全文获取类型
收费全文 | 18701篇 |
免费 | 1871篇 |
国内免费 | 561篇 |
专业分类
电工技术 | 5504篇 |
综合类 | 935篇 |
化学工业 | 3619篇 |
金属工艺 | 911篇 |
机械仪表 | 807篇 |
建筑科学 | 1058篇 |
矿业工程 | 449篇 |
能源动力 | 2190篇 |
轻工业 | 259篇 |
水利工程 | 269篇 |
石油天然气 | 1035篇 |
武器工业 | 233篇 |
无线电 | 808篇 |
一般工业技术 | 1579篇 |
冶金工业 | 660篇 |
原子能技术 | 99篇 |
自动化技术 | 718篇 |
出版年
2024年 | 83篇 |
2023年 | 269篇 |
2022年 | 627篇 |
2021年 | 661篇 |
2020年 | 826篇 |
2019年 | 594篇 |
2018年 | 498篇 |
2017年 | 766篇 |
2016年 | 868篇 |
2015年 | 733篇 |
2014年 | 1260篇 |
2013年 | 952篇 |
2012年 | 1302篇 |
2011年 | 1605篇 |
2010年 | 1101篇 |
2009年 | 1031篇 |
2008年 | 926篇 |
2007年 | 1163篇 |
2006年 | 1034篇 |
2005年 | 833篇 |
2004年 | 771篇 |
2003年 | 671篇 |
2002年 | 554篇 |
2001年 | 468篇 |
2000年 | 402篇 |
1999年 | 288篇 |
1998年 | 182篇 |
1997年 | 163篇 |
1996年 | 140篇 |
1995年 | 99篇 |
1994年 | 77篇 |
1993年 | 42篇 |
1992年 | 30篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1964年 | 1篇 |
1960年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Spherical LiNi1/3Co1/3Mn1/3O2 cathode particles were resynthesized by a carbonate co-precipitation method using spent lithium-ion batteries (LIBs) as a raw material. The physical characteristics of the Ni1/3Co1/3Mn1/3CO3 precursor, the (Ni1/3Co1/3Mn1/3)3O4 intermediate, and the regenerated LiNi1/3Co1/3Mn1/3O2 cathode material were investigated by laser particle-size analysis, scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), thermogravimetry–differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 was studied by continuous charge–discharge cycling and cyclic voltammetry. The results indicate that the regenerated Ni1/3Co1/3Mn1/3CO3 precursor comprises uniform spherical particles with a narrow particle-size distribution. The regenerated LiNi1/3Co1/3Mn1/3O2 comprises spherical particles similar to those of the Ni1/3Co1/3Mn1/3CO3 precursor, but with a narrower particle-size distribution. Moreover, it has a well-ordered layered structure and a low degree of cation mixing. The regenerated LiNi1/3Co1/3Mn1/3O2 shows an initial discharge capacity of 163.5 mA h g?1 at 0.1 C, between 2.7 and 4.3 V; the discharge capacity at 1 C is 135.1 mA h g?1, and the capacity retention ratio is 94.1% after 50 cycles. Even at the high rate of 5 C, LiNi1/3Co1/3Mn1/3O2 delivers the high capacity of 112.6 mA h g?1. These results demonstrate that the electrochemical performance of the regenerated LiNi1/3Co1/3Mn1/3O2 is comparable to that of a cathode synthesized from fresh materials by carbonate co-precipitation. 相似文献
12.
《Energy Policy》2015
The low price of lead-acid, the most popular battery, is often used in setting cost targets for emerging energy storage technologies. Future cost reductions in lead acid batteries could increase investment and time scales needed for emerging storage technologies to reach cost-parity. In this paper the first documented model of cost reductions for lead-acid batteries is developed. Regression to a standard experience curve using 1989–2012 data yield a poor fit, with R2 values of 0.17 for small batteries and 0.05 for larger systems. To address this problem, battery costs are separated into material and residual costs, and experience curves developed for residual costs. Depending on the year, residual costs account for 41–86% of total battery cost. Using running-time averages to address volatility in material costs, a 4-year time average experience curve for residual costs yield much higher R2, 0.78 for small and 0.74 for large lead-acid batteries. The learning rate for residual costs in lead-acid batteries is 20%, a discovery with policy implications. Neglecting to consider cost reductions in lead-acid batteries could result in failure of energy storage start-ups and public policy programs. Generalizing this result, learning in incumbent technologies must be understood to assess the potential of emerging ones. 相似文献
13.
分析了蓄电池组在使用过程受损的原因,介绍了一种蓄电池组在线修复的新技术,即扫描共振频率技术的基本工作原理,并进一步分析、介绍了该在线修复方法所采用的主要新技术和独特的优点。 相似文献
14.
15.
16.
超级电容器在汽车启动中的应用 总被引:2,自引:0,他引:2
根据超级电容器的结构特性,介绍在汽车启动过程中如何利用超级电容器减小对车内其他电子设备的干扰,改善汽车的启动性能,延长蓄电池使用寿命. 相似文献
17.
上海秀派公司坚持自己的技术长项——2.45GHz有源RFID,充分发扬该种RFID的特长,记者采访该公司时了解到了开发方面的很多细节、成功案例和实施经验。我们不但非常推崇该公司的“锲而不舍”的意志,而且还意识到如果秀派公司的成功经验一旦辐射到中国的RFID行业中,一定会把这项在国外诞生的技术更好地植根于中国的土壤,使之更加适合中国的实用环境。 相似文献
18.
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
19.
20.