全文获取类型
收费全文 | 17691篇 |
免费 | 816篇 |
国内免费 | 859篇 |
专业分类
电工技术 | 436篇 |
技术理论 | 2篇 |
综合类 | 725篇 |
化学工业 | 250篇 |
金属工艺 | 382篇 |
机械仪表 | 1311篇 |
建筑科学 | 474篇 |
矿业工程 | 310篇 |
能源动力 | 231篇 |
轻工业 | 142篇 |
水利工程 | 89篇 |
石油天然气 | 186篇 |
武器工业 | 189篇 |
无线电 | 1945篇 |
一般工业技术 | 700篇 |
冶金工业 | 380篇 |
原子能技术 | 253篇 |
自动化技术 | 11361篇 |
出版年
2024年 | 11篇 |
2023年 | 152篇 |
2022年 | 189篇 |
2021年 | 308篇 |
2020年 | 348篇 |
2019年 | 231篇 |
2018年 | 263篇 |
2017年 | 403篇 |
2016年 | 458篇 |
2015年 | 451篇 |
2014年 | 925篇 |
2013年 | 762篇 |
2012年 | 900篇 |
2011年 | 1225篇 |
2010年 | 796篇 |
2009年 | 868篇 |
2008年 | 1019篇 |
2007年 | 1312篇 |
2006年 | 1263篇 |
2005年 | 1251篇 |
2004年 | 1123篇 |
2003年 | 1060篇 |
2002年 | 790篇 |
2001年 | 584篇 |
2000年 | 475篇 |
1999年 | 405篇 |
1998年 | 309篇 |
1997年 | 222篇 |
1996年 | 220篇 |
1995年 | 200篇 |
1994年 | 136篇 |
1993年 | 108篇 |
1992年 | 68篇 |
1991年 | 59篇 |
1990年 | 50篇 |
1989年 | 49篇 |
1988年 | 43篇 |
1987年 | 35篇 |
1986年 | 35篇 |
1985年 | 36篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 31篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
Tracking-by-detection (TBD) is a significant framework for visual object tracking. However, current trackers are usually updated online based on random sampling with a probability distribution. The performance of the learning-based TBD trackers is limited by the lack of discriminative features, especially when the background is full of semantic distractors. We propose an attention-driven data augmentation method, in which a residual attention mechanism is integrated into the TBD tracking network as supplementary references to identify discriminative image features. A mask generating network is used to simulate changes in target appearances to obtain positive samples, where attention information and image features are combined to identify discriminative features. In addition, we propose a method for mining hard negative samples, which searches for semantic distractors with the response of the attention module. The experiments on the OTB2015, UAV123, and LaSOT benchmarks show that this method achieves competitive performance in terms of accuracy and robustness. 相似文献
2.
树形结构作为一种非线性数据结构,在程序执行过程中的演变过程较为抽象,尤其是在对其进行加工型操作时,容易发生内存泄漏。针对编程初学者难以掌握树形结构的逻辑演变过程,以及在程序中发生内存泄漏错误时调试较为困难的问题,文中提出了一种对程序调试过程中树形结构的演变过程进行可视化呈现的处理模型TEVM(Tree Evaluation Visualization Model)。针对单个可视化程序在调试步骤前和调试步骤后的两个树形结构,设计了一种将树形结构转换为线性表示的结构对比算法,得出了它们的包括泄漏树在内的结构差异;同时设计了一种树形结构布局方法,并计算它们的布局差异。根据结构差异和布局差异生成可视化演变序列,调用绘图引擎对该序列进行解析和执行,从而完成对树形结构及其演变过程的动态、平滑和直观的可视化呈现,帮助编程初学者快速理解树形结构相关程序的执行过程,提升调试效率。将TEVM模型集成于一个面向编程实训教学的集成开发环境原型Web AnyviewC中,取得了较好的应用效果。 相似文献
3.
经典谱聚类算法将数据聚类转为图划分问题,在分析其Normalized Cut函数与传统加权核k-means等价基础上,设计了一种基于抽样改进加权核k-means算法的大规模数据集谱聚类算法,算法通过加权核k-means迭代优化避免Laplacian矩阵特征分解的大量资源占用,通过随机映射得到近似奇异值分解,并由近似奇异向量确定各点数据权重及抽样概率,以此得到快速合理抽样,通过数据抽样并将聚类中心约束到抽样点生成的子空间中,避免全部核矩阵的使用,从而降低经典算法的时间空间复杂度。实验结果表明,改进算法在保持与经典算法相近精度基础上,大幅提高了聚类效率,实验验证了改进算法的有效性。 相似文献
4.
在新数据源与技术方法的支撑下,
把握城市在场人口的时空分布特征,对于了
解居民对城市资源时空配置的差异化需求
和城市空间的精细化管理有重要意义。以北
京中心城区为例,本文利用2017年连续4周
的联通手机信令数据,以500 m×500 m尺度
的栅格单元分析在场人口的分布、流动性及
时段变化特征。研究结果表明:一、在场人
口主要分布在六环以内,呈现“多组团状”分
布,部分空间单元在场人口高达居住人口的
6~38倍;二、在场人口的流动性形成依托环
线的明显的圈层结构,二环以内的第一圈层
随机流动性人口居多,二环至五环之间的第
二圈层规律流动性人口居多,五环以外的第
三圈层静止人口居多;三、北京市工作日在场
人口较休息日更多,一天中局部空间的在场人口密度波动极大,并且各类典型城市空间具有鲜明的时段变化规律。最后,提出面向在场人口
的城市设施配置及人口管理的思考和建议。 相似文献
5.
