全文获取类型
收费全文 | 567篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 189篇 |
金属工艺 | 18篇 |
机械仪表 | 24篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 36篇 |
轻工业 | 59篇 |
水利工程 | 5篇 |
无线电 | 27篇 |
一般工业技术 | 62篇 |
冶金工业 | 58篇 |
原子能技术 | 6篇 |
自动化技术 | 97篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 41篇 |
2021年 | 57篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 39篇 |
2012年 | 25篇 |
2011年 | 27篇 |
2010年 | 18篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 12篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有597条查询结果,搜索用时 15 毫秒
101.
Joanna A. Bartkowska Dariusz Bochenek 《Journal of Materials Science: Materials in Electronics》2018,29(20):17262-17268
Multiferroics with negative value of dielectric constant are very promising materials because of their modern applicability. These materials can be used as materials for the construction of electromagnetic radiation shields. The subject of the research is multiferroic BiFeO3–PbFe1/2Nb1/2O3 (BF–PFN) ceramics. For all multiferroic materials the following studies are conducted: SEM, EDS and the temperature dependence of dielectric constant ε′(T). Above a certain temperature (different for different chemical compositions) the value of dielectric constant reaches negative values. Such the behavior of the dielectric constant may indicate that the polarization inside the material has a reverse direction to the external electric field. That is, the electric field inside the material counteracts the applied external electric field. The obtaining materials also show negative dielectric losses. The Axelrod model is used to explain the mechanism that causes negative dielectric loss. 相似文献
102.
Dariusz M. Bielinski Ludomir Slusarski Stanley Affrossman Mark Hartshorne Richard A. Pethrick 《应用聚合物科学杂志》1995,56(7):853-867
Physical properties of surface modified synthetic elastomers were studied to understand the factors that reduce friction and provide advantages in practical use. Bromination, iodination, sulfonation, and chlorination were investigated. The coefficient of friction μ was measured using a modified version of the pin-on-disc apparatus. The surface energy, morphology, mechanical properties, and extent of chemical modification were also measured. An increased stiffness and microroughness were found to correlate with changes in the coefficient of friction. Sulfonation (100% H2SO4) was found to be the most effective and universally acceptable method of chemical treatment from a tribological point of view. © 1995 John Wiley & Sons, Inc. 相似文献
103.
Hans‐Peter Heim 《大分子材料与工程》2002,287(11):723-728
In gas assisted injection moulding the melt front advancement has a considerable effect on the gas penetration. The evaluation of an appropriate melt filling is an important step to avoid instabilities in the process sequence. Taking a sample moulded part a procedure is presented that enables the part designer to evaluate required melt and gas injection points according to the gas injection technique. Using finite element simulations, different calculations for the melt front advancement lead to the correct gate location.
104.
Lipophilic organic contaminants in the Rhine river, Germany 总被引:1,自引:0,他引:1
Detailed gas chromatographic-mass spectrometric analyses applied to eight Rhine river water samples constituted a comprehensive characterization of the low molecular weight organic contamination. Within the group of predominant anthropogenic contaminants, only a few compounds were characterized as frequently detected or priority pollutants. Numerous compounds exhibiting physiological or ecotoxicological properties are only rarely reported or still unnoticed riverine contaminants. Information on environmental behaviour or ecotoxicological effects is still limited for most of these substances. In particular, several brominated compounds (mono- and dibrominated (methoxyphenyl)propionic acids and hydroxymethylacetophenones) were identified for the first time as environmental contaminants. Quantitative analyses differentiated five groups of pollutants with respect to their concentration profiles. The spatial distribution and the intensity of emission sources on the one hand and the environmental stability as well as the tendency to adsorb on the particulate matter on the other hand determined the quantitative occurrence of individual compounds. 相似文献
105.
The paper presents an idea for the enhancement of a building's thermal insulation component by adding into the structure a thin layer of a phase-change material (PCM). The proposed solution can be dedicated, for example, to an external partition of lightweight construction. The capacity for latent heat storage allowed it to stabilize the temperature inside the insulation layer in a daily cycle and to minimize the temperature difference between the internal and external surfaces. In this paper, different positions of a PCM layer in the thermal insulation of an external wall were analysed. The main goal of this work was to find the best position of the PCM layer, taking into account the indoor temperature and the meteorological conditions. The authors propose two parameters: the amount of stored energy and the dynamism of the charging/discharging processes. Taking into account large temperature fluctuations on the external surface during summer and winter, it was concluded that, for this specific case, the most appropriate solution would be an external position of the PCM with a melting temperature of 20°C. 相似文献
106.
