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81.
On the basis of the cluster model (CM) structure of the lithium isotopes the (7Li, 6Li) reaction may be interpreted as resulting from either the n-d or n-τ cluster interaction instead of the conventionally used n-6Li interaction. For the 12C(7Li, 6Li)13Cgs. transition it is shown, that the CMDWBA analysis gives quite comparable results with the recoilless HIDWBA and the “exact” finite range DWBA calculation. 相似文献
82.
Mitsuyuki Shizuya Yuji Baba Takuro Nagai Minoru Osada Kosuke Kosuda Satoshi Takenouchi Yoshio Matsui Eiji Takayama-Muromachi 《Journal of solid state chemistry》2007,180(1):249-259
We synthesized a new cobalt oxide (CaOH)1.14CoO2 by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of CdI2-type CoO2 layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. 相似文献
83.
Kuroyanagi M Shimomae M Nagashima Y Muto N Okuda T Kawahara N Nakane T Sano T 《Chemical & pharmaceutical bulletin》2005,53(12):1519-1523
In the course of research on the bioactive constituents of woody plants in the Cyugoku area of Japan, a methanol extract of the leaves of Alnus japonica were found to have strong antioxidative activity. Ethyl acetate soluble and n-buthanol soluble fractions of the methanol extract had a potent antioxidative effect. Both fractions were purified by silica gel column chromatography and HPLC using an ODS column to give four new diarylheptanoids along with known diarylheptanoids and flavonoids. These new compounds were elucidated to be 7-(3,4-dihydroxyphenyl)-5-hydroxy-1-(4-hydroxyphenyl)-3-heptanone-5-O-beta-D-xylopyranoside (1), 1-(3,4-dihydroxyphenyl)-5-hydroxy-7-(4-hydroxyphenyl)-3-heptanone-5-O-beta-D-xylopyranoside (2), 1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxy-3-heptanone-5-O-[2-(2-methylbutenoyl)]-beta-D-xylopyranoside (3) and 1,7-bis-(3,4-dihydroxyphenyl)-5-methoxy-3-heptanone (4) using spectral methods and especially 1H-, 13C-NMR and 2D-NMR measurements. The isolated compounds including their main constituent, oregonin (5), were tested for antioxidative activity. Some of these compounds having two catechol structures showed potent antioxidative activity. Compounds having one catechol structure showed moderate antioxidative activity, but a peracetate of 5 having no catechol structure exhibited no antioxidative activity. Thus the catechol structure of the diarylheptanoids is indispensable for antioxidative activity. 相似文献
84.
Synthesis of monodisperse polystyrene microspheres by dispersion polymerization using sodium polyaspartate 总被引:1,自引:0,他引:1
We prepared monodisperse polystyrene microspheres by dispersion polymerization using sodium polyaspartate (PAspNa) as a dispersion
stabilizer in an ethanol/water medium. The influence of reaction parameters, i.e., the volume fraction of ethanol in the medium,
stabilizer concentration, and the monomer concentration, on the average diameter of the prepared polystyrene microspheres
and its distribution were investigated. Polystyrene microspheres were successfully prepared, and the average diameter of the
prepared monodisperse polystyrene microspheres was controlled by adjusting the reaction parameters. The zeta potential of
the microspheres and the time course of conversion, the particle diameter and its distribution, and particle numbers were
also examined. It was found that PAspNa as a dispersion stabilizer provides an environmentally benign process for the preparation
of monodisperse polymer microspheres by dispersion polymerization. 相似文献
85.
