全文获取类型
收费全文 | 3467篇 |
免费 | 182篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 66篇 |
综合类 | 3篇 |
化学工业 | 683篇 |
金属工艺 | 145篇 |
机械仪表 | 244篇 |
建筑科学 | 51篇 |
矿业工程 | 2篇 |
能源动力 | 150篇 |
轻工业 | 379篇 |
水利工程 | 39篇 |
石油天然气 | 4篇 |
无线电 | 573篇 |
一般工业技术 | 738篇 |
冶金工业 | 221篇 |
原子能技术 | 49篇 |
自动化技术 | 315篇 |
出版年
2024年 | 5篇 |
2023年 | 44篇 |
2022年 | 60篇 |
2021年 | 106篇 |
2020年 | 52篇 |
2019年 | 75篇 |
2018年 | 90篇 |
2017年 | 77篇 |
2016年 | 106篇 |
2015年 | 87篇 |
2014年 | 129篇 |
2013年 | 200篇 |
2012年 | 242篇 |
2011年 | 294篇 |
2010年 | 209篇 |
2009年 | 203篇 |
2008年 | 216篇 |
2007年 | 169篇 |
2006年 | 164篇 |
2005年 | 119篇 |
2004年 | 125篇 |
2003年 | 100篇 |
2002年 | 123篇 |
2001年 | 100篇 |
2000年 | 68篇 |
1999年 | 64篇 |
1998年 | 127篇 |
1997年 | 70篇 |
1996年 | 50篇 |
1995年 | 28篇 |
1994年 | 31篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3662条查询结果,搜索用时 15 毫秒
151.
Debabrata Pradhan Jong-Gwan Ahn Dong-Jin Kim Seoung-Won Lee 《Korean Journal of Chemical Engineering》2009,26(3):736-741
The ferrous oxidation ability of Acidithiobacillus ferrooxidans was studied in the presence of Ni2+, V4+ and Mo6+ in 9 K media in order to implement the culture in the bioleaching of spent catalyst. The rate of iron oxidation decreased
with increasing concentration of metal ions, but the rate of inhibition was metal-ion dependent. The tolerance limit was critical
at a concentration of 25 g/L Ni2+, 5 g/L V4+ and 0.03 g/L Mo6+. The growth rate of microorganisms was negligible at concentrations of 6 g/L V4+ and 0.04 g/L Mo6+. Levels and degree of toxicity of these ions have been quantified in terms of a toxicity index (TI). The toxicity order of
metal ions was found to be Mo6+>V4+>Ni2+. The significance and relevance of multi-metal ion tolerance in Acidithiobacillus ferrooxidans has been highlighted with respect to bioleaching of spent refinery catalyst. 相似文献
152.
Seokyoung Ahn Seong Jin Park Shiwoo Lee Sundar V. Atre Randall M. German 《Powder Technology》2009,193(2):162-169
It is essential to study and optimize multiple objective functions such as binder system design, feedstock, part geometry, mold design, and processing conditions in order to develop a successful powder injection molding process. A powder with different combinations of binder systems and a binder system with different combinations of powder systems were investigated with a combined experimental and simulation study. First, an experimental rheological study was performed to evaluate the influence of the powder/binder combinations on the rheological behavior and thermal stability of carbonyl iron and stainless steel powder injection molding (PIM) feedstocks. Second, based on the characterization of the feedstock, the simulation study revealed that the pressure-related parameters such as wall shear stress, injection pressure, and clamping force were mainly dependent on the binder system and not much on the powder characteristics, in the range of particle attributes studied. Third, to the temperature-related parameters such as melt front temperature difference and cooling time, binder selection is more critical than powder selection. Fourth, for the velocity-related parameter, maximum shear rate, the selection of both powder and binder system is critical in control. It is demonstrated that the simulation study is essential in the development stage for successful PIM. 相似文献
153.
