全文获取类型
收费全文 | 104篇 |
免费 | 5篇 |
专业分类
化学 | 90篇 |
力学 | 1篇 |
数学 | 2篇 |
物理学 | 16篇 |
出版年
2022年 | 4篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有109条查询结果,搜索用时 13 毫秒
1.
The self-assembly mechanisms of polyoxometalates (POMs) are still a matter of discussion owing to the difficult task of identifying all the chemical species and reactions involved. We present a new computational methodology that identifies the reaction mechanism for the formation of metal-oxide clusters and provides a speciation model from first-principles and in an automated manner. As a first example, we apply our method to the formation of octamolybdate. In our model, we include variables such as pH, temperature and ionic force because they have a determining effect on driving the reaction to a specific product. Making use of graphs, we set up and solved 2.8 × 105 multi-species chemical equilibrium (MSCE) non-linear equations and found which set of reactions fitted best with the experimental data available. The agreement between computed and experimental speciation diagrams is excellent. Furthermore, we discovered a strong linear dependence between DFT and empirical formation constants, which opens the door for a systematic rescaling.The self-assembly mechanisms of polyoxometalates (POMs) are still a matter of discussion owing to the difficult task of identifying all the chemical species and reactions involved. The POMSimulator deals with that complexity in an automated manner. 相似文献
2.
The focused ion beam lift-out technique for scanning electron microscope (SEM) and transmission electron microscope (TEM) sample preparation was shown to be applicable to copper/low-k dielectric semiconductor technology. High resolution SEM, TEM, and scanning transmission electron microscope analyses were performed on metal contacts and resist vias with no evidence of the interface damage or metal smearing commonly observed with mechanical polishing. Ion milling of the sample ex situ to the substrate provided decoration and adjustment of the exposed plane of the section when necessary for SEM analysis. 相似文献
3.
Estefanía Moreno-Gordaliza Sven J. van der Lee Ayşe Demirkan Cornelia M. van Duijn Johan Kuiper Petrus W. Lindenburg Thomas Hankemeier 《Analytica chimica acta》2016
A new capillary isotachophoresis (cITP) method for lipoprotein profiling with superior lipoprotein coverage compared to previous methods has been developed, resolving twice as many lipoprotein species (18 peaks/fractions) in serum or plasma in less than 9.5 min. For this, a novel mixture of 24 spacers, including amino acids, dipeptides and sulfonic acids, was developed and fine-tuned, using predictive software (PeakMaster) and testing of spiked serum samples. Lipoprotein peaks were identified by serum-spiking with reference lipoproteins. Compatibility with common lipophilic stains for selective lipoprotein detection with either UV/Vis or laser-induced fluorescence was demonstrated. A special new capillary with a neutral coating (combining water-compatible OV1701-OH deactivation and methylation) was used for the first time for electrodriven separations, allowing very stable separations in a pH 8.8–9.4 gradient system, being functional for more than 100 injections. Excellent reproducibility was achieved, with coefficients of variation lower than 2.6% for absolute migration times. Comparison was performed with human plasma samples analyzed by NMR, leading to similar results with cITP after multivariate statistics, regarding group-clustering and lipoprotein species correlation. The new cITP method was applied to the analysis of serum samples from a LDL receptor knock-out mice model fed either a normal diet or a western-type diet. Differences in the lipoprotein levels and in the sublipoprotein types were detected, showing a shift to more atherogenic particles due to the high cholesterol diet. In summary, this novel method will allow more detailed and informative profiling of lipoprotein particle subtypes for cardiovascular disease research. 相似文献
4.
The ac Stark effect was used to induce resonant energy transfer between translationally cold 85Rb Rydberg atoms. When a 28.5 GHz dressing field was set at specific field strengths, the two-atom dipole-dipole process 43d5/2+43d5/2-->45p3/2+41f was dramatically enhanced, due to induced degeneracy of the initial and final states. This method for enhancing interactions is complementary to dc electric-field-induced resonant energy transfer, but has more flexibility due to the possibility of varying the applied frequency. 相似文献
5.