Takuro Miki Takumi Ogawa Tetsuhiko Isobe Hocine Sfihi 《Journal of Sol-Gel Science and Technology》2004,32(1-3):73-77
Acetylcellulose (AC)/silica and polyvinylpyrrolidone (PVP)/silica composites were prepared by the sol–gel method from Si(OCH3)4-AC-HNO3-H2O-tetrahydrofuran-CH3OC2H4OH and Si(OCH3)4-PVP-(CH3COOH or NH3)-H2O-CH3OH-CH3OC2H4OH solutions. AC/silica composites were composed of micrometer-sized particles rich in silica and a matrix rich in AC, while PVP/silica composites were single-phase on the SEM length scale. The AC/silica composites exhibited elastic-plastic behavior, and had excellent machinability without chipping on cutting with an electric saw while the PVP/silica composites showed less plasticity and machinability. Youngs modulus and bending strength were increased by post-drying, 1.8–2.8 GPa and 49–88 MPa, respectively, for the AC/silica composites, and 1.0–3.9 GPa and 17–79 MPa, respectively, for the PVP/silica composites. 相似文献
86.
Nobuhiro Matsumoto Takuro Watanabe Kenji Kato 《Accreditation and quality assurance》2005,10(7):382-385
There are many error sources in the preparation of primary reference gas mixtures by the gravimetric method. One of the error
sources is the adsorption/desorption of moisture on the external gas cylinder surface. Variation of relative humidity in atomospheric
air around the cylinder during the preparation process may cause an error in the mass measurement of the gas cylinder. Effect
of the adsorption/desorption on the surface is dependent on the condition of the external cylinder surface. In this study,
various types of cylinders are precisely weighed under different humidity conditions. Hairline finish and shot blast finish
are preferable treatments for the external cylinder surface in our experiments. The use of cylinders with painted surface
should be avoided as possible if the humidity control in the rooms is insufficient.Table 1 Tested cylinders with various finishes on external surfaces 相似文献
87.
A species-specific isotope dilution (ID) method is described for the determination of mono-, di, and tri-butyltin compounds in sediment by gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS), where the mixture of 118Sn-enriched butyltin compounds synthesized in our laboratory was used as a spike. A correction method for the mass bias, a quantitative extraction of the butyltins from sediment, and an assay for the concentration of the standard solution for the reverse ID procedure were investigated to achieve a reliable ID analysis. The spike solution was added with tri-propyltin (TPrT), and the butyltins were extracted by mechanical shaking into acetic acid-tropolone-toluene. The extracted butyltins were ethylated with sodium tetraethylborate and measured by GC-ICP-MS. The mass bias correction factor for the butyltins was calculated with the measured area ratio of 120Sn/118Sn of TPrT in each chromatographic run, and the correction was carried out. The mass bias was well corrected with this in-run correction (the standard uncertainties of the corrected 120Sn/118Sn for the butyltins were in the range 0.03-0.45%, typically 0.25%, with triplicate measurement corresponding to 0.02-0.37% mass bias). The extraction efficiency of mono-butyltin (MBT) from sediment was improved by using tropolone-toluene as the solvent. Well-defined standard solutions for the reverse-ID procedure could be obtained by an assay for the purities of the natural abundance butyltin chloride reagents used for preparing the standard solutions. Overall uncertainties associated with the present method were estimated, where the sediment certified reference materials, PACS-2 and BCR 646, were analyzed. The uncertainty arising from the extraction was the main contributor to the overall uncertainties for MBT and di-butyltin (DBT) determinations, while with the case of tri-butyltin (TBT) determination the uncertainties arising from the purity of TBT chloride reagent used for preparing the standard solution was a large contributor to the overall uncertainties although the uncertainty arising from the extraction was also a main contributor. The analytical results of MBT, DBT, and TBT in both reference materials, except for MBT results in PACS-2, were in good agreement with the certified values in each. The result of MBT in PACS-2 (0.677 +/- 0.049 microg g(-1) as tin, mean +/- expanded uncertainty) was significantly higher than the certified value (0.45 +/- 0.05 microg g(-1)), but closely matched with the lately reported values (Rajendran, Tao, Nakazato and Miyazaki, Analyst, 2000, 125, 1757: 0.62 +/- 0.02 microg g(-1); Chiron, Roy, Cottier and Jeannot, J. Chromatogr. A, 2000, 879, 137: 0.634 +/- 0.082 microg g(-1); Alonso, Encinar, Gonzalez and Sanz-Medal, Anal. Bioanal. Chem., 2002, 373, 432: 0.64 +/- 0.04 microg g(-1). The present method is concluded to be reliable for the determination of MBT, DBT, and TBT in sediment. 相似文献
88.
