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1.
Ni + Mo + Si composite coatings were prepared by co-deposition of nickel with molybdenum and silicon powders from a nickel solution in which Mo and Si particles were suspended by stirring. The layers have been deposited on a carbon steel substrate (St3S) under galvanostatic conditions. The content of Si in deposited layers was about 2-5 wt.% depending on deposition current density and the value of electric charge. For comparison Ni + Mo composite coatings were obtained under analogous current conditions. Composite coatings of enhanced Si content (15 wt.%) were deposited from an electrolyte in which 40 g/dm3 of Si covered with electroless plated nickel was dispersed. Deposition current density was equal 0.1 A/cm2 and the value of electric charge Q = 500 C/cm2. The thickness of the coatings was about 100-300 μm depending on their kind, electric charge and the deposition current density. Surface and cross-section morphology were investigated by scanning electron microscope (SEM). All deposited coatings are characterized by great, developed surface area. No internal stresses causing their cracking were observed. Chemical composition of the layers was determined by X-ray fluorescence spectroscopy (XRF) method and quantitative X-ray analysis (QXRD). It was stated, that the content of molybdenum and silicon in Ni + Mo + Si coatings depends on deposition current density and the amount of the powder in bath. The results of structural investigation of the obtained layers by the X-ray diffraction (XRD) method show, that they consist in crystalline Mo or Mo and Si phases built into Ni matrix. Moreover, Ni + Mo + Si composite coatings were modified by thermal treatment. It has been found that the thermal treatment of Ni + Mo + Si composite coatings caused that the new phases (NiSi, Mo2Ni3Si and Ni6Mo6C1.06) were obtained. 相似文献
2.
在0.3mm直径的铅笔芯上电修饰聚苯胺,封入玻璃毛细管中,并与Ag/AgCl电极组合成复合微型pH电极.经实验测试,该电极的pH响应特性良好,在pH1~11的线性范围内,能斯特斜率为(-56.4±0.5)mV/pH,线性相关系数不小于0.996.作为参比的Ag/AgCl电极性能稳定.由于电极是复合微型化的,所以可用于活体微区测定. 相似文献
3.
N. Etxebarria G. Arana R. Antolín G. Borge T. Posada J. C. Raposo 《Accreditation and quality assurance》2007,12(11):575-580
Electrolytic manganese is an important alloying element for aluminium and steel melts. It is mainly added to melts of aluminium
in the holding furnace as tablets or minitablets (compressed compacts of manganese and aluminium powders). Selenium derivates
are usually added during the production of electrolytic manganese, so some selenium is present in the alloys produced when
electrolytic manganese is added to the aluminium furnace. Since the selenium contents of many alloys are of concern from health
and environmental perspectives, their values should be provided. In this work, a laboratory reference material (LRM) based
on electrolytic manganese was produced to assure our routine quality control method, where selenium is analysed by hydride
generation followed by optical emission spectrometry with inductively coupled plasma (HG–ICP–OES). Therefore, the present
paper describes in detail the preparation procedure for and the results from homogeneity and stability studies performed on
electrolytic manganese LRM. For this purpose, a commercial electrolytic manganese lot was selected and the main factors involved
in the preparation of the material (pretreatment step, homogenization, bottling and storage) were carefully studied and established
in order to guarantee the long-term stability of the LRM. The results obtained showed that the LRM developed was a fit-for-purpose
material for the quality control of the routine analysis of selenium. 相似文献
4.
Petra Spitzer Bruno Rossi Yves Gaignet Stéphane Mabic Uwe Sudmeier 《Accreditation and quality assurance》2005,10(3):78-81
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 S cm–1 at 25.0 °C, resistivity >1 M cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.Milipore, Milli-Q and Elix are registered trademarks of Millipore Corporation. 相似文献
5.
Norbert V. Fehringer Dalia M. Gilvydis Stephen M. Walters Colin F. Poole 《Journal of separation science》1992,15(2):124-127
The combination of open tubular column gas chromatography with electrolytic conductivity detection has been evaluated for the determination of nitrogen-containing pesticide residues in food extracts. Optimization of the column position at the column-detector interface was crucial to the successful operation of the detector. The signal-to-noise ratio and response stability of the detector are greatly influenced by the composition of the electrolyte solvent. Large volume splitless injections using retention gaps and optimized detector operating conditions enabled pesticide residues in food extracts to be determined at sub parts-per-million levels. Although the electrolytic conductivity detector is less sensitive than the thermionic ionization detector, its greater nitrogen selectivity can he crucial to the determination of nitrogen-containing contaminants in food extracts, particularly in complex mixtures where phosphorus-containing contaminants or matrix compounds are also present. 相似文献
6.
Summary A gas chromatographic methodology with selective detection is presented for the analysis in wines and corks of pentachlorophenol residues, which are suspected to be the most likely precursors of some off-flavours described in several wine samples. After derivatisation, pentachlorophenol acetate residues were monitored by electrolytic conductivity detection and/or mass spectrometric detection in the selective ion mode at m/z 264 and 266. Recoveries varied from 80 to 96% for wine samples fortified with 5 to 100 g l–1 and from 83 to 91% for corks (fortified at 25 to 100 g kg–1). The proposed methodology allowed for a determination limit of g l–1 for wine and 10 g kg–1 for corks. 相似文献
7.
8.
将锌汞齐能还原二硫代二乙酸(DTDGA)成巯基乙酸(TGA)的原理和碘量法滴定相结合,对电还原DTDGA合成TGA反应液中的DTDGA进行定量分析,测定结果的相对标准偏差为0.37%,加标平均回收率100.6%。 相似文献
9.
研究了氧化吸收硫化氢反应和电解制氢相结合从硫化氢中回收氢气和硫磺的方法,用实验考查了不同参数对氧化吸收硫化氢反应过程的影响,并对电解制氢和氧化吸收硫化氢反应的匹配进行了初步研究,结果表明,在氧化吸收硫化氢反应过程中,反应压力、原料气总进气流串和搅拌速度的影响较为显著,在目前实验条件下,硫化氢的吸收率已达肪%,如果改善实验条件,硫化氢的吸收率还会进一步提高。在电解制氢和氧化液再生反应过程中,电解反应在低电压(1.2v)下进行,阴极析出纯氢气;阳极再生氧化液,循环使用,且再生Fe ̄(2+)为Fe ̄(3+)的电流效率为100%. 相似文献
10.
Wang-bing Zhang Xin-an Yang Yuan-yuan Ma Hai-xia Zhu Shang-bing Wang 《Microchemical Journal》2011,97(2):201-206
The determination of trace concentrations of Hg in water samples by the use of electrolytic cold vapor generation (ECVG) system and AFS was studied. Several buffer solutions were used and the detection limits with these systems were found to be by a factor of 1–2 lower than in the conventional electrolytic cold vapor generation system. Comparing with the traditional inorganic acid, phosphate buffer solution (PBS) increased the signal intensity of Hg vapor from electrolytic generation on Pt cathode and reduced the impact of cathode erosion on the stability of signal intensity. Moreover, buffer solution has better interference tolerance. The effects of the electrolytic conditions and interference ions on the ECVG have been studied. Under optimized conditions and with PBS as catholyte the detection limit for Hg was found to be 0.27 ng L−1. The relative standard deviation was 2.8% for 11 consecutive measurements of 1 μg L−1 Hg. This method has been applied in the determination of inorganic Hg in Yangtze River water. 相似文献