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91.
92.
Andy J. Tomlinson Linda M. Benson Stephen Jameson Douglas H. Johnson Stephen Naylor 《Journal of the American Society for Mass Spectrometry》1997,8(1):15-24
The limited loading of capillary electrophoresis (CE) leads to relatively poor concentration limits of detection. In this work a unique method for analyte preconcentration with capillary electrophoresis-mass spectrometry (CE-MS) is described. A cartridge containing an impregnated membrane is installed at the inlet of the CE capillary, and we term this approach membrane preconcentration capillary electrophoresis-mass spectrometry (mPC-CE-MS). The analysis of in vivo derived metabolites, peptides, and proteins is described showing the wide applicability of the technology in the analysis of numerous compound classes ranging in molecular weight from 200–60,000 u. In particular, we describe the direct mPC-CE-MS analysis of urine obtained from a patient receiving the neuroleptic drug haloperidol. Three metabolites were found in the urine, and two of them are implicated in the Parkinsonian-like side effects caused by taking this drug. The technique is also applied to the analysis of major histocompatibility complex class I peptides obtained from EG-7 cells. Furthermore, the clinical potential of this approach is described by the direct analysis of urine from a patient suffering from multiple myeloma, as well as aqueous humor derived from a patient undergoing surgery. Finally we show that the use of mPC-ME-MS in conjunction with either analyte stacking (small organic molecules such as metabolites) or moving-boundary transient isotachophoresis (peptides and proteins) after analytes have been eluted from the adsorptive membrane affords optimal performance and no compromise in CE mass spectrometry performance. 相似文献
93.
Using KCl/ZnSO4 eutectic it has been shown that cooling the melt into a room temperature enclosure forms a lamellar structure, whereas cooling into a heated enclosure (225 °C) forms a conglomerate structure, while an enclosure temperature of 125 °C gave a partially conglomerate structure with some lamellae in process of forming conglomerates.Consideration of the thermal gradients imposed on solidification and consequently the relative time available during which the ions are sufficiently mobile to rearrange their positions, can explain the observation that lamellar structures are formed by higher melting point eutectics, whereas eutectics of lower melting point form conglomerate structures. 相似文献
94.
Kumari Rinki Pradip K. Dutta Andy J. Hunt James H. Clark Duncan J. Macquarrie 《Macromolecular Symposia》2009,277(1):36-42
A novel chitosan-formaldehyde porous derivative (scaffolds) was prepared by reaction of 85% deacetylated chitosan with 37% aq. formaldehyde using supercritical carbon dioxide (sc. CO2). Prior to reaction, the chitosan hydrogel was prepared in 1% aq. acetic acid (AcOH) and formaldehyde. The prepared hydrogel was subjected to solvent exchange. The identity of the Schiff base was confirmed by Fourier transform infrared spectroscopy (FTIR). The chitosan-derivative was evaluated by thermal analysis, scanning electron microscopy, and porosimetry analysis. Overall, the sc. CO2 assisted chitosan derivative opens new perspectives as biomedical material. 相似文献
95.
This work deals with a new wave migration model for the determination of an impact location for non-isotropic plates. The method is based on the wave propagation after the impact. The evaluation and processing of the signals of at least four sensors allow for the calculation of the impact location from the runtime of the signals. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
96.
Thomas D. Foust Andy Aden Abhijit Dutta Steven Phillips 《Cellulose (London, England)》2009,16(4):547-565
With the world’s focus on rapidly deploying second generation biofuels technologies, there exists today a good deal of interest
in how yields, economics, and environmental impacts of the various conversion processes of lignocellulosic biomass to transportation
fuels compare. Although there is a good deal of information regarding these conversion processes, this information is typically
very difficult to use on a comparison basis because different underlying assumptions, such as feedstock costs, plant size,
co-product credits or assumed state of technology, have been utilized. In this study, a rigorous comparison of different biomass
to transportation fuels conversion processes was performed with standard underlying economic and environmental assumptions
so that exact comparisons can be made. This study looked at promising second-generation conversion processes utilizing biochemical
and thermochemical gasification technologies on both a current and an achievable state of technology in 2012. The fundamental
finding of this study is that although the biochemical and thermochemical processes to ethanol analyzed have their individual
strengths and weaknesses, the two processes have very comparable yields, economics, and environmental impacts. Hence, this
study concludes that based on this analysis there is not a distinct economic or environmental impact difference between biochemical
and thermochemical gasification processes for second generation ethanol production. 相似文献
97.
