全文获取类型
收费全文 | 7247篇 |
免费 | 359篇 |
国内免费 | 302篇 |
专业分类
电工技术 | 82篇 |
综合类 | 248篇 |
化学工业 | 1578篇 |
金属工艺 | 1598篇 |
机械仪表 | 320篇 |
建筑科学 | 121篇 |
矿业工程 | 262篇 |
能源动力 | 1035篇 |
轻工业 | 58篇 |
水利工程 | 14篇 |
石油天然气 | 67篇 |
武器工业 | 31篇 |
无线电 | 154篇 |
一般工业技术 | 1207篇 |
冶金工业 | 971篇 |
原子能技术 | 76篇 |
自动化技术 | 86篇 |
出版年
2024年 | 17篇 |
2023年 | 180篇 |
2022年 | 198篇 |
2021年 | 243篇 |
2020年 | 277篇 |
2019年 | 198篇 |
2018年 | 165篇 |
2017年 | 180篇 |
2016年 | 152篇 |
2015年 | 203篇 |
2014年 | 404篇 |
2013年 | 318篇 |
2012年 | 444篇 |
2011年 | 606篇 |
2010年 | 407篇 |
2009年 | 433篇 |
2008年 | 406篇 |
2007年 | 489篇 |
2006年 | 419篇 |
2005年 | 340篇 |
2004年 | 301篇 |
2003年 | 299篇 |
2002年 | 253篇 |
2001年 | 205篇 |
2000年 | 184篇 |
1999年 | 146篇 |
1998年 | 102篇 |
1997年 | 84篇 |
1996年 | 53篇 |
1995年 | 36篇 |
1994年 | 36篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7908条查询结果,搜索用时 15 毫秒
171.
金精矿矿浆电解过程中矿粒及Fe(Ⅱ)的阳极氧化 总被引:1,自引:0,他引:1
研究了在云南元阳金精矿矿浆电解过程中 ,矿粒及Fe(Ⅱ )在石墨阳极上氧化过程动力学 ,测绘了矿粒及Fe(Ⅱ )在石墨阳极上的极化曲线 ,发现矿粒的阳极氧化分为 3个阶段。研究了各种因素对Fe(Ⅱ )阳极氧化电流密度的影响 ,并求出Fe(Ⅱ )阳极氧化过程的动力学参数 ,在 2 5~ 2 8℃时 ,i0 在 ( 3 1 6~ 6)× 1 0 - 5A·cm- 2 之间 ,k为 4 37× 1 0 - 1 2 ~ 1×1 0 - 8cm·s- 1 。 相似文献
172.
采用复合强韧化工艺,对7A04铝合金的组织和性能进行了研究。结果表明,通过熔体净化、晶粒细化、强化均匀化、锻造及分级固溶处理能明显改善和提高7A04高强铝合金的综合性能,而且可以大大减少均匀化处理的保温时间。 相似文献
173.
Xu-hui Zhao Yu Zuo Jing-mao Zhao Jin-ping Xiong Yu-ming Tang 《Surface & coatings technology》2006,200(24):6846-6853
The electrochemical behaviors of anodized aluminum in neutral NaCl and Na2SO4 solutions were studied using electrochemical impedance spectroscopy (EIS). The results reveal that there is a self-sealing process for unsealed anodic film in neutral NaCl and Na2SO4 solutions. The resistance of the porous layer (Rp) and the capacitance of the barrier layer (CPEb) increase and the capacitance of the porous layer (CPEp) decreases with immersion time in the initial stage. Corrosion resistance provided by the anodic film is improved by the self-sealing process of the porous layer. However, chloride ions have an opposite effect. The improving effect of the self-sealing process on film resistance is decreased with the increase of chloride concentration of the solution. 相似文献
174.
Zihan Ma Xiaofei Lu Sunghyun Park Tatsuya Shinagawa Masashi Okubo Kazuhiro Takanabe Atsuo Yamada 《Advanced functional materials》2023,33(25):2214466
Hydrogen is a promising alternative to fossil fuels that can reduce greenhouse gas emissions. Decoupled water electrolysis system using a reversible proton storage redox mediator, where the oxygen evolution reaction and hydrogen evolution reaction are separated in time and space, is an effective approach to producing hydrogen gas with high purity, high flexibility, and low cost. To realize fast hydrogen production in such a system, a redox mediator capable of releasing protons rapidly is required. Herein, α-MoO3, with an ultrafast proton transfer property that can be explained by a dense hydrogen bond network in the lattice oxygen arrays of HxMoO3, is examined as a high-rate redox mediator for fast hydrogen production in acidic electrolytes. The α-MoO3 redox mediator shows both a large capacity of 204 mAh g−1 and fast hydrogen production at a current rate of 10 A cm−2(≈153 A g−1), outperforming most of the previously reported solid-state redox mediators. 相似文献
175.
