全文获取类型
收费全文 | 295篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 31篇 |
综合类 | 2篇 |
化学工业 | 80篇 |
金属工艺 | 9篇 |
机械仪表 | 12篇 |
建筑科学 | 7篇 |
矿业工程 | 2篇 |
能源动力 | 13篇 |
轻工业 | 45篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 22篇 |
一般工业技术 | 44篇 |
冶金工业 | 12篇 |
原子能技术 | 8篇 |
自动化技术 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 21篇 |
2016年 | 20篇 |
2015年 | 9篇 |
2014年 | 17篇 |
2013年 | 33篇 |
2012年 | 19篇 |
2011年 | 19篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有325条查询结果,搜索用时 218 毫秒
81.
Introducing a specific clean extraction procedure with a minimal matrices effect for food colorant determination is still a challengeable topic and highly recommended. Mixed hemimicelle solid-phase extraction method, based on cetyltrimethylammonium bromide-coated Fe3O4/SiO2 nanoparticles as a novel, simple, and fast preconcentration method, was applied for preconcentration and fast isolation of three synthetic food colorants in foodstuff matrices prior to HPLC-UV-vis determination. The influence of different parameters on extraction efficiency such as surfactant amount, sample pH, time of extraction, desorption condition, and nanoparticles concentration was optimized. Under the optimized conditions, a preconcentration factor of 100 was achieved by extracting 10 mL sample. The limit of detection for the three synthetic food colorants including Tartrazine, Sunset yellow FCF, and Quinoline yellow is 2.50, 1.25, and 2.12 μg/L, respectively. The proposed method was applicable for extraction and preconcentration of three food colorants in various food samples with the food dye contents in the range of 13–105 μg/L. 相似文献
82.
83.
Ying Lin Fanghui Yin Yuhao Liu Liming Wang Yunfeng Zhao Masoud Farzaneh 《应用聚合物科学杂志》2019,136(24):47652
Liquid silicone rubber (LSR) products outdoors are often subjected to high intensity of ultraviolet (UV)-A radiation. However, the influence of UV-A radiation on LSR is rarely studied. To study the influence of UV-A radiation on LSR, the surface of LSR with UV-A aging time was characterized by tests at different detection depths [X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR)]. The operation properties (thermal stability and mechanical and electrical properties) for outdoor insulators were also analyzed. It was found that the porous surface and the loose layer of LSR increased, but the growth rate of them decreased as UV-A aging time increased. SiO2 fillers were lost in the surface. C H bonds in CH3 and CH3 in Si CH3 increased with aging time. The increased crosslinking density increased the thermal stability, hardness, dielectric loss tangent, relative dielectric constant, and volume resistivity and decreased elongation-at-break. The mechanical strength initially increased and then decreased. Based on the proposed aging mechanism, the UV-A resistance of LSR can be improved by reducing the amount of hydrogen-containing silicone oil and by increasing the molecular weight of raw rubber. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47652. 相似文献
84.
Samaneh Sanjari Hanieh Mohammad Gholizadeh Farzaneh Vahabzadeh 《Chemical Engineering Communications》2019,206(3):289-300
Cyclodextrin glucanotransferase (CGTase) production was studied using loofa-immobilized Bacillus sp. DSM 2523 and starch substrate. The bacterial cells from 2- and 4-day old cultures were used in the flask studies. Loofa and chitosan were added for cell immobilization and cell flocculation, respectively, and different treatments were considered according to the timing of their addition. The cell responses were evaluated for their degree of cell immobilization and level of CGTase activity. With the use of the selected treatment, testing was carried out in an airlift reactor with a net draft tube having specific geometric properties. The cell capacity for reusability also was examined. The production of CGTase was higher in the second cycle in the reactor operated at 0.25 vvm where the enzyme activity reaching 0.20?U/ml within 2?h. In the flask experiments, CGTase activity reached 0.23?U/ml after 19?h in the second cycle. 相似文献
85.
86.
87.
88.
In this study the structural and electronic properties of III-nitride monolayers XN(X=B, Al, Ga and In) under different percentages of homogeneous and shear strain are investigated using the full potential linearized augmented plane wave within the density functional theory. Geometry optimizations indicate that GaN and InN monolayers get buckled under compressive strain.Our calculations show that the free-strains of these four monolayers have an indirect band gap. By applying compressive biaxial strain, a transition from indirect to direct band gap occurs for GaN and InN, while the character of band gap for BN and AlN is not changed. Under tensile strain, only BN monolayer behaves as direct band gap semiconductor. In addition, when the shear strain is applied, only InN undergoes an indirect to direct band gap transition. Furthermore, the variations of band gap versus strain for III-nitride monolayers have been calculated. When a homogeneous uniform strain, in the range of [.10%, +10%], is applied to the monolayers, the band gap can be tuned for from 3.92 eV to 4.58 eV for BN, from 1.67 eV to 3.46 eV for AlN, from0.24 eV to 2.79 eV for GaN and from 0.60 eV to 0.90 eV for InN. 相似文献
89.
Influences of nonassociated flow rules on three-dimensional seismic stability of loaded slopes 总被引:1,自引:1,他引:0
The influences of soil dilatancy angle on three-dimensional (3D) seismic stability of locally-loaded slopes in nonassociated flow rule materials were investigated using a new rotational collapse mechanism and quasi-static coefficient concept. Extended Bishop method and Boussinesq theorem were employed to establish the stress distribution along the rupture surfaces that are required to obtain the rate of internal energy dissipation for the nonassociated flow rule materials in rotational collapse mechanisms. Good agreement was observed by comparing the current results with those obtained using the translational or rotational mechanisms and numerical finite difference method. The results indicate that the seismic stability of slopes reduces by decreasing the dilatancy angle for nonassociated flow rule materials. The amount of the mentioned decrease is more significant in the case of mild slopes in frictional soils. A nearly infinite slope under local loading, whether its critical failure surface is 2D or 3D, not only depends on the magnitude of the external load, but also depends on the dilatancy angle of soil and the coefficient of seismic load. 相似文献
90.
On the chloride-induced pitting of ultra fine grains 5052 aluminum alloy produced by accumulative roll bonding process 总被引:1,自引:0,他引:1
Mehdi Fadaei Naeini Mohammad Hossain ShariatMehdi Eizadjou 《Journal of Alloys and Compounds》2011,509(14):4696-4700
Pitting corrosion susceptibility of ultra fine grain (UFG) 5052 aluminum alloy (AA 5052) sheets highly deformed by accumulative roll-bonding (ARB) was investigated in 3.5 wt% NaCl solution using potentiodynamic polarization, cyclic voltammetry and immersion tests. The morphology of localized attacks was analyzed by SEM-EDS. Pitting corrosion resistance of samples was diminished with increasing the number of ARB passes which is presumably due to microstructure refinement and increasing the defect density. 相似文献