全文获取类型
收费全文 | 30047篇 |
免费 | 4639篇 |
国内免费 | 2369篇 |
专业分类
电工技术 | 2109篇 |
综合类 | 2361篇 |
化学工业 | 11568篇 |
金属工艺 | 1560篇 |
机械仪表 | 1821篇 |
建筑科学 | 1719篇 |
矿业工程 | 998篇 |
能源动力 | 883篇 |
轻工业 | 1077篇 |
水利工程 | 724篇 |
石油天然气 | 1017篇 |
武器工业 | 402篇 |
无线电 | 1562篇 |
一般工业技术 | 3657篇 |
冶金工业 | 922篇 |
原子能技术 | 491篇 |
自动化技术 | 4184篇 |
出版年
2024年 | 170篇 |
2023年 | 489篇 |
2022年 | 946篇 |
2021年 | 1130篇 |
2020年 | 1224篇 |
2019年 | 1035篇 |
2018年 | 1095篇 |
2017年 | 1329篇 |
2016年 | 1414篇 |
2015年 | 1488篇 |
2014年 | 2044篇 |
2013年 | 2270篇 |
2012年 | 2487篇 |
2011年 | 2421篇 |
2010年 | 1843篇 |
2009年 | 1876篇 |
2008年 | 1565篇 |
2007年 | 1872篇 |
2006年 | 1641篇 |
2005年 | 1368篇 |
2004年 | 1095篇 |
2003年 | 966篇 |
2002年 | 835篇 |
2001年 | 746篇 |
2000年 | 638篇 |
1999年 | 607篇 |
1998年 | 483篇 |
1997年 | 347篇 |
1996年 | 336篇 |
1995年 | 274篇 |
1994年 | 209篇 |
1993年 | 175篇 |
1992年 | 150篇 |
1991年 | 94篇 |
1990年 | 96篇 |
1989年 | 82篇 |
1988年 | 38篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 34篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 13篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1959年 | 9篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Ashraf Bastawros Abhijit Chandra Yongjin Guo Bo Yan 《Journal of Electronic Materials》2002,31(10):1022-1031
The role of a porous pad in controlling material-removal rate (MRR) during the chemical-mechanical planarization (CMP) process
has been studied numerically. The numerical results are used to develop a phenomenological model that correlates the forces
on each individual abrasive particle to the applied nominal pressure. The model provides a physical explanation for the experimentally
observed domains of pressure-dependent MRR, where the pad deformation controls the load sharing between active-abrasive particles
and direct pad-wafer contact. The predicted correlations between MRR and slurry characteristics, i.e., particle size and concentration,
are in agreement with experimentally measured trends reported by Ouma1 and Izumitani.2 相似文献
92.
93.
94.
The objective of the present study is to develop multi-functioned coating to the components, which are made of copper with electroplated Ni and are widely used for steel making industry. In this paper, we report the mechanical and thermal properties of Ni based superalloys with carbide sprayed by high velocity oxygen fuel (HVOF), and the detailed effects of sprayed material, spraying conditions, and initial powder structure on these properties. It was found that, among commercial Ni self-fluxing alloys (without fusing treatment), coating with a carbon content of 0.58 mass% had the most preferable properties, with a good balance of the hardness, strength, and thermal shock resistance. The thermal shock resistance depended not only on the strength of the coating but also on the volume contraction when tested at high temperatures. For the several developed Ni based superalloys with carbide, Ni20Cr8Mo5Fe–WC and Ni16Cr15Mo3–WC demonstrated the prominent adhesion strength and thermal shock resistance with high Galvanic corrosion resistance through optimized spraying condition. Also, 20 mass% NiCr–Cr3C2 coating sprayed by using employed relatively small primary particle succeeded in achieving the multi-superior properties; high adhesion strength, high corrosion resistance and thermal shock resistance. 相似文献
95.
Ground rubber tire (GRT) powder was maleated in an internal mixer using maleic anhydride and dicumyl peroxide at 160°C. Maleated GRT was characterized by using X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, wettability, and differential scanning calorimetry. The physical properties of the dynamically vulcanized 60 : 40, rubber : plastic composition based on acrylated high‐density polyethylene as the plastic phase and ethylene propylene diene rubber containing maleated GRT as the rubber phase were found to be greater than the corresponding composition containing nonmaleated GRT. The blend was found to be reprocessable, like themoplastic elastomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 370–378, 2002; DOI 10.1002/app.10348 相似文献
96.
丁腈橡胶/导电粒子复合材料的正温度系数(PTC)特性 总被引:7,自引:0,他引:7
将导电粒子碳黑和铜粉分别与丁腈橡胶混合制备导电聚合物复合材料,其中碳黑(N550)/丁腈橡胶复合材料的电阻率随温度的变化呈现较强的正温度系数(PTC)效应。讨论了掺入导电粒子浓度、结构和表面性质以及混炼硫化工艺等对该类材料的室温电阻率及PTC效应的影响。 相似文献
97.
Recent developments of high-performance NEOMAX magnets 总被引:6,自引:0,他引:6
For further improvement in achieving extremely high magnetic properties of Nd- Fe- B sintered magnets, extensive investigation
has been done to densify the magnet up to the theoretical value, to increase the volume fraction of the Nd
2Fe14B matrix phase, and to achieve a high degree of alignment. By controlling chemical composition and the amount of constituent
phases,improving particle size distribution, and adopting the isostatic pressing method to get better alignment of fine particles,
we have succeeded in obtaining a high-performance magnet having residual flux density (Br) of 1.495 T (14.95 kG), maximum energy product [(BH)max] of 431 kj/m3 (54.2 MGOe), and intrinsic coercivity (iHc) of 845 kA/m (10.62 kOe). 相似文献
98.
In close-coupled gas atomization(CCGA), the influences of melt superheat on breakup process are fundamental to obtain desired or finer powder. Based on a series of Cu atomization experiment under different superheating conditions, the influences of melt superheat on breakup process were studied. Experimental results indicate that as the melt superheat is increased to 150, 200, 250 and 300 K, the mean particle size (D50) decreases consequently to 34.9, 32.3, 30.9 and 19.7 μm. Theoretical analysis reveals that the primary breakup and secondary breakup processes are close coupled, and the melt superheat radically influences the melt properties, and plays a crucial role on governing the filming process of primary breakup and the atomization modes of secondary breakup. There exists a strong nonlinear decrease of contact angle of melt to nozzle orifice wall when the superheat is increased fi'om 250 K to 300 K, leading to a marked fall of the film thickness formed in primary breakup, and D50 of copper powders is therefore sharply reduced. However, the log-normal distribution feature of particle size has not been substantially improved. 相似文献
99.
T. M. Morris 《Journal of the Institute of Brewing》1987,93(1):13-17
Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values. 相似文献
100.