全文获取类型
收费全文 | 551篇 |
免费 | 82篇 |
国内免费 | 45篇 |
专业分类
综合类 | 31篇 |
化学工业 | 234篇 |
金属工艺 | 61篇 |
机械仪表 | 11篇 |
建筑科学 | 21篇 |
矿业工程 | 19篇 |
能源动力 | 7篇 |
轻工业 | 9篇 |
水利工程 | 4篇 |
石油天然气 | 93篇 |
武器工业 | 2篇 |
无线电 | 19篇 |
一般工业技术 | 111篇 |
冶金工业 | 49篇 |
原子能技术 | 5篇 |
自动化技术 | 2篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 29篇 |
2019年 | 34篇 |
2018年 | 30篇 |
2017年 | 32篇 |
2016年 | 30篇 |
2015年 | 22篇 |
2014年 | 22篇 |
2013年 | 27篇 |
2012年 | 31篇 |
2011年 | 26篇 |
2010年 | 29篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 21篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 30篇 |
2002年 | 23篇 |
2001年 | 29篇 |
2000年 | 15篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有678条查询结果,搜索用时 15 毫秒
1.
研制了一种新型微合金非调质钢。通过合理设计合金成分,改善熔炼脱氧过程,控制钢中氧化物的组成、分布、形状和尺寸,在研制钢中形成微细的氧化物夹杂作为晶内铁素体最有利的析出位置。通过晶内铁素体的析出细化了晶粒,提高了钢的强度与韧性。将研制的新型微合金非调质钢用于拖拉机的牵引插销是可行且有效的。 相似文献
2.
低碳微合金钢中的晶内铁素体及组织控制 总被引:1,自引:0,他引:1
回顾和评述了晶内铁素体的发现、发展及其与组织控制的关系.介绍了晶内铁素体的形核机制和影响晶内铁素体形成的因素,讨论了晶内铁素体的三维形态和长大动力学,并从以上几方面分析了晶内铁素体对低碳微合金钢组织细化的重要作用和影响. 相似文献
3.
Abstract— Initial fatigue crack propagation mechanisms at near threshold conditions were studied for four nickel-alloyed, powder-metallurgy (PM) steels. Fatigue fracture surfaces were obtained by testing smooth rectangular specimens at 30 Hz and under constant amplitude and zero mean stress conditions. Materials based on Distaloy AE were used in two densities, namely 7.15 and 7.45 g/cm3 .
All the fracture surfaces were composed of three morphological regions (i) a macrocrack initiation region Rl where cracks propagated preferentially through particles (ii) a macrocrack growth region R2 and (iii) an unstable crack growth region R3 where cracks propagated preferentially between particles. Initial fatigue crack growth, in region R1, was controlled by the propagation of short cracks whose dimensions were comparable to the material microstructure. The subsequent fatigue crack growth in regions R2 and R3 was controlled by ductile rupture between microvoids. Transparticle fracture in region R1 was independent of pore distribution, while interparticle fracture in regions R2 and R3 was dependent on pore distribution. 相似文献
All the fracture surfaces were composed of three morphological regions (i) a macrocrack initiation region Rl where cracks propagated preferentially through particles (ii) a macrocrack growth region R2 and (iii) an unstable crack growth region R3 where cracks propagated preferentially between particles. Initial fatigue crack growth, in region R1, was controlled by the propagation of short cracks whose dimensions were comparable to the material microstructure. The subsequent fatigue crack growth in regions R2 and R3 was controlled by ductile rupture between microvoids. Transparticle fracture in region R1 was independent of pore distribution, while interparticle fracture in regions R2 and R3 was dependent on pore distribution. 相似文献
4.
The solubility of sulfur in chromia has been studied in H2-H2O-H2S tagged with35S at 973 and 1173 K at low oxygen and sulfur partial pressures typical for coal gasification-systems. For monocrystalline samples, it has been shown that sulfur-containing species are only present adsorbed on the surface of the specimens and can be removed by ultrasonic cleaning in acetone. The surface coverage after 4 weeks of exposure to H2-H2O-H2S was between 2.8 and 19.3% of a monolayer. In polycrystalline chromia, sulfur was located only in pores and cracks of the sample. In dense, compact areas of the specimens the solubility of sulfur was below the detection limit of autoradiography, which was estimated to be better than 0.17 ppm. 相似文献
5.
