全文获取类型
收费全文 | 4098篇 |
免费 | 124篇 |
国内免费 | 87篇 |
专业分类
电工技术 | 56篇 |
技术理论 | 2篇 |
综合类 | 99篇 |
化学工业 | 932篇 |
金属工艺 | 585篇 |
机械仪表 | 107篇 |
建筑科学 | 173篇 |
矿业工程 | 741篇 |
能源动力 | 316篇 |
轻工业 | 191篇 |
水利工程 | 21篇 |
石油天然气 | 21篇 |
武器工业 | 2篇 |
无线电 | 61篇 |
一般工业技术 | 463篇 |
冶金工业 | 426篇 |
原子能技术 | 43篇 |
自动化技术 | 70篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 79篇 |
2021年 | 69篇 |
2020年 | 93篇 |
2019年 | 85篇 |
2018年 | 68篇 |
2017年 | 74篇 |
2016年 | 81篇 |
2015年 | 72篇 |
2014年 | 164篇 |
2013年 | 213篇 |
2012年 | 184篇 |
2011年 | 326篇 |
2010年 | 253篇 |
2009年 | 279篇 |
2008年 | 263篇 |
2007年 | 265篇 |
2006年 | 254篇 |
2005年 | 216篇 |
2004年 | 176篇 |
2003年 | 171篇 |
2002年 | 132篇 |
2001年 | 107篇 |
2000年 | 107篇 |
1999年 | 89篇 |
1998年 | 80篇 |
1997年 | 53篇 |
1996年 | 65篇 |
1995年 | 74篇 |
1994年 | 49篇 |
1993年 | 22篇 |
1992年 | 35篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有4309条查询结果,搜索用时 15 毫秒
81.
P204萃取分离锑铁工艺研究 总被引:1,自引:0,他引:1
萃取分离锑铁是脆硫锑铅矿矿浆电解工艺过程的一个环节。P2 0 4可选择性地在NH4 Cl介质溶液中萃取铁。在 35 %(体积百分数 )P2 0 4、相比 (O/A) 1∶1、3级连续逆流萃取条件下 ,铁萃取率达 80 %~ 84%,锑、银基本不被萃取。含Fe总 1~ 1 4g/L的萃余液可返回矿浆电解循环使用。 相似文献
82.
An integrated coal pyrolysis process with iron ore reduction is proposed in this article. As the first step, iron oxide reduction is studied in a fixed bed reactor using simulated coal pyrolysis gas with benzene as a model tar compound. Variables such as reduction temperature, reduction time and benzene concentration are studied. The carbon deposition of benzene results in the retarded iron reduction at low temperatures. At high temperatures over800 °C, the presence of benzene in the gas can promote iron reduction. The metallization can reach up to 99% in20 min at 900 °C in the presence of benzene. Significant increases of hydrogen and CO/CO2 ratio are observed in the gas. It is indicated that iron reduction is accompanied by the reforming and decomposition of benzene. The degree of metallization and reduction increases with the increasing benzene concentration. Iron oxide can nearly completely be converted into cementite with benzene present in the gas under the experimental conditions. No sintering is found in the reduced sample with benzene in the gas. 相似文献
83.
The iron oxide nanoparticles were loaded onto self-organized TiO2 nanotube layers grown by anodization of Ti in fluoride containing electrolytes. The nanoparticles were obtained by electrodepositing method in glycerol/water/FeCl3·6H2O electrolytes at room temperature. The X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) measurements showed that the nanoparticles consisted of iron nanocrystalline (Fe) and magnetite (Fe3O4). The hematite (α-Fe2O3) structure was obtained by annealing in air at 450 °C. The growth mechanism of the nanoparticles and their morphology were also described. Furthermore, the nanoparticles exhibited good ferromagnetic properties at room temperature. 相似文献
84.
戴骏 《安徽冶金科技职业学院学报》2014,24(2):70-74
通过对并购前后宝钢集团经济绩效的分析和比较,对这一战略并购的后果做出分析和判断,并据此对我国钢铁行业的健康发展,特别是战略并购的方向目标、市场机制、风险管理等方面提出改进建议。 相似文献
85.
The use of an iron dispersed catalyst, derived from Fe3(CO)12, for extra-heavy crude oil upgrading using methane as source of hydrogen was studied. The upgrading reactions were carried out batchwise in a stainless-steel 300 ml Parr reactor with 250 ppm of Fe at a temperature of 410-420 °C, a pressure of 11 MPa of CH4, and a residence time of 1 h. In the presence of Fe3(CO)12, the reaction of Hamaca extra-heavy crude oil led to a reduction of two orders of magnitude in the viscosity (from 500 to 1.3 Pa s), 14% reduction in sulfur content, and 41% conversion of the >500 °C fraction in the upgraded product with respect to the original crude. The iron catalyst was isolated from the coke produced from the upgrading reaction and was analyzed by XPS, EDAX, and Mössbauer spectroscopy. The results indicated the presence of a Fe-V mixed sulfide species with a composition ca. (Fe0.6V0.4)zS, where z is in the range 0.8-0.9. 相似文献
86.
