全文获取类型
收费全文 | 101篇 |
免费 | 9篇 |
专业分类
机械仪表 | 1篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
石油天然气 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 1篇 |
冶金工业 | 92篇 |
自动化技术 | 7篇 |
出版年
2017年 | 1篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2005年 | 3篇 |
2002年 | 8篇 |
2001年 | 1篇 |
1999年 | 3篇 |
1998年 | 36篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1977年 | 1篇 |
1976年 | 6篇 |
排序方式: 共有110条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
黄如芬 《中国材料科技与设备》2008,5(1):40-42
通过对不同粒级的石英、方解石、滑石、硅灰石等粉体进行介电性能测量,获得不同频率激励下的电容值和损耗值,分析了粉体粒度及空隙率对粉体堆积态介电常数之间的变化关系。实验结果表明,堆积体空隙率随粒度的增大而提高,堆积态介电损耗随粒度增大而减小,即介电损耗随堆积体空隙率减小而增大。 相似文献
45.
The GUM modelling, its Bayesian modification and the Monte Carlo method (MCM) to estimate the uncertainty are compared in two practical measurement situations (finding reference value of relative humidity and a generic chemical instrumental analysis procedure). The results of the three approaches agree very well when there are no dominant input quantities with type A evaluated uncertainty estimated from small number of repeated measurements. In the opposite case the GUM gives underestimated expanded uncertainties (by up to 20–25%), compared to both other approaches. Analysis of the practical measurement situations reveals that even in the case of several dominating input quantities of similar uncertainty contributions, if one of them is distributed according to the t-distribution and has a low number (3–4) of degrees of freedom, the output quantity cannot be safely assumed Normally distributed and in such a case coverage factor 2 is not an equivalent to 95% coverage level. 相似文献
46.
RM Schapira JH Wiessner JF Morrisey UA Almagro LD Nelin 《Canadian Metallurgical Quarterly》1998,19(2):308-315
Cold air inhalation and exercise-induced bronchoconstriction (EIB) have both been used as measures of bronchial responsiveness. Both stimuli are often combined in the Nordic climate. The main objective of the present study was to investigate the climatic influence of cold temperatures upon exercise-induced asthma. The secondary aims were: (a) to assess metacholine bronchial hyper-responsiveness and EIB in children with bronchial asthma (n = 32; mean age 10.8 years) compared to children with other chronic lung diseases (CLD) (n = 26, mean age 10.1 years); and (b) to assess the influence of cold air inhalation upon EIB in the two groups of children. Methods used were: (a) the metacholine concentration causing a reduction in FEV1 of 20% (PC20-M), (b) maximum FEV1 fall (delta FEV1) after submaximal treadmill run (EIB test); and (c) delta FEV1 after submaximal treadmill run while inhaling cold (-20 degrees C) dry air (CA-EIB test). Geometric mean PC20-M did not differ significantly between the asthma children (1.28 mg ml-1) and the CLD children (2.90 mg ml-1). In the asthma children, mean delta FEV1 after EIB test was 12.8% vs 21.8% after adding cold air (P < 0.0001), compared to 5.2 and 7.4%, respectively (P = 0.03), in the CLD group. Maximum sensitivity and specificity for the EIB test were 69.8% at a fall in FEV1 of 6.8%; for the CA-EIB test, 72% at a fall in FEV1 of 10.2%; and for metacholine provocation, 56% at a PC20-M of 1.5 mg ml-1. In conclusion, children with bronchial asthma are substantially more sensitive to cold air than children with CLD, and EIB is markedly increased by cold air inhalation in asthmatic children, maintaining the specificity of the EIB test and increasing the sensitivity. The low sensitivity of the EIB test is probably influenced by the use of inhaled steroids. Metacholine inhalation test has less specificity and sensitivity in discriminating asthma from other chronic lung diseases. 相似文献
47.
The identification of polar microcontaminants in surface water is an important issue in environmental analysis. Liquid chromatography/mass spectrometry (LC/MS) is frequently applied for this purpose. However, even in combination with tandem mass spectrometry (MS/MS), unambiguous identification of the compounds detected is often difficult. The potential of an alternative strategy, based on the ability of an orthogonal-acceleration time-of-flight mass spectrometer to routinely perform accurate mass determination at 10 ppm in on-line LC/MS, is explored. On-line solid-phase extraction LC electrospray orthogonal-acceleration time-of-flight mass spectrometry is shown to enable the determination of pesticides from various compound classes in surface water in the concentration range of 0.1 to 10 micrograms/L. In addition, the ability to discriminate and unambiguously identify pesticides in mixtures of isobaric and/or isomeric compounds is investigated. 相似文献
48.
UA Badrising ML Maat-Schieman SG van Duinen JG van Dijk JJ Verschuuren AR Wintzen 《Canadian Metallurgical Quarterly》1998,142(11):553-557
In 3 patients, a 72-year-old man, a 62-year-old man and a 73-year-old woman with weakness of respectively the quadriceps femoris, the finger flexors and the pharyngeal muscles, the diagnosis of 'inclusion body myositis' was made. This is a rare, slowly progressive skeletal muscle disorder which is more common in men and after the age of fifty. The activity of serum creatine kinase is often 2-5 times the highest normal value. The electromyogram pattern is myopathic, but can also display neuropathic changes (exclusively). Inclusion body myositis is often misdiagnosed, which can lead to an inappropriate treatment or approach. A frozen muscle biopsy is needed to make cryostat sections for demonstration of myositis with rimmed vacuoles. 相似文献
49.
To provide quantitative information on the sites that promote polymerization of sickle hemoglobin (HbS) after formation of the initial hydrophobic bond involving Val-6(beta) [E6V(beta)] and also to provide hemoglobins with an enhanced polymerization that could be used in a mouse model for sickle cell anemia, we have expressed recombinant double, triple, and quadruple HbS mutants with substitutions on both the alpha- and beta-chains, E6V(beta)/E121R(beta), D75Y(alpha)/E6V(beta)/E121R(beta) and D6A(alpha)/D75Y(alpha)/E6V(beta)/E121R(beta). These recombinant hemoglobins were extensively characterized by high-performance liquid chromatography analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, amino acid analysis, and mass spectroscopy. They retained the functional properties of the Hb tetramer and polymerized in a linear manner at progressively lower Hb concentration as a function of the degree of substitution, suggesting that these remote sites (alphaD6A, alphaD75Y, and betaE121R) on the alpha- and beta-chains exhibit additive, enhanced polymerization properties. The quadruple mutant has a polymerization concentration close to that of the purified SAD hemoglobin from transgenic mouse red blood cells consisting of HbS, Hb Antilles, and Hb D-Punjab. Normal mouse Hb increases the polymerization concentration of each mutant. Thus, the general approach of using recombinant Hbs as described here should prove useful in elucidating the quantitative aspects of the mechanism of HbS polymerization and in identifying the contribution of individual sites to the overall process. The strategy described here demonstrates the feasibility of a systematic approach to achieve future recombinant HbS mutants that could provide a new generation of the transgenic mouse model for sickle cell anemia. 相似文献
50.