Synthesis of Thermally Stable χ-Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene
Okorn Mekasuwandumrong Hiroshi Kominami Piyasan Praserthdam Masashi Inoue 《Journal of the American Ceramic Society》2004,87(8):1543-1549
Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumina. 相似文献
6.
Keizo Uematsu Jin-Young Kim Masayori Miyashita Nozomu Uchida Katsuichi Saito 《Journal of the American Ceramic Society》1990,73(8):2555-2557
The internal structure of spray-dried alumina granules was characterized by optical microscopy by immersing them in a liquid having a refractive index close to that of alumina. This method provides a unique technique for the detailed analysis of the internal structure of spray-dried granules. 相似文献
7.
8.
模铸非调质钢中铁素体在晶内MnS上的形成 总被引:1,自引:0,他引:1
为确认模铸非调质钢晶内铁素体的形成能力,对其钢材组织中的晶内铁素体相变形核位置作了光学显微镜观察,SEM/EDS和CMA分析。证实使钢中氧化物分散可调整MnS的大小和数量。模铸非调质钢中同样存在氧化物—MnS—V(C,N)复合夹杂物上形成晶内铁素体的过程。由于降低Mn量提高γ—α相变温度增加相变驱动力,相应增大了晶内铁素体形核概率,研究钢中铁素体在晶内MnS上的形核概率可大于0.9,明显优于现有研究结果,可弥补模铸钢铁素体形核位置的不足,获得理想的晶内铁素体组织。 相似文献
9.
Bolun Peng Quanqian Lyu Miaomiao Li Shuo Du Jintao Zhu Lianbin Zhang 《Advanced functional materials》2023,33(18):2214045
Solar steam generation (SSG) through hydrogel-based evaporators has shown great promise for freshwater production. However, developing hydrogel-based evaporators with stable SSG performance in high-salinity brines remains challenging. Herein, phase-separated polyzwitterionic hydrogel-based evaporators are presented with sponge-like structures comprising interconnected pores for stable SSG performance, which are fabricated by photopolymerization of sulfobetaine methacrylate (SBMA) in water-dimethyl sulfoxide (DMSO) mixed solvents. It is shown that driven by competitive adsorption, the structures of the resulting poly(sulfobetaine methacrylate) (PSBMA) hydrogels can be readily tuned by the volume ratio of DMSO to achieve phase separation. The optimized phase-separated PSBMA hydrogels, combining the unique anti-polyelectrolyte effects of polyzwitterionic hydrogels, demonstrate a rapid water transport capability in brines. After introducing photothermal polypyrrole particles on the surface of the phase-separated PSBMA hydrogel evaporators, a stable water evaporation rate of ≈2.024 kg m−2 h−1 and high solar-to-vapor efficiency of ≈97.5% in a 3.5 wt.% brine are obtained under simulated solar light irradiation (1.0 kW m−2). Surprisingly, the evaporation rates remain stable even under high-intensity solar irradiation (2.0 kW m−2). It is anticipated that the polyzwitterionic hydrogel evaporators with sponge-like porous structures will contribute to developing SSG technology for high-salinity seawater applications. 相似文献
10.
稀土和Ca、Mg元素对高强度钢焊接热影响区组织和韧性的影响 总被引:1,自引:0,他引:1
研究了低合金高强度非调质中厚板钢中添加稀土(REM)和Ca、Mg微量元素对大线高能焊接热影响区(HAZ)显微组织微细化和晶内针状铁素体(IAF)形成的影响.结果表明,添加REM和Ca、Mg元素可在钢的HAZ中形成弥散稳定的氧硫化物(CeCa)2O2S和(CeMg)2O2,热轧奥氏体化(1450℃)和焊接热输入10 kJ/mm时都十分稳定,比传统采用TiN强化的钢具有更优良的低温韧性.有效地控制细小弥散的氧硫化合物,能获得适中的奥氏体有效晶粒尺寸和提供HAZ中形成晶内针状铁素体及稳定活性的形核位置.促进晶内铁素体协同形核生长,有效地使得HAZ组织微细化. 相似文献