共查询到20条相似文献,搜索用时 31 毫秒
1.
~~China's imports and exports of tungsten,molybdenum,tin and antimony by category~~ 相似文献
2.
Essia Hannachi Yassine Slimani Muhammad Nawaz R.Sivakumar Zayneb Trabelsi R.Vignesh Sultan Akhtar Munirah A.Almessiere Abdulhadi Baykal Ghulam Yasin 《中国稀土学报(英文版)》2023,41(5):682-688
Yttrium(Y) and cerium(Ce) co-doped ZnO nanoparticles(NPs) were synthesized via the simple sol-gel auto-combustion route.The effect of Ce and Y doping on the structure,morphology,optical,Zeta potential,and photocatalytic activities of ZnO NPs was examined by Fourier transform infrared(FTIR)spectrometer,X-ray diffraction(XRD),transmission electron microscope(TEM),UV-vis spectrophotometer,and Zetasizer instrument.XRD data show that the fabricated samples crystallize into a hexagonal wurtzite struct... 相似文献
3.
This article reviews the evidence for using modalities and/or exercise treatment in patients with nonspecific low back pain. Poor evidence of efficacy exists for the use of modalities in this patient group. Exercises are beneficial for patients with subacute and chronic nonspecific low back pain. Further studies are needed for type, frequency, duration, and intensity of exercises. 相似文献
4.
Maria Milanova Joana Zaharieva Iliya Manolov Miroslava Getzova Dimitr To dorovsky 《中国稀土学报(英文版)》2010,(Z1):66-74
The paper presents the results of the synthesis of complexes of the ty pe Eu(DBM) 3 and Eu(DBM) 3·Q(DBM-dibenzoylmethane,Q-1,10-phenantroline or 4,7-d iphenyl-1,10-phenantroline) and of Tb-and Nd-complexes with the newly-synthesis ed coumarin derivates 3,3’-[(4-chlorphenyl) methylene) bis(4-hydroxy-2H-chromen-2-one) ,3,3’-[(3,5-dimethoxy-4-hydroxy) methylene) bis(4-hydroxy-2H-chromen-2-one) ,etc. Elemental and thermogravimetric analysis,IR,UV,NMR and fluorescence spe ctroscopy and X-ray analysis were applied for characterisation of the complexes. Some peculiarities of the synthetic procedures for both types of complexes were discussed and the influence of the synthetic approach,pH of the reaction mediu m,temperature of synthesis and drying of the complexes on the composition,stab ility and optical properties was reported. The immobilisation of the complexes i n thin films based on sol-gel produced SiO2 and on polymethylmethacrylate was st udied. The optimal conditions for preparation of the matrices(composition of th e starting system,temperature and time of sol aging,etc.) were recommended. Th e film morphology was evaluated by fluorescence,scanning electron and atomic fo rce microscopy. The interaction of the lanthanide ions with the matrices and the influence of their nature,the effect of the in-situ polymerisation and other f actors on photoluminescent excitation and emission spectra and excited state lif e-times of the complexes were followed. The effect of the second ligand on the p hotoluminescence properties of the immobilised diketonates was further elucidate d. Processes involved in the thermal decomposition of the complexes and microcom posites produced on their base were proposed. Preliminary results on the pharmac ological properties of the coumarin complexes reported showed unambiguously high er cytotoxicity of the Nd complex in comparison with that of the respective ligand. 相似文献
5.
A forum was held recently in Beijing onChina's policies concerning tungsten, anti-mony, tin and zinc. Since China has ad-vantages in these metals resources in theworld and to improve China's export rev-enue from these metals, it is very impor-tant to strengthen export administrationand keep an orderly market. 相似文献
6.
The grades of ultra-pure ferritic stainless steels,especially the grades used in automobile exhaust system,were reviewed.The dependence of properties on alloying elements,the refining facilities,and the mechanism of the reactions in steel melts were described in detail.Vacuum,strong stirring,and powder injection proved to be effective technologies in the melting of ultra-pure ferritic stainless steels.The application of the ferritic grades was also briefly introduced. 相似文献
7.
8.
