全文获取类型
收费全文 | 20402篇 |
免费 | 1989篇 |
国内免费 | 1303篇 |
专业分类
电工技术 | 1442篇 |
综合类 | 1608篇 |
化学工业 | 3766篇 |
金属工艺 | 2906篇 |
机械仪表 | 1440篇 |
建筑科学 | 1111篇 |
矿业工程 | 402篇 |
能源动力 | 1291篇 |
轻工业 | 704篇 |
水利工程 | 246篇 |
石油天然气 | 323篇 |
武器工业 | 178篇 |
无线电 | 1343篇 |
一般工业技术 | 3162篇 |
冶金工业 | 1288篇 |
原子能技术 | 188篇 |
自动化技术 | 2296篇 |
出版年
2024年 | 82篇 |
2023年 | 315篇 |
2022年 | 418篇 |
2021年 | 573篇 |
2020年 | 647篇 |
2019年 | 606篇 |
2018年 | 534篇 |
2017年 | 690篇 |
2016年 | 651篇 |
2015年 | 638篇 |
2014年 | 1030篇 |
2013年 | 1170篇 |
2012年 | 1194篇 |
2011年 | 1583篇 |
2010年 | 1216篇 |
2009年 | 1301篇 |
2008年 | 1186篇 |
2007年 | 1508篇 |
2006年 | 1270篇 |
2005年 | 1031篇 |
2004年 | 952篇 |
2003年 | 794篇 |
2002年 | 733篇 |
2001年 | 613篇 |
2000年 | 527篇 |
1999年 | 440篇 |
1998年 | 384篇 |
1997年 | 310篇 |
1996年 | 247篇 |
1995年 | 218篇 |
1994年 | 201篇 |
1993年 | 136篇 |
1992年 | 108篇 |
1991年 | 77篇 |
1990年 | 72篇 |
1989年 | 62篇 |
1988年 | 37篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1964年 | 3篇 |
1956年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
We propose all printed and highly stable organic resistive switching device (ORSD) based on graphene quantum dots (G-QDs) and polyvinylpyrrolidone (PVP) composite for non-volatile memory applications. It is fabricated by sandwiching G-QDs/PVP composite between top and bottom silver (Ag) electrodes on a flexible substrate polyethylene terephthalate (PET) at ambient conditions through a cost effective and eco-friendly electro-hydrodynamic (EHD) technique. Thickness of the active layer is measured around 97 nm. The proposed ORSD is fabricated in a 3 × 3 crossbar array. It operates switching between high resistance state (HRS) and low resistance state (LRS) with OFF/ON ratio ∼14 for more than 500 endurance cycles, and retention time for more than 30 days. The switching voltage for set/reset of the devices is ±1.8 V and the bendability down to 8 mm diameter for 1000 cycles are tested. The elemental composition and surface morphology are characterized by XPS, FE-SEM, and microscope. 相似文献
3.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
4.
A vacuum-annealed La0.6Ca0.4CoO3−x was consecutively oxygenated in air at temperatures decreasing from 800 to 100 °C, and its electrocatalytic activities for oxygen reduction and evolution were then measured as a function of the oxygenation temperature. The valence of Co cation, changing between +2 and +3, was found susceptible to annealing either in vacuum or air. The catalytic activities initially decrease monotonically as the oxygenation temperature was decreased from 800 to 300 °C, as a result of increasing oxygen content, and then rise abruptly with the oxygen reduction activity reaching a maximum at 200 °C and the oxidation activity at 150 °C. X-ray photoelectron spectroscopy analysis indicated that the enhancements by the low-temperature oxygenation involved increased OH coverage and less charged cations at surface. The results clearly reveal the importance of the post-calcination annealing process for optimizing the performance of La0.6Ca0.4CoO3−x in air electrode applications. 相似文献
5.
6.
Effect of Stoichiometry on Properties of Rare-Earth-Based Hydrogen Storage Alloy for Nickel-Metal Hydride Secondary Battery 总被引:2,自引:0,他引:2
Effect of stoichiometry on microstructures, electrochemical properties and PCT characteristics of the alloys MI(Ni0.71Co0.15-Al0.06Mn0.08)x (MI=Lanthanum-rich Michmetal, x=4.6~5.2) have been investigated. The lattice constants a, c, and cellvolumes of non-stoichiometric alloys are bigger than those of the stoichiometric alloy. With the increasing stoichiometry x,the value of a decreases, and the value of c and cell volume increases except for those of the stoichiometric alloy; the plateaupressure of PCT curve, discharge capacity and cycling stability all increase. The alloy with x=5.2 shows the highest dischargecapacity and the best cycling stability among the studied alloys. 相似文献
7.
本文用计算机数字模拟方法研究了电活性分子多层Z型L-B膜修饰电极的循环伏安行为。计算了电极与修饰L-B膜分子第一层之间的电荷转移速度常数K_o,L-B膜分子层间的电荷转移速度常数k_i;对峰电位差△E_p及阳极峰面积Q的影响,以及在不同条件下各层分子的氧化态分数随扫描时间的变化。为研究和设计电活性分子修饰电极的实际体系提供了大量数据和信息。 相似文献
8.
9.
3D characterization and analysis of particle shape using X-ray microtomography (XMT) 总被引:2,自引:0,他引:2
C.L. Lin 《Powder Technology》2005,154(1):61-69
10.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献