全文获取类型
收费全文 | 578730篇 |
免费 | 66422篇 |
国内免费 | 43634篇 |
专业分类
电工技术 | 51568篇 |
技术理论 | 2篇 |
综合类 | 61674篇 |
化学工业 | 71150篇 |
金属工艺 | 39459篇 |
机械仪表 | 40861篇 |
建筑科学 | 45197篇 |
矿业工程 | 23716篇 |
能源动力 | 15142篇 |
轻工业 | 57723篇 |
水利工程 | 19507篇 |
石油天然气 | 20138篇 |
武器工业 | 9238篇 |
无线电 | 63331篇 |
一般工业技术 | 50075篇 |
冶金工业 | 23530篇 |
原子能技术 | 9270篇 |
自动化技术 | 87205篇 |
出版年
2024年 | 1435篇 |
2023年 | 8934篇 |
2022年 | 21712篇 |
2021年 | 28332篇 |
2020年 | 20389篇 |
2019年 | 12896篇 |
2018年 | 13495篇 |
2017年 | 16117篇 |
2016年 | 13362篇 |
2015年 | 23891篇 |
2014年 | 31608篇 |
2013年 | 37524篇 |
2012年 | 48554篇 |
2011年 | 50921篇 |
2010年 | 48368篇 |
2009年 | 46049篇 |
2008年 | 47700篇 |
2007年 | 46871篇 |
2006年 | 40263篇 |
2005年 | 32742篇 |
2004年 | 23300篇 |
2003年 | 15610篇 |
2002年 | 14642篇 |
2001年 | 13341篇 |
2000年 | 10724篇 |
1999年 | 4961篇 |
1998年 | 2549篇 |
1997年 | 2109篇 |
1996年 | 1813篇 |
1995年 | 1563篇 |
1994年 | 1165篇 |
1993年 | 1067篇 |
1992年 | 861篇 |
1991年 | 614篇 |
1990年 | 550篇 |
1989年 | 490篇 |
1988年 | 356篇 |
1987年 | 243篇 |
1986年 | 225篇 |
1985年 | 153篇 |
1984年 | 126篇 |
1983年 | 91篇 |
1982年 | 76篇 |
1981年 | 114篇 |
1980年 | 198篇 |
1979年 | 142篇 |
1978年 | 39篇 |
1976年 | 59篇 |
1959年 | 108篇 |
1951年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Li-Xiang Wu Lin-Lin Zhu Yang You Rui-Lin Lin Qing-Qing Liu Wei-Ming Guo Hua-Tay Lin Kevin Paul Plucknett 《Ceramics International》2021,47(1):935-942
Dense pressure-sintered reaction-bonded Si3N4 (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu2O3–MgO–Y2O3 sintering additive. The addition of Eu2O3–MgO–Y2O3 was shown to promote full nitridation of the Si powder. The nitrided Si3N4 particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu2O3–MgO–Y2O3 were nitrided at 1400 °C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu2O3 doping, were 98.3 ± 0.2%, 17.8 ± 0.8 GPa, 697.0 ± 67.0 MPa, and 7.3 ± 0.3 MPa m1/2, respectively. The thermal conductivity was 73.6 ± 0.2 W m?1 K?1, significantly higher than the counterpart without Eu2O3 doping, or with ZrO2 doping by conventional methods. 相似文献
2.
3.
The exosome-mediated response can promote or restrain the diseases by regulating the intracellular pathways, making the exosome become an effective marker for diagnosis and therapeutic control at the single-cell level. However, real-time analysis is hard to be achieved with traditional approaches because the exosomes usually need to be enriched by ultracentrifugation for a measurable signal-to-noise ratio. Recently developed label-free single-molecule imaging approaches may become an real-time quantitative tool for the analysis of single exosomes and related secretion behaviors of single living cells owing to their extreme sensitivity. 相似文献
4.
5.
6.
7.
目的 为了更科学地研究和检验可穿戴产品的适合性,提出一种适合性检验方法,能够精确保留现实环境中的产品佩戴关系,并能将现实与虚拟的适合性检验研究相结合,得到合理的适合性检验结果.方法 以虚拟现实眼镜的适合性检验为例,通过高精度的三维测量技术将现实环境中的人、产品以及人—产品佩戴关系转化为三维虚拟信息,并以人—产品佩戴三维模型为参考基准对齐人和产品的虚拟模型,得到保留现实佩戴关系的人—产品佩戴模型组,再应用偏差分析法得出人—机佩戴区域的可视化适合性结果和统计数据,结合主观评价方法进一步分析产品的适合性.结论 虚实结合的产品适合性检验方法可在虚拟环境中高精度地保留现实环境中的人—产品佩戴关系,并能得到可视化的适合性检验结果,为检验和指导产品的适合性提供依据. 相似文献
8.
9.
Mingming Yang Siwei Long Yunzhong Zhu Haozhe Ma Shaopeng Lin Jiliang Quan Biao Wang 《Ceramics International》2021,47(2):1970-1975
LiNbO3 crystals activated by Sm3+ and co-doped with Zr4+ (Sm:Zr:LN) or Hf4+ (Sm:Hf:LN) were prepared by the Czochralski method. Detailed investigation on spectroscopic properties was conducted on the frame of Judd-Ofelt (J-O) theory. The J-O intensity parameters Ωi (i = 2, 4, 6), fluorescence branching ratios and radiative lifetime of excited level 4G5/2 were determined. Furthermore, the thermal stability of the strong orange-red emissions obtained under near-UV excitation in both crystals was evaluated. As high as 100% and 97% of integrated intensities at room temperature in Sm:Zr:LN and Sm:Hf:LN respectively were retained at 423 K, demonstrating the suppressed thermal attenuation. The temperature sensing performance based on fluorescence intensity ratio strategy was degraded at higher temperatures with relatively low sensitivities, while the shift of CIE chromaticity coordinates of Sm:Zr:LN and Sm:Hf:LN in the orange-red region was insignificant, demonstrating the color constancy with increasing temperature. With the efficient and thermally stable orange-red luminescence, Sm:Zr:LN and Sm:Hf:LN could serve as promising candidate materials for near-UV excited white light-emitting diodes. 相似文献
10.
Carlo Dal Lin Claudia Maria Radu Giuseppe Vitiello Paola Romano Albino Polcari Sabino Iliceto Paolo Simioni Francesco Tona 《International journal of molecular sciences》2021,22(1)
Mechanical vibrations seem to affect the behaviour of different cell types and the functions of different organs. Pressure waves, including acoustic waves (sounds), could affect cytoskeletal molecules via coherent changes in their spatial organization and mechano-transduction signalling. We analyzed the sounds spectra and their fractal features. Cardiac muscle HL1 cells were exposed to different sounds, were stained for cytoskeletal markers (phalloidin, beta-actin, alpha-tubulin, alpha-actinin-1), and studied with multifractal analysis (using FracLac for ImageJ). A single cell was live-imaged and its dynamic contractility changes in response to each different sound were analysed (using Musclemotion for ImageJ). Different sound stimuli seem to influence the contractility and the spatial organization of HL1 cells, resulting in a different localization and fluorescence emission of cytoskeletal proteins. Since the cellular behaviour seems to correlate with the fractal structure of the sound used, we speculate that it can influence the cells by virtue of the different sound waves’ geometric properties that we have photographed and filmed. A theoretical physical model is proposed to explain our results, based on the coherent molecular dynamics. We stress the role of the systemic view in the understanding of the biological activity. 相似文献