全文获取类型
收费全文 | 2038篇 |
免费 | 359篇 |
国内免费 | 113篇 |
学科分类
工业技术 | 2510篇 |
出版年
2024年 | 21篇 |
2023年 | 135篇 |
2022年 | 182篇 |
2021年 | 238篇 |
2020年 | 161篇 |
2019年 | 152篇 |
2018年 | 136篇 |
2017年 | 145篇 |
2016年 | 120篇 |
2015年 | 136篇 |
2014年 | 139篇 |
2013年 | 147篇 |
2012年 | 107篇 |
2011年 | 152篇 |
2010年 | 93篇 |
2009年 | 89篇 |
2008年 | 67篇 |
2007年 | 47篇 |
2006年 | 48篇 |
2005年 | 32篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 9篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有2510条查询结果,搜索用时 46 毫秒
1.
Multimedia Tools and Applications - Tree species classification is a necessary and challenging task for both multimedia technique and forestry engineering. Continuous developments in multimedia and... 相似文献
2.
为了实现主观题智能阅卷,本文提出了一个基于多特征融合的主观题智能阅卷算法.首先,分别设计两种算法:关键词相似度算法和语义相似度算法,计算学生答案和标准答案之间的关键词相似度和语义相似度;然后,以题目的 题型和科目作为特征值,分别计算出两相似度的权值,并利用权值计算出学生答案的得分实验表明,本文提出的算法,能有效主观题智能阅卷算法的准确性,具有较好的应用前景. 相似文献
3.
4.
Yanan Xu Kai Wang Jianwei Han Cong Liu Yabin An Qinghai Meng Chen Li Xiong Zhang Xianzhong Sun Yaosheng Zhang Lijuan Mao Zhixiang Wei Yanwei Ma 《Advanced materials (Deerfield Beach, Fla.)》2020,32(45):2005531
Smart and wearable electronics have aroused substantial demand for flexible portable power sources, but it remains a large challenge to realize scalable production of wearable batteries/supercapacitors with high electrochemical performance and remarkable flexibility simultaneously. Here, a scalable approach is developed to prepare wearable solid-state lithium-ion capacitors (LICs) with superior performance enabled by synergetic engineering from materials to device architecture. Nitrogen-doped hierarchical carbon (HC) composed of 1D carbon nanofibers welded with 2D carbon nanosheets is synthesized via a unique self-propagating high-temperature synthesis (SHS) technique, which exhibits superior electrochemical performance. Subsequently, inspired by origami, here, wave-shaped LIC punch-cells based on the above materials are designed by employing a compatible and scalable post-imprint technology. Finite elemental analysis (FEA) confirms that the bending stress of the punch-cell can be offset effectively, benefiting from the wave architecture. The wearable solid-state LIC punch-cell exhibits large energy density, long cyclic stability, and superior flexibility. This study demonstrates great promise for scalable fabrication of wearable energy-storage systems. 相似文献
5.
Chenglai Xin Rong Yuan Jiang Wu Qingyuan Wang Yanan Zhou 《Ceramics International》2021,47(3):3411-3420
A novel method for fabricating a nano-Cu/Si3N4 ceramic substrate is proposed. The nano-Cu/Si3N4 ceramic substrate is first fabricated using spark plasma sintering (SPS) with the addition of nanoscale multilayer films (Ti/TiN/Ti/TiN/Ti) as transition layers. The microstructures of the nano-Cu metal layer and the interface between Cu and Si3N4 are investigated. The results show that a higher SPS temperature increases the grain size of the nano-Cu metal layer and affects the hardness. The microstructure of the transition layer evolves significantly after SPS. Ti in the transition layer can react with Si3N4 and with nano-Cu to form interfacial reaction layers of TiN and Ti–Cu, respectively; these ensure stronger bonding between nano-Cu and Si3N4. Higher SPS temperatures improve the diffusion ability of Ti and Cu, inducing the formation of Ti3Cu3O compounds in the nano-Cu metal layer and Ti2Cu in the transition layer. This study provides an important strategy for designing and constructing a new type of ceramic substrate. 相似文献
6.