Gang Wang Wan Jiang Guangzhao Bai Libin Wu 《Journal of the American Ceramic Society》2003,86(4):731-34
A type of aluminosilicate that has a good wetting property for molybdenum disilicide (MoSi2 ) was added to a MoSi2 matrix to study the effects on the microstructure and low-temperature oxidation. It was found that the composites had not only good low-temperature oxidation resistance but also high thermal shock resistance when the added oxides formed a network microstructure in the matrix. There was no appreciable oxidation gain for MoSi2 /oxide composites with a network microstructure at 773 K for 2500 h. The results indicate that microstructure design is a simple and effective solution to preventing the low-temperature oxidation of MoSi2 . 相似文献
87.
Concrete interlocking blocks (CIBs) are utilized in a variety of commercial, municipal, and industrial applications. Superior engineering properties, low maintenance, ease of placement and removal, reuse of original blocks, aesthetic appeal, and immediate availability are the primary reasons for choosing concrete block pavement over other paving surfaces. It is a common practice to pigment building materials, such as mortar, concrete pavers, concrete roof tiles, and prefabricated concrete products; CIBs are colored using iron oxide pigments. This article presents experimental results detailing the properties of CIBs dyed with pigments. The results of these experiments are as follows: Because the particles of iron oxide pigments are finer than those of brown iron oxide, interlocking blocks mixed with the former acquired higher color strength than with the latter. Additional analysis determined a definite relationship between the flexural strength and the absorption ratio of pigment-dyed blocks; the correlation coefficient (R2) of interlocking blocks at 91 days was .90. It is suggested that if iron oxide pigments are to be used to color CIBs, the pigment-to-cement ratio should be below 4%. 相似文献
88.
89.
《Ceramics International》2023,49(4):5997-6005
Due to the escalating demand for electronic dependability and defense security, there has been a surge in research into broadband and lightweight microwave absorbers. Porous composites that are lightweight and plentiful in interfaces have the potential to be high-performance absorbers due to their ability to attenuate waves in a balanced manner and match impedance. “Using a solvothermal technique we generated FeSe2/rGO composites with a porous topology. By varying the weight of rGO, the electromagnetic properties of FeSe2/rGO composites may be finely tuned. Impedance matching and attenuation capability are both improved as a direct result of the porous structure and the appropriate electromagnetic parameters. FeSe2/rGO composites benefit from the tunable composition, porous structure, and strong synergistic effect between FeSe2 and rGO sheets and display outstanding microwave absorption performance with an ultrabroad bandwidth approaching 5.2 GHz with a thin thickness of 1.6 mm which covers 75% of the studied frequency range. At the same thickness, a significant reflection loss of ?43.7 dB is attained. This work not only enables the tuning of electromagnetic parameters but also expands the use of high-performance microwave absorption devices. Remarkable microwave absorption ability, of the porous composites FeSe2/rGO can be utilized as a high-performance microwave absorber.” 相似文献
90.
《Ceramics International》2023,49(19):30924-30936
Rare earth ion substitution is one of the most important methods for adjusting the magnetic properties of M-type hexagonal ferrites; however, the regularity of these phase formations has rarely been studied. In this work, La substituted Sr hexaferrite LaxSr1-xO·nFe2O3 (La-SrM, 4.9 ≤ n ≤ 6.0, 0 ≤ x ≤ 0.6) was prepared using the traditional ceramic method. The effects of the Fe/Sr molar ratio (n), calcining temperature, and La3+ substitution (x) on SrM phase formation, the crystalline structure, and magnetic properties were investigated. With an increase of x up to a maximum value of 0.5–0.6, a higher calcining temperature is required to form the single M-phase of La-SrM samples. However, the optimal n values of single-phase La-SrM samples differ as the La substitution varies: when x = 0.1, n = 5.5–6.0; x = 0.2, n = 5.5–5.9; x = 0.3, 0.4 and 0.5, n = 5.7–5.8. The magnetic measurements show that La0.2Sr0.8O·5.8Fe2O3 has the highest specific saturation magnetization (σs), which is 2.2% higher than that of unsubstituted SrM (SrO·6Fe2O3), while the anisotropic field (HA), the anisotropic constant (K1), and Neel point (TN) of La3+ substituted SrM decreased. Detailed structure analyses were conducted to explain the changes in magnetic properties. Fe3+ in the spin-up 2a sublattice of LaxSr1-xO·5.8Fe2O3 decreased by approximately 5% from 98.5% (x = 0) to 93.85% (x = 0.4) with an increase in x. Additionally, a small amount of Fe3+ was reduced to Fe2+ in the spin-down 4f2 sublattice with the maximum reduction amount of 4.13% reached at x = 0.2, thereby improving σs. The decrease in the bond angle of (4f1) Fe3–O2–Fe5 (12k), (2a) Fe1–O4–Fe3 (4f1), and (4f1) Fe3–O4–Fe5 (12k) lead to the weakening of Fe–O–Fe superexchange of La-SrM so that HA, K1, and Tn decreased with increasing values of x. This work lays a solid foundation for the study of process regulation and ion substitution of permanent magnet ferrite. 相似文献