全文获取类型
收费全文 | 10362篇 |
免费 | 1146篇 |
国内免费 | 483篇 |
专业分类
电工技术 | 58篇 |
综合类 | 465篇 |
化学工业 | 2563篇 |
金属工艺 | 3573篇 |
机械仪表 | 489篇 |
建筑科学 | 74篇 |
矿业工程 | 266篇 |
能源动力 | 90篇 |
轻工业 | 193篇 |
水利工程 | 4篇 |
石油天然气 | 246篇 |
武器工业 | 68篇 |
无线电 | 308篇 |
一般工业技术 | 1939篇 |
冶金工业 | 1544篇 |
原子能技术 | 76篇 |
自动化技术 | 35篇 |
出版年
2024年 | 32篇 |
2023年 | 189篇 |
2022年 | 337篇 |
2021年 | 361篇 |
2020年 | 466篇 |
2019年 | 364篇 |
2018年 | 356篇 |
2017年 | 445篇 |
2016年 | 374篇 |
2015年 | 435篇 |
2014年 | 585篇 |
2013年 | 629篇 |
2012年 | 636篇 |
2011年 | 716篇 |
2010年 | 527篇 |
2009年 | 560篇 |
2008年 | 404篇 |
2007年 | 676篇 |
2006年 | 681篇 |
2005年 | 595篇 |
2004年 | 519篇 |
2003年 | 390篇 |
2002年 | 307篇 |
2001年 | 259篇 |
2000年 | 203篇 |
1999年 | 172篇 |
1998年 | 150篇 |
1997年 | 110篇 |
1996年 | 104篇 |
1995年 | 68篇 |
1994年 | 71篇 |
1993年 | 36篇 |
1992年 | 49篇 |
1991年 | 33篇 |
1990年 | 40篇 |
1989年 | 35篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
通过粉末冶金法制备了Ti-xCr、Ti-yCu及Ti-xCr-yCu钛基材料,研究了Cr、Cu含量对其相组成、显微组织、压缩屈服强度、弹性模量以及切削加工性能的影响规律。结果表明:随Cr含量的增加,Ti-xCr钛基材料依次出现了Ti_4Cr、TiCr_2及Cr相,其压缩屈服强度表现出先增大后减小的趋势,当Cr含量为10%时其屈服强度达到最大值(710 MPa),同时,添加Cr元素有利于降低钛基材料的弹性模量,最低可达25 GPa。添加Cu元素的钛基材料,随Cu含量的增加,Ti_2Cu相增加,并且显微组织细化,屈服强度降低;弹性模量受Cu含量影响较小而受烧结温度影响较大。添加Cr和Cu元素的钛基材料,其显微组织主要为网篮组织,弹性模量低于纯钛,其中添加Cu元素有利于细化层片,添加Cr元素有利于细化等轴组织。此外,Cr含量为5%时,钛基材料具有较佳的切削加工性能。 相似文献
13.
Christopher Fleming 《工业材料与腐蚀》2019,70(9):1617-1632
Hexagonal boron nitride (h‐BN) coatings on Ti‐6Al‐4V substrates undergo complete decomposition in air at 900 °C. This fate is similar to that of this ceramic material on chromia‐former alloys, and unlike that of a mass of powder treated in isolation. As the ceramic and alloy oxidize concurrently, outwardly diffusing aluminum (III) ions but not the predominant titanium (IV) ions react with the boron trioxide that forms around the h‐BN basal plane peripheries. Resultant aluminum borate is incorporated into the growing scale and the boron trioxide diffusion barrier is depleted. By this mechanism, the oxidation of h‐BN is maintained at an enhanced rate, until both this material and its oxide completely decompose. Liberated nitrogen from the oxidation of h‐BN can enter the underlying scale as a randomly distributed solute in rutile solid solution. The post‐coating oxide‐atmosphere interface comprises elongated aluminum borate crystallites protruding through at the boundaries between 3–5 at% nitrogen‐doped rutile grains. It differs significantly from that of oxidized, uncoated Ti‐6Al‐4V, which is occupied by a thin α‐alumina layer atop rutile. This interface does not change with an additional 72 h of heat‐treatment. 相似文献
14.