D. Raja Satish Fitsum Feyissa D. Ravi Kumar 《Materials and Manufacturing Processes》2017,32(12):1345-1352
Cryorolling is a severe plastic deformation (SPD) process used to obtain ultrafine-grained aluminum alloy sheets along with higher strength and hardness than in conventional cold rolling, but it results in poor formability. An alternative method to improve both strength and formability of cryorolled sheets by warm forming after cryorolling without any post-heat treatment is proposed in this work. The formability of cryorolled AA6061 Al alloy sheets in the warm working temperature range is characterized in terms of forming limit diagrams (FLDs) and limiting dome height (LDH). Strain distributions and thinning in biaxially stretched samples are studied. Hardness of the formed samples is correlated with ultimate tensile strength to estimate post-forming mechanical properties. The limit strains and LDH have been found to be higher than in the case of the conventional processing route (cold rolled, annealed and formed at room temperature), making this hybrid route capable of producing sheet metal parts of aluminum alloys with high strength and formability. In order to combine the advantages of enhanced formability and better post-forming strength than the conventional cold rolled and annealed sheets, warm forming at 250°C has been found to be suitable for this alloy in the temperature range that has been studied. 相似文献
176.
Andres Amador García-Granada Giovanni Gomez-Gras Ramón Jerez-Mesa Guillermo Reyes 《Materials and Manufacturing Processes》2017,32(11):1279-1289
Ball-burnishing induces compressive residual stresses on treated materials by the effect of plastic deformation. The result is an increase in the fatigue life of the treated part, retarding the initiation of cracks on the surface. Compressive residual stresses have been previously measured by X-ray diffraction near the surface, revealing considerably high values at the maximum analyzed depth, in relation to other finishing processes such as shot peening. However, the maximum analyzed depth is very limited by using this technique. In this paper, the incremental hole drilling (IHD) technique is tested to measure residual stresses, being able to reach a 2-mm measuring depth. To that objective, a commercial strain gage is used and calibrated using finite element model simulations. A second Finite Element Model based on material removal rate is developed to obtain the equations to calculate the strain release through IHD. Finally, residual stresses are measured experimentally with that technique on two different materials, confirming that ball-burnishing increases the compressive residual stresses in layers up to 0.5?mm deep for the testing conditions, which is a good response to industrial needs. The method proves to be suitable, simple and inexpensive way to measure the value of these tensions. 相似文献
177.
In this study, the very high cycle fatigue (VHCF) properties of 7050-T7451 aluminum alloy and its friction stir welding (FSW) butt welds have been investigated. The results show that the failure of FSW joints still occurs at 7.0 × 108 cycles. The fatigue properties of the FSW joints are superior to those of the base material, especially in the super long life regime. Most fatigue cracks initiate at the thermo-mechanically affected zone and heat affected zone on the advancing side of the FSW joints, and the susceptibility of these zones to fatigue is attributed to the metallurgical heterogeneity. 相似文献
178.
Duyao Zhang Shoujin Sun Dong Qiu Mark A. Gibson Matthew S. Dargusch Milan Brandt Ma Qian Mark Easton 《Advanced Engineering Materials》2018,20(5)
179.
First-principles calculations of binary Al compounds: Enthalpies of formation and elastic properties
Jiong Wang Shun-Li ShangYi Wang Zhi-Gang MeiYong-Feng Liang Yong Du Zi-Kui Liu 《Calphad》2011,35(4):562-573
Systematic first-principles calculations of energy vs. volume (E-V) and single crystal elastic stiffness constants (cij’s) have been performed for 50 Al binary compounds in the Al-X (X = Co, Cu, Hf, Mg, Mn, Ni, Sr, V, Ti, Y, and Zr) systems. The E-V equations of state are fitted by a four-parameter Birch-Murnaghan equation, and the cij’s are determined by an efficient strain-stress method. The calculated lattice parameters, enthalpies of formation, and cij’s of these binary compounds are compared with the available experimental data in the literature. In addition, elastic properties of polycrystalline aggregates including bulk modulus (B), shear modulus (G), Young’s modulus (E), B/G (bulk/shear) ratio, and anisotropy ratio are calculated and compared with the experimental and theoretical results available in the literature. The systematic predictions of elastic properties and enthalpies of formation for Al-X compounds provide an insight into the understanding and design of Al-based alloys. 相似文献
180.
The Al-Li-Zn system was critically assessed using the CALPHAD technique. The solution phases (liquid, bcc, fcc and hcp) were described by the substitutional solution model. The compounds Al2Li3 and Al4Li9 in the Al-Li system had homogeneity ranges of Zn and were treated as (Al,Zn)2Li3 and (Al,Zn)4Li9 in the Al-Li-Zn system, respectively. The compounds αLi2Zn3, βLi2Zn3, αLi2Zn5, βLi2Zn5 and αLiZn4 in the Li-Zn system had no solubility of the third component Al in the Al-Li-Zn system. A two-sublattice model (Al,Li,Zn)0.2(Al,Li,Zn)0.8 was applied to describe the compound βLiZn4 in the Al-Li-Zn system in order to cope with the order-disorder transition between hexagonal close-packed solution (hcp-A3) and βLiZn4 with the Mg-type structure. The ternary compound τ2 with a NaTl-type structure (B32) had the same structure with the compounds AlLi in the binary Al-Li system and LiZn in the binary Li-Zn system. In the present work, the three compounds AlLi, LiZn and τ2 were treated as one phase by a two-sublattice model (Al,Li,Zn)0.5(Al,Li,Zn)0.5 in order to cope with the order-disorder transition between B32(AlLi, LiZn and τ2) and body-centered cubic solid solution (bcc-A2). The ternary intermetallic compounds τ1 and τ3 in the Al-Li-Zn system were treated as the formula Li(Al,Zn)2 and (AlLi,Zn)Zn3, respectively. A set of self-consistent thermodynamic parameters describing the Gibbs energy of each individual phase as a function of composition and temperature in the Al-Li-Zn system was obtained. 相似文献