], that (G/P)?0 - the closure of the top-dimensional cell - is contractible. Concerning our result on the boundaries of cells, even the special case that the boundary of the top-dimensional cell (G/P)>0 is homotopic to a sphere, is new for all G/P other than projective space. 相似文献
16.
Vinyl Sulfonate Esters: Efficient Chain Transfer Agents for the 3D Printing of Tough Photopolymers without Retardation 下载免费PDF全文
Dr. Konstanze Seidler Dr. Markus Griesser Markus Kury Dr. Reghunathan Harikrishna Dr. Peter Dorfinger Dr. Thomas Koch Anastasiya Svirkova Prof. Martina Marchetti‐Deschmann Prof. Juergen Stampfl Prof. Norbert Moszner Dr. Christian Gorsche Prof. Robert Liska 《Angewandte Chemie (International ed. in English)》2018,57(29):9165-9169
The formation of networks through light‐initiated radical polymerization allows little freedom for tailored network design. The resulting inhomogeneous network architectures and brittle material behavior of such glassy‐type networks limit the commercial application of photopolymers in 3D printing, biomedicine, and microelectronics. An ester‐activated vinyl sulfonate ester (EVS) is presented for the rapid formation of tailored methacrylate‐based networks. The chain transfer step induced by EVS reduces the kinetic chain length of the photopolymer, thus shifting the gel point to higher conversion, which results in reduced shrinkage stress and higher overall conversion. The resulting, more homogeneous network is responsible for the high toughness of the material. The unique property of EVS to promote nearly retardation‐free polymerization can be attributed to the fact that after the transfer step no polymerizable double bond is formed, as is usually seen in classical chain transfer agents. Laser flash photolysis, theoretical calculations, and photoreactor studies were used to elucidate the fast chain transfer reaction and exceptional regulating ability of EVS. Final photopolymer networks exhibit improved mechanical performance making EVS an outstanding candidate for the 3D printing of tough photopolymers. 相似文献
17.
Methods for automatic computation of IR intensities and Raman activities are described using vibrational self-consistent field (VSCF) and vibrational configuration interaction (VCI) wave functions. Inclusion of effects due to anharmonicity in the potential energy and property surfaces are found to improve the results substantially as compared to experimental data. Sample calculations employing water and formaldehyde are presented, allowing for comparison between different vibrational methods. The convergence with respect to excitation level in VCI and the extent of mode coupling in the potential and property expansions is investigated. In addition, different electronic methods used for generating the potential and property surfaces, namely CCSD, CCSD(T), DFT/B3LYP, and DFT/CAM-B3LYP have been compared. Details of the potential and property surfaces may have significant effects on the IR and Raman intensities. 相似文献
18.
Corina Flangea Catalin Schiopu Eugen Sisu Alina Serb Michael Przybylski Daniela G. Seidler Alina D. Zamfir 《Analytical and bioanalytical chemistry》2009,395(8):2489-2498
Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent
disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous
system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in the
functional diversity of neurons, brain development, and some of its pathological states. To investigate the sulfation pattern
of CS/DS structures expressed in CNS, we introduced here a novel method based on an advanced system encompassing fully automated
chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap multistage mass spectrometry
(MS2–MS3) by collision-induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans,
was particularly applied to structural investigation of disaccharides obtained by β-elimination and digestion with chondroitin
B and AC I lyase of hybrid CS/DS chains from wild-type mouse brain. Screening in the chip-MS mode of DS disaccharide fraction
resulting after depolymerization with chondroitin B lyase revealed molecular ions assigned to monosulfated disaccharide species
having a composition of 4,5-Δ-[IdoA-GalNAc]. By optimized CID MS2–MS3, fragment ions supporting the localization of sulfate ester group at C4 within GalNAc were produced. Chip ESI MS profiling
of CS disaccharide fraction obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase indicated the
occurrence of mono- and bisulfated 4,5-Δ-[GlcA-GalNAc]. The site of oversulfation was determined by MS2–MS3, which provided sequence patterns consistent with a rare GlcA-3-sulfate–GalNAc-6-sulfate structural motif.
相似文献
19.
KM Davis BA Mattern JI Pacold T Zakharova D Brewe I Kosheleva RW Henning TJ Graber SM Heald GT Seidler Y Pushkar 《The journal of physical chemistry letters》2012,3(14):1858-1864
The paradigm of "detection-before-destruction" was tested for a metalloprotein complex exposed at room temperature to the high x-ray flux typical of third generation synchrotron sources. Following the progression of the x-ray induced damage by Mn Kβ x-ray emission spectroscopy, we demonstrated the feasibility of collecting room temperature data on the electronic structure of native Photosystem II, a trans-membrane metalloprotein complex containing a Mn(4)Ca cluster. The determined non-damaging observation timeframe (about 100 milliseconds using continuous monochromatic beam, deposited dose 1*10(7) photons/μm(2) or 1.3*10(4) Gy, and 66 microseconds in pulsed mode using pink beam, deposited dose 4*10(7) photons/μm(2) or 4.2*10(4) Gy) is sufficient for the analysis of this protein's electron dynamics and catalytic mechanism at room temperature. Reported time frames are expected to be representative for other metalloproteins. The described instrumentation, based on the short working distance dispersive spectrometer, and experimental methodology is broadly applicable to time-resolved x-ray emission analysis at synchrotron and x-ray free-electron laser light sources. 相似文献
20.
Dr. Kathrin Junge Konstanze Möller Bianca Wendt Shoubhik Das Dr. Dirk Gördes Prof. Dr. Kerstin Thurow Prof. Dr. Matthias Beller 《化学:亚洲杂志》2012,7(2):314-320
The combination of ZnEt2 and chiral pyridinebisoxazoline (pybox) or pyridinebisimidazoline (pybim) ligands catalyzed the asymmetric hydrosilylation of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones. Under mild conditions, high yields and good enantioselectivities were achieved. ESI measurements allowed for the characterization of the active catalyst. 相似文献