The reduction of chromium-bearing vanadium–titanium magnetite sinter (CVTMS) by CO was investigated at 1123–1223?K. The reduction degree increased with increasing temperature. The isothermal reduction kinetics of CVTMS was analysed, according to Sharp analysis and ln–ln analysis, the kinetic mechanism of reduction process for all samples in different basicity can be represented as f(α)?=?1.61(1?α)[?ln(1?α)]1–1/1.61. The reaction activation energy of all samples (R?=?1.9, 2.1, 2.3, obtained according to the components of the materials burdening used in sintering process) at different reaction degrees were calculated by the model-free method. And the pre-exponential factors of reaction also were calculated by the mathematical method. The rate controlling step for the reduction process under the present reduction condition was chemical reaction. 相似文献
15.
16.
研究了轧制变形量及退火温度对T9S钛合金板材显微组织和室温力学性能的影响。结果表明:增加成品轧制变形量,板材组织破碎更充分,退火后形成等轴α相、拉长α相和晶间β相组织形貌,变形流线比较明显,板材室温强度和硬度升高,伸长率降低,弹性模量增加。随着退火温度升高,板材室温强度和硬度逐渐降低,伸长率逐渐提高,横向弹性模量逐渐减小,纵向弹性模量先增加后减小。经(750~790) ℃×45 min空冷退火处理后的板材可以获得较好的强度和塑性的匹配。 相似文献
17.
Meihua Hu Ning Bi Mingming Liu Shangsheng Li Taichao Su 《International Journal of Applied Ceramic Technology》2020,17(4):1629-1635
TiB2–B4C composites were in situ synthesized and consolidated by high pressure synthesis method from a mixture of TiC and B powders at the pressure and temperature of 5.0 GPa and 1500℃-1900℃. The phase composition, microstructure, density, hardness, thermal conductivity, and electrical resistivity of TiB2–B4C composites were analyzed. As the increase in the synthesis temperature, the products were TiB2 and B4C phases and that crystallinity improved. TiB2–B4C composites were dense without obvious pores. TiB2–B4C composites synthesized at 1800℃ obtained the optimized performance, including the relative density of 98.2%, the Vickers hardness of 31.7 ± 1.2 GPa with the load of 9.8 N, the thermal conductivity of 30.3 ± 0.7 W/(m K), and the electrical resistivity of 3.3 × 10−3 Ω cm, respectively. The grain size of the TiB2–B4C composites changed with the increase in synthesis temperature, leading to the changes in hardness, thermal conductivity, and electrical resistivity. 相似文献
18.
19.
Libo Mei Chunming Wang Yuhang Wei Sufen Xiao Yungui Chen 《International Journal of Hydrogen Energy》2018,43(14):7102-7107
The titanium dihydride (TiH2) powder metallurgy has been attracted a lot of attention, but TiH2 powder is difficult to press moulding. In this paper, the titanium hydride powder metallurgy including TiH2 and unsaturated titanium hydrides (TiH1.5) was investigated simultaneously compared with pure titanium metal powder metallurgy. The results indicates that the titanium hydride powder metallurgy is accompanied by the deoxidation self-purification effect during dehydrogenation process for both of TiH2 and TiH1.5, which have higher sintering density than pure titanium. There are the three stages relative to densification rate, namely the slow, rapid and full densification stages for all of three materials. The compressive yield strengths increase rapidly in the rapid densification stage and are unchangeable almost in the full densification stage after holding 2 h at 1300 °C. The titanium hydride powder metallurgy is helpful to obtain much better mechanical properties than the pure titanium metal powder metallurgy. Here the compressive yield strength of the as-sintered TiH2 compact with the maximum hydrogen content is the best but has very small difference compared with that of the as-sintered TiH1.5 compact after full sintering densification. 相似文献
20.
Yan-chun ZHU Qing-xue HUANG Xiao-hui SHI Mei-rong SHUAI Wei-dong ZENG Yong-qing ZHAO Zhi-quan HUANG Li-feng MA 《中国有色金属学会会刊》2018,28(8):1521-1529
The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25V-15Cr-0.3Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect (length-to-width) ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti5Si3 phase by TEM. 相似文献