全文获取类型
收费全文 | 25425篇 |
免费 | 2495篇 |
国内免费 | 1235篇 |
专业分类
电工技术 | 1427篇 |
技术理论 | 5篇 |
综合类 | 1848篇 |
化学工业 | 4390篇 |
金属工艺 | 1464篇 |
机械仪表 | 1477篇 |
建筑科学 | 1953篇 |
矿业工程 | 733篇 |
能源动力 | 622篇 |
轻工业 | 2803篇 |
水利工程 | 418篇 |
石油天然气 | 1334篇 |
武器工业 | 173篇 |
无线电 | 3054篇 |
一般工业技术 | 2894篇 |
冶金工业 | 1101篇 |
原子能技术 | 228篇 |
自动化技术 | 3231篇 |
出版年
2024年 | 168篇 |
2023年 | 527篇 |
2022年 | 942篇 |
2021年 | 1255篇 |
2020年 | 910篇 |
2019年 | 825篇 |
2018年 | 904篇 |
2017年 | 921篇 |
2016年 | 835篇 |
2015年 | 1108篇 |
2014年 | 1368篇 |
2013年 | 1536篇 |
2012年 | 1713篇 |
2011年 | 1618篇 |
2010年 | 1464篇 |
2009年 | 1397篇 |
2008年 | 1329篇 |
2007年 | 1234篇 |
2006年 | 1209篇 |
2005年 | 970篇 |
2004年 | 743篇 |
2003年 | 926篇 |
2002年 | 1165篇 |
2001年 | 951篇 |
2000年 | 662篇 |
1999年 | 590篇 |
1998年 | 346篇 |
1997年 | 304篇 |
1996年 | 284篇 |
1995年 | 227篇 |
1994年 | 175篇 |
1993年 | 138篇 |
1992年 | 96篇 |
1991年 | 78篇 |
1990年 | 72篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 17篇 |
1986年 | 20篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1959年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
With the rapid development of Internet of Things (IoT), the issue of trust in distributed routing systems has attracted more research attention. The existing trust management frameworks, however, suffer from some possible attacks in hostile environments, such as false accusation, collusion, on-off, and conflicting behavior. Therefore, more comprehensive models should be proposed to predict the trust level of nodes on potential routes more precisely, and to defeat several kinds of possible attacks. This paper makes an attempt to design an attack-resistant trust management model based on beta function for distributed routing strategy in IoT. Our model can evaluate and propagate reputation in distributed routing systems. We first describe possible attacks on existing systems. Our model is then proposed to establish reliable trust relations between self-organized nodes and defeat possible attacks in distributed routing systems. We also propose a theoretical basis and skeleton of our model. Finally, some performance evaluations and security analyses are provided to show the effectiveness and robustness of our model compared with the existing systems. 相似文献
903.
遥感分类旨在从图像光谱中提取资源环境监测可用的地理信息,然而基于模式分类的图像处理技术受光谱漂移影响而缺乏历史样本重复利用的有效策略,制约着有限目标样本下遥感分类精度的提高.针对该问题,本文构建了基于改进的贝叶斯ARTMAP神经网络的迁移学习遥感影像分类算法,通过提高谐振匹配性来抑制类别扩散,利用节点的离散增量期望最大化参数更新策略,将历史遥感样本中的地物分类先验信息迁移到目标模型当中.实验结果表明本文方法能有效利用历史遥感数据弥补缺少目标训练数据的不足,相比于其他样本利用策略大幅提高遥感影像分类精度. 相似文献
904.
Xue Xiangyang 《电子科学学刊(英文版)》1996,13(1):40-47
A new scheme is presented to design a rotated Barnes-Wall lattice based vector quantizer(LVQ). The construction method of the LVQ and its fast quantizing algorithm are described at first. Then gain-shape lattice vector quantizer(GSLVQ) with LVQ as shape quantizer is discussed. Finally the GSLVQ is used in image-sequence coding and good experimental results are obtained. 相似文献
905.
A Universal Platform for Macromolecular Deliveryinto Cells Using Gold Nanoparticle Layers via the Photoporation Effect 下载免费PDF全文
Zhonglin Lyu Feng Zhou Qi Liu Hui Xue Qian Yu Hong Chen 《Advanced functional materials》2016,26(32):5787-5795
Although promising, it is challenging to develop a simple and universal method for the high‐efficiency delivery of biomacromolecules into diverse cells. Here, a universal delivery platform based on gold nanoparticle layer (GNPL) surfaces is proposed. Upon laser irradiation, GNPL surfaces show such good photothermal properties that absorption of the laser energy causes a rapid increase in surface temperature, leading to enhanced membrane permeability of the cultured cells and the diffusion of macromolecules into the cytosol from the surrounding medium. The high‐efficiency delivery of different macromolecules such as dextran and plasmid DNA into different cell types is achieved, including hard‐to‐transfect mouse embryonic fibroblasts (mEFs) and human umbilical vein endothelial cells (HUVECs), while cell viability is well maintained under optimized irradiation conditions. The platform vastly outperforms the leading commercial reagent, Lipofectamine 2000, especially in transfecting hard‐to‐transfect cell lines (plasmid transfection efficiency: ≈53% vs ≈19% for mEFs and ≈44% vs ≈8% for HUVECs). Importantly, as the gold nanoparticles (GNPs) constituting the GNPL are firmly immobilized together, the potential cytotoxicity caused by endocytosis of GNPs is effectively avoided. This platform is reliable, efficient, and cost‐effective with high‐throughput and broad applicability across different cell types, opening up an innovative avenue for high‐efficiency intracellular delivery. 相似文献
906.
907.
908.
909.
910.