全文获取类型
收费全文 | 333488篇 |
免费 | 82493篇 |
国内免费 | 54040篇 |
专业分类
电工技术 | 38338篇 |
技术理论 | 12篇 |
综合类 | 32997篇 |
化学工业 | 46287篇 |
金属工艺 | 33527篇 |
机械仪表 | 17010篇 |
建筑科学 | 24624篇 |
矿业工程 | 17749篇 |
能源动力 | 13018篇 |
轻工业 | 30990篇 |
水利工程 | 10886篇 |
石油天然气 | 19569篇 |
武器工业 | 5380篇 |
无线电 | 46905篇 |
一般工业技术 | 45370篇 |
冶金工业 | 12746篇 |
原子能技术 | 3431篇 |
自动化技术 | 71182篇 |
出版年
2024年 | 2873篇 |
2023年 | 6490篇 |
2022年 | 9151篇 |
2021年 | 11901篇 |
2020年 | 13074篇 |
2019年 | 21250篇 |
2018年 | 23058篇 |
2017年 | 24866篇 |
2016年 | 24276篇 |
2015年 | 25218篇 |
2014年 | 25742篇 |
2013年 | 26394篇 |
2012年 | 27295篇 |
2011年 | 24662篇 |
2010年 | 22800篇 |
2009年 | 19301篇 |
2008年 | 17406篇 |
2007年 | 16255篇 |
2006年 | 14805篇 |
2005年 | 12523篇 |
2004年 | 13167篇 |
2003年 | 10803篇 |
2002年 | 10546篇 |
2001年 | 9150篇 |
2000年 | 8028篇 |
1999年 | 7243篇 |
1998年 | 5872篇 |
1997年 | 5143篇 |
1996年 | 4858篇 |
1995年 | 4612篇 |
1994年 | 3834篇 |
1993年 | 3348篇 |
1992年 | 3117篇 |
1991年 | 2256篇 |
1990年 | 1739篇 |
1989年 | 1629篇 |
1988年 | 1228篇 |
1987年 | 444篇 |
1986年 | 376篇 |
1985年 | 258篇 |
1984年 | 180篇 |
1983年 | 136篇 |
1982年 | 184篇 |
1981年 | 184篇 |
1980年 | 133篇 |
1976年 | 234篇 |
1975年 | 210篇 |
1972年 | 236篇 |
1971年 | 128篇 |
1960年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
1.
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to... 相似文献
2.
4.
边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明:和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。 相似文献
6.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
7.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. 相似文献
8.
9.
KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability. 相似文献
10.
Jia Dai Xiang Cheng Xiaofeng Li Zhisheng Wang Yufeng Wang Jing Zheng Jun Liu Jiawei Chen Changjin Wu Jinyao Tang 《Advanced functional materials》2021,31(48):2106204
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency. 相似文献