全文获取类型
收费全文 | 4837篇 |
免费 | 526篇 |
国内免费 | 207篇 |
专业分类
电工技术 | 84篇 |
综合类 | 418篇 |
化学工业 | 1198篇 |
金属工艺 | 260篇 |
机械仪表 | 129篇 |
建筑科学 | 1333篇 |
矿业工程 | 94篇 |
能源动力 | 133篇 |
轻工业 | 204篇 |
水利工程 | 63篇 |
石油天然气 | 134篇 |
武器工业 | 15篇 |
无线电 | 281篇 |
一般工业技术 | 1043篇 |
冶金工业 | 105篇 |
原子能技术 | 47篇 |
自动化技术 | 29篇 |
出版年
2024年 | 11篇 |
2023年 | 79篇 |
2022年 | 87篇 |
2021年 | 118篇 |
2020年 | 156篇 |
2019年 | 182篇 |
2018年 | 158篇 |
2017年 | 174篇 |
2016年 | 202篇 |
2015年 | 218篇 |
2014年 | 316篇 |
2013年 | 277篇 |
2012年 | 403篇 |
2011年 | 390篇 |
2010年 | 272篇 |
2009年 | 352篇 |
2008年 | 245篇 |
2007年 | 351篇 |
2006年 | 294篇 |
2005年 | 244篇 |
2004年 | 173篇 |
2003年 | 135篇 |
2002年 | 154篇 |
2001年 | 109篇 |
2000年 | 98篇 |
1999年 | 76篇 |
1998年 | 59篇 |
1997年 | 66篇 |
1996年 | 41篇 |
1995年 | 31篇 |
1994年 | 29篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有5570条查询结果,搜索用时 15 毫秒
41.
42.
厚壁方矩形管冷弯效应对比分析 总被引:2,自引:0,他引:2
为了对厚壁型钢管的冷弯工艺改进、性能分析、结构强度设计和数值模拟结果的验证提供重要依据,进行了冷弯厚壁钢管上截取的平板件、弯角件、母材和相应方、矩形截面短柱的力学性能试验研究,获得了短柱全截面屈服强度相对于母材强度的提高值。分别运用北美等国厚壁冷弯型钢规范、国内薄壁冷弯型钢规范以及相关文献中的修正规范,对我国厚壁冷弯方矩形型钢管全截面强度进行设计和对比分析。结果表明:因冷弯工艺不同,国外公式计算的结果高于国内短柱实测值,国内厚壁冷弯型钢的强度设计不能照搬现有的国外厚壁冷弯型钢设计规范;国内薄壁公式能否适用要视型钢的冷作硬化效应程度决定;原料的强屈比和冷弯应变程度越大,则冷作硬化效应越大;焊接热使板件受到低温"退火"的作用不可忽略,其常常导致竖直配辊冷弯厚壁矩形型钢时,两竖直侧平板件强度低于母材。 相似文献
43.
44.
45.
46.
Cactus‐Like Hollow Cu2‐xS@Ru Nanoplates as Excellent and Robust Electrocatalysts for the Alkaline Hydrogen Evolution Reaction 下载免费PDF全文
Donghwan Yoon Jaeyoung Lee Bora Seo Byeongyoon Kim Hionsuck Baik Sang Hoon Joo Kwangyeol Lee 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(29)
The development of Pt‐free electrocatalysts for the hydrogen evolution reaction (HER) recently is a focus of great interest. While several strategies are developed to control the structural properties of non‐Pt catalysts and boost their electrocatalytic activities for the HER, the generation of highly reactive defects or interfaces by combining a metal with other metals, or with metal oxides/sulfides, can lead to notably enhanced catalytic performance. Herein, the preparation of cactus‐like hollow Cu2‐x S@Ru nanoplates (NPs) that contain metal/metal sulfide heterojunctions and show excellent catalytic activity and durability for the HER in alkaline media is reported. The initial formation of Ru islands on presynthesized Cu1.94S NPs, via cation exchange between three Cu+ ions and one Ru3+, induces the growth of the Ru phase, which is concomitant with the dissolution of the Cu1.94S nanotemplate, culminating in the formation of a hollow nanostructure with numerous thin Ru pillars. Hollow Cu2‐x S@Ru NPs exhibit a small overpotential of 82 mV at a current density of ?10 mA cm?2 and a low Tafel slope of 48 mV dec?1 under alkaline conditions; this catalyst is among state‐of‐the‐art HER electrocatalysts in alkaline media. The excellent performance of hollow Cu2‐x S@Ru NPs originates from the facile dissociation of water in the Volmer step. 相似文献
47.
Jingwu Zheng Feifan Song Shenglei Che Wangchang Li Yao Ying Jing Yu Liang Qiao 《Advanced Powder Technology》2018,29(6):1474-1480
In the present work, the porous hollow carbon spheres loaded with NiFe2O4 nanoparticles have been successfully prepared via ultrasonic spray pyrolysis technique at 700?°C and the associated formation mechanism has been studied. The as-prepared NiFe2O4/carbon microspheres with the diameter of about 3–5?µm and the specific surface area of 236.6889?m2?g?1 exhibit good monodispersity and an abundance of mesopores of about 40?nm size. Notably, the 20?nm NiFe2O4 nanoparticles are encapsulated by carbon microspheres and disperse homogeneously inside the carbon matrix. We could tune the relative content of ferrite and carbon sphere via adjusting the composition of the solution used for synthesis and the carbonization temperature. Consequently, some interesting properties can be obtained by combining the magnetic NiFe2O4 nano powder and the electrically conductive porous carbon, which renders the resulting composite suitable for promising applications in electromagnetic wave absorption, treatment of polluted water, catalyst design, energy storage, batteries and so on. 相似文献
48.
Donglin He Ping Li Wei Wang Qi Wan Jian Zhang Kai Xi Xiumei Ma Zhiwei Liu Lin Zhang Xuanhui Qu 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(5)
Although silicon‐based materials are ideal candidate anodes for high energy density lithium‐ion batteries, the large volumetric expansion seriously damages the integrity of the electrodes and impedes commercial processes. Reasonable electrode design based on adjustable structures of silicon and strong binders prepared by a facile method is still a great challenge. Herein, a three‐pronged collaborative strategy via hollow nanocubes, amorphous Void@SiOx@C, and in situ cross‐linked polyacrylic acid and d ‐sorbitol 3D network binder (c‐PAA‐DS) is adopted to maintain structural/electrode integrality and stability. The all‐integrated c‐PAA‐DS/Void@SiOx@C electrode delivers excellent mechanical property, which is attributed to ductility of the c‐PAA‐DS binder and high adhesion energy between Void@SiOx@C and c‐PAA‐DS calculated by density functional theory. Benefiting from the synergistic effect of accommodation of the hollow structure, protection of outer carbon shell, amorphous Void@SiOx@C, and strong adhesive c‐PAA‐DS binder, c‐PAA‐DS/Void@SiOx@C shows excellent electrochemical performance. Long cycling stability with a reversible capacity of 696 mAh g?1 is obtained, as well as tiny capacity decay after 500 cycles at 0.5 A g?1 and high‐rate performance. The prelithiated Void@SiOx@C||LiNi0.5Co0.2Mn0.3O2 (NCM523) full cell is also assembled and shows a reversible capacity of 157 mAh g?1 at 0.5 C, delivering an excellent capacity retention of 94% after 160 cycles. 相似文献
49.
50.