全文获取类型
收费全文 | 116342篇 |
免费 | 9177篇 |
国内免费 | 4574篇 |
专业分类
电工技术 | 6472篇 |
技术理论 | 5篇 |
综合类 | 7898篇 |
化学工业 | 20279篇 |
金属工艺 | 6706篇 |
机械仪表 | 7116篇 |
建筑科学 | 9740篇 |
矿业工程 | 3223篇 |
能源动力 | 3078篇 |
轻工业 | 7888篇 |
水利工程 | 2155篇 |
石油天然气 | 6825篇 |
武器工业 | 892篇 |
无线电 | 12385篇 |
一般工业技术 | 13686篇 |
冶金工业 | 5530篇 |
原子能技术 | 1388篇 |
自动化技术 | 14827篇 |
出版年
2024年 | 325篇 |
2023年 | 1778篇 |
2022年 | 2831篇 |
2021年 | 4282篇 |
2020年 | 3349篇 |
2019年 | 2786篇 |
2018年 | 3193篇 |
2017年 | 3664篇 |
2016年 | 3149篇 |
2015年 | 4303篇 |
2014年 | 5508篇 |
2013年 | 6760篇 |
2012年 | 7496篇 |
2011年 | 8052篇 |
2010年 | 7017篇 |
2009年 | 6843篇 |
2008年 | 6617篇 |
2007年 | 6352篇 |
2006年 | 6590篇 |
2005年 | 5827篇 |
2004年 | 3931篇 |
2003年 | 3264篇 |
2002年 | 3006篇 |
2001年 | 2597篇 |
2000年 | 2886篇 |
1999年 | 3246篇 |
1998年 | 2621篇 |
1997年 | 2151篇 |
1996年 | 2175篇 |
1995年 | 1762篇 |
1994年 | 1424篇 |
1993年 | 1029篇 |
1992年 | 830篇 |
1991年 | 647篇 |
1990年 | 446篇 |
1989年 | 388篇 |
1988年 | 324篇 |
1987年 | 200篇 |
1986年 | 131篇 |
1985年 | 95篇 |
1984年 | 60篇 |
1983年 | 37篇 |
1982年 | 47篇 |
1981年 | 30篇 |
1980年 | 27篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1965年 | 2篇 |
1959年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
地质特征认识对煤层气开发效果起着重要作用。在资源特征相差不大的情况下,发现煤层气相邻井的产量差异仍较大。排除工程因素后,通过选取8类地质参数,细致比对了保德区块低产井与邻井的参数特征,筛查出其关键因素为煤层微幅构造与顶板封盖条件,其中以微幅构造为主。据此,重新认识并划分出区块新的次生褶皱背斜单元、向斜单元和斜坡单元,获得了不同次生褶皱构造单元的开发特征。结果表明,高、低产井分布与次生褶皱背斜、向斜相关性高达92%。其中:高产井主要分布在次生褶皱背斜变化较缓、呈隆起状的“平台”,且煤层顶板以泥岩、碳质泥岩为主,封盖性较好;低产井主要分布在次生褶皱向斜,同一井台各井开发效果差异表现为从向斜条带轴部—向斜条带内—向斜条带外的煤层气井平均单井产量不断增加,到向斜轴部的距离大于向斜曲率半径73.5%的范围为主力产气区,小于向斜曲率半径40.0%范围为产水主力区。这对煤层气新井部署、生产管理、开发调整等,具有一定的指导意义。 相似文献
92.
93.
94.
Shuangjian Li Xiaoqin Zhao Yulong An Duanduan Liu Huidi Zhou Jianmin Chen 《Ceramics International》2018,44(15):17864-17872
Thermal sprayed ceramic coatings have extensively been used in components to protect them against friction and wear. However, the poor lubricating ability severely limits their application. Herein, yttria-stabilized zirconia (YSZ)/MoS2 composite coatings were successfully fabricated on steel substrate with the combination of thermal spraying technology and hydrothermal reaction. Results show that the synthetic MoS2 powders are composed of numbers of ultra-thin sheets (about 7 ~ 8?nm), and the sheet has obvious lamellar structure. After vacuum impregnation and hydrothermal reaction, numbers of MoS2 powders, look like flowers, generate inside the plasma sprayed YSZ coating. Moreover, the growing point of the MoS2 flower is the intrinsic micro-pores of YSZ coating. The friction and wear tests under high vacuum environment indicate that the composite coating has an extremely long lifetime (>?100,000 cycles) and possesses a low friction coefficient less than 0.1, which is lower by about 0.15 times than that of YSZ coating. Meanwhile, the composite shows an extremely low wear rate (2.30?×?10?7 mm3 N?1 m?1) and causes slight wear damage to the counterpart. The excellent lubricant and wear-resistant ability are attributed to the formation of MoS2 transfer films and the ultra-smooth of the worn surfaces of hybrid coatings. 相似文献
95.
文章介绍了目前旋转式压缩机主要零部件的材料状况,详细论述了金属基复合材料、陶瓷基复合材料在旋转压缩机上的应用情况及前景,为复合材料在压缩机领域的应用提供指导。 相似文献
96.
Guankui Long Yecheng Zhou Mingtao Zhang Randy Sabatini Abdullah Rasmita Li Huang Girish Lakhwani Weibo Gao 《Advanced materials (Deerfield Beach, Fla.)》2019,31(17)
Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics. 相似文献
97.
Wang Lu-di Zhou Wei Xing Ying Liu Na Movahedipour Mahmood Zhou Xiao-guang 《浙江大学学报:C卷英文版》2019,20(3):405-413
Frontiers of Information Technology & Electronic Engineering - Reconstruction of a 12-lead electrocardiogram (ECG) from a serial 3-lead ECG has been researched in the past to satisfy the need... 相似文献
98.
Yejun Wu Bowen Yan Juan Zhou Huizhang Lian Xiaojun Yu Jianxin Zhao Hao Zhang Wei Chen Daming Fan 《Journal of food science》2020,85(10):3282-3292
99.
100.
Hechun Cao Hui Zheng Lining Fan Zifeng Cheng Jianwei Zhou Qiong Wu Peng Zheng Liang Zheng Yang Zhang 《International Journal of Applied Ceramic Technology》2020,17(2):813-822
In this study, yttrium iron garnet co-doped with Zn and Zr atoms with a chemical formula Y3ZnxZrxFe(5−2x)O12 (x = 0.0-0.3) has been successfully prepared by the solid-state reaction method. The effects of doping concentration on the microstructure, crystal structure, magnetic properties, and dielectric properties of Y3ZnxZrxFe(5−2x)O12 were investigated. The microstructure analysis indicates that co-doping of YIG with Zn and Zr can effectively reduce the grain size of the ceramic. The crystal structure results reveal that the doping concentration of Zn–Zr has substantial influence on the lattice parameters of YIG, such as, increases the lattice constant, crystal cell size, and interplanar spacing. However, the second phase of ZrO2 appears once x ≥ 0.15. Additionally, the dielectric properties of YIG ferrite can be regulated using this Zn–Zr co-doping method. Zn–Zr co-doping can improve the dielectric stability and reduce the dielectric loss at high temperature. The magnetization measurement shows that the saturation magnetization is stabilized at x < 0.15, and the magnetic loss is decreased with the increase in the doping concentration. Overall, the findings show that the ceramic with x = 0.1 exhibits better properties included high saturation magnetization (24.607 emu/g), low magnetic loss (0.0025 @ 1 MHz), and relatively low dielectric loss (496 @ 400°C). 相似文献