全文获取类型
收费全文 | 98032篇 |
免费 | 17285篇 |
国内免费 | 20441篇 |
专业分类
化学 | 42211篇 |
晶体学 | 2183篇 |
力学 | 4188篇 |
综合类 | 1915篇 |
数学 | 8868篇 |
物理学 | 26873篇 |
无线电 | 49520篇 |
出版年
2024年 | 542篇 |
2023年 | 1681篇 |
2022年 | 3617篇 |
2021年 | 3630篇 |
2020年 | 3242篇 |
2019年 | 3026篇 |
2018年 | 2941篇 |
2017年 | 4124篇 |
2016年 | 3441篇 |
2015年 | 4798篇 |
2014年 | 6051篇 |
2013年 | 7284篇 |
2012年 | 7836篇 |
2011年 | 8122篇 |
2010年 | 8004篇 |
2009年 | 8256篇 |
2008年 | 8668篇 |
2007年 | 8334篇 |
2006年 | 7759篇 |
2005年 | 6587篇 |
2004年 | 5225篇 |
2003年 | 3690篇 |
2002年 | 3347篇 |
2001年 | 3361篇 |
2000年 | 3327篇 |
1999年 | 1747篇 |
1998年 | 882篇 |
1997年 | 660篇 |
1996年 | 643篇 |
1995年 | 606篇 |
1994年 | 552篇 |
1993年 | 564篇 |
1992年 | 488篇 |
1991年 | 366篇 |
1990年 | 345篇 |
1989年 | 348篇 |
1988年 | 232篇 |
1987年 | 224篇 |
1986年 | 179篇 |
1985年 | 154篇 |
1984年 | 149篇 |
1983年 | 97篇 |
1982年 | 92篇 |
1981年 | 102篇 |
1980年 | 70篇 |
1979年 | 86篇 |
1978年 | 31篇 |
1977年 | 26篇 |
1976年 | 20篇 |
1959年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
63.
随着光纤通信技术的迅速发展,网络运维管理面临着前所未有的挑战。文中深入分析了人工智能如何优化光纤通信网络的运维管理。首先,提出了传统光纤通信网络运维中存在的问题。其次,详细分析了人工智能技术如深度学习、知识图谱及自动化流程等在光纤通信网络运维中的具体应用,以供参考。 相似文献
64.
In this paper, a dual-band and reflective polarization converter based on metasurface is proposed. Its unit cell is composed of two layers of metal plates separated by a dielectric substrate. The simulation results show that the proposed converter is able to convert x- or y-polarized incident waves into cross-polarized waves perfectly in frequency bands of 6.75—10.59 GHz and 17.78—19.61 GHz, and the polarization conversion ratio (PCR) is nearly 100%, which can also convert linearly polarized waves into circularly polarized waves at four frequencies. It can be widely used in applications of radar satellites, antenna design and telecommunication with the function of realizing polarization conversion in two bands and achieving high PCR simultaneously. 相似文献
65.
Ruiqi Li Lian Chen Qin Ji Qing Liang Ying Zhu Wei Fu Tianyou Chen Hongwei Duan Wenshan He Zushun Xu Xiaofang Dai Jinghua Ren 《Advanced functional materials》2023,33(37):2213292
Radiotherapy is identified as a crucial treatment for patients with glioblastoma, but recurrence is inevitable. The efficacy of radiotherapy is severely hampered partially due to the tumor evolution. Growing evidence suggests that proneural glioma stem cells can acquire mesenchymal features coupled with increased radioresistance. Thus, a better understanding of mechanisms underlying tumor subclonal evolution may develop new strategies. Herein, data highlighting a positive correlation between the accumulation of macrophage in the glioblastoma microenvironment after irradiation and mesenchymal transdifferentiation in glioblastoma are presented. Mechanistically, elevated production of inflammatory cytokines released by macrophages promotes mesenchymal transition in an NF-κB-dependent manner. Hence, rationally designed macrophage membrane-coated porous mesoporous silica nanoparticles (MMNs) in which therapeutic anti-NF-κB peptides are loaded for enhancing radiotherapy of glioblastoma are constructed. The combination of MMNs and fractionated irradiation results in the blockage of tumor evolution and therapy resistance in glioblastoma-bearing mice. Intriguingly, the macrophage invasion across the blood-brain barrier is inhibited competitively by MMNs, suggesting that these nanoparticles can fundamentally halt the evolution of radioresistant clones. Taken together, the biomimetic MMNs represent a promising strategy that prevents mesenchymal transition and improves therapeutic response to irradiation as well as overall survival in patients with glioblastoma. 相似文献
66.
67.
68.
69.
70.