全文获取类型
收费全文 | 61547篇 |
免费 | 5787篇 |
国内免费 | 3212篇 |
专业分类
电工技术 | 3818篇 |
技术理论 | 1篇 |
综合类 | 5809篇 |
化学工业 | 9653篇 |
金属工艺 | 3124篇 |
机械仪表 | 3343篇 |
建筑科学 | 4527篇 |
矿业工程 | 1472篇 |
能源动力 | 1342篇 |
轻工业 | 7603篇 |
水利工程 | 1262篇 |
石油天然气 | 2176篇 |
武器工业 | 578篇 |
无线电 | 6343篇 |
一般工业技术 | 5946篇 |
冶金工业 | 4793篇 |
原子能技术 | 584篇 |
自动化技术 | 8172篇 |
出版年
2024年 | 299篇 |
2023年 | 982篇 |
2022年 | 1980篇 |
2021年 | 2472篇 |
2020年 | 1938篇 |
2019年 | 1546篇 |
2018年 | 1609篇 |
2017年 | 1840篇 |
2016年 | 1724篇 |
2015年 | 2450篇 |
2014年 | 3306篇 |
2013年 | 3709篇 |
2012年 | 4293篇 |
2011年 | 4756篇 |
2010年 | 4387篇 |
2009年 | 4193篇 |
2008年 | 4283篇 |
2007年 | 3968篇 |
2006年 | 3671篇 |
2005年 | 2954篇 |
2004年 | 2126篇 |
2003年 | 1703篇 |
2002年 | 1749篇 |
2001年 | 1453篇 |
2000年 | 1141篇 |
1999年 | 889篇 |
1998年 | 1308篇 |
1997年 | 843篇 |
1996年 | 635篇 |
1995年 | 481篇 |
1994年 | 355篇 |
1993年 | 322篇 |
1992年 | 129篇 |
1991年 | 146篇 |
1990年 | 101篇 |
1989年 | 93篇 |
1988年 | 91篇 |
1987年 | 62篇 |
1986年 | 60篇 |
1985年 | 43篇 |
1984年 | 12篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 30篇 |
1980年 | 42篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 97篇 |
1976年 | 175篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from... 相似文献
12.
Thermoresponsive behavior and rheology of SiO2–hyaluronic acid/poly(N‐isopropylacrylamide) (NaHA/PNIPAm) core–shell structured microparticles
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
13.
14.
15.
In this study, 0.95?Sr0.7Ba0.3Nb2O6-0.05CaTiO3-x wt% Er2O3 ceramics (SBNCTEx; x?=?0–5) were synthesized using traditional solid-state method, and we investigated the microstructure, energy storage properties as well as the relationship between dielectric breakdown strength and interfacial polarization. As compared with pure 0.95?Sr0.7Ba0.3Nb2O6-0.05CaTiO3 ceramics, the Er2O3 dopants suppressed the grain growth of SBNCTEx, and the doped ones showed the dense microstructure. The secondary phase was found for x?≥?1 according to the EDS results, and the influence of the secondary phase on relative dielectric breakdown strength has also been studied. The dielectric breakdown strength increased from 18.1?kV/mm to 34.4?kV/mm, which is good for energy storage. The energy storage density of 0.28?J/cm3 and the energy storage efficiency of 91.4% were obtained in the SBNCTE5 ceramics. The results indicate that SBNCTE ceramics can be used as energy storage capacitors. 相似文献
16.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献
17.
为提高稀疏表示跟踪模型性能,提出一种分段加权的反向稀疏跟踪算法,将跟踪问题转化为在贝叶斯框架下寻找概率最高的候选对象问题,构造不同的分段权重函数来分别度量候选目标与正负模板的判别特征系数。通过池化来降低跟踪结果的不确定性干扰,选择正负模板加权系数差值最大的候选表示作为跟踪结果。实验表明,在光照变化、遮挡、快速运动、运动模糊情况下,所提出的算法可以确保跟踪结果的准确性和鲁棒性。 相似文献
18.
性能效率是APP软件的重要质量属性,但目前缺乏APP软件性能效率的通用模型。分析了APP软件的性能特征,基于ISO/IEC 25010标准提出了APP软件的性能效率模型,定义了APP软件性能效率的子特性和度量指标。基于提出的APP软件性能效率模型,通过实验对APP软件的性能效率进行了度量及相关分析。 相似文献
19.
Junling Guo Huayu Pei Ying Dou Siyuan Zhao Guosheng Shao Jinping Liu 《Advanced functional materials》2021,31(18):2010499
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed. 相似文献
20.
A microchannel heat exchanger with a triangular wave and symmetrical triangular wave structure was proposed in this paper. In addition, a new N-type microchannel heat exchanger was developed to balance the heat transfer performance and pressure drop. The relationship between different configurations of the N structure of the microchannel and the heat transfer performance was analyzed. The results showed that, at a high inlet flow rate, the symmetrical triangular wave microchannel had the best heat transfer performance, followed by the triangular wave microchannel and the straight channel. At the same flow rate, the degree of disturbance of the fluid was highest in the symmetrical N-structure microchannel, and an excellent heat transfer effect was observed. 相似文献