全文获取类型
收费全文 | 257篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 78篇 |
金属工艺 | 3篇 |
机械仪表 | 5篇 |
建筑科学 | 7篇 |
矿业工程 | 2篇 |
能源动力 | 16篇 |
轻工业 | 16篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 17篇 |
一般工业技术 | 38篇 |
冶金工业 | 23篇 |
原子能技术 | 4篇 |
自动化技术 | 53篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 18篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 17篇 |
2009年 | 14篇 |
2008年 | 7篇 |
2007年 | 14篇 |
2006年 | 2篇 |
2005年 | 10篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有270条查询结果,搜索用时 0 毫秒
91.
Mykola Kakazey Marina Vlasova Martha Dominguez-Patiño Ismael Leon Momcilo Ristic 《Journal of Materials Science》2007,42(17):7116-7122
Kinetics of defects formation, reaction process and formation of solid solution in powder mixtures of ZnO and MnO2 induced by prolonged mechanical treatment (MT) have been investigated (X-ray, FTIR, EPR). At MT in zones of deformation-destruction the different defects (\( {\text{V}}_{{\text{Zn}}}^ - :{\text{Zn}}_{\text{i}}^{\text{0}} \) (I), \( {\text{V}}_{{\text{Zn}}}^ - \) (II), and \( {\text{(V}}_{{\text{Zn}}}^ - {\text{)}}_{\text{2}}^ - \) (III) centers at all) are forming. The defects have various physical and chemical properties, and have different activation energies of annealing, Eact The part of these defects is responsible for the processes of hydration and carbonation of samples. In turn, the formation of defects is accompanied by development of various mechanothermical processes, which increase temperature of the sample, T MT, with the increasing of duration of MT, t MT. The increasing of t MT activates the reactionary processes: promotes a consecutive annealing the «low-temperature» defects having small values of Eact (I, II and III) and also leads to formation of Mn2+-doped Zn(OH)2. With the further increase of t MT, the process of MT is accompanied by an increasing of temperature of samples up to equilibrium, T eq and accumulation of “high-temperature” defects in the sample. As a result, in the sample the conditions for intensification of volumetric diffusion processes and formation of Mn2+-doped ZnO were created. 相似文献
92.
High concentrations of radon exist in several workplaces like tourist caves mainly because of the low ventilation rates existing at these enclosures. In this sense, in its 1990 publication, the ICRP recommended that high exposures of radon in workplaces should be considered as occupational exposure. In developed caves in which guides provide tours for the general public great care is needed for taking remedial actions concerning radon, because in some circumstances forced ventilation may alter the humidity inside the cave affecting some of the formations or paintings that attract tourists. Tourist guides can work about 1900 h per year, so the only option to protect them and other cave workers from radon exposure is to apply an appropriate system of radiation protection mainly based on limitation of exposure by restricting the amount of time spent in the cave. Because of the typical environmental conditions inside the caves, the application of these protecting actions requires to know some indoor air characteristics like particle concentration, as well as radon progeny behaviour in order to get more realistic effective dose values In this work the results of the first two set of radon measurements program carried out in 10 caves located in the region of Cantabria (Spain) are presented. 相似文献
93.
Ambient surfaces are examined by mass spectrometry at distances of up to 3 m from the instrument without any prior sample preparation. Non-proximate versions of the desorption electrospray ionization (DESI) and desorption atmospheric pressure chemical ionization experiments are shown to allow rapid, sensitive, and selective detection of trace amounts of active ingredients in pharmaceutical drug formulations, illicit drugs (methamphetamine, cocaine, and diacetylmorphine), organic salts, peptides, chemical warfare agent simulants, and other small organic compounds. Utilizing an ion transport tube to transport analyte ions to the mass spectrometer, nonproximate DESI allows one to collect high-quality, largely interference-free spectra with signal-to-noise (S/N) ratios of more than 100. High selectivity is achieved by tandem mass spectrometry and by reactive DESI, a variant experiment in which reagents added into the solvent spray allow bond-forming reactions with the analyte. Ion/molecule reactions were found to selectively suppress the response of mixture components other than the analyte of interest in nonproximate-DESI. Flexible ion transport tubing is also investigated, allowing performance similar to stainless steel tubing in the transport of ions from the sample to the mass spectrometer. Transfer tube temperature effects are examined. A multiple sprayer DESI source capable of analyzing a larger sample area was evaluated to decrease the sampling time and increase sample throughput. Low nanogram detection limits were obtained for the compounds studied from a wide variety of surfaces, even those present in complex matrixes. 相似文献
94.
