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41.
Ingvar Lindgren 《International journal of quantum chemistry》1996,57(4):683-695
A review is given of many-body perturbation methods, particularly in the all-order and coupled-cluster forms. Relativistic many-body schemes are analyzed in terms of one- and two-photon potentials, derived by means of QED. A complete second-order (nonradiative) calculation for He-like ions is presented, including repeated Breit interactions as well as the effects of retardation and of negative-energy states, but omitting the Lamb shift. Numerical results of some Lamb-shift calculations are also given. From the analysis, conclusions can be drawn concerning the accuracy of certain relativistic many-body approaches. © 1996 John Wiley & Sons, Inc. 相似文献
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The rotational spectra of the normal and Si-d2 isotopomers of the chair form of silacyclohexane have been measured by microwave absorption spectroscopy. A partial r0 structure has been obtained. The rotational spectra of some, the most intense, vibrational satellites have also been measured. They belong to the ring-puckering motions. Their vibrational energies and their shifts of planar moments of inertia with respect to the ground state indicate that the amplitude of these vibrations is larger than in cyclohexane. The dipole moment has also been determined: μa = 0.75(2), μc = 0.280(2), and μtot = 0.80(2) D. 相似文献
47.
GC×GC-ECD: a promising method for the determination of dioxins and dioxin-like PCBs in food and feed
Haglund P Korytár P Danielsson C Diaz J Wiberg K Leonards P Brinkman UA de Boer J 《Analytical and bioanalytical chemistry》2008,390(7):1815-1827
There is a need for cost-efficient alternatives to gas chromatography (GC)–high-resolution mass spectrometry (HRMS) for the
analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food and feed. Comprehensive two-dimensional
GC–micro electron capture detection (GC×GC-μECD) was tested and all relevant (according to the World Health Organisation,
WHO) PCDD/Fs and PCBs could be separated when using a DB-XLB/LC-50 column combination. Validation tests by two laboratories
showed that detectability, repeatability, reproducibility and accuracy of GC×GC-μECD are all statistically consistent with
GC-HRMS results. A limit of detection of 0.5 pg WHO PCDD/F tetrachlorodibenzo-p-dioxin equivalency concentration per gram of fish oil was established. The reproducibility was less than 10%, which is below
the recommended EU value for reference methods (less than 15%). Injections of vegetable oil extracts spiked with PCBs, polychlorinated
naphthalenes and diphenyl ethers at concentrations of 200 ng/g showed no significant impact on the dioxin results, confirming
in that way the robustness of the method. The use of GC×GC-μECD as a routine method for food and feed analysis is therefore
recommended. However, the data evaluation of low dioxin concentrations is still laborious owing to the need for manual integration.
This makes the overall analysis costs higher than those of GC-HRMS. Further developments of software are needed (and expected)
to reduce the data evaluation time. Combination of the current method with pressurised liquid extraction with in-cell cleanup
will result in further reduction of analysis costs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
48.
A double stranded DNA based fluorescence bioprobe for anticancer agent (doxorubicin) detection is described. This method provides a new way for sensitive DNA/drug interaction study by a homogeneous assay. The probe employs the long-wavelength intercalating fluorophore TOTO-3® (TT3). The anticancer agent, doxorubicin, which interacts with the DNA-TT3 complex, was indirectly measured by the decrease in the fluorescence intensity. Various oligonucleotides with different sequences were examined. Doxorubicin has preference for the oligonucleotide 5′AGCACG3′. Enhanced fluorescence observed for the TT3 intercalation with this oligonucleotide makes the DNA-dye complex a suitable bioprobe for doxorubicin detection by competitive assay. A home-built CCD camera setup was applied along with 384 well plate assay format for high throughput fluorescence imaging. The detection limit can be as low as 25 ng mL−1 with an upper limit of 100 μg mL−1. The recovery test with spiked serum sample shows that this method can be a potential routine method for therapeutic drug monitoring (TDM). 相似文献
49.
Zhaunerchyk V Geppert WD Vigren E Hamberg M Danielsson M Larsson M Thomas RD Kaminska M Osterdahl F 《The Journal of chemical physics》2007,127(1):014305
We report an investigation into the dissociative recombination of the azide radical cation, N(3) (+). The reaction rate constant has been measured to be 6.47 x 10(-7) cm(3) s(-1) at room temperature. This value is smaller than those reported earlier for the ion-electron neutralization of N(3) (+) at nitrogen atmospheric pressure. A strong propensity to dissociate through the N(2)+N channel has been observed. 相似文献
50.
A study of specific interactions between lectins and glycoproteins has been carried out using surface plasmon resonance (SPR) in a flow-injection mode. Lectins were covalently immobilised on the surfaces of the microfluidic sensor chip via amine coupling and serum glycoproteins were injected into the flow channels. Specific lectin-glycoprotein interactions caused the shift of refractive index proportional to the mass concentration accumulated on the channel surface. Lectins showed different affinity to the tested glycoproteins and each glycoprotein displayed its own lectin-binding pattern. It is possible to distinguish and identify even glycoproteins with similar sugar structures by simple and quick screening. The working conditions of the assay were optimised. The lectin-based SPR made it possible to carry out the label-free detection of glycoproteins within a broad concentration range with a good linearity. Regeneration conditions for the surface of the sensor chip were found and optimised. Combination of 10 mM HCl and 10 mM glycine-HCl (pH 2.5) removes the bound glycoproteins from the lectin surface without damaging it. The kinetic and affinity parameters of lectin-glycoprotein binding were evaluated. The proposed method was tested on human glycosylated serum. Combination of the lectin panel with SPR is suitable both for specific screening and for sensitive assay of serum glycoproteins. 相似文献