全文获取类型
收费全文 | 78750篇 |
免费 | 8856篇 |
国内免费 | 5105篇 |
专业分类
电工技术 | 3618篇 |
综合类 | 6023篇 |
化学工业 | 14112篇 |
金属工艺 | 10474篇 |
机械仪表 | 7210篇 |
建筑科学 | 4123篇 |
矿业工程 | 2479篇 |
能源动力 | 2428篇 |
轻工业 | 8245篇 |
水利工程 | 1770篇 |
石油天然气 | 2023篇 |
武器工业 | 819篇 |
无线电 | 7208篇 |
一般工业技术 | 11281篇 |
冶金工业 | 3793篇 |
原子能技术 | 1958篇 |
自动化技术 | 5147篇 |
出版年
2024年 | 332篇 |
2023年 | 1550篇 |
2022年 | 2317篇 |
2021年 | 2915篇 |
2020年 | 3040篇 |
2019年 | 2812篇 |
2018年 | 2697篇 |
2017年 | 3181篇 |
2016年 | 3098篇 |
2015年 | 3261篇 |
2014年 | 4461篇 |
2013年 | 5275篇 |
2012年 | 5642篇 |
2011年 | 5984篇 |
2010年 | 4204篇 |
2009年 | 4322篇 |
2008年 | 4018篇 |
2007年 | 5089篇 |
2006年 | 4556篇 |
2005年 | 3685篇 |
2004年 | 3196篇 |
2003年 | 2652篇 |
2002年 | 2351篇 |
2001年 | 1962篇 |
2000年 | 1751篇 |
1999年 | 1435篇 |
1998年 | 1156篇 |
1997年 | 1047篇 |
1996年 | 939篇 |
1995年 | 697篇 |
1994年 | 622篇 |
1993年 | 527篇 |
1992年 | 418篇 |
1991年 | 280篇 |
1990年 | 276篇 |
1989年 | 204篇 |
1988年 | 173篇 |
1987年 | 86篇 |
1986年 | 99篇 |
1985年 | 78篇 |
1984年 | 66篇 |
1983年 | 54篇 |
1982年 | 75篇 |
1981年 | 37篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 7篇 |
1976年 | 3篇 |
1959年 | 10篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
电器外壳制品形状结构复杂,有两处侧凸(孔)较难处理。通过对矩形孔内侧凸的结构分析,在其局部设计了分型面,避免了使用侧向抽芯机构;对侧孔部位设计了斜顶杆侧向抽芯机构,其结构简单、紧凑。模具采用一模二腔、平衡式布局,采用经扁推杆由制品内部进料的潜伏式浇口,S型流道。在NX 8.0中完成了模具结构设计。经实践证明,该模具结构合理,产品合格。 相似文献
43.
We model developable surfaces by wrapping a planar figure around cones and cylinders. Complicated developables can be constructed by successive mappings using cones and cylinders of different sizes and shapes. We also propose an intuitive control mechanism, which allows a user to select an arbitrary point on the planar figure and move it to a new position. Numerical techniques are then used to find a cone or cylinder that produces the required mapping. Several examples demonstrate the effectiveness of our technique. 相似文献
44.
45.
46.
In this research, the three‐dimensional structural and colorimetric modeling of three‐dimensional woven fabrics was conducted for accurate color predictions. One‐hundred forty single‐ and double‐layered woven samples in a wide range of colors were produced. With the consideration of their three‐dimensional structural parameters, three‐dimensional color prediction models, K/S‐, R‐, and L*a*b*‐based models, were developed through the optimization of previous two‐dimensional models which have been reported to be the three most accurate models for single‐layered woven structures. The accuracy of the new three‐dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔECMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two‐dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔECMC(2:1) from 10.30 to 5.25 units on average after the three‐dimensional modeling. 相似文献
47.
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
48.
目的: 建立快速灵敏的LC-MS/MS法测定人血浆中阿莫西林浓度,并用于两种阿莫西林胶囊的一致性评价。方法: 采用岛津公司LCMS-8060型LC-MS/MS仪,以MRM模式测定阿莫西林(m/z 366.00/114.00)的浓度,d4-阿莫西林作内标(m/z 370.10/114.05),离子源为ESI源。色谱柱选用Waters ACQUITY BEH C18(2.1×50 mm,1.7 μm),梯度洗脱。血浆样本加入内标,经甲醇沉淀蛋白后取上清液进样检测。结果: 所建方法经验证,其线性、准确度、精密度、最低定量限、提取回收率、特异性、基质效应、稳定性等各项指标均符合CFDA的指导原则及最新核查标准要求,并较文献报道中的方法有处理简单、灵敏度高、色谱峰形好的优点。结论: 所建方法快速、灵敏,适用于人血浆中阿莫西林浓度的检测。用于一致性评价的样本实测,两种制剂生物等效。 相似文献
49.
50.
Enhanced gravity, or centrifugal, separators have revolutionised gold processing over the past decades, significantly increasing the recovery of fine (−100 μm) free gold. One of the main drawbacks of centrifugal gravity concentrators is the large volume of water required (even if it is all recycled). With water becoming an ever increasingly important “commodity”, reducing this is of importance both from an environmental and a monetary point of view. This work investigated operating a laboratory scale Knelson Concentrator with a dry feed and using air as the fluidising medium. The feed used was a synthetic mixture of tungsten and quartz, used to mimic a gold ore. The response surface method and central composite design techniques were used to design the experiments and to model the results, with the experimental variables being the bowl speed (G-Level), air fluidising pressure and the feed rate. The models corresponded well to the experimental results, indicating that for this experimental setup, the optimal conditions were a bowl G-Level of 40 G, a feed rate of 220 g/min and an air fluidising pressure of 8 psi. 相似文献