Growing public awareness of environmental hazards has led to an increased demand for public health authorities to investigate geographical clustering of diseases. Although such cluster analysis is nearly always ineffective in identifying causes of disease, it often has to be used to address public concern about environmental hazards. Interpreting the resulting data is not straightforward, however, and this paper presents a guide for the non-specialist. The pitfalls include the fact that cluster analyses are usually done post hoc, and not as a result of a prior hypothesis. This is particularly true for investigations prompted by reported clusters, which have the inherent danger of overestimating the disease rate through "boundary shrinkage" of the population from which the cases are assumed to have arisen. In disease surveillance the problem of making multiple comparisons can be overcome by testing for clustering and autocorrelation. When rates of disease are illustrated in disease maps undue focus on areas where random fluctuation is greatest can be minimised by smoothing techniques. Despite the fact that cluster analyses rarely prove fruitful in identifying causation, they may-like single case reports-have the potential to generate new knowledge. 相似文献
9.
In this study a series of trivalent lanthanum complexes with 4-(R)-cinnamate (4-Rcinn, R=H(1), MeO(2), Cl(3)) and 4-methoxyphenylacetate ligands (4) were prepared and their antifungal activity against Candida albicans, Aspergillus niger and Trichophyton mentagrophytes were examined. Compounds 1-4 were synthesized by a metathesis reaction and fully characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, fluorescence spectra, thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC) and X-ray diffraction powder patterns. In emission studies, it was observed that lu-minescence intensity was enhanced in the presence of lanthanide ion. The results of X-ray diffraction patterns indicated that all com-plexes studied exhibited crystalline structure. Thermal behavior by TG, DTG, and DSC studies permitted to estimating the hydration degree of the compounds and showed the formation of decomposition products like lanthanum oxide. Determined by antifungal stud-ies, lanthanum complexes 1-4 demonstrated antifungal activity toward all pathogenic fungal strains tested. Compounds 2 and 4 showed significant growth inhibition for A. niger and C. albicans, respectively. 相似文献
10.
11.
RareearthinorganiccompoundshavebeenwidelyusedasmicroelementfertilizerinagricultureinChina .ItwasdiscoveredthatcropsproductioncouldbeincreasedbyusingRE .Themechanismoftheincreaseofproduc tionattcactedincreasinglycloseattention .Pre viousstudiesshowedthatR… 相似文献
12.
These minutes are the official record of the actions of the Association taken during the year by both the Board of Directors (the Board) and the Council of Representatives (Council). The roll of representatives was called at each Council meeting, and more than a quorum answered to their names. Reference is made in these minutes to various reports, some of which will be published elsewhere. Copies of these reports were distributed to Council and are on file in the Central Office. As long as the supply lasts, extra copies of many of the reports are available from the Central Office. These minutes are arranged in topical rather than chronological order, and subheadings are used when appropriate. The main topical headings are I. Minutes of Meetings; II. Elections, Awards, Membership, and Human Resources; III. Ethics; IV. Board of Directors; V. Divisions and State, Provincial, and Territorial Psychological Associations; VI. Organization of the APA; VII. Publications and Communications; VIII. Convention Affairs; IX. Educational Affairs; X. Professional Affairs; XI. Scientific Affairs; XII. Public Interest; XIII. Ethnic Minority Affairs; XIV. International Affairs; XV. Central Office; and XVI. Financial Affairs. Changes to the language of the American Psychological Association (APA) Bylaws, Association Rules, or motions of the items are noted as follows throughout these proceedings: Bracketed material is to be deleted; underlined material is to be added. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Eisenberg Nancy; Valiente Carlos; Spinrad Tracy L.; Cumberland Amanda; Liew Jeffrey; Reiser Mark; Zhou Qing; Losoya Sandra H. 《Canadian Metallurgical Quarterly》2009,45(4):988
The purpose of the study was to examine the relations of effortful control (EC), impulsivity, and negative emotionality to at least borderline clinical levels of symptoms and change in maladjustment over four years. Children’s (N = 214; 77% European American; M age = 73 months) externalizing and internalizing symptoms were rated by parents and teachers at 3 times, 2 years apart (T1, T2, and T3) and were related to children’s adult-rated EC, impulsivity, and emotion. In addition, the authors found patterns of change in maladjustment were related to these variables at T3 while controlling for the T1 predictor. Externalizing problems (pure or co-occurring with internalizing problems) were associated with low EC, high impulsivity, and negative emotionality, especially anger, and patterns of change also related to these variables. Internalizing problems were associated with low impulsivity and sadness and somewhat with high anger. Low attentional EC was related to internalizing problems only in regard to change in maladjustment. Change in impulsivity was associated with change in internalizing primarily when controlling for change in externalizing problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
Comments on the meta-analytic review by E. L. Deci et al (see record 1999-01567-001) concerning the effects of extrinsic rewards on intrinsic motivation. Meta-analyses indicated that rewards increase perceived self-determination and that rewards' effects on intrinsic motivation depend on the performance requirement. Reward for meeting vague performance standards reduced the subsequent choice to carry out the task and did not affect self-reported interest. Reward for meeting absolute performance standards did not affect free choice but increased self-reported interest. Reward for exceeding others increased both free choice and self-reported interest. Applied studies commonly found positive or null relationships between reward and intrinsic motivation. The findings suggest that reward procedures requiring ill-defined or minimal performance convey task triviality, thereby decreasing intrinsic motivation. Reward procedures requiring specific high task performance convey a task's personal or social significance, increasing intrinsic motivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
16.