Mixed convection heat transfer and fluid flow fields inside a lid-driven trapezoidal cavity were studied numerically. The cavity horizontal walls were thermally insulated while the inclined side walls were maintained isothermally at different temperatures. Forced convection was induced by moving the hotter right inclined side wall. The problem is formulated using the stream function–vorticity procedure. Together with the established boundary conditions on the right moving wall, the problem is solved by the finite difference method. The Richardson number Ri (0.01–10) and inclination angle of the side walls Φ (66–80°) were considered as pertinent parameters and investigated in two lid-driven cases: aiding and opposing directions. The results show that the behavior of Nusselt number is different from Richardson number depending on the direction of the lid. The inclination angle of the side walls was found to have a significant effect on Nusselt number when Ri was relatively low (≤1); otherwise, a negligible effect of Φ on Nusselt number was recorded. 相似文献
95.
Motto P Dimonte A Rattalino I Demarchi D Piccinini G Civera P 《Nanoscale research letters》2012,7(1):113
This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions
in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and
can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps
(with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled
by a custom hardware and the related software system. The studies were carried out through experiments and simulations of
organic molecules, in particular oligothiophenes. 相似文献
96.
Aromatic diamine monomers, including o-phenylenediamine (oPD), p-phenylenediamine (pPD), 4,4′-diaminodiphenylenemethane (DADPM) and benzidine (BZN), were polymerized by chemical oxidation using sodium persulfate, potassium persulfate, and ammonium persulfate as oxidant catalysts. Aluminium-triflate (Al(OTf)3) was also used for the first time as a co-catalyst under various polymerization conditions. The homopolymers obtained are characterized by FT-IR, 1H and 13C NMR, GPC, WAXD, DSC and TGA. The yield, solubility, structure and molecular weight of the polymers are significantly dependent on the oxidative catalyst and polymerization conditions. The polymers show different molecular structures, good thermal stability and decompose above 400 °C in nitrogen. 相似文献
97.
98.
Heating, ventilation and air conditioning (HVAC) systems are the most energy consuming building services representing approximately half of the final energy use in the building sector and between one tenth and one fifth of the energy consumption in developed countries. Despite their significant energy use, there is a lack of a consistent and homogeneous framework to efficiently guide research and energy policies, mainly due to the complexity and variety of HVAC systems but also to insufficient rigour in their energy analysis. This paper reviews energy related aspects of HVAC systems with the aim of establishing a common ground for the analysis of their energy efficiency. The paper focuses on the map of energy flow to deliver thermal comfort: the HVAC energy chain. Our approach deals first with thermal comfort as the final service delivered to building occupants. Secondly, conditioned spaces are examined as the systems where useful heat (or coolth) is degraded to provide comfort. This is followed by the analysis of HVAC systems as complex energy conversion devices where energy carriers are transformed into useful heat and coolth, and finally, the impact of HVAC energy consumption on energy resources is discussed. 相似文献
99.
The solubility parameter and the Flory–Huggins interaction parameter of two EVA (ethylene–vinyl acetate) copolymers, each one with different vinyl acetate content, are calculated by using inverse gas chromatography technique. The influence of the vinyl acetate percentage is analyzed and indicates that the polymer–solvent interactions are stronger in the case of the copolymer with the highest vinyl acetate percentage. The results also point to the fact that the most favorable solvents for the studied materials are the aromatic‐type ones. Finally, from the calculated values of the polymer solubility parameter (16.3 MPa0.5 for EVA 460 and 15.1 MPa0.5 for EVA410, at 50°C), it can be noticed that the solubility parameter of the EVA copolymer with the largest vinyl acetate content is the closest to the solubility parameter of pure vinyl acetate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
100.
Gonzalo Alduncin Ismael Herrera 《Computer Methods in Applied Mechanics and Engineering》1984,42(3):257-271
There are two main approaches to the formulation of boundary methods, these are boundary integral equations and approximations by complete systems of solutions (Trefftz method). The latter has been the subject of extensive studies by one of the authors oriented to clarifying the foundations of the method and increasing its versatility. The present paper is devoted to explain the application of this procedure to free boundary problems such as Signorini and friction problems in elasticity. 相似文献