Co-fermentation of sewage sludge and algae was performed for enhancing the hydrogen production, and the effect of Fe2+ on co-fermentation process was examined. Results showed that both co-fermentation process and Fe2+ addition promoted hydrogen production. Highest hydrogen production of 28 mL/100 mL (14.8 mL H2/g VSadded) was obtained from the co-fermentation group with 600 mg/L Fe2+ addition, which was 2.15 times, 2.00 times and 1.87 times of mono-fermentation of sludge, mono-fermentation of algae, and the co-fermentation group without Fe2+ addition. Both volatile solids and protein degradation were stimulated by co-fermentation process. Microbial analysis showed that co-fermentation groups with Fe2+ addition enriched Clostridium sensu stricto 13, Clostridium tertium and Terrisporobacter, which were positively correlated with cumulative hydrogen production. This study suggested that the co-fermentation of sludge and algae in the presence of Fe2+ could significantly improve the hydrogen production by stimulating the hydrogen-producing metabolism. 相似文献
7.
Mengyu Hong Chi-Tang Ho Xin Zhang Ruilin Zhang Yanan Liu 《International Journal of Food Science & Technology》2021,56(7):3311-3321
The human body hosts enormous diversity of microbiota. Recently, the importance of microbial communities to host physiology has been recognised. Evidence is now emerging that the bidirectional communication between the central nervous system and gastrointestinal tract may affect human nerves, cognition and behaviour through the gut-brain axis (GBA). Although the connection between enteropathy and neurological diseases has been found, it now seems intestinal microorganisms represent the direct mediator of psychopathology. The interactions between host neurological function and intestinal microbiota suggested dietary is a possible way to alleviate psychopathological and neurodegenerative diseases. This review discusses the possible effect of intestinal microbiota on the changes of nerves and emotions in human brain. Maintaining healthy diet strategies should be an important part of preventing neurological diseases and psychopathologies caused by systemic metabolic changes. We hope to provide a novel insight for the design of dietary therapies from the perspective of GBA. 相似文献
8.
通过调制电磁波的相位和振幅可以达到控制电磁波的目的,为了实现超材料器件对电磁波的不同响应,利用仿真软件CST,设计了一系列基于全介质超材料的波前控制器件,包括电磁波偏转器件和聚焦透镜。通过引入不同的梯度相位差,达到调制折射电磁波偏转方向的目的,且当器件满足不同的相位分布时,透镜的焦点位置可以被定量调节。这些全介质超材料器件可通过3D打印技术快速制备,具备经济友好的特点,在微波成像系统和通信领域具有广泛的应用前景。 相似文献
9.
为有效提高热塑性淀粉塑料(TPS)的力学和耐水性能,本文提出用不同波长的紫外光照的方法来实现TPS表面的光交联改性。将光引发剂2,4,6?三甲基苯甲酰基二苯基氧化膦(TPO)的乙醇溶液涂覆于TPS表面后进行紫外光照射,研究了不同紫外光波长(254、308、365 nm)对TPS交联度、力学性能、动态力学性能、耐水性和吸湿性的影响。结果表明,与254 nm和365 nm紫外光照后的样品相比,308 nm光照后TPS样品的拉伸、弯曲和冲击强度最大,分别为4.1 MPa,2.7 MPa和96.8 kJ/m2;TPS中淀粉富集区的玻璃化转变温度(Tα)、甘油富集区的玻璃化转变温度(Tβ)分别达最高为-37.48 ℃和50.32 ℃,表面接触角最大为75 °,吸水性能也得到显著改善,交联度结果证实此时形成了最佳的交联结构。 相似文献
10.
利用盐酸预处理TEOS得到的硅凝胶为硅源,铝酸钠为铝源,通过水热合成法制备了一种晶粒尺寸和孔径大小可控的NaP分子筛.利用不同时间酸解TEOS得到的硅凝胶合成NaP分子筛,但合成的样品杂晶较多且形貌不规整;采用正交试验,通过调节晶化时间、晶化温度、溶液pH值和水硅比,以达到样品提纯、形貌规整的目的.对样品进行SEM、XRD、N2物理吸附等表征,分析样品的形貌、结晶度和孔径分布等.并对样品进行铜离子吸附性能测试,得到NaP分子筛对Cu2+的有效去除率为98.9%.利用预先酸解TEOS得到的硅凝胶合成NaP分子筛的方法,为工业污水净化提供一定的理论依据及指导. 相似文献