全文获取类型
收费全文 | 364篇 |
免费 | 8篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 29篇 |
金属工艺 | 1篇 |
机械仪表 | 9篇 |
建筑科学 | 16篇 |
能源动力 | 38篇 |
轻工业 | 26篇 |
石油天然气 | 2篇 |
无线电 | 16篇 |
一般工业技术 | 44篇 |
冶金工业 | 113篇 |
原子能技术 | 1篇 |
自动化技术 | 67篇 |
出版年
2024年 | 3篇 |
2021年 | 5篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 19篇 |
2012年 | 9篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 15篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1946年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 31 毫秒
51.
William L Warren Duane Dimos Bruce A. Tuttle Donald M. Smyth 《Journal of the American Ceramic Society》1994,77(10):2753-2757
We have coupled electron paramagnetic resonance (EPR) and polarization–voltage measurements to understand the effects of reducing ambients on the remanent polarization and density of paramagnetic centers in BaTiO3 , single crystals. Two types of reducing ambients were explored; one was done under vacuum (slightly reducing) and the second was performed in forming gas (very reducing). It is found that the vacuum anneal caused a reduction in the remanent polarization and a concomitant decrease in the isolated Fe3+ EPR resonance. The Fe3+ –Vo complex EPR signal was relatively unaffected by this vacuum anneal. By injecting charge using an ultraviolet (UV) light and an applied bias combination, the polarization and the isolated Fe3+ signal intensity were restored, thereby suggesting that the suppression of the remanent polarization is due to trapping of electronic charge at the domain walls. For the forming gas anneal, we observe a much larger decrease in remanent polarization with an accompanying decrease in both the isolated Fe3+ and Fe3+ –Vo complex EPR signals. For this anneal, charge injection by the UV light/bias combination did not restore the polarization nor the EPR densities. The remanent polarization, the isolated Fe3+ , and the Fe3+ –Vo Vo complex could be restored only by a reoxidizing anneal, suggesting that ionic defects {oxygen vacancies) are now responsible for pinning the domain walls. Collectively, these results suggest reducing anneals can suppress the amount of switchable polarization in BaTiO3 by either electronic or ionic trapping mechanisms. 相似文献
52.
Like psychomotor stimulants, a weak amphetamine-like agent, such as phenylpropanolamine, enhances the analgesic effects of morphine (MOR). Thus, it is possible that full psychomotor stimulant potency is not required to increase the analgesic action of opiates. The validity of this assumption is here tested by studying the ability of (-)-norpseudoephedrine (NPE), an enantiomer of phenylpropanolamine and a metabolite of cathinone, to influence both the analgesic effects of MOR and its discriminative stimulus properties. In mice NPE (5.6-10.0-17.0 mg/kg i.p.) did not prolong the latency to lick or to remove paws from a plate warmed at 54 degrees C. However, it significantly potentiated the analgesic effect of 3.2 mg/kg of MOR. These results were replicated in rats by use of the formalin test, which measures the numbers of hind paw flinches produced by injecting 50 microl of formalin into the dorsal surface of the paw. The higher dose of NPE (17 mg/kg) increased the effect of sub-analgesic doses of MOR (0.56 and 1.0 mg/kg). In rats trained to discriminate between 0.5 mg/kg of amphetamine and solvent in a two-lever operant behavior reinforced by water access. NPE induced a dose-dependent increment of drug lever responding from 0% at 1.0 mg/kg to 100% at 32.0 mg/kg. In contrast, NPE did not generalize for the MOR cue up to the dose of 56.0 mg/kg, which produced a substantial reduction of the response rate. However, when given in combination, NPE attenuated the discriminative effects of MOR and potentiated its inhibitory action on the response rate. These results exclude a direct action of NPE on the mu opiate system. In conclusion, NPE preserves amphetamine-like properties and these properties are probably responsible for the interaction of the drug with the analgesic and discriminative effects of MOR. Therefore, this study contradicts the assumption that the analgesic effects of MOR can be enhanced by a sympathomimetic drug that lacks significant psychostimulant actions. 相似文献
53.
A confusing number of measures are used to describe the effect sizes from clinical trials or systematic reviews. Absolute measures (absolute risk reduction, number needed to treat) and relative measures (relative risk reduction, relative risk or odds ratio) may give not just different numerical answers but convey different messages. This paper describes the role and meaning of the different measures, advises on their interpretation, and highlights the importance of taking into account the initial risk when assessing effect sizes from published studies. 相似文献
54.
TR Smyth 《Canadian Metallurgical Quarterly》1994,20(1):27-36
The distribution of type I interleukin-1 receptor (IL-1R1) mRNA in the rat brain was examined by in situ hybridization technique. IL-1R1 mRNA was expressed in several brain regions including the anterior olfactory nucleus, medial thalamic nucleus, posterior thalamic nucleus, basolateral amygdaloid nucleus, ventromedial hypothalamic nucleus, arcuate nucleus, median eminence, mesencephalic trigeminal nucleus, motor trigeminal nucleus, facial nucleus and Purkinje cells of the cerebellum. Furthermore, we identified neuronal expression of IL-1R1 mRNA using simultaneous detection (double in situ hybridization) of IL-1R1 mRNA with neuron specific enolase mRNA. In addition to the expression in neuronal cells, IL-1R1 mRNA was also expressed on the vascular walls and the epithelial cells of the choroid plexus and the ventricles. These findings suggest the possibility that IL-1 produces its multiple effects on the central nervous system through the actions not only on neuronal cells but also on endothelial and epithelial cells. 相似文献
55.
