全文获取类型
收费全文 | 104篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 7篇 |
能源动力 | 2篇 |
轻工业 | 6篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 19篇 |
一般工业技术 | 15篇 |
冶金工业 | 18篇 |
原子能技术 | 2篇 |
自动化技术 | 12篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1987年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有106条查询结果,搜索用时 31 毫秒
81.
82.
This study focuses, firstly, on the pricing of electricity in the Finnish retail market. In particular, the impact of the ownership structure on prices is tested empirically. Secondly, the influence of low-cost electricity sources on retail prices is considered. The question about whether the average fuel costs rather than the wholesale price determine the retail prices is thus addressed. The supply side behaviour characterised may explain the passivity of client activity in the seemingly competitive Finnish market. 相似文献
83.
Vertical distribution and activity contents of 210Pb and 210Po were investigated in forest soils of Scots pine-dominated (Pinus sylvestris L.) stands from seven different locations in Finland. The mean total inventory in the soil profile, up to 20 cm, of 210Pb was 4.0 kBq m− 2 (range 3.1-5.0 kBq m− 2) and 210Po 5.5 kBq m− 2 (range 4.0-7.4 kBq m− 2), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the 210Po/210Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of 210Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bq kg− 1) of 210Pb clearly correlated with organic matter and the Fe, Al and Mn concentrations in soil indicating that radioactive lead is associated both with humic substances and the oxides of iron, aluminium and manganese. Radioactive lead was also seen to follow the behavior of stable lead. No systematic correlation between polonium and soil properties was seen. 相似文献
84.
Scots pine (Pinus sylvestris) chips were pre-treated with alkaline solutions (alkali charges of 1, 2, 3, 4, 6, and 8% of NaOH on the oven-dried wood material) at 130°C and 150°C for various treatment times (30, 60, 90, and 120 minutes). Under these conditions, 2.0–13.6% of the wood d.s. was dissolved into the aqueous hydrolysates. The soluble organic fraction was primarily characterized in terms of carbohydrates (monosaccharides and oligo-/polysaccharides) and their alkali-catalyzed degradation products: aliphatic carboxylic acids containing, besides non-volatile hydroxy carboxylic acids, volatile formic and acetic acids. With increasing alkali charge, temperature, and time, the enhanced formation of various hydroxy monocarboxylic acids was detected. Under the most drastic pre-treatment conditions, two-thirds of the total organic fraction dissolved was composed of various aliphatic carboxylic acids, the residual material being mainly degraded lignin and extractives. Only relatively small concentrations of carbohydrates and trace amounts of furans were found. 相似文献
85.
A cooled receiver with some novel features and a noise temperature of 80?140 K double sideband in the frequency range 75?95 GHz has been built for radio astronomical observations. The quasioptical beam switch is followed by a 3 mm Schottky mixer and FET amplifier at 1.4 GHz. For calibration the receiver is provided with a cold reference load within the Dewar. 相似文献
86.
UM Lepola AG Wade EV Leinonen HJ Koponen J Frazer I Sj?din JT Penttinen T Pedersen HJ Lehto 《Canadian Metallurgical Quarterly》1998,59(10):528-534
BACKGROUND: The objective of this study was to evaluate the efficacy and tolerability of citalopram in the long-term treatment of adult outpatients with panic disorder with or without agoraphobia. METHOD: Patients in this double-blind, parallel-group trial were assigned to 1 of 3 fixed dosage ranges of citalopram (10 or 15 mg/day, 20 or 30 mg/day, or 40 or 60 mg/day), 1 dosage range of clomipramine (60 or 90 mg/day), or placebo. After the completed 8-week acute treatment period, the eligible patients could continue the treatment for up to 1 year. Of the 475 patients who were randomly assigned for the short-term trial, 279 agreed to continue double-blind treatment at their assigned doses. The primary efficacy measure used was the Clinical Anxiety Scale panic attack item, and the response was defined as no panic attacks (score of 0 or 1). The other key measures used were the Physician's Global Improvement Scale, the Patient's Global Improvement Scale, and the Hamilton Rating Scale for Anxiety (HAM-A). RESULTS: In all drug-treated groups, except the group receiving the lowest citalopram dose, the treatment outcome was generally better than with placebo. As determined by a life table analysis of response, the probability of response during the 12 months was significantly greater with all treatment regimens than with placebo (p < .05), with citalopram 20 or 30 mg/day demonstrating the best response. Panic attacks tended to disappear in all patients remaining in the study until the end of follow-up. Analysis of the difference in the number of patients in different treatment groups remaining in the study (perhaps the best measure of long-term efficacy) also demonstrated that the patients treated with citalopram in dosage ranges of 20 or 30 mg/day and 40 or 60 mg/day had better response than placebo-treated patients (p < .0002 and p < .004, respectively). HAM-A and Global Improvement Scale scores also showed that patients treated with active drug showed greater improvement than placebo-treated patients. All treatment groups showed no new or exceptional adverse event clusters. CONCLUSION: Citalopram in the dosage range of 20 to 60 mg/day is effective, well tolerated, and safe in the long-term treatment of patients who have panic disorder. 相似文献
87.