We demonstrate that the temperature-dependent phase behaviors of parallel and perpendicular cylinder-forming block copolymers are governed by domain-domain segregation forces inherently present in block copolymer material itself. With increasing temperature, a parallel cylinder-forming block copolymer experienced a parallel cylinder straightening process before the order-disorder transition (ODT) and did not show long-range composition fluctuations near the ODT temperature due to the weak segregation forces between the block domains. A perpendicular cylinder-forming block copolymer with a strong segregation force between the block domains displayed cylinder orientation transition from perpendicular to parallel below the ODT temperature. On the other hand, a perpendicular cylinder-forming block copolymer material with an exceptionally strong segregation force between the block domains maintained its initial perpendicular cylinder orientation up to near the ODT temperature. In both cases of perpendicular cylinder-forming block copolymers, submicrometer-scale long-range composition fluctuations were observed well above the ODT temperature due to their intrinsically strong segregation forces between the block domains. 相似文献
154.
Synthesis of mesoporous materials SBA-15 and CMK-3 from fly ash and their application for CO2 adsorption 总被引:1,自引:0,他引:1
A supernatant solution of silicate species extracted from coal fly ash in a power plant by alkali fusion was used in acidic
condition to prepare a mesoporous silica SBA-15. The SBA-15 was used as a template for the synthesis of a mesoporous carbon
CMK-3 using sucrose as a carbon source. Characterization of the produced mesoporous materials by XRD, N2 adsorption-desorption, SEM, and TEM confirmed the formation of well-ordered hexagonal mesostructures. Textural properties
were found close to those prepared by pure chemicals. SBA-15 after polyethyleneimine impregnation and CMK-3 were tested for
carbon dioxide adsorption, successfully demonstrating the possibility of recycling the industrial waste product in a power
plant into a useful adsorbent. 相似文献
155.
Saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) show different effects on the development of insulin resistance.
In this study, we compared the effect of dietary SFA and MUFA on the insulin signaling pathway in the skeletal muscle of a
type 2 diabetic animal model. Twenty-nine-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were randomly divided
into three groups and fed one of the following diets for 3 weeks; a normal chow diet, an SFA (lard oil) enriched or a MUFA
(olive oil) enriched high-fat diet. The vastus lateralis muscle was used for analyses. Insulin tolerance test showed improved
insulin sensitivity in rats fed the MUFA diet, as compared to those fed the SFA diet (p < 0.001). The SFA diet reduced IRS-1 expression and phosphorylated PI3K levels in skeletal muscle, as compared with a chow
diet (p < 0.001, respectively). On the contrary, muscle IRS-2 expression and phosphorylated ERK1/2 was significantly increased in
rats fed the SFA diet (p < 0.001, respectively). Membrane translocation of glucose transporter type 4 decreased in the skeletal muscle of rats fed
the SFA diet, as compared to those fed a chow diet (p < 0.001). These changes in insulin signaling pathway in skeletal muscle were not observed in rats fed the MUFA diet. In conclusion,
the beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3K insulin signaling pathway
which was altered by dietary SFA. 相似文献
156.
Y- and Si-based oxide nanopowders were synthesized by a hydrothermal reaction of Y or Si powders with NaOH or LiOH aqueous
solution. Nanoparticles with different morphology such as elongated nanospheres, flower-like nanoparticles and nanowires were
produced by a control of processing parameters, in particular, the starting composition of solution. The preliminary result
of electrochemical examination showed that the hydrothermally processed nanowires exhibit high initial capacities of Li-ion
storage: 653 mAh/g for Y2O3 nanowires as anode materials and 186 mAh/g for Li2Si2O5 nanowires as cathode materials in a Li secondary cell. Compared to the powder with elongated sphere or flower-like shapes,
the nanowires showed a higher Li-ion capacity and a better cycle property. 相似文献
157.
