全文获取类型
收费全文 | 88篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 14篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
建筑科学 | 3篇 |
轻工业 | 7篇 |
无线电 | 25篇 |
一般工业技术 | 5篇 |
冶金工业 | 28篇 |
自动化技术 | 4篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2011年 | 1篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1958年 | 1篇 |
1920年 | 1篇 |
排序方式: 共有89条查询结果,搜索用时 15 毫秒
1.
2.
The development of adipose tissue in the chick embryo was investigated using two groups of fertile eggs which differed by
1.7-fold in their initial yolk lipid levels. The triacylglycerol content of the subcutaneous adipose depot in both groups
increased dramatically from day 12 of the 21-day embryonic period, attaining a maximal value just prior to hatching. During
this period, the amount of triacylglycerol deposited in the adipose tissue was very highly correlated with the amount of lipid
transferred from the yolk. The triacylglycerol content of the depot was also dependent on the initial yolk lipid content.
During the hatching period, the amount of adipose triacylglycerol remained approximately constant in the group with the higher
initial yolk lipid content but, in the case of the group with the lower initial yolk lipid levels, decreased by approximately
25%. The size distribution of adipocytes isolated from the tissue was determined by computerized image analysis microscopy.
The mean adipocyte diameter increased from approximately 6 to 35 μm between days 12 and 19, irrespective of the initial yolk
content, although development within the eggs with the lower initial yolk content resulted in a decrease in cell size over
the hatching period. Both the triacylglycerol and phospholipid fractions of the isolated adipocytes contained substantial
proportions (approximately 6%, w/w) of docosahexaenoic acid (DHA) at days 12 and 14, and lower levels of this fatty acid at
the later stages. The amount (mg/depot) of DHA in adipose triacylglycerol decreased dramatically over the hatching period.
The amount (mg/brain) of DHA in brain phospholipid increased by more than 5-fold between day 12 of development and hatching.
A possible explanation for the data may be that DHA is preferentially mobilized from adipose tissue in order to deliver the
fatty acid to the developing neural tissues in a form suitable for uptake. 相似文献
3.
Wen-I Li Michael Perzl Joachim Heyder Robert Langer Joseph D. Brain K.-H. Englmeier Ralph W. Niven David A. Edwards 《Journal of aerosol science》1996,27(8):1269-1286
The results of numerical simulations of the aerodynamics and of solid aerosol deaggregation phenomena arising in the process of airflow through various model human oropharyngeal cavities are reported. Special attention is given to the relevance of these simulations to the inhalation of dry-powder therapeutic aerosols. Several two- and three-dimensional mouth and throat geometries (terminating just beyond the larynx) are considered. Cross-sectional area-averaged viscous stress values are numerically determined as a function of distance from the mouth opening. These values, ranging from approximately 10 to 500 dyn cm−2, are compared with estimates of Van der Waals attractive forces per unit area of particle-particle contact so as to evaluate the ability of the flowing airstream to deaggregate aerosol particles that enter the mouth in an aggregated state (held together principally by Van der Waals attractive forces). Estimates of airstream viscous stress differ markedly depending on whether the geometry is two- or three-dimensional. Quantitative differences between flow in a 90°-bend model and an oropharyngeal geometry numerically reconstructed from a cast of a human mouth and throat are especially significant in regards to the ability of the airstream to break apart particle agglomerates. For all geometries it is observed that increasingly smaller particle agglomerates may potentially be separated as the airflow rate increases from 30 to 2001 min−1. At the highest airflows, aggregated particles of diameter near to or even below 1 μm may potentially be separated by the airflow. If separation of particle agglomerates is to occur, it appears far more likely to take place in the throat than in the mouth. This is especially apparent for the more physiologically faithful oropharyngeal geometries considered. 相似文献
5.
The crosspolarisation efficiency of a reflector antenna is the ratio between the peak crosspolarisation from the complete antenna to that from the feed. The results of a parametric study into this factor for parabolic reflectors fed by a mathematical model of a common class of feeds are presented, and it is concluded that the efficiency is typically ?4 to ?6 dB. 相似文献
6.
Twenty-two female monkeys (Macaca irus) were given lead acetate by an intramuscular route during pregnancy and/or lactation.A high dose of lead (5 mg Pb2+/kg/day) can induce abortions and death in pregnant monkeys.At a lower dose (1 mg Pb2+/kg/day), the foetus can be exposed to lead via placenta and/or maternal milk. Studies using optical microscopy showed the typical renal lesions in mothers treated during pregnancy (five months) and an erythrodiapedesis in cerebral matter of the new-born at birth. 相似文献
7.