In the Internet of Things (IoT), a huge amount of valuable data is generated by various IoT applications. As the IoT technologies become more complex, the attack methods are more diversified and can cause serious damages. Thus, establishing a secure IoT network based on user trust evaluation to defend against security threats and ensure the reliability of data source of collected data have become urgent issues, in this paper, a Data Fusion and transfer learning empowered granular Trust Evaluation mechanism (DFTE) is proposed to address the above challenges. Specifically, to meet the granularity demands of trust evaluation, time–space empowered fine/coarse grained trust evaluation models are built utilizing deep transfer learning algorithms based on data fusion. Moreover, to prevent privacy leakage and task sabotage, a dynamic reward and punishment mechanism is developed to encourage honest users by dynamically adjusting the scale of reward or punishment and accurately evaluating users’ trusts. The extensive experiments show that: (i) the proposed DFTE achieves high accuracy of trust evaluation under different granular demands through efficient data fusion; (ii) DFTE performs excellently in participation rate and data reliability. 相似文献
6.
为了探讨在安卓平台上构建医用图像采集系统的开发个案,分析通过以智能手机、平板电脑为核心安卓设备通过拍照获得化验单数据后进行文本识别并提交智慧医疗系统的解决方案。本文首先通过二值化算法形成低阈值图像数据,使用卷积神经元网络算法对文本进行逐一识别,使用K-means算法对识别后的单字文本进行字段记录值的整合并形成元数据库服务于其他智慧医疗系统模块。在使用9000组数据对神经元网络进行前期训练的前提下,该系统的识别准确率达到了99.5%以上。本系统具有一定的可行性,对未来智慧医疗的系统开发有实践意义。 相似文献
7.
《Ceramics International》2021,47(20):28086-28105
Refractory castables develop microstructures after curing that behave as partially saturated porous media. Upon heating (during its drying stage), the steam generated by the physical and chemically bond water can result in pore pressurization and explosive spalling. Numerical modeling can provide guidelines for designing safer heat-up profiles and also a better understanding of the mechanisms that lead to catastrophic damage. This work aims to review the fundamentals and models available, providing insightful thoughts on the current trends of the drying phenomena of ceramic compositions. The review also highlights that there are models better oriented to result in reasonable predictions of pore pressure values and others focused on a more accurate representation of the main physical phenomena that take place during heating. According to the findings, there are still various challenges to attain accurate models with high applicability capable of yielding safer and more efficient drying of refractory castables. 相似文献
8.
A PID-incorporated Latent Factorization of Tensors Approach to Dynamically Weighted Directed Network Analysis 下载免费PDF全文
Hao Wu Xin Luo MengChu Zhou Muhyaddin J. Rawa Khaled Sedraoui Aiiad Albeshri 《IEEE/CAA Journal of Automatica Sinica》2022,9(3):533-546
A large-scale dynamically weighted directed network (DWDN) involving numerous entities and massive dynamic interaction is an essential data source in many big-data-related applications, like in a terminal interaction pattern analysis system (TIPAS). It can be represented by a high-dimensional and incomplete (HDI) tensor whose entries are mostly unknown. Yet such an HDI tensor contains a wealth knowledge regarding various desired patterns like potential links in a DWDN. A latent factorization-of-tensors (LFT) model proves to be highly efficient in extracting such knowledge from an HDI tensor, which is commonly achieved via a stochastic gradient descent (SGD) solver. However, an SGD-based LFT model suffers from slow convergence that impairs its efficiency on large-scale DWDNs. To address this issue, this work proposes a proportional-integral-derivative (PID)-incorporated LFT model. It constructs an adjusted instance error based on the PID control principle, and then substitutes it into an SGD solver to improve the convergence rate. Empirical studies on two DWDNs generated by a real TIPAS show that compared with state-of-the-art models, the proposed model achieves significant efficiency gain as well as highly competitive prediction accuracy when handling the task of missing link prediction for a given DWDN. 相似文献
9.
《International Journal of Hydrogen Energy》2021,46(59):30267-30287
This work aims to improve the existing monitoring systems MS for two grid-connected PV stations GCPVS of URERMS ADRAR, to eliminate its limitations. This improvement consists of developing an MS which is used for two PV stations with different configurations. This MS contains new LabVIEW-based monitoring software for visualizing real-time measured data and evaluating GCPVS performance. In addition, it illustrates the 2D and 3D real-time relationships of PV system parameters, which allow us to understand the dynamic behavior of PV system components. This developed monitoring software synchronizes also the various data acquisition units DAU of GCPVS, allowing simultaneous data access.To perform a reliable performance analysis and a comparative study of different GCPVS based on accurate measurements, the sensor's calibration is performed with its DAU. The MS autonomy is ensured by integrating developed PV-UPS. A graphical user interface is provided for the evaluation of PV-UPS performance. 相似文献
10.
城镇群体系发展战略影响下,小城
镇作为联系中心城市与乡村的节点,将迎来
高速发展的契机。面对小城镇的现状,需要
在前期分析阶段引入定量研究的方法,针对
小城镇的特点,进行相对应的规划设计。规
划分析技术的引入为小城镇的规划编制工作
提供了有效的辅助手段,通过对数据工具的
高效利用,可以有效地提升现状分析的深度
与精度。本文将以小城镇为研究对象,建立
结合有意识公共参与及基于开放数据的规划
现状分析框架,或可成为小城镇规划设计中
挖掘问题,辅助决策,指导设计的工具。 相似文献