全文获取类型
收费全文 | 2438篇 |
免费 | 51篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 181篇 |
金属工艺 | 9篇 |
机械仪表 | 21篇 |
建筑科学 | 13篇 |
能源动力 | 21篇 |
轻工业 | 214篇 |
水利工程 | 3篇 |
石油天然气 | 7篇 |
无线电 | 42篇 |
一般工业技术 | 99篇 |
冶金工业 | 1784篇 |
原子能技术 | 10篇 |
自动化技术 | 80篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 32篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 22篇 |
2017年 | 38篇 |
2016年 | 35篇 |
2015年 | 31篇 |
2014年 | 29篇 |
2013年 | 44篇 |
2012年 | 38篇 |
2011年 | 66篇 |
2010年 | 27篇 |
2009年 | 39篇 |
2008年 | 33篇 |
2007年 | 30篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 18篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 58篇 |
1998年 | 593篇 |
1997年 | 322篇 |
1996年 | 213篇 |
1995年 | 86篇 |
1994年 | 85篇 |
1993年 | 96篇 |
1992年 | 14篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 27篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 19篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 40篇 |
1976年 | 87篇 |
1975年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有2491条查询结果,搜索用时 0 毫秒
91.
Vanesa Losada Jorge Barros‐Velzquez Jos M. Gallardo Santiago P. Aubourg 《European Journal of Lipid Science and Technology》2004,106(12):844-850
Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its effect on lipid damage (hydrolysis and oxidation) was evaluated during the chilled storage of a fatty fish species, sardine (Sardina pilchardus). Slurry ice treatment was checked alone and in combination with ozone and compared to traditional flake icing during a 22‐day storage. Different lipid damage indices (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compounds, FR) were checked and compared to sensory assessment and nucleotide degradation (K value). According to lipid hydrolysis (FFA) and oxidation (PV and FR) developments, slurry ice showed an inhibitory effect (p <0.05) on lipid damage during storage, as well as an inhibition of nucleotide autolytic degradation. Ozonised slurry ice did not provide differences (p >0.05) from slurry ice alone when considering lipid hydrolysis, nucleotide degradation and some lipid oxidation indices (PV and FR), although a higher (p <0.05) TBA‐i was observed at day 22 of storage when compared to flake ice and slurry ice treatments. However, a lower (p <0.05) fluorescence development was observed for fish treated under ozonised slurry ice when compared to traditionally iced fish. Sensory assessment showed a higher shelf life for fish samples treated under ozonised slurry ice than for their counterparts under slurry ice (15 d versus 12 d), while flake icing led to a far shorter shelf life (5 d). According to sensory and biochemical (lipid matter and nucleotide) analysis, slurry ice has proved to be a promising technology for damage inhibition and quality retention in a fatty fish species such as sardine. Ozonised slurry ice was also shown to be useful, since a longer shelf life was obtained in the present experiment and a pro‐oxidant effect of ozone on sardine lipids was not proved. 相似文献
92.
S. de Barros P. P. Kenedi S. M. Ferreira S. Budhe A. J. Bernardino L. F. G. Souza 《The Journal of Adhesion》2017,93(8):599-612
Adhesively bonded joints can support a longer fatigue life if compared to conventional joining techniques, provided that a set of requirements is fulfilled. One of the most important requirements is the mechanical preparation of the bonded joint surface, which improves the joint interface adhesion. The aim of this work is to investigate the influence of surface roughness of mild steel substrates on fatigue behavior in adhesive bonded plates. To accomplish this objective, three different surface treatments were used on A36 steel substrate specimens, namely sand blasting, grit blasting, and bristle blasting. Bonded plate specimens, using end-notched flexure format, with a thin adhesive epoxy layer were manufactured and tested, under mode II loading condition, in both static and dynamic tests. The results confirm the importance of surface treatment of the substrate on the fatigue life, confirming that adhesively bonded joints have significant performance differences when subjected to static and dynamic loadings. 相似文献
93.
94.
