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91.
O.F. Kalman 《Molecular physics》2013,111(2):397-412
A discussion is given on the changes obtainable in the asymmetry parameter β with vibrational state of the ion in the approximation involving fixed direction of body-frame orientation during the electron ejection. The R dependence of the electronic matrix elements is taken into account by calculation of appropriate displaced oscillator integrals. Inclusion of a nuclear matrix element gives in most cases negligible effect for the direct ionization. βν′ are calculated for H2 and N2. Expected variations in βν′ are compared with recent experimental data on N2 and CO. Higher partial waves and their effect on βν′ are discussed. 相似文献
92.
Mark Tahtouh John R. Kalman Brian J. Reedy 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):257-277
Four novel cyanoacrylates, 2‐cyanoethyl 2‐cyanoacrylate, 1‐cyanoethyl 2‐cyanoacrylate, trideuteromethyl 2‐cyanoacrylate and pentadeuteroethyl 2‐cyanoacrylate have been synthesized using a Diels‐Alder protection/deprotection route involving anthracene. The common route for the synthesis of alkyl 2‐cyanoacrylates was found to be unsatisfactory for the production of small quantities of the targeted cyanoacrylates, which have potential as reagents for the mid‐infrared spectral imaging of fingerprints on difficult surfaces. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
93.
Comprehensive carbohydrate analysis of glycoproteins from human biological samples and biotherapeutics are important from diagnostic and therapeutic points of view. This review summarizes the current state-of-the-art liquid phase separation techniques used in N-glycosylation analysis. The different liquid chromatographic techniques and capillary electrophoresis methods are critically discussed in detail. Miniaturization of these methods is also important to increase throughput and decrease analysis time. The sample preparation and labeling methods for asparagine linked oligosaccharides are also addressed. 相似文献
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96.
Dr. Patrick Hemberger Dr. Andras Bodi Dr. Thomas Gerber Dr. Max Würtemberger Prof. Dr. Udo Radius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7090-7099
The photoionization and dissociative photoionization of Im(iPr)2, 1,3‐diisopropylimidazolin‐2‐ylidene, was investigated by imaging photoelectron photoion coincidence (iPEPICO) with vacuum ultraviolet (VUV) synchrotron radiation. A lone‐pair electron of the carbene carbon atom is removed upon ionization and the molecular geometry changes significantly. Only 0.5 eV above the adiabatic ionization energy, IEad=7.52±0.1 eV, the carbene cation fragments, yielding propene or a methyl radical in parallel dissociation reactions with appearance energies of 8.22 and 8.17 eV, respectively. Both reaction channels appear at almost the same photon energy, suggesting a shared transition state. This is confirmed by calculations, which reveal the rate‐determining step as hydrogen‐atom migration from the isopropyl group to the carbene carbon center forming a resonance‐stabilized imidazolium ion. Above 10.5 eV, analogous sequential dissociation channels open up. The first propene‐loss fragment ion dissociates further and another methyl or propene is abstracted. Again, a resonance‐stabilized imidazolium ion acts as intermediate. The aromaticity of the system is enhanced even in vertical ionization. Indeed, the coincidence technique confirms that a real imidazolium ion is produced by hydrogen transfer over a small barrier. The simple analysis of the breakdown diagram yields all the clues to disentangle the complex dissociative photoionization mechanism of this intermediate‐sized molecule. Photoelectron photoion coincidence is a promising tool to unveil the fragmentation mechanism of larger molecules in mass spectrometry. 相似文献
97.
Donald F. Smith Andras Kiss Franklin E. Leach III Errol W. Robinson Ljiljana Paša-Tolić Ron M. A. Heeren 《Analytical and bioanalytical chemistry》2013,405(18):6069-6076
Biological tissue imaging by secondary ion mass spectrometry has seen rapid development with the commercial availability of polyatomic primary ion sources. Endogenous lipids and other small bio-molecules can now be routinely mapped on the sub-micrometer scale. Such experiments are typically performed on time-of-flight mass spectrometers for high sensitivity and high repetition rate imaging. However, such mass analyzers lack the mass resolving power to ensure separation of isobaric ions and the mass accuracy for elemental formula assignment based on exact mass measurement. We have recently reported a secondary ion mass spectrometer with the combination of a C60 primary ion gun with a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) for high mass resolving power, high mass measurement accuracy, and tandem mass spectrometry capabilities. In this work, high specificity and high sensitivity secondary ion FT-ICR MS was applied to chemical imaging of biological tissue. An entire rat brain tissue was measured with 150 μm spatial resolution (75 μm primary ion spot size) with mass resolving power (m/Δm 50%) of 67,500 (at m/z 750) and root-mean-square measurement accuracy less than two parts-per-million for intact phospholipids, small molecules and fragments. For the first time, ultra-high mass resolving power SIMS has been demonstrated, with m/Δm 50%?>?3,000,000. Higher spatial resolution capabilities of the platform were tested at a spatial resolution of 20 μm. The results represent order of magnitude improvements in mass resolving power and mass measurement accuracy for SIMS imaging and the promise of the platform for ultra-high mass resolving power and high spatial resolution imaging. Figure
C60 secondary ion FT-ICR MS provides unprecedented mass resolving power and mass accuracy for SIMS imaging of biological tissue sections. Overlaid selected ion images from rat brain (left) and high spatial resolution imaging of organic dye underneath a TEM grid (right). 相似文献
98.
We address partition problems of Erd?s and Hajnal by showing that for all , if and carries a -dense ideal. If is measurable we show that for where is a very large ordinal less than that is closed under all primitive recursive ordinal operations.
Received: 27 June 2001 / Revised version: 5 December 2001 / Published online: 4 February 2003
The first author was partially supported by NSF grant DMS-0101155 and the Equipe d'Analyse Univ. of Paris 6. The second author
was partially supported by NSF grants DMS-0072560 and DMS-9704477. 相似文献
99.