A field study of 1146 drivers and passengers of vehicles equipped with motorized passive belts was conducted in shopping malls and other locations in the states of Arizona and Indiana. The Indiana data was collected the summer of 1994 and the Arizona data the summer of 1995. Shoulder belt use by drivers and passengers was 93.4% in Indiana and 87.8% in Arizona. Lap belt use was 65% in Indiana and 69.9% in Arizona. Over 99% of drivers in both states knew that a manually fastened lap belt was provided along with the motorized shoulder belt. Most drivers agreed that they are supposed to wear the lap belt (96.3% in Indiana and 94.3% in Arizona) and said that the vehicle they were driving provided a warning signal when the lap belt was not fastened (75.7% in Indiana and 79.4% in Arizona). Most drivers were also aware of warning labels telling them to use their lap belt (63.9% in Indiana and 68.2% in Arizona). 相似文献
88.
Different types (pyramidal, convoluted, wedge, flat) of absorber panel made by several manufacturers have been measured at 107 and 183 GHz. These measurements revealed a rapid degradation of the quality of absorbers from 107 to 183 GHz: reflectivity increased nearly 10 dB. The best absorbers have reflectivities below -40 dB at 107 GHz and about -35 dB at 183 GHz.<> 相似文献
89.
Kristen Oldenburger Xinran Lehto Richard Feinberg Mark Lehto Gavriel Salvendy 《Behaviour & Information Technology》2008,27(1):63-77
This research utilized the critical incident technique (CIT) to identify factors influencing customer satisfaction and retention of customers participating in e-commerce transactions. Customers were asked in telephone interviews to discuss both particularly satisfying and dissatisfying (or critical) incidents they had experienced when using web sites to conduct transactions. Each customer also provided demographic information, rated their satisfaction with the experience and ecommerce provider, and was asked how often they purchased products from the provider prior to and after the incident. Analysis revealed 662 citations by customers of items contributing to either positive or negative experiences. Exploratory text-mining analysis revealed that the majority of positive items pertained to the transaction (38%), product (25%), or website (23%), and to customer support (35%) or the transaction for negative items (30%). Approximately 86% of customers citing positive items said they were very likely to use the e-commerce site again, compared to 22% of customers citing negative items. Customer support and user experience both seemed to play an important mediating role on the criticality of negative incidents. Over 70% of first time users and customers who said customer support ignored or refused their requests for assistance said they were unlikely to return to the site, compared to 20% when customer support was said to be responsive. Correlation analysis confirmed that negative incidents tended to be more critical than positive ones, and more so for first time customers. 相似文献
90.
Bengt Fornberg Erik Lehto Collin Powell 《Computers & Mathematics with Applications》2013,65(4):627-637
Traditional finite difference (FD) methods are designed to be exact for low degree polynomials. They can be highly effective on Cartesian-type grids, but may fail for unstructured node layouts. Radial basis function-generated finite difference (RBF-FD) methods overcome this problem and, as a result, provide a much improved geometric flexibility. The calculation of RBF-FD weights involves a shape parameter . Small values of (corresponding to near-flat RBFs) often lead to particularly accurate RBF-FD formulas. However, the most straightforward way to calculate the weights (RBF-Direct) becomes then numerically highly ill-conditioned. In contrast, the present algorithm remains numerically stable all the way into the limit. Like the RBF-QR algorithm, it uses the idea of finding a numerically well-conditioned basis function set in the same function space as is spanned by the ill-conditioned near-flat original Gaussian RBFs. By exploiting some properties of the incomplete gamma function, it transpires that the change of basis can be achieved without dealing with any infinite expansions. Its strengths and weaknesses compared with the Contour-Padé, RBF-RA, and RBF-QR algorithms are discussed. 相似文献