全文获取类型
收费全文 | 10772篇 |
免费 | 916篇 |
国内免费 | 661篇 |
专业分类
电工技术 | 318篇 |
综合类 | 1104篇 |
化学工业 | 986篇 |
金属工艺 | 1353篇 |
机械仪表 | 431篇 |
建筑科学 | 2134篇 |
矿业工程 | 545篇 |
能源动力 | 300篇 |
轻工业 | 82篇 |
水利工程 | 1794篇 |
石油天然气 | 1981篇 |
武器工业 | 67篇 |
无线电 | 88篇 |
一般工业技术 | 514篇 |
冶金工业 | 413篇 |
原子能技术 | 64篇 |
自动化技术 | 175篇 |
出版年
2024年 | 55篇 |
2023年 | 142篇 |
2022年 | 322篇 |
2021年 | 373篇 |
2020年 | 367篇 |
2019年 | 297篇 |
2018年 | 300篇 |
2017年 | 348篇 |
2016年 | 387篇 |
2015年 | 379篇 |
2014年 | 596篇 |
2013年 | 542篇 |
2012年 | 766篇 |
2011年 | 733篇 |
2010年 | 511篇 |
2009年 | 569篇 |
2008年 | 542篇 |
2007年 | 680篇 |
2006年 | 715篇 |
2005年 | 610篇 |
2004年 | 503篇 |
2003年 | 455篇 |
2002年 | 389篇 |
2001年 | 343篇 |
2000年 | 261篇 |
1999年 | 229篇 |
1998年 | 158篇 |
1997年 | 166篇 |
1996年 | 105篇 |
1995年 | 118篇 |
1994年 | 98篇 |
1993年 | 62篇 |
1992年 | 56篇 |
1991年 | 34篇 |
1990年 | 36篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
1.
2.
Abrasive water jet technology can be used for micro-milling using recently developed miniaturized nozzles. Abrasive water jet (AWJ) machining is often used with both the nozzle tip and workpiece submerged in water to reduce noise and contain debris. This paper compares the performance of submerged and unsubmerged abrasive water jet micro-milling of channels in 316L stainless steel and 6061-T6 aluminum at various nozzle angles and standoff distances. The effect of submergence on the diameter and effective footprint of AWJ erosion footprints was measured and compared. It was found that the centerline erosion rate decreased with channel depth due to the spreading of the jet as the effective standoff distance increased, and because of the growing effect of stagnation as the channel became deeper. The erosive jet spread over a larger effective footprint in air than in water, since particles on the jet periphery were slowed much more quickly in water due to increased drag. As a result, the width of a channel machined in air was wider than that in water. Moreover, it was observed that the instantaneous erosion rate decreased with channel depth, and that this decrease was a function only of the channel cross-sectional geometry, being independent of the type of metal, the jet angle, the standoff distance, and regardless of whether the jet was submerged or in air, in either the forward or backward directions. It is shown that submerged AWJM results in narrower features than those produced while machining in air, without a decrease in centerline etch rate. 相似文献
3.
《Ceramics International》2022,48(8):10506-10515
The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm3. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities. 相似文献
4.
Shengyue Gu Shouyang Zhang Fei Liu Wei Li 《Journal of the European Ceramic Society》2018,38(15):5082-5091
Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m2 with the linear and mass ablation rates are 0.16?μm?s?1 and ?0.028?mg?s?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating. 相似文献
5.
6.
7.
琼东南盆地深水区经历了断陷、断拗和拗陷3大构造演化和沉积充填阶段,主要发育4种沉积体系,相应地形成了4类主要储层:1)陵三段扇三角洲或滨海相砂岩储层;2)三亚、梅山组滨浅海相砂岩储层;3)三亚—莺黄组低位体储层;4)梅山组台地边缘礁滩灰岩储层。平面上,储层发育具有明显的分带性,可划分为:北部浅水陆架滨岸砂岩、三角洲砂岩储层发育带;中央坳陷低位体储层发育带;南部永乐隆起区碳酸盐岩储层发育带。深水区主要位于后2个带,每个带储层发育的控制因素不同,可以进一步划分为多个储层发育区。每个储层发育区存在多套储盖组合,每套储盖组合在多个储层区中发育。其中台地灰岩储层可能成为南部隆起区具有重要意义的勘探层系。 相似文献
8.
9.
10.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献