全文获取类型
收费全文 | 1155篇 |
免费 | 47篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 33篇 |
综合类 | 3篇 |
化学工业 | 214篇 |
金属工艺 | 12篇 |
机械仪表 | 48篇 |
建筑科学 | 49篇 |
能源动力 | 67篇 |
轻工业 | 80篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 107篇 |
一般工业技术 | 202篇 |
冶金工业 | 156篇 |
原子能技术 | 13篇 |
自动化技术 | 203篇 |
出版年
2023年 | 23篇 |
2022年 | 30篇 |
2021年 | 68篇 |
2020年 | 34篇 |
2019年 | 50篇 |
2018年 | 51篇 |
2017年 | 30篇 |
2016年 | 62篇 |
2015年 | 43篇 |
2014年 | 50篇 |
2013年 | 82篇 |
2012年 | 65篇 |
2011年 | 91篇 |
2010年 | 55篇 |
2009年 | 53篇 |
2008年 | 50篇 |
2007年 | 45篇 |
2006年 | 36篇 |
2005年 | 32篇 |
2004年 | 33篇 |
2003年 | 25篇 |
2002年 | 22篇 |
2001年 | 28篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有1206条查询结果,搜索用时 31 毫秒
41.
42.
A new kind of anhydrous, transparent, and flexible potassium dihydrogen phosphate (KH2PO4 or KDP)/polyvinyl alcohol (PVA) composite in the form of film (0.10 mm) has been prepared by solution casting technique. KDP is well dispersed in the polymer matrix as observed from the microstructural studies. Frequency and temperature dependent dielectric properties of the composites have been studied with varying KDP concentrations. The PVA/KDP composite films exhibited extraordinarily high relative permittivity ε′ ∼ 430 (80 times higher compared with pure PVA and even higher than KDP) near the percolation threshold (ϕC = 2.5 wt % KDP) with low dielectric losses (∼ 0.15) at 1 kHz and room temperature. Such flexible, low loss and high dielectric permittivity material has enormous importance for application in devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
43.
Images are full of information and most often, little information is desired for subsequent processing. Hence, region of interest has key importance in image processing. Quadtree image segmentation has been widely used in many image processing applications to locate the region of interest for further processing. There are also variable block-size image coding techniques to effectively reduce the number of transmitted parts. This paper presents quadtree partition technique as a pre-processing step in image processing to determine what part should be more heterogeneous than the others. It also introduces an idea to solve the problem of squared images. Finally, proposed approach is implemented and analysed. The simulation of the Matlab code of the quadtree is represented by all algorithms and the figures. Thus, achieved results are promising in the state of the art. 相似文献
44.
A series of symmetrical optical brighteners based on stilbene-oxadiazole derivatives were prepared by the simple synthetic route of a condensation reaction between 4,4′-dicarboxystilbene and N,N′-carbonyldiimidazole reagent, forming stilbene 4,4′-ethene-1,2-diyldibenzohydrazide as a key intermediate. The obtained compounds were characterised by analysis of nuclear magnetic resonance, mass spectrometry, and elemental analysis data. The absorption maximum wavelength, fluorescence emission wavelength, and fluorescence quantum yield were measured in N,N-dimethylformamide solution at room temperature, and the fluorescence properties of the prepared compounds in the solid state were observed and measured. The compounds exhibited bluish and greenish fluorescence emission, with the fluorescence quantum yield in the range 0.2–0.8; the effects of substituents on the emission spectra of these compounds were interpreted. The prepared compounds were applied as optical brighteners to polyester and polyamide-6 fabrics at various concentrations, and their CIE whiteness index and fastness properties were studied. 相似文献
45.
The study has focused on electricity generation from organic acid-rich bio-substrate like star fruit (Averrhoa carambola). The sap of star fruit was selected as an electrolyte due to the presence of significant amounts of organic acids such as citric acid and ascorbic acid. To preserve the sap, 2% phenol by volume was used to reduce the growth of microorganisms, and the addition of phenol did not affect the initial pH. It was observed that due to an increase in the electrode surface area, reaction rate and current generation had been amplified. Internal resistance also decreased rapidly because of the large electrode surface area. Furthermore, internal resistance was the significant barrier in electricity generation, which was also successfully controlled by the baffle flow agitation system. Moreover, the baffle flow agitation system reduces the formation of dead zones and increases the total dissolved solids inside the electrochemical cell compartments during operation. 相似文献
46.
47.
Metallurgical and Materials Transactions A - The increase in use of dual-phase (DP) steel grades by vehicle manufacturers to enhance crash resistance and reduce body car weight requires the... 相似文献
48.
A side-chain type benzoxazine-functional cellulose has been developed using click chemistry via the reaction of ethynyl-monofunctional benzoxazine monomer and azide-functional cellulose. The synthesis, crosslinking, and thermal properties of the benzoxazine-functional cellulose are studied by NMR, FTIR, DSC, and TGA. The crosslinking reaction of the benzoxazine side-chain unusually takes place at low-temperatures in comparison to an ordinary benzoxazine resins. Upon crosslinking, the polymer shows high char yield of 40%, which is a marked improvement from a mere 4% of the unfunctionalized cellulose. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
49.
Relatively high purity of nitrogen atom encapsulated fullerene (N@C60) has been synthesized by an electron beam superimposed radio frequency (RF) discharge plasma method. Nitrogen species are characterized by an optical emission spectroscopy (OES); and a relationship between optical emission spectra and the purity of N@C60 has been examined. It is observed that the increased amount of nitrogen molecule ions impinging on the sublimated fullerenes enhance the synthesis of N@C60. Here, it is cleared that the efficient synthesis of N@C60 is possible by controlling the parameters of electron beam superimposed RF plasma. As a consequence, comparatively high purity of about 0.08% of N@C60 has been obtained. 相似文献
50.
Lauren Darr Mia Cunicelli Hem Bhandari Kristin Bilyeu Feng Chen Tarek Hewezi Zenglu Li Carl Sams Vince Pantalone 《Journal of the American Oil Chemists' Society》2020,97(1):49-56
Soybean [Glycine max (L.) Merr.] oil with high oleic acid (>75%) has increased oxidative stability and health benefits that are valuable for food, fuel, and industrial products. It has been determined that two naturally occurring mutations in genes FAD2-1A and FAD2-1B can combine to produce high oleic soybeans. The objective of this study was to test the effect of these mutant alleles on seed yield and oil and protein concentration. Molecular markers assisted in the creation of a population of 48 BC3F2:4 lines (93.75% expected genome commonality). Each line was classified into one of four genotypic groups where both FAD2-1A and FAD2-1B genes were either homozygous wild type or mutant, respectively. Twelve lines for each genotypic group were evaluated in three replications at six locations across Tennessee. There was no seed yield difference between the high oleic genotypic group and the other groups (P < 0.05). On the other hand, there were differences in fatty acid profiles and oil and protein concentrations. In combination, the mutant FAD2-1A and FAD2-1B alleles produced a mean of 803.1 g kg−1 oleic acid. This is, on average, approximately 500 g kg−1 more oleic acid compared to soybean lines with only one mutant FAD2-1 allele. The high oleic double mutant group had more total oil (228.0 g kg−1) and protein (401.0 g kg−1) compared to all other genotypic groups (P < 0.05). Overall, this specific combination of mutant FAD2-1A and FAD2-1B alleles appears to generate conventional high oleic soybeans without a yield drag. 相似文献