56.
AD Bernstein AJ Camm JD Fisher RD Fletcher RH Mead AW Nathan V Parsonnet AF Rickards NP Smyth R Sutton 《Canadian Metallurgical Quarterly》1993,16(9):1776-1780
A new generic code, patterned after and compatible with the NASPE/BPEG Generic Pacemaker Code (NBG Code) was adopted by the NASPE Board of Trustees on January 23, 1993. It was developed by the NASPE Mode Code Committee, including members of the North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG). It is abbreviated as the NBD (for NASPE/BPEG Defibrillator) Code. It is intended for describing the capabilities and operation of implanted cardioverter defibrillators (ICDs) in conversation, record keeping, and device labeling, and incorporates four positions designating: (1) shock location; (2) antitachycardia pacing location; (3) means of tachycardia detection; and (4) antibradycardia pacing location. An additional Short Form, intended only for use in conversation, was defined as a concise means of distinguishing devices capable of shock alone, shock plus antibradycardia pacing, and shock plus antitachycardia and antibradycardia pacing. 相似文献
57.
D. Glenn Kennedy H. Desmond Shortt Steven R.H. Crooks Paul B. Young Henrietta J. Price Wesley G. Smyth 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(5):683-691
The administration of anabolic steroids, for the purposes of growth promotion, to food-producing animals is banned in the EU. Among the compounds covered by this prohibition is ß-nortestosterone (β-NT). This hormone is known to occur naturally in stallions and boars, and its main bovine metabolite, α-nortestosterone (α-NT), occurs naturally in pregnant cows and neonatal calves. However, neither compound is believed to occur naturally in male cattle. During 2006, the presence of α-NT and, on occasion, β-NT was confirmed in male cattle (bulls and steers) slaughtered in Northern Ireland on welfare grounds, as a result of acute injury. Subsequent investigations revealed no evidence of abuse at any of the farms involved and revealed that the phenomenon also occurred in three other regions of the EU, in similarly injured animals. A hypothetical link to release of the adrenal steroid, dehydroepiandrosterone (DHEA), in response to the stress of the injury was tested. Following the intravenous administration of DHEA to two normal steers, β-NT (but not α-NT) was confirmed in the urine of one steer. Thus, it may be concluded that both β-NT and, by implication, α-NT can occur naturally in male cattle (or a specific cohort thereof) in contrast to previously accepted scientific knowledge. 相似文献
58.
Nanostructured films of the conducting polymer polyaniline (PANI) were prepared by its potentiostatic polymerization in the presence of thin polystyrene (PS) nanoparticle templates. Two sizes of PS nanoparticles were used (50 and 100 nm) and electron microscopic analysis showed that core–shell composite films of PANI (PANI–PS50 and PANI–PS100) and, following removal of the PS, hollow structures (PANI50 and PANI100) were formed due to the growth mechanism of PANI around the PS templates. The electrochemical behaviour of the PANI-modified electrodes was studied by cyclic voltammetry, chronocoulometry and amperometry in the presence of nitrite and it was found that nitrite reduction was enhanced by the nanostructuring of the films. The electrocatalysis was dependent on the size of the template, being more pronounced at 50 nm than at 100 nm. The hollow PANI50 film was also a better catalyst than PANI–PS50, whereas for structures based on 100 nm templates, the composite film was better. Such behaviour could be explained in terms of larger surface area and surface concentration of PANI50 and PANI–PS50 films on the electrodes and by higher differential capacitance of those films. 相似文献
59.
Smyth C Fassioli F Scholes GD 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2012,370(1972):3728-3749
We review various methods for measuring delocalization in light-harvesting complexes. Direct relations between inverse participation ratios (IPRs) and entanglement measures are derived. The B850 ring from the LH2 complex in Rhodopseudomonas acidophila is studied. By analysing electronic energy transfer dynamics in the B850 ring using different metrics for quantifying excitonic delocalization, we conclude that measures of entanglement are far more robust (in terms of time scale, temperature and level of decoherence) than IPRs, and are therefore more appropriate for the purpose of studying the time evolution of coherence in a system. 相似文献
60.
Non-concentrated evacuated tube heat pipe solar collectors have been reported to show higher fluid temperatures with improved thermal performance in the low to medium temperature range (?60 °C) due to low heat losses but suffer higher heat losses at the medium to higher temperature range (?80 °C) which reduces their efficiency compared to concentrated evacuated tube heat pipe solar collectors. To operate as stand-alone systems capable of attaining temperatures in the range of 70-120 °C, an innovative concentrator augmented solar collector can be an attractive option. The performance of a combined low-concentrator augmented solar collector in an array of evacuated tube heat pipe solar collectors defined as concentrator augmented evacuated tube heat pipe array (CAETHPA) and an array of evacuated tube heat pipe collectors (ETHPC) were tested and compared and results presented in this paper. The analysis of the experimental data allows concluding that the use of a CAETHPA is a more efficient alternative for integrating renewable energy into buildings with higher fluid temperature response, energy collection and lower heat loss coefficient compared to the use of evacuated tube heat pipe collector array (ETHPA). 相似文献