Pipe relining via in situ epoxy lining is used to remediate corroded plumbing or distribution systems. This investigation examined the effects on odour, TOC, THM formation and disinfectant demand in water exposed to epoxy-lined copper pipes used for home plumbing. The study was conducted in accordance with the Utility Quick Test, a migration/leaching method for utilities to conduct sensory analysis of materials in contact with drinking water. The test was performed using water with no disinfectant and levels of chlorine and monochloramines representative of those found in the distribution system. Panelists repeatedly and consistently described a "plastic/adhesive/putty" odour in the water from the pipes. The odour intensity remained relatively constant for each of two subsequent flushes. Water samples stored in the epoxy-lined pipes showed a significant increase in the leaching of organic compounds (as TOC), and this TOC was demonstrated to react with free chlorine to form trichloromethane. Water stored in the pipes also showed a marked increase in disinfectant demand relative to the water stored in glass control flasks. A study conducted at a full scale installation at an apartment demonstrated that after installation and regular use, the epoxy lining did not yield detectable differences in water quality. 相似文献
107.
Baej Grodner Mariola Napirkowska Dariusz Maciej Pisklak 《International journal of molecular sciences》2021,22(21)
Background: Acid phosphatase and its regulation are important objects of biological and clinical research and play an important role in the development and treatment of prostate and bone diseases. The newly patented aminoalkanol (4-[2-hydroxy-3-(propan-2-ylamino)propyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (I) and (4-[3-(dimethylamino)-2-hydroxypropyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (II) derivatives have potential anticancer activity, and their influence on enzymatic activity can significantly impact the therapeutic effects of acid phosphatase against many diseases. Therefore, in this study, we investigated the action of compounds (I) and (II) on acid phosphatase. Methods: Capillary electrophoresis was used to evaluate the inhibition of acid phosphatase. Lineweaver–Burk plots were constructed to compare the Km of this enzyme in the presence of inhibitors (I) or (II) with the Km in solutions without these inhibitors. Results: Compound (I) showed a stronger competitive inhibition against acid phosphatase, whereas derivative (II) showed a weaker competitive type of inhibition. The detailed kinetic studies of these compounds showed that their type and strength of inhibition as well as affinity depend on the kind of substituent occurring in the main chemical molecule. Conclusions: This study is of great importance because the disclosed inhibition of acid phosphatase by compounds (I) and (II) raises the question of whether these compounds could have any effect on the treatment possibilities of prostate diseases. 相似文献
108.
Marcin Grniak Dariusz L. Szlachetko Natalia Oldrzyska Aleksandra M. Naczk Agata Mieszkowska Lidia Boss Marek S. Zitara 《International journal of molecular sciences》2021,22(21)
The phylogeny of the genus Paphiopedilum based on the plastome is consistent with morphological analysis. However, to date, none of the analyzed nuclear markers has confirmed this. Topology incongruence among the trees of different nuclear markers concerns entire sections of the subgenus Paphiopedilum. The low-copy nuclear protein-coding gene PHYC was obtained for 22 species representing all sections and subgenera of Paphiopedilum. The nuclear-based phylogeny is supported by morphological characteristics and plastid data analysis. We assumed that an incongruence in nuclear gene trees is caused by ancestral homoploid hybridization. We present a model for inferring the phylogeny of the species despite the incongruence of the different tree topologies. Our analysis, based on six low-copy nuclear genes, is congruent with plastome phylogeny and has been confirmed by phylogenetic network analysis. 相似文献
109.
Identification of loading conditions resulting in roller slippage in gearbox bearings of large wind turbines 下载免费PDF全文
The dynamic loads on the rollers inside the bearings of large wind turbine gearboxes operating under transient conditions are presented with a focus on identifying conditions leading to slippage of rollers. The methodology was developed using a multi‐body model of the drivetrain coupled with aeroelastic simulations of the wind turbine system. A 5 MW reference wind turbine is considered for which a three‐stage planetary gearbox is designed on the basis of upscaling of an actual 750 kW gearbox unit. Multi‐body dynamic simulations are run using the ADAMS software using a detailed model of the gearbox planetary bearings to investigate transient loads inside the planet bearing. It was found that assembly and pre‐loading conditions have significant influence on the bearing's operation. Also, the load distribution in the gearbox bearings strongly depends on wind turbine operation. Wind turbine start‐up and shut‐down under normal conditions are shown to induce roller slippage, as characterized by loss of contacts and impacts between rollers and raceways. The roller impacts occur under reduced initial pre‐load on opposite sides of the load zone followed by stress variation, which can be one of the potential reasons leading to wear and premature bearing failures. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
110.
Aleksandra Świerczyńska Dariusz Fydrych Grzegorz Rogalski 《International Journal of Hydrogen Energy》2017,42(38):24532-24540
This article reports the effect of underwater wet welding parameters and conditions on the diffusible hydrogen content in deposited metal for welding with a self-shielded flux cored wire. The diffusible hydrogen content in deposited metal was determined using the glycerin method according to the Plackett-Burman design determining the significance of the effect of the stick out length, welding current, arc voltage, travel speed and water salinity. The results of the measurements of the diffusible hydrogen content in deposited metal ranged from 25.85 to 44.12 ml/100 g. The effect of all the tested factors is statistically significant. An equation was also developed, the analysis of which showed, that the hydrogen content cannot be reduced by technological methods below 21 ml/100 g. 相似文献