全文获取类型
收费全文 | 275264篇 |
免费 | 77915篇 |
国内免费 | 51141篇 |
专业分类
电工技术 | 34472篇 |
技术理论 | 2篇 |
综合类 | 28739篇 |
化学工业 | 37499篇 |
金属工艺 | 30242篇 |
机械仪表 | 12811篇 |
建筑科学 | 19918篇 |
矿业工程 | 15971篇 |
能源动力 | 10649篇 |
轻工业 | 27228篇 |
水利工程 | 9389篇 |
石油天然气 | 16975篇 |
武器工业 | 4610篇 |
无线电 | 40438篇 |
一般工业技术 | 39249篇 |
冶金工业 | 10207篇 |
原子能技术 | 2382篇 |
自动化技术 | 63539篇 |
出版年
2024年 | 2865篇 |
2023年 | 5901篇 |
2022年 | 8100篇 |
2021年 | 10006篇 |
2020年 | 11743篇 |
2019年 | 20137篇 |
2018年 | 21829篇 |
2017年 | 23499篇 |
2016年 | 22903篇 |
2015年 | 23292篇 |
2014年 | 22942篇 |
2013年 | 23023篇 |
2012年 | 23143篇 |
2011年 | 19940篇 |
2010年 | 18085篇 |
2009年 | 15103篇 |
2008年 | 12954篇 |
2007年 | 12199篇 |
2006年 | 10682篇 |
2005年 | 9507篇 |
2004年 | 10739篇 |
2003年 | 8942篇 |
2002年 | 8540篇 |
2001年 | 7524篇 |
2000年 | 6617篇 |
1999年 | 6158篇 |
1998年 | 5139篇 |
1997年 | 4550篇 |
1996年 | 4303篇 |
1995年 | 4161篇 |
1994年 | 3455篇 |
1993年 | 3068篇 |
1992年 | 2893篇 |
1991年 | 2124篇 |
1990年 | 1675篇 |
1989年 | 1546篇 |
1988年 | 1181篇 |
1987年 | 390篇 |
1986年 | 345篇 |
1985年 | 231篇 |
1984年 | 162篇 |
1983年 | 114篇 |
1982年 | 168篇 |
1981年 | 163篇 |
1980年 | 123篇 |
1976年 | 232篇 |
1975年 | 209篇 |
1972年 | 237篇 |
1971年 | 129篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
3.
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
4.
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
5.
Tao Feng Mingde Tong Shuotian Yao Hejun Li Shifeng Wen Hongjiao Lin 《Journal of the European Ceramic Society》2021,41(1):158-166
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. 相似文献
6.
7.
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
8.
9.
本文通过对巡检仪进行示值稳定性、重复性的试验,探讨热电偶的选择与巡检仪示值之间的关系,以确定校准方法,指导使其有效溯源. 相似文献
10.
Safa Meraghni Labib Sadek Terrissa Meiling Yue Jian Ma Samir Jemei Noureddine Zerhouni 《International Journal of Hydrogen Energy》2021,46(2):2555-2564
Prognostics and health management of proton exchange membrane fuel cell (PEMFC) systems have driven increasing research attention in recent years as the durability of PEMFC stack remains as a technical barrier for its large-scale commercialization. To monitor the health state during PEMFC operation, digital twin (DT), as a smart manufacturing technique, is applied in this paper to establish an ensemble remaining useful life prediction system. A data-driven DT is constructed to integrate the physical knowledge of the system and a deep transfer learning model based on stacked denoising autoencoder is used to update the DT with online measurement. A case study with experimental PEMFC degradation data is presented where the proposed data-driven DT prognostics method has applied and reached a high prediction accuracy. Furthermore, the predicted results are proved to be less affected even with limited measurement data. 相似文献