Hyung Tag Lim Hongzhe Liu Kyung Hyun Ahn Seung Jong Lee Joung Sook Hong 《Korean Journal of Chemical Engineering》2010,27(2):705-715
Ethylene-methacrylic acid ionomer (Surlyn) with concentration up to 20 wt% based on total weight of polymer resin was added
into polypropylene (PP)/organoclay hybrids. The microstructure, rheological properties, crystallization properties and mechanical
properties of the obtained nanocomposites have been investigated. The addition of ionomer markedly enlarged interlayer spacing
of the platelets and led to an improved degree of exfoliation. Moreover, clay silicates were found to selectively disperse
either inside the ionomer phase or at the phase boundary. Compared to the binary immiscible blends, an improved interfacial
adhesion was achieved for PP/Surlyn/OMMT hybrids. Unlike PP/Surlyn binary blends, the viscoelastic properties of the hybrids
significantly increased with increasing Surlyn concentration, which could be attributed to the improved clay dispersion and
the contribution of silicate layers at the interface between PP and Surlyn. A synergistic role between Surlyn and clay was
also found to suppress the crystallization of PP matrix. In addition, PP/Surlyn/OMMT hybrids exhibited superior tensile strain
compared to the corresponding PP/PP-g-MA/OMMT. Both tensile strength and elongation at break showed maximum at Surlyn concentration
of 5 wt%. By comparing the experimental tensile yield strength with model prediction, it was suggested that the clay platelets
localized at the interface could play a role of interfacial activation to some extent. 相似文献
158.
Hee Jung Kim Ji Eun Park Myung Gil Choi Sangdoo Ahn Suk-Kyu Chang 《Dyes and Pigments》2010,84(1):54-58
A novel, Hg2+-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg2+-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg2+ selectivity. The Hg2+ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg2+ ions was 4.3 × 10−6 mol L−1 and the conjugate dye could be used as a chemosensor for the analysis of Hg2+ ions in aqueous environments. 相似文献
159.
Joon-Ho Shin Jong-Hwa Kim Ki-Won Kim Hyo-Jun Ahn 《Metals and Materials International》2002,8(4):417-422
Lead acid batteries have had restricted applications because of relatively low energy density below 50Wh/kg. Many efforts have achieved lighter battery components such as separators, connections and containers etc. Thus, the most important problem of the lead acid battery is to improve the low capacity of the active material in the positive electrode. The purpose of this study is to improve the utilization of the active material in the lead dioxide electrode for the lead acid battery through the production of lead oxide with better physicochemical characteristics through cementation. A cementation reaction was performed in 1.0wt.%HCl solution using pure magnesium plate as the reductant. We investigated the utilization of the active material and discharge characteristics of the positive electrode with a current density ranging from 3.4 to 108.8mAcm−2. As a result, the active material utilization was about 72% at 3.48 mAcm−2 and increased with decreasing current density. The discharge characteristics according to current density are especially very good at high current density 相似文献
160.
Young Suk Kim Sang Bok Ahn Dong Joon Oh Sung Soo Kim Yong Moo Cheong 《Metals and Materials International》2002,8(3):241-246
With the aim of assessing the degradation of Zr−2.5Nb pressure tubes operating in the Wolsong unit-1 nuclear power plant, characterization tests are being conducted on irradiated Zr−2.5Nb tubes removed after 10-year operation. The examined tube had been exposed to temperatures ranging from 264 to 306°C and a neutron fluence of 8.9×1021 n/cm2 (E>1 MeV) at the maximum. Tensile tests were carried out at temperatures ranging from RT to 300°C. The density of a-type and c-type dislocations was examined on the irradiated Zr-2.5Nb tube using a transmission electron microscope. Neutron irradiation up to 8.9×1021 n/cm2 (E>1 MeV) yielded an increase in a-type dislocation density of the Zr−2.5Nb pressure tube to 7.5×1014 m−2, which was highest at the inlet of the tube exposed to the low temperature of 275°C. In contranst, the c-component dislocation density did not change with irradiation, keeping an initial dislocation density of 0.8×1014 m−2 over the whole length of the tube. As expected, the neutron irradiation increased mechanical strength by about 17–26% in the transverse direction and by 34–39% in the longitudinal direction compared to that of the unirradiated tube at 300°C. The change in the mechanical properties with irradiation is discussed in association with the microstructural change as a function of temperature and neutron fluence. 相似文献