全文获取类型
收费全文 | 176500篇 |
免费 | 16658篇 |
国内免费 | 8978篇 |
专业分类
电工技术 | 12453篇 |
技术理论 | 11篇 |
综合类 | 12562篇 |
化学工业 | 28214篇 |
金属工艺 | 9934篇 |
机械仪表 | 11501篇 |
建筑科学 | 14635篇 |
矿业工程 | 5571篇 |
能源动力 | 5166篇 |
轻工业 | 11926篇 |
水利工程 | 3645篇 |
石油天然气 | 10069篇 |
武器工业 | 1859篇 |
无线电 | 20625篇 |
一般工业技术 | 19569篇 |
冶金工业 | 7801篇 |
原子能技术 | 2130篇 |
自动化技术 | 24465篇 |
出版年
2024年 | 681篇 |
2023年 | 2876篇 |
2022年 | 5334篇 |
2021年 | 7773篇 |
2020年 | 5809篇 |
2019年 | 4712篇 |
2018年 | 5133篇 |
2017年 | 5875篇 |
2016年 | 5086篇 |
2015年 | 7494篇 |
2014年 | 9111篇 |
2013年 | 10800篇 |
2012年 | 12384篇 |
2011年 | 13122篇 |
2010年 | 11651篇 |
2009年 | 11116篇 |
2008年 | 10782篇 |
2007年 | 9967篇 |
2006年 | 9986篇 |
2005年 | 8584篇 |
2004年 | 5783篇 |
2003年 | 4631篇 |
2002年 | 4318篇 |
2001年 | 3878篇 |
2000年 | 3917篇 |
1999年 | 3919篇 |
1998年 | 3118篇 |
1997年 | 2674篇 |
1996年 | 2470篇 |
1995年 | 2146篇 |
1994年 | 1679篇 |
1993年 | 1226篇 |
1992年 | 1021篇 |
1991年 | 759篇 |
1990年 | 571篇 |
1989年 | 483篇 |
1988年 | 395篇 |
1987年 | 267篇 |
1986年 | 178篇 |
1985年 | 100篇 |
1984年 | 65篇 |
1983年 | 42篇 |
1982年 | 70篇 |
1981年 | 50篇 |
1980年 | 43篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1965年 | 3篇 |
1959年 | 13篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
针对顶梁部件焊接过程中的变形,采用ANSYS有限元分析的方式对焊接过程中的温度场及变形进行仿真分析,结果显示,温度应力及残余应力的影响是产生变形的主要原因.针对顶梁的焊接变形,提出了相应的控制措施,以减小顶梁的焊接变形,提高液压支架的生产效率及性能,为煤矿的开采提供有效的理论支撑. 相似文献
93.
Zu Guoqing Lu Yukuan Yan Yi Zhang Xiaoming Zhao Jingwei Du Wei Ran Xu Jiang Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500... 相似文献
94.
95.
中央美院青岛创业中心项目为角部重叠的回字形山地建筑,采用了框架-剪力墙结构体系.主体建筑结构总高度为54m,坐落在三个台地上,每两个相邻台地高差10m左右.掉层处采用"掉层脱开式且有拉梁"的方式进行结构布置.结合山地建筑结构的基本概念和受力特点,介绍了本项目的结构处理方式和设计难点,采用PKPM,MIDAS Building,SAUSAGE软件对结构进行了弹性反应谱法分析、弹性时程分析、动力弹塑性时程分析和抗震性能设计,同时针对各种不利因素采取了相应的加强措施,确保了结构安全. 相似文献
96.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献
97.
以用户为中心的可见光通信协作传输是近年来出现的新架构,这导致虚拟小区之间出现重叠。为避免导频污染问题,每个虚拟小区中的光接入点(AP)或者虚拟小区中选择相同AP的用户发送的训练序列应该是正交的。针对可见光通信中以用户为中心的协作网络,研究训练资源的正交分配问题,提出了一种新的导频分配算法,联合导频分配和用户选择问题,以期最大限度地增加虚拟小区内可被接入的用户数。分析和仿真结果表明,该导频分配方案可以有效改善导频污染问题,提高训练资源利用率,并且相比已有的导频分配方案,性能有所改进。 相似文献
98.
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
99.
Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride) 下载免费PDF全文
Mengjiao Zhang Weihong Wu Shaorui He Xue Wang Yunhong Jiao Hongqiang Qu Jianzhong Xu 《Polymer International》2018,67(4):445-452
The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO3) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO3 and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO3. In addition, the incorporation of AC and MoO3 greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO3 was 10 phr, PVC/AC/MoO3 had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m?2 and 0.1472 m2 s?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO3, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO3 produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry 相似文献
100.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献