全文获取类型
收费全文 | 96501篇 |
免费 | 19839篇 |
国内免费 | 2938篇 |
专业分类
电工技术 | 4501篇 |
技术理论 | 1篇 |
综合类 | 4145篇 |
化学工业 | 26240篇 |
金属工艺 | 3411篇 |
机械仪表 | 4459篇 |
建筑科学 | 6919篇 |
矿业工程 | 1514篇 |
能源动力 | 2675篇 |
轻工业 | 10781篇 |
水利工程 | 1606篇 |
石油天然气 | 3018篇 |
武器工业 | 489篇 |
无线电 | 13980篇 |
一般工业技术 | 18205篇 |
冶金工业 | 3417篇 |
原子能技术 | 927篇 |
自动化技术 | 12990篇 |
出版年
2024年 | 248篇 |
2023年 | 919篇 |
2022年 | 1693篇 |
2021年 | 2672篇 |
2020年 | 3178篇 |
2019年 | 4585篇 |
2018年 | 4596篇 |
2017年 | 5150篇 |
2016年 | 5445篇 |
2015年 | 6090篇 |
2014年 | 6686篇 |
2013年 | 8348篇 |
2012年 | 6482篇 |
2011年 | 6478篇 |
2010年 | 6218篇 |
2009年 | 5974篇 |
2008年 | 5391篇 |
2007年 | 5150篇 |
2006年 | 4939篇 |
2005年 | 4144篇 |
2004年 | 3415篇 |
2003年 | 3234篇 |
2002年 | 3386篇 |
2001年 | 2840篇 |
2000年 | 2562篇 |
1999年 | 1934篇 |
1998年 | 1330篇 |
1997年 | 1096篇 |
1996年 | 1008篇 |
1995年 | 807篇 |
1994年 | 658篇 |
1993年 | 584篇 |
1992年 | 423篇 |
1991年 | 321篇 |
1990年 | 307篇 |
1989年 | 213篇 |
1988年 | 186篇 |
1987年 | 117篇 |
1986年 | 97篇 |
1985年 | 65篇 |
1984年 | 56篇 |
1983年 | 38篇 |
1982年 | 40篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
本文将完全互补码(Complete Complementary Code, CCC)应用于多输入多输出(Multiple Input Multiple Output, MIMO)雷达目标探测中,针对具有非零多普勒的多目标检测问题,提出一种基于广义普洛黑-修-莫尔斯(Generalized Prouhet-Thue-Morse, GPTM)序列和二项式系数加权的信号处理方法。该方法分别在发射端和接收端进行处理,在发射端采用GPTM序列设计方法调整脉冲的发射顺序,以降低由多普勒引起的距离旁瓣;在接收端通过二项式设计(Binomial Design, BD)方法为各接收脉冲加上不同权重,扩大目标多普勒附近的清洁区。为综合上述两次处理的优势,将两次处理得到的距离多普勒谱进行逐点最小化处理,得到最终的距离多普勒谱,然后进行有序恒虚警检测。仿真结果表明,本文所提的信号处理方法具有良好的旁瓣抑制效果和多普勒分辨率,能够有效检测出非零多普勒目标。 相似文献
2.
Kelin Hu Feipeng Wang Yuyang Yan Hongcheng Liu Zijia Shen 《Ceramics International》2021,47(11):15228-15236
In this paper, a novel hybrid structure of Pd doped ZnO/SnO2 heterojunction nanofibers with hexagonal ZnO columns was one step synthesized from electrospun precursor nanofibers. Due to the synergistic effect of hexagonal ZnO, SnO2 and Pd, the structure exhibited excellent hydrogen (H2) gas sensing properties. At low-temperature of 120 °C, the response (Ra/Rg) to 100 ppm H2 gas exceeded 160, the response/recovery time was only 20 s and 6 s respectively and the limit of detection was only 0.5 ppm. Meanwhile, it also had good selectivity for H2 gas and excellent linearity. In addition, the materials were characterized by XRD, FESEM, HRTEM, XPS, and the synthesis mechanism and gas sensing mechanism were proposed. 相似文献
3.
4.
Bijan Nasri‐Nasrabadi Akif Kaynak Shayan Seyedin Zahra Komeily‐Nia Abbas Z Kouzani 《Polymer International》2019,68(5):922-928
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry 相似文献
5.
6.
Sheng Mingming Yang Rongkun Gong Hongyu Zhang Yujun Lin Xiao Jing Jie 《Journal of Materials Science》2022,57(10):5805-5824
Journal of Materials Science - With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of... 相似文献
7.
Yajing Qi Yuying Yang Alkassoumi Hassane Hamadou Qiuyun Shen Bin Xu 《International Journal of Food Science & Technology》2022,57(4):2104-2112
Wheat bran is rich in functional ingredients, but the high level of lipase limits its applications. Tempering–preservation treatment (at 70–90 °C with moisture of 20%–40% for 1–4 h) was exploited for stabilising wheat bran and its effect on polyphenols was investigated. The results showed that more lipase was inactivated at higher tempering moisture, temperature and longer time. The optimum condition for inactivation of wheat bran lipase was 30% moisture and 90 °C for 4 h. The inactivation rate reached 93.8% with a residual enzyme activity of 0.264 U g−1. Under the optimum condition, the sum of free phenolic acids rose from 25.4 to 55.8 µg g−1. As for bound phenolic acids, there was a slight increase of hydroxybenzoic acid derivatives but a slight decrease of hydroxycinnamic acid derivatives. The total contents of phenolic acids before and after stabilisation were not significantly different. This study showed the possibility of using tempering–preservation as an efficient method for inactivation of wheat bran lipase while maintaining its phenolic compounds, which could be used in the production of whole wheat flour. 相似文献
8.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production. 相似文献
9.
Telecommunication Systems - Machine to Machine technology has a broad application prospect in the 5G network, but there is a bottleneck in the energy consumption of intelligent devices powered by... 相似文献
10.
Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl3) and hexamethyldisilazane (HN(SiMe3)2) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl3 and HN(SiMe3)2 to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl3 and HN(SiMe3)2 alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl3 with more heat released compared to that for the introduction of HN(SiMe3)2. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions. 相似文献