K. Dias Da Cunha J. A. M. Pereira C. V. Barros Leite 《Aerosol science and technology》2013,47(5):453-464
The aim of this study was to apply the PIXE (Particle Induced X-ray Emission) and PDMS (Plasma Desorption Mass Spectrometry) techniques to characterize airborne dust particles containing metals. Aerosols generated at a mineral-sand processing plant were characterized in this study. The aerosol samples were collected at a plant that processes mineral sands to obtain rutile, ilmenite, zircon, and monazite concentrates. A cascade impactor with six stages was used to collect mineral dust particles with aerodynamic diameters in the range of 0.64 to 19.4 mum. The particles impacted on each stage of the cascade impactor were analyzed by PIXE, which permits the determination of the elemental mass air concentration and the MMAD (Mass Median Aerodynamic Diameter). The chemical compositions of the aerosol samples were identified by PDMS analysis. This study shows that, by using PIXE and PDMS techniques, it is possible to determine the chemical compounds in which the elements are associated in the aerosol particles. Based on the results of the PIXE analysis, the elemental mass concentrations and the MMADs were determined. 相似文献
95.
96.
Single-wall carbon nanotubes (SWNTs) prepared by the arc discharge method were oxidized using nitric acid. The samples were analyzed by using Raman scattering and Fourier transformed infrared spectroscopy (FTIR). The FTIR results indicate the presence of -COOH acid groups in the treated samples. The up shifts observed in the radial breathing mode frequencies suggest that SWNTs behave as donors after the acid treatment, with charge transfer occurring from the nanotubes to the -COOH groups. Ab initio calculations of SWNTs interacting with -COOH acid groups support the charge transfer process from the nanotubes to the carboxyl groups. 相似文献
97.
Celia Salazar Miriam Barros Alvaro A. Elorza Lina María Ruiz 《International journal of molecular sciences》2022,23(1)
Mitochondrial respiratory supercomplex formation requires HIG2A protein, which also has been associated with cell proliferation and cell survival under hypoxia. HIG2A protein localizes in mitochondria and nucleus. DNA methylation and mRNA expression of the HIGD2A gene show significant alterations in several cancers, suggesting a role for HIG2A in cancer biology. The present work aims to understand the dynamics of the HIG2A subcellular localization under cellular stress. We found that HIG2A protein levels increase under oxidative stress. H2O2 shifts HIG2A localization to the mitochondria, while rotenone shifts it to the nucleus. HIG2A protein colocalized at a higher level in the nucleus concerning the mitochondrial network under normoxia and hypoxia (2% O2). Hypoxia (2% O2) significantly increases HIG2A nuclear colocalization in C2C12 cells. In HEK293 cells, chemical hypoxia with CoCl2 (>1% O2) and FCCP mitochondrial uncoupling, the HIG2A protein decreased its nuclear localization and shifted to the mitochondria. This suggests that the HIG2A distribution pattern between the mitochondria and the nucleus depends on stress and cell type. HIG2A protein expression levels increase under cellular stresses such as hypoxia and oxidative stress. Its dynamic distribution between mitochondria and the nucleus in response to stress factors suggests a new communication system between the mitochondria and the nucleus. 相似文献
98.
Caroline D. Capitani Ana Carolina L. Carvalho Diogo P. Rivelli Silvia B. M. Barros Inar A. Castro 《European Journal of Lipid Science and Technology》2009,111(11):1090-1099
The antioxidant activity of natural and synthetic compounds was evaluated using five in vitro methods: ferric reducing/antioxidant power (FRAP), 2,2‐diphenyl‐1‐picrylhydradzyl (DPPH), oxygen radical absorption capacity (ORAC), oxidation of an aqueous dispersion of linoleic acid accelerated by azo‐initiators (LAOX), and oxidation of a meat homogenate submitted to a thermal treatment (TBARS). All results were expressed as Trolox equivalents. The application of multivariate statistical techniques suggested that the phenolic compounds (caffeic acid, carnosic acid, genistein and resveratrol), beyond their high antioxidant activity measured by the DPPH, FRAP and TBARS methods, showed the highest ability to react with the radicals in the ORAC methodology, compared to the other compounds evaluated in this study (ascorbic acid, erythorbate, tocopherol, BHT, Trolox, tryptophan, citric acid, EDTA, glutathione, lecithin, methionine and tyrosine). This property was significantly correlated with the number of phenolic rings and catecholic structure present in the molecule. Based on a multivariate analysis, it is possible to select compounds from different clusters and explore their antioxidant activity interactions in food products. 相似文献
99.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
100.
The Rise of Web Service Ecosystems 总被引:4,自引:0,他引:4
The convergence of Internet marketplaces and service-oriented architectures has spurred the growth of Web service ecosystems. This paper articulates a vision for Web service ecosystems, discusses early manifestations of this vision, and presents a unifying architecture to support the emergence of larger and more sophisticated ecosystems 相似文献