全文获取类型
收费全文 | 37971篇 |
免费 | 2817篇 |
国内免费 | 1072篇 |
专业分类
电工技术 | 1495篇 |
技术理论 | 1篇 |
综合类 | 1360篇 |
化学工业 | 6706篇 |
金属工艺 | 1621篇 |
机械仪表 | 1760篇 |
建筑科学 | 2651篇 |
矿业工程 | 736篇 |
能源动力 | 1035篇 |
轻工业 | 2755篇 |
水利工程 | 614篇 |
石油天然气 | 1349篇 |
武器工业 | 217篇 |
无线电 | 3359篇 |
一般工业技术 | 5254篇 |
冶金工业 | 5233篇 |
原子能技术 | 508篇 |
自动化技术 | 5206篇 |
出版年
2023年 | 478篇 |
2022年 | 881篇 |
2021年 | 1188篇 |
2020年 | 968篇 |
2019年 | 895篇 |
2018年 | 965篇 |
2017年 | 1057篇 |
2016年 | 1035篇 |
2015年 | 1313篇 |
2014年 | 1694篇 |
2013年 | 2564篇 |
2012年 | 2208篇 |
2011年 | 2280篇 |
2010年 | 1960篇 |
2009年 | 1813篇 |
2008年 | 1934篇 |
2007年 | 1926篇 |
2006年 | 1699篇 |
2005年 | 1524篇 |
2004年 | 1091篇 |
2003年 | 1035篇 |
2002年 | 978篇 |
2001年 | 733篇 |
2000年 | 638篇 |
1999年 | 611篇 |
1998年 | 554篇 |
1997年 | 496篇 |
1996年 | 499篇 |
1995年 | 488篇 |
1994年 | 398篇 |
1993年 | 392篇 |
1992年 | 363篇 |
1991年 | 225篇 |
1990年 | 290篇 |
1989年 | 320篇 |
1988年 | 245篇 |
1987年 | 239篇 |
1986年 | 245篇 |
1985年 | 283篇 |
1984年 | 274篇 |
1983年 | 239篇 |
1982年 | 230篇 |
1981年 | 229篇 |
1980年 | 182篇 |
1979年 | 197篇 |
1978年 | 183篇 |
1977年 | 187篇 |
1976年 | 170篇 |
1975年 | 188篇 |
1974年 | 175篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
为提高低信噪比下高分辨一维距离像目标识别性能,提出扩展稀疏表示的噪声稳健目标特征提取方法。本方法通过对稀疏表示的扩展,实现对目标高分辨一维距离像局部特征与全局特征的提取。其中,在训练阶段利用支持向量理论与字典学习原理,对特征提取字典进行优化提高特征向量的可分性。在测试阶段,利用因子分析模型匹配方法对去噪声字典进行优化,从而实现对噪声的有效抑制,保证了目标识别系统的噪声稳健性。利用实测数据对本方法性能进行测试,结果表明本方法可在低信噪比条件下有效地恢复目标高分辨一维距离像,并实现较高的识别正确率。 相似文献
12.
13.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
14.
15.
Sarah Gilgunn Keefe Murphy Henning Stckmann Paul J. Conroy T. Brendan Murphy R. William Watson Richard J. OKennedy Pauline M. Rudd Radka Saldova 《International journal of molecular sciences》2020,21(23)
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies. 相似文献
16.
17.
18.
19.
<正>悉尼理工大学工程和计算机系系馆位于市区的显赫地段,旨在重新给大学城市校区注入活力,成为悉尼商务中心南端的门户。建筑本体如同一件雕塑作品,迥然和周围的传统建筑风格相异。建筑地上14层,地下4层,设有先进的演讲厅、学术办公室、会议室、学习和研究实验室、营业咖啡厅、娱乐区、停车场,并在隔壁建筑旁设计自行车停靠处。 相似文献
20.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献