YOU Xiang-mi JIANG Zhou-hua LI Hua-bing 《钢铁研究学报(英文版)》2007,14(4):24-30
The grades of ultra-pure ferritic stainless steels, especially the grades used in automobile exhaust system, were reviewed. The dependence of properties on alloying elements, the refining facilities, and the mechanism of the reactions in steel melts were described in detail. Vacuum, strong stirring, and powder injection proved to be effective technologies in the melting of ultra-pure ferritic stainless steels. The application of the ferritic grades was also briefly introduced. 相似文献
17.
These minutes are the official record of the actions of the American Psychological Association taken during the year by both the Board of Directors and the Council of Representatives. Reference is made in there minutes to various reports, some of which will be published elsewhere. Copies of the reports are distributed to Council and are on file in the Central Office. The minutes are arranged in topical, rather than chronological, order, and subheading are used when appropriate. The main topical headings are I. Minutes of Meetings; II. Elections, Awards, Membership, and Human Resources; III. Ethics; IV. Board of Directors; V. Divisions and State and Provincial Associations; VI. Organization of the APA; VII. Publications and Communications; VIII. Convention Affairs; IX. Educational Affairs; X. Professional Affairs; XI. Scientific Affairs; XII. Public Interest; XIII. Ethnic Minority Affairs; XIV. International Affairs; XV. Central Office; XVI. Financial Affairs; and XVII. Communications Concerning Outside Organizations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
These minutes are the official record of the actions of the Association taken during the year by both the Board of Directors (the Board) and the Council of Representatives (Council). The roll of representatives was called at each Council meeting, and more than a quorum answered to their names. Reference is made in these minutes to various reports, some of which will be published elsewhere. Copies of these reports were distributed to Council and are on file in the Central Office. As long as the supply lasts, extra copies of many of the reports are available from the Central Office. These minutes are arranged in topical rather than chronological order, and subheadings are used when appropriate. The main topical headings are I. Minutes of Meetings; II. Elections, Awards, Membership, and Human Resources; III. Ethics; IV. Board of Directors; V. Divisions and State, Provincial, and Territorial Associations; VI. Organization of the APA; VII. Publications and Communications; VIII. Convention Affairs; IX. Educational Affairs; X. Professional Affairs; XI. Scientific Affairs; XII. Public Interest; XIII. Ethnic Minority Affairs; XIV. International Affairs; XV. Central Office; and XVI. Financial Affairs. Changes to the language of the American Psychological Association (APA) Bylaws, Association Rules, or motions of the items are noted as follows throughout these proceedings: Bracketed material is to be deleted; underlined material is to be added. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
19.
Europium and terbium complexes with strong fluorescence intensity and long fluorescence lifetime were prepared. By replacing half of the europium or terbium ion with M (M = Zn^2+, Cd^2+, and Cr^3+) using the doped method, and then incorporating it with 18-crown-6 ether and terephthalic acid, six heteronuclear samples EuZnLL'Cl3·3H2O(1), EuCdLL2'Cl3·5H2O(2), EuCrLL'Cl4· 4H2O(3), TbZnLL'Cl3·4H2O(4), TbCdLL'2Cl3·4H2O(5), and TbCrLL'2Cl4 ·4H2O(6) (L = terephthalic acid, L'= 18-Crown-6 ether) were obtained. The elemental analysis, molar conductivities, rare earth complexometry, Fourier Transform Infrared Spectroscopy (FT-IR), ultraviolet (UV), TGA, fluorescence intensity, and fluorescence lifetime of the samples were measured. The results showed that there were good luminescence properties for heteronuclear complexes (1), (2), (4), and (5), which were even stronger than those of the homonuclear complexes Eu2LL'2Cl4·4H2O and Tb2LL'2Cl4 ·4H2O, but the luminescence properties of EuCrLL'Cl4·4H2O, TbCrLL'Cl4·4H2O were very weak. A possible luminescence mechanism was suggested by the organic-inorganic doped mechanism and the law of intramolecular energy transfer. 相似文献