全文获取类型
收费全文 | 836篇 |
免费 | 2篇 |
专业分类
化学工业 | 3篇 |
轻工业 | 6篇 |
无线电 | 3篇 |
一般工业技术 | 9篇 |
冶金工业 | 804篇 |
自动化技术 | 13篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2001年 | 2篇 |
1999年 | 32篇 |
1998年 | 244篇 |
1997年 | 138篇 |
1996年 | 95篇 |
1995年 | 55篇 |
1994年 | 36篇 |
1993年 | 42篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1977年 | 21篇 |
1976年 | 52篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有838条查询结果,搜索用时 31 毫秒
831.
832.
833.
Initial caries attack and progression rates of posterior approximal carious lesions were assessed based on 12-year-old school children residing on the Isle of Wight. Bitewing radiographs of a sub-sample of 165 subjects were randomly selected from the control group of a dentifrice clinical trial which took place between 1984 and 1987. Of the approximal surfaces that were caries-free at the first examination 71 per cent of the same surfaces remained caries-free after three years, an overall initial caries attack rate averaging 10.7 per cent per annum. Of the mesial surfaces of first permanent molars, 455 were initially caries-free, 67 per cent of which remained so after a three year period. The attack rate of this specified surface was 12.4 per cent per annum. The majority of surfaces that were caries-free at the start of the investigation would therefore be expected to remain so at least three years later. Caries progression appeared to be a slow process with only 12 per cent of initially carious outer enamel surface lesions penetrating into dentine after one year. After two years this had increased to 46 per cent and after three years, to 62 per cent. For a similarly defined group of individuals it would appear likely that the majority of early enamel lesions would not reach dentine within two years. For a substantial number of subjects this would extend to at least three years. 相似文献
834.
Fetal mice testes convert pregnenolone-16-3H and progesterone-4-14C to testosterone in organ culture. The 3H/14C ratio in progesterone and testosterone fractions isolated from culture media suggests the importance of the delta5-3 beta hydroxysteroid pathway in our experimental conditions. LH decreases radioactive testosterone production and increases the activity of the kelta4-3-ketosteroid pathway. 相似文献
835.
MN Starkman 《Canadian Metallurgical Quarterly》1980,2(4):289-293
This paper deals with the ways in which the psychological responses of renal transplant donors and recipients interfere with the developmental tasks of adolescence. The characteristic responses of donors and recipients in general are briefly reviewed. The special problems of the adolescent who has received a transplant from a parent are considered. Interference with the separation-individuation process is discussed. Also considered is the difficulty posed to the development of sexual identity. Excerpts from brief therapy are presented that illustrate the characteristic psychological conflicts described. 相似文献
836.
The effects of a new series of glutarimide compounds have been studied in acetylcholine induced auricular fibrillation in anaesthetized cats and epinephrine induced ventricular arrhythmmias in conscious pigeons. Some of the compounds showed varying degree of protective action against experimental arrhythmias. However these compounds were found to be less potent than quinidine. The mechanism of antiarrhythmic action has been discussed. 相似文献
837.
Cashew kernels are thermally processed to facilitate the removal of their outer skin (testa). Infrared (IR) processing of cashew kernels for differential drying is a novel approach. Processed cashew kernels are valued for their colour, size and texture. The kinetics of colour change and the effect of thermal processing on compressive strength (indicator of brittleness) during IR drying of cashew kernels were investigated. Kernels with testa were dried for different durations (15–55 min) over a range of temperatures (55–95 °C). The change in colour was expressed as total colour difference and browning index. The colour values increased with increasing drying temperature and duration, indicating darkening of the kernel colour. Increase in drying duration reduced the compressive strength, imparting the desired brittleness to the kernel. Optimisation of the drying conditions by response surface methodology and the peelability factor indicated that the best results could be obtained when cashew kernels were dried at 55 °C for 55 min. Copyright © 2004 Society of Chemical Industry 相似文献
838.
Goltz MN Gandhi RK Gorelick SM Hopkins GD Smith LH Timmins BH McCarty PL 《Environmental science & technology》2005,39(22):8963-8970
Two technologies in combination, cometabolic bioremediation and in-well vapor stripping, were applied to reduce trichloroethylene (TCE) concentrations in groundwater at a contaminant source area without the need to pump contaminated groundwater to the surface for treatment. The vapor-stripping well reduced source TCE concentrations (as high as 6-9 mg/L) by over 95%. Effluent from the well then flowed to two bioremediation wells, where additional reductions of approximately 60% were achieved. TCE removal was extensively monitored (for research and not regulatory purposes) using an automated system that collected samples about every 45 min at 55 locations over an area of approximately 50 x 60 m2. During 4.5 months of system operation, total TCE mass removal was 8.1 kg, 7.1 kg of which resulted from in-well vapor stripping and 1.0 kg from biotreatment. The system reduced the average TCE concentration of about 3000 microg/L in the source-zone groundwater to about 250 microg/L in water leaving the treatment zone, effecting greater than 92% TCE removal. A 6 month rebound study after system operation ceased found TCE concentrations then increased significantly in the treatment zone due to diffusion from the fractured rock below and perhaps other processes, with mass increases of about 1.5 kg in the lower aquifer and 0.3 kg in the upper aquifer. 相似文献