Petrus Zwart John Taylor Simon Morton Randall Cayford Gerald Fontenay Marc Allaire 《Synchrotron Radiation News》2015,28(2):22-27
The Berkeley Center for Structural Biology (BCSB) operates and develops a suite of protein crystallography beamlines at the Advanced Light Source (ALS) located at Lawrence Berkeley National Laboratory (LBNL). Although the ALS was conceived as a low-energy (1.9-GeV), third-generation synchrotron source of vacuum ultraviolet (VUV) and soft X-ray radiation, it was realized during the development of the facility in the mid-1990s that a multipole wiggler coupled with brightness-preserving optics would result in a beamline whose performance in the energy range of 5 to 15 keV would be sufficient for most protein crystallographic experiments. Later, the hard X-ray capabilities of the ALS were expanded by the addition of three superconducting bending magnets, resulting in additional protein crystallography facilities at the ALS [1]. 相似文献
6.
Kovacik V Patoprsty V Lattova E Petrus L Ovcharenko V Pihlaja K 《Journal of mass spectrometry : JMS》1999,34(12):1322-1327
O-Isopropylidene and O-benzylidene acetals of common 2, 6-anhydro-1-deoxy-1-nitroalditols (beta-D-glyco- pyranosylnitromethanes) derived from D-glucose, D-galactose and D-mannose were studied by electron ionization (EI) mass spectrometry. Fragment pathways of the title compounds were studied using accurate mass measurements, collision-induced dissociation, B/E and B2/E measurements of selected ions and mass spectra of O-deuterium-labelled compound. The fragmentation pathways and some differences found among the mass spectra of stereoisomers are discussed. Noteworthy is the splitting off of the (.)NO(2) radical and elimination of acetone from the molecular ions of 4, 6-O-benzylidene-2, 3-O-isopropylidene-beta-D-galactopyranosylnitromethane. This fragmentation route of relatively high abundance was not observed in the case of D-gluco and D-manno analogues. The differences in the EI mass spectra of stereoisomers may help to provide some information serving for the estimation of the stereochemical arrangement of compounds of this type. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
Yu. V. Migalina A. Yu. Sani I. M. Balog V. V. Petrus I. I. Ershova V. G. Lendel 《Chemistry of Heterocyclic Compounds》1989,25(6):610-612
The addition of selenium tetrabromide to the olefinic bond of N-substituted allylacetic acid amides (reagent molar ratio 21) proceeds counter to Markownikoff's rule with the formation of tetrahydrofuran derivatives. The addition of tellurium tetrahalides under the same conditions (reagent molar ratio 11) proceeds in accordance with Markownikoff's rule with the formation of tetrahydropyran derivatives.Communication 10 in the series Electrophilic reactions of halides of elements of the sixth group; see [1] for Communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 743–745, June, 1989. 相似文献
8.
Wearing surgical face masks is among the measures taken to mitigate coronavirus disease (COVID-19) transmission and deaths. Lately, concern was expressed about the possibility that gases from respiration could build up in the mask over time, causing medical issues related to the respiratory system. In this research study, the carbon dioxide concentration and ethylene in the breathing zone were measured before and immediately after wearing surgical face masks using the photoacoustic spectroscopy method. From the determinations of this study, the C2H4 was established to be increased by 1.5% after one hour of wearing the surgical face mask, while CO2 was established to be at a higher concentration of 1.2% after one hour of wearing the surgical face mask, when the values were correlated with the baseline (control). 相似文献
9.
Florine Cavelier Sylvie Gomez Robert Jacquier Muriel Llinares Jean-Luc Mercadier Clment Petrus Jean Verducci 《Tetrahedron: Asymmetry》1993,4(12)
This work describes a convenient and accurate method for optical purity determination of α-hydroxy acids. Their derivatization with commercially available valine methyl ester affords diastereoisomers easily separable by HPLC using achiral C18 columns. 相似文献
10.
Petrus A. C. Raats 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1968,19(4):606-613
Zusammenfassung In dieser Arbeit wird die Mechanik poröser Körper im Rahmen einer Theorie der Mischungen behandelt. Es werden poröse Körper betrachtet, die aus einer festen Phase und einer willkürlichen Zahl flüssiger Phasen bestehen. Einige bekannte Gleichungen für zwei- und dreiphasige Körper werden als Spezialfälle abgeleitet. 相似文献