Gokulakrishnan Soundararajan Cyril Koughia Andy Edgar Chris Varoy Safa Kasap 《Journal of Non》2011,357(11-13):2475-2479
We report the optical properties of a fluorochlorozirconate (FCZ) glass with the composition 53% ZrF4, 20% NaF, 3.5% AlF3, 3% LaF3, 0.5% InF3, (20 ? x)% BaCl2, x% BaF2 with x varying from 0% to 2%, and doped with various amounts of trivalent erbium by the addition of ErCl3. Annealing of the as-prepared glass in inert (N2) or reducing (5%H2 + 95%Ar) atmospheres at temperatures that ensure the conversion of the glass into a glass-ceramic by the nucleation of BaCl2 nanocrystals, does not significantly change any of Er3+ related absorption and photoluminescence (PL) characteristics. We have carried out a Judd–Ofelt analysis of the absorption spectra and obtained Ω2 = (1.92 ± 0.3) × 10? 20 cm2, Ω4 = (0.88 ± 0.16) × 10? 20 cm2 and Ω6 = (0.59 ± 0.08) × 10? 20 cm2, and also the radiative lifetimes of the 4I13/2→4I15/2, 4I11/2→4I15/2 and 4S3/2→4I15/2 bands. The radiative lifetime from the Judd–Ofelt analysis for the 4I13/2→4I15/2 band is in good agreement with the experimentally measured PL decay time. The examination of the optical properties of powdered samples with different average particle size does not show any photon trapping effects. We have determined the spectral absorption and emission cross-sections and then estimated the possible spectral optical gain for varying degrees of relative populations of the 4I13/2 and 4I15/2 manifolds. 相似文献
98.
In this paper, we propose a discrepancy rule-based method to automatically choose the regularization parameters for total variation image restoration problems. The regularization parameters are adjusted dynamically in each iteration. Numerical results are shown to illustrate the performance of the proposed method. 相似文献
99.
Vitamin K(1) is a fat-soluble vitamin required for the gamma-carboxylation of vitamin K-dependent proteins. Recent work has suggested an important role for vitamin K(1) in bone health beyond its more established function in the control and regulation of blood coagulation. However, current UK recommended intakes do not reflect this recent evidence. The use of stable isotopes provides a powerful tool to investigate vitamin K kinetics, turnover and absorption in man, although published methods have reported difficulties in the extraction and analysis of isotope ratios of vitamin K in human plasma. In this paper, we report a new methodology for the extraction and measurement of isotope ratios in vitamin K(1). Sample clean-up is achieved with liquid-liquid extraction, enzyme hydrolysis with lipase and cholesterol esterase, and solid-phase extraction. Isotopic analysis of the pentafluoropropionyl derivative of vitamin K(1) is performed by gas chromatography/mass spectrometry (GC/MS). The limit of quantitation is equivalent to at least 0.3 nmol/L and the method is demonstrated to be linear over a range of enrichments. This method provides a robust alternative to previous work requiring the use of semi-preparative high-performance liquid chromatography (HPLC). 相似文献
100.
Two inline matrix diversion methods were developed for the sensitive analysis of perchlorate in a matrix comprising up to 1000 mg l−1 of chloride, sulfate and bicarbonate ions using suppressed ion chromatography and conductivity detection. The first method used a cryptand C1 concentrator column, which exhibited a high selectivity for perchlorate ion over the other matrix anions. After retaining the sample anions in a concentrator column derivatized with a crytpand phase, a rinse step was implemented with a weak base to divert the matrix ions to waste while selectively retaining perchlorate in the concentrator column for subsequent analysis. The analysis was done using a 2 mm IonPac® AS16 or 2 mm IonPac® AS20 separator column. The second method was a two-dimensional matrix diversion method with a focus on improving the detection sensitivity. The first dimension was used to achieve some resolution of the matrix ions from perchlorate. The perchlorate ion was then diverted into a concentrator column for subsequent analysis in the second dimension. By pursuing analysis using a 4 mm IonPac® AS16 or IonPac® AS20 column in the first dimension and subsequently pursuing analysis using a 2 mm IonPac® AS16 or IonPac® AS20 column format, excellent sensitivities were achieved when the first and second dimensions were operated at the same linear flow velocity (cm min−1). While sensitive detection of perchlorate in the low μg l−1 regime was achieved by the above methods in the presence of matrix ions, superior recovery for perchlorate was demonstrated under a variety of matrix concentrations by the second method. 相似文献