Inagaki K Takatsu A Watanabe T Kuroiwa T Aoyagi Y Okamoto K 《Analytical and bioanalytical chemistry》2004,378(5):1265-1270
A new marine sediment reference material (NMIJ CRM 7301-a) for butyltins analysis was prepared and certified by the National Metrological Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original material of the sediment was collected at a bay near industrial activities in Japan. The sediment material was air-dried, sieved, homogenized, and packaged into 1,000 glass bottles (60 g each). Certification of NMIJ CRM 7301-a was carried out at NMIJ using two different types of species-specific isotope dilution mass spectrometry: isotope dilution–ethylation–gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) and isotope dilution–ethylation–gas chromatography/mass spectrometry (GC/MS). A mixture of 118Sn-enriched monobutyltin, dibutyltin, and tributyltin was synthesized in our laboratory and was used as a spike for both techniques. Certified values are given for tributyltin (0.044±0.004 mg kg–1 as Sn), dibutyltin (0.056±0.006 mg kg–1 as Sn, and monobutyltin (0.058±0.013 mg kg–1 as Sn), being at lower levels than currently available sediment CRMs for the analysis of organotins. 相似文献
89.
Access to Air‐Stable 1,3‐Diphosphacyclobutane‐2,4‐diyls by an Arylation Reaction with Arynes 下载免费PDF全文
Yasuhiro Ueta Prof. Dr. Koichi Mikami Prof. Dr. Shigekazu Ito 《Angewandte Chemie (International ed. in English)》2016,55(26):7525-7529
Tuning of the physicochemical properties of the 1,3‐diphosphacyclobutane‐2,4‐diyl unit is attractive in view of materials applications. The use of arynes is shown to be effective for installing relatively electron rich aryl substituents into the open‐shell singlet P‐heterocyclic system. Treatment of the sterically encumbered 1,3‐diphosphacyclobuten‐4‐yl anion with ortho‐silylated aryl triflates in the presence of fluoride under appropriate conditions afforded the corresponding 1‐aryl 1,3‐diphosphacyclobutane‐2,4‐diyls. The air‐stable open‐shell singlet P‐heterocycles exhibit considerable electron‐donating character, and the aromatic substituent influences the open‐shell character, which is thought to be related to the property of p‐type semiconductivity. The P‐arylated 1,3‐diphosphacyclobutane‐2,4‐diyl systems can be further utilized as detectors of hydrogen fluoride (HF), which causes a remarkable change in their photoabsorption properties. 相似文献
90.
Matsumoto N Shimosaka T Watanabe T Kato K 《Analytical and bioanalytical chemistry》2008,391(6):2061-2069
One method of preparing a primary reference gas mixture is the gravimetric blending method. Uncertainty of a few mg in mass
measurements is unavoidable when preparing reference gas mixtures under current laboratory conditions with our facilities,
equipment, and materials. There are many sources of errors when using this method. In this study, several sources of errors
were re-evaluated for our process for preparation of carbon dioxide in synthetic air. As a consequence of the re-evaluation,
it was found that some sources of errors had significant effects on gravimetric concentrations of the gas mixtures. These
sources are: (1) different masses of the reference cylinder and sample cylinder (an error in the readings of the electronic
mass comparator), (2) leakage of the inner gas from valves of the cylinders, and (3) cooling of the gas cylinder caused by
filling with high-pressure liquefied carbon dioxide gas. When the mass measurements were performed under uncontrolled conditions,
the errors due to sources (1), (2), and (3) were as high as 20 mg, 24 mg, and 13 mg, respectively. In this paper, the detailed
results from re-evaluation of these sources of errors are discussed.
Figure Evaluation of the source of error (1) 相似文献