Robinson Jason D.; Cinciripini Paul M.; Carter Brain L.; Lam Cho Y.; Wetter David W. 《Canadian Metallurgical Quarterly》2007,15(4):390
Negative affect reduction has been postulated to be a key feature of cigarette smoking. In the present study, facial electromyography (EMG), heart rate (HR), and skin conductance response (SCR) were used to evaluate the affective significance of acute nicotine administration and overnight withdrawal. Smokers (N = 115) attended four 90-min laboratory assessment sessions scheduled approximately 3 days apart. The sessions provided a complete crossing of 2 prelaboratory deprivation conditions (12-hr deprived vs. nondeprived) with 2 drug conditions (nicotine vs. placebo nasal spray). During each session, smokers viewed affective slides while facial EMG, HR, and SCR were recorded. Results indicated that for women, nicotine nasal spray resulted in lower corrugator EMG activity during both smoking-deprived and nondeprived sessions, compared with placebo. However, nondeprived women also showed an increase in zygomaticus EMG when given nicotine compared with placebo spray, whereas smoking-deprived women demonstrated a decrease in the zygomaticus response to nicotine compared with placebo. With men, nicotine also appeared to lower corrugator during deprivation, but not nondeprivation, compared with placebo spray, though the contrast only approached significance. With zygomaticus EMG, nicotine spray decreased men's zygomaticus responding during nondeprivation but not during deprivation, compared with placebo spray. The HR results reflected the stimulatory properties of the drug rather than nicotine's affective properties, whereas SCR was unresponsive to our experimental manipulations. The corrugator EMG results support negative reinforcement models of smoking that postulate that acute nicotine use reduces withdrawal-driven negative affect. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
D. H. Brain 《纺织学会志》2013,104(10):493-505
An absolute method of seam-strength testing is described. The effects of fabric type and gauge length on seam strength are examined. The effects of the type of sewing thread used and various measures of thread strength on the accuracy of seam-strength prediction are also investigated. A simple method of determining the minimum loop strength of a thread is described. The efficiency of this value, corrected for one aspect of fabric construction, for seam-strength prediction is discussed. 相似文献
9.
Charles F. Bellows Ramon M. Molina Joseph D. Brain 《Journal of the Royal Society Interface》2011,8(58):711-719
Parasitized erythrocytes are ingested by murine hepatic macrophages during malaria infection. We non-invasively monitored how this altered the motion of intracellular phagosomes in Kupffer cells using magnetometry. Submicrometric γFe2O3 particles were injected prior to malaria infection. They were cleared from the blood, primarily by Kupffer cells, and retained within their phagosomes. The mice were periodically magnetized. After removing this external magnet, the aligned iron particles created a remnant magnetic field (RMF) which then decayed (relaxation), reflecting the motion of particle-containing phagosomes. After baseline measurements of relaxation, the mice were injected intravenously with Plasmodium chabaudi-parasitized or normal murine red blood cells (RBCs). During the next 15 days, relaxation measurements, parasitaemia and haematocrit values were monitored. At 6 days post injection with 3 × 107 parasitized RBCs, relaxation rates had decreased. At this time, all mice had parasitaemias greater than 58 per cent and haematocrits less than 20 per cent. At day 7, while the parasitaemias were declining, the rate of relaxation continued to decrease. Throughout the experiment, relaxation remained constant in animals injected with normal RBCs. Electron microscopy revealed Kupffer cells filled with damaged and parasitized erythrocytes, and haemoglobin degradation pigment. We conclude that ingestion and metabolism of parasitized erythrocytes by liver macrophages during malaria infection decreases their organelle motion with likely consequences of compromised host defences. 相似文献
10.
The microstructure of ultra-high molecular weight polyethylene (UHMWPE) has been studied using a range of techniques. Both the unprocessed base powder and ram-extruded polymer have been examined using optical microscopy, scanning and transmission electron microscopy and small-angle light scattering. By examining the microstructure of samples compression moulded at a range of temperatures, techniques have been developed to assess the degree of consolidation of the processed polymer. The raw polymer is a powder with a particle size in the range 50-250 microm. These particles are themselves agglomerates of much finer particles typically 0.5-1 microm in size. It has been suggested that these sub-micron particles may be the origin of the sub-micron wear debris found in tissues around total joint replacements. However, examination of the ram-extruded polymer, from which implants are machined, shows a different structure from the powder, with no evidence of retention of the 0.5-1 microm structure seen in the powder in the processed material. It thus appears that the similarity in size between the sub-micron wear debris particles and the fine structure seen in the unprocessed UHMWPE resin is coincidental. Processed UHMWPE does show a 'memory' of the grain boundaries between powder particles and the degree of consolidation can be assessed by observing the distinctiveness of these boundaries. 相似文献