全文获取类型
收费全文 | 50120篇 |
免费 | 6244篇 |
国内免费 | 4334篇 |
专业分类
电工技术 | 4503篇 |
综合类 | 4999篇 |
化学工业 | 6657篇 |
金属工艺 | 3075篇 |
机械仪表 | 3567篇 |
建筑科学 | 4258篇 |
矿业工程 | 1656篇 |
能源动力 | 1576篇 |
轻工业 | 5694篇 |
水利工程 | 1675篇 |
石油天然气 | 1473篇 |
武器工业 | 736篇 |
无线电 | 5756篇 |
一般工业技术 | 4842篇 |
冶金工业 | 1679篇 |
原子能技术 | 871篇 |
自动化技术 | 7681篇 |
出版年
2024年 | 288篇 |
2023年 | 826篇 |
2022年 | 1963篇 |
2021年 | 2604篇 |
2020年 | 1784篇 |
2019年 | 1267篇 |
2018年 | 1400篇 |
2017年 | 1573篇 |
2016年 | 1435篇 |
2015年 | 2277篇 |
2014年 | 2740篇 |
2013年 | 3188篇 |
2012年 | 4096篇 |
2011年 | 4208篇 |
2010年 | 4088篇 |
2009年 | 3829篇 |
2008年 | 3953篇 |
2007年 | 3907篇 |
2006年 | 3615篇 |
2005年 | 2901篇 |
2004年 | 2186篇 |
2003年 | 1475篇 |
2002年 | 1427篇 |
2001年 | 1296篇 |
2000年 | 943篇 |
1999年 | 463篇 |
1998年 | 160篇 |
1997年 | 142篇 |
1996年 | 111篇 |
1995年 | 88篇 |
1994年 | 51篇 |
1993年 | 77篇 |
1992年 | 56篇 |
1991年 | 47篇 |
1990年 | 38篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 20篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1965年 | 5篇 |
1959年 | 10篇 |
1958年 | 1篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Wenlong Song Shoujun Wang Yang Lu Xuan Zhang Zixiang Xia Kai Sun Guangming Xin 《Ceramics International》2021,47(9):12631-12640
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed. 相似文献
2.
3.
一次性医用手套是能够防止人们交叉感染的常用防护用品。随着新冠肺炎疫情在全球范围的迅速蔓延,疫情防控一线以及广大普通民众对一次性医用手套的需求与日俱增,其标准也受到广泛关注。本文对中国国家标准涉及一次性使用医用手套的4项产品标准进行了解读,并分析它们与国外同种产品标准间的对应关系以及重点指标的差异。 相似文献
4.
5.
6.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
7.
提出一种基于随机光栅与高反射布拉格光栅(FBG)相结合的可调谐随机光纤激光器。利用980nm泵浦光源泵浦一段7m长的掺铒光纤(EDF)进行增益放大,由随机光栅提供随机反馈。随机光栅长7cm,具有约10000个折射率修改点,这些点由飞秒激光逐点写入,并沿光纤方向随机分布,两点相邻间隔小于10μm。同时,利用中心波长为1548nm的高反射FBG来组成半开放腔结构,实现了随机激光的输出。实验测得的泵浦阈值功率仅为18mW,斜率效率高达13.2%,并通过改变FBG的中心波长,实现了输出激光波长的可调谐,调谐范围为4.45nm(1548.04~1552.49nm)。得益于半开放式激光腔的设计和EDF的高增益,整个系统具有阈值低、效率高、结构简单等优点。 相似文献
8.
申浩 《苏州科技学院学报(工程技术版)》2015,(2):61-65
解释了跨界借鉴的含义,并阐述了其在建筑立面创新设计中运用的可能性和积极意义。通过案例分析,提出建筑立面跨界借鉴的内容和方式。 相似文献
9.
Lei He Yan Xuan Feng Zhang Xue Wang Huaqing Pan Junfeng Ren Meina Chen 《International Journal of Hydrogen Energy》2021,46(1):1096-1105
Bulk and surface properties of proton stability and transportation in Y and Nd co-doped BaCeO3 (BCYN), especially the effect of Nd segregation, were investigated by first-principles calculations. Since the structure of doped BaCeO3 at the operating temperature of proton-conducting has been unclear for a long time, we have summarized the latest experimental results and calculated the structure of the asymmetric BCYN for the first time. The results show that compared with Y, Nd doping promotes oxygen vacancy formation, however reduces proton stability. Our calculation can also provide a possible explanation for the formation of space charge layer at the grain boundary of doped BaCeO3 in experiment. Unlike the stable Y in BCYN, Nd is calculated to be easily segregated, which can facilitate both proton hydration and proton transportation near the surface. Moreover, Nd segregation at the grain boundary is predicted to be beneficial for proton transportation between grains. 相似文献
10.
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can... 相似文献