全文获取类型
收费全文 | 702639篇 |
免费 | 16769篇 |
国内免费 | 6069篇 |
专业分类
电工技术 | 16489篇 |
技术理论 | 11篇 |
综合类 | 7026篇 |
化学工业 | 106628篇 |
金属工艺 | 27815篇 |
机械仪表 | 25294篇 |
建筑科学 | 22113篇 |
矿业工程 | 5661篇 |
能源动力 | 19773篇 |
轻工业 | 57270篇 |
水利工程 | 7475篇 |
石油天然气 | 15608篇 |
武器工业 | 713篇 |
无线电 | 86619篇 |
一般工业技术 | 129614篇 |
冶金工业 | 118432篇 |
原子能技术 | 12855篇 |
自动化技术 | 66081篇 |
出版年
2022年 | 5528篇 |
2021年 | 9060篇 |
2020年 | 6888篇 |
2019年 | 7466篇 |
2018年 | 11151篇 |
2017年 | 11556篇 |
2016年 | 11803篇 |
2015年 | 9681篇 |
2014年 | 14576篇 |
2013年 | 35103篇 |
2012年 | 22605篇 |
2011年 | 29250篇 |
2010年 | 23667篇 |
2009年 | 25841篇 |
2008年 | 26441篇 |
2007年 | 25785篇 |
2006年 | 24164篇 |
2005年 | 21791篇 |
2004年 | 19352篇 |
2003年 | 18730篇 |
2002年 | 17425篇 |
2001年 | 17523篇 |
2000年 | 16541篇 |
1999年 | 17967篇 |
1998年 | 39607篇 |
1997年 | 27999篇 |
1996年 | 21657篇 |
1995年 | 16452篇 |
1994年 | 14257篇 |
1993年 | 13936篇 |
1992年 | 9995篇 |
1991年 | 9294篇 |
1990年 | 9016篇 |
1989年 | 8460篇 |
1988年 | 8025篇 |
1987年 | 6799篇 |
1986年 | 6500篇 |
1985年 | 7519篇 |
1984年 | 6810篇 |
1983年 | 6172篇 |
1982年 | 5692篇 |
1981年 | 5773篇 |
1980年 | 5361篇 |
1979年 | 5088篇 |
1978年 | 4929篇 |
1977年 | 5655篇 |
1976年 | 7263篇 |
1975年 | 4254篇 |
1974年 | 3984篇 |
1973年 | 4126篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
102.
C. Doga Demirhan William W. Tso Joseph B. Powell Efstratios N. Pistikopoulos 《American Institute of Chemical Engineers》2019,65(7):e16498
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019 相似文献
103.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
104.
105.
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which... 相似文献
106.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献
107.
针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。 相似文献
108.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
109.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
110.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献