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111.
Use of neutron activation analysis for the characterization of single-wall carbon nanotube materials
Rolf Zeisler Rabia Oflaz Rick L. Paul Jeffrey A. Fagan 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):561-567
Instrumental neutron activation analysis (INAA) and prompt gamma neutron activation analysis (PGAA) were used to characterize
a variety of single-wall carbon nanotube (SWCNT) materials from different principal production processes, as well as a material
containing SWCNTs together with other carbon species, catalyst residues, and trace element contaminants to be issued by the
National Institute of Standards and Technology for characterization and distribution as Standard Reference Material SRM 2483
Carbon Nanotube Soot. INAA proved to be well suited for the direct determination of catalyst and contaminant trace elements
requiring only minimal sample preparation. PGAA complemented the INAA data in particular with determinations of the light
elements. Carbon and hydrogen results provided information on the materials purity and storage properties. Strategies for
the quality assurance of the measurements in these new materials were developed. INAA and PGAA data were provided for the
value assignment of mass fractions of catalyst and trace elements in the candidate SRM and a systematic overview was obtained
of the catalyst and trace element contaminants associated with each of the major production routes. 相似文献
112.
V Novakova RZ Kobak R Kučera K Kopecky M Miletin V Krepsová J Ivincová P Zimcik 《Dalton transactions (Cambridge, England : 2003)》2012,41(35):10596-10604
A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide-alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ(Δ) = 0.58-0.64) retaining significant fluorescence emission (Φ(F) = 0.026-0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL(-1)) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer. 相似文献
113.
Yu LL Jarrett JM Davis WC Kilpatrick EL Oflaz R Turk GC Leber DD Valentin L Morel-Espinosa M Blount BC 《Analytical and bioanalytical chemistry》2012,404(6-7):1877-1886
Perchlorate, an inorganic anion, has recently been recognized as an environmental contaminant by the US Environmental Protection Agency. Urine is the preferred matrix for assessment of human exposure to perchlorate. Although the measurement technique for perchlorate in urine was developed in 2005, the calibration and quality assurance aspects of the metrology infrastructure for perchlorate are still lacking in that there is no certified reference material (CRM) traceable to the International System of Units. To meet the quality assurance needs in biomonitoring measurements of perchlorate and the related anions that affect thyroid health, the National Institute of Standards and Technology (NIST), in collaboration with the Centers for Disease Control and Prevention (CDC), developed Standard Reference Material (SRM) 3668 Mercury, Perchlorate, and Iodide in Frozen Human Urine. SRM 3668 consists of perchlorate, nitrate, thiocyanate, iodine, and mercury in urine at two levels that represent the 50th and 95th percentiles, respectively, of the concentrations (with some adjustments) in the US population. It is the first CRM being certified for perchlorate. Measurements leading to the certification of perchlorate were made collaboratively at NIST and CDC using three methods based on liquid or ion chromatography tandem mass spectrometry. Potential sources of bias were analyzed, and results were compared for the three methods. Perchlorate in SRM 3668 Level I urine was certified to be 2.70?±?0.21?μg?L(-1), and for SRM 3668 Level II urine, the certified value is 13.47?±?0.96?μg?L(-1). 相似文献
114.
The incorporation of yttrium in bioactive glasses (BGs) could lead to a new generation of radionuclide vectors for cancer therapy, with high biocompatibility, controlled biodegradability and the ability to enhance the growth of new healthy tissues after the treatment with radionuclides. It is essential to assess whether and to what extent yttrium incorporation affects the favourable properties of the BG matrix: ideally, one would like to combine the high surface reactivity typical of BGs with a slow release of radioactive yttrium. Molecular Dynamics simulations show that, compared to a BG composition with the same silica fraction, incorporation of yttrium results in two opposing effects on the glass durability: a more fragmented silicate network (leading to lower durability) and a stronger yttrium-mediated association between separate silicate fragments (leading to higher durability). The simulations also highlight a high site-selectivity and some clustering of yttrium cations, which are likely linked to the observed slow rate of yttrium released from related Y-BG compositions. Optimisation of yttrium BG compositions for radiotherapy applications thus depends on the delicate balance between these effects. 相似文献
115.
Rabia Akta? Abdullah Alt?n Fatma Ta?delen 《Journal of Computational and Applied Mathematics》2011,235(16):4825-4833
The main object of this paper is to construct a two-variable analogue of Jacobi polynomials and to give some properties of these polynomials. We show that these polynomials are orthogonal, then we obtain various recurrence formulas for them. Furthermore, we give some integral representations for these polynomials. 相似文献
116.
Fast semipreparative HPLC enantioseparation of four axially chiral biscarbostyrils (4,4′-bisquinoline-2-ones) using ULMO as a π-acidic Pirkle type chiral stationary phase leads to two racemizing pairs (1,2; kobs 1.6 × 10−4 and 3.0 × 10−4 s−1 at 28 °C) and two stable ones (3,4). 3 was stabilized by a crown ether linkage from pos. 6 to 6′, and 4 had sterically demanding bromo substituents in pos. 3 and 3′. On-column generated temperature-dependent chromatograms of 1 and 2 were fitted with Auto-DHPLCy2k and DCXplorer. For cpd 2 both programs delivered similar ΔG values of 90 and 93 kJ/mol, well comparable with the 99 kJ/mol calculated with the B3LYP/6-31G (d) procedure. At temperatures of high conversion DCXplorer delivered inconsistent series of rate constants for the more tailing and less resolved tetramethoxy derivative 1. We connect this problem with an almost impossible halfwidth calculation of tailing peak pairs which are weakly resolved. However, this problem could be observed only in the case of tetramethoxy derivative 1. Stochastic generated data of Auto-DHPLCy2k could be used at a lower percentage of conversion only while the theoretical plate model did not deliver useful data at temperatures of very low conversion but fitted well high conversion chromatogram series of 1 and 2. 相似文献
117.
Jahangir Mondal Amit K. Manna Kalyani Rout Sunil K. Singh Jnan P. Naskar 《International journal of environmental analytical chemistry》2013,93(12):1160-1174
ABSTRACTA new fluorescent-colorimetric chemosensor L has been synthesised by Schiff base condensation reaction between 1,8-diaminooctane and 4-nitro-benzaldehyde in very good yields. Its photo-luminescent properties and selective detection properties for hydrazine have been examined. The synthesised chemosensor exhibited highly selective fluorescence on-off response for hydrazine amongst a wide range of different metal cations, anions and amines, along with the bare eye colour change from colourless to yellow based on intermolecular hydrogen-bond interaction. The limit of detection of the chemosensor L was estimated as 9.77 × 10?8 M or 3.12 × 10?6 g L?1 for hydrazine which is extremely below the limit set by the World Health Organization (WHO) and the binding stoichiometry was proposed to be 1 : 2 based on 1H NMR spectroscopic techniques and the Job’s plot analysis. The proposed sensing mechanism is the hydrogen-bonding interaction which has further been established by Density Functional Theory (Functional Density Theory (DFT)) studies. This recognition feature of sensor L makes it an efficient chemosensor for hydrazine detection in different water samples. 相似文献
118.
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120.
Michele M. Schantz Danielle Cleveland N. Alan Heckert John R. Kucklick Stefan D. Leigh Stephen E. Long Jennifer M. Lynch Karen E. Murphy Rabia Olfaz Adam L. Pintar Barbara J. Porter Savelas A. Rabb Stacy S. Vander Pol Stephen A. Wise Rolf Zeisler 《Analytical and bioanalytical chemistry》2016,408(16):4257-4266