全文获取类型
收费全文 | 15271篇 |
免费 | 2656篇 |
国内免费 | 1929篇 |
专业分类
电工技术 | 2271篇 |
技术理论 | 1篇 |
综合类 | 1794篇 |
化学工业 | 396篇 |
金属工艺 | 282篇 |
机械仪表 | 1098篇 |
建筑科学 | 555篇 |
矿业工程 | 262篇 |
能源动力 | 404篇 |
轻工业 | 179篇 |
水利工程 | 265篇 |
石油天然气 | 220篇 |
武器工业 | 259篇 |
无线电 | 1626篇 |
一般工业技术 | 1136篇 |
冶金工业 | 672篇 |
原子能技术 | 42篇 |
自动化技术 | 8394篇 |
出版年
2024年 | 102篇 |
2023年 | 472篇 |
2022年 | 784篇 |
2021年 | 900篇 |
2020年 | 941篇 |
2019年 | 709篇 |
2018年 | 561篇 |
2017年 | 719篇 |
2016年 | 748篇 |
2015年 | 903篇 |
2014年 | 1070篇 |
2013年 | 1131篇 |
2012年 | 1275篇 |
2011年 | 1286篇 |
2010年 | 1018篇 |
2009年 | 1085篇 |
2008年 | 987篇 |
2007年 | 1051篇 |
2006年 | 829篇 |
2005年 | 613篇 |
2004年 | 476篇 |
2003年 | 346篇 |
2002年 | 277篇 |
2001年 | 259篇 |
2000年 | 213篇 |
1999年 | 160篇 |
1998年 | 143篇 |
1997年 | 93篇 |
1996年 | 87篇 |
1995年 | 77篇 |
1994年 | 84篇 |
1993年 | 57篇 |
1992年 | 51篇 |
1991年 | 40篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1983年 | 9篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1966年 | 13篇 |
1965年 | 9篇 |
1964年 | 11篇 |
1963年 | 7篇 |
1959年 | 7篇 |
1957年 | 9篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
21.
为有效预测矿井内煤与瓦斯突出的危险程度,对其影响因素做了分析与探讨,分别构建了基于粒子群优化算法以及遗传算法支持向量机的煤与瓦斯突出预测模型,并且通过实例对两种模型预测的准确性进行了验证。分别利用单项以及综合指标、BP神经网络以及PSO-SVM模型、GA-SVM模型,对寺河煤矿二号井的突出区域进行预测比较。结果表明,PSO-SVM的预测模型不仅可以在小样本数据中预测出煤与瓦斯突出程度的大小,而且综合预测结果更加精确,其在解决矿井内煤与瓦斯突出的小样本数据中显示出更加强大、通用的性能。 相似文献
22.
Electrocardiogram is the most commonly used tool for the diagnosis of cardiologic diseases. In order to help cardiologists to diagnose the arrhythmias automatically, new methods for automated, computer aided ECG analysis are being developed. In this paper, a Modified Artificial Bee Colony (MABC) algorithm for ECG heart beat classification is introduced. It is applied to ECG data set which is obtained from MITBIH database and the result of MABC is compared with seventeen other classifier's accuracy.In classification problem, some features have higher distinctiveness than others. In this study, in order to find higher distinctive features, a detailed analysis has been done on time domain features. By using the right features in MABC algorithm, high classification success rate (99.30%) is obtained. Other methods generally have high classification accuracy on examined data set, but they have relatively low or even poor sensitivities for some beat types. Different data sets, unbalanced sample numbers in different classes have effect on classification result. When a balanced data set is used, MABC provided the best result as 97.96% among all classifiers.Not only part of the records from examined MITBIH database, but also all data from selected records are used to be able to use developed algorithm on a real time system in the future by using additional software modules and making adaptation on a specific hardware. 相似文献
23.
This paper investigates the N-policy M/M/1 queueing system with working vacation and server breakdowns. As soon as the system becomes empty, the server begins a working vacation. The server works at a lower service rate rather than completely stopping service during a vacation period. The server may break down with different breakdown rates during the idle, working vacation, and normal busy periods. It is assumed that service times, vacation times, and repair times are all exponentially distributed. We analyze this queueing model as a quasi-birth–death process. Furthermore, the equilibrium condition of the system is derived for the steady state. Using the matrix-geometric method, we find the matrix-form expressions for the stationary probability distribution of the number of customers in the system and system performance measures. The expected cost function per unit time is constructed to determine the optimal values of the system decision variables, including the threshold N and mean service rates. We employ the particle swarm optimization algorithm to solve the optimization problem. Finally, numerical results are provided, and an application example is given to demonstrate the applicability of the queueing model. 相似文献
24.
随着大数据和云计算的技术的深入应用,人工智能时代的机器学习和深度学习更需要日益增长的数据,因此数据安全与隐私保护变得更加迫切。本文介绍人工智能的定义以及特征,探究数据安全和隐私保护现状,分析数据安全和隐私保护面临的诸多问题,并提出在人工智能时代对数据安全和隐私保护的措施。 相似文献
25.
《矿业科学技术学报(英文版)》2020,30(6):747-757
Digitalisation in mining refers to the use of computerised or digital devices or systems and digitised data that are to reduce costs, improve business productivity, and transform mining practices. However, it remains increasingly difficult for mining companies to decide which digital technologies are most relevant to their needs and individual mines. This paper provides an overview of digital technologies currently relevant to mining companies as presented and discussed by mining journals, the media and insight reports of leading consultancy agencies. Relevant technologies were systematically identified using text-mining techniques, and network analyses established the relations between significant technologies. Results demonstrated that currently 107 different digital technologies are pursued in the mining sector. Also, an analysis of the actual implementation of digital technologies in 158 active surface and underground mines reveals a limited uptake of digital technologies in general and that the uptake increases with the run-of-mine production. Large-scale mining operations appear to select and apply digital technologies suitable to their needs, whereas operations with lower production rates do not implement the currently available digital technologies to the same extent. These minor producers may require other digital transformation solutions tailored to their capabilities and needs and applicable to their scale of operations. 相似文献
26.
人工智能的原理及应用 总被引:7,自引:0,他引:7
介绍了人工智能的发展,并对改进的神经网络专家系统的优越性做了介绍,指出了神经网络专家系统广阔的应用前景及实现。 相似文献
27.
随着印制电路板产业飞速发展,其引发的环境问题日益受到广泛的关注。然而长期以来如何有效地进行环境冲击评估是业内研究的重点和难点。而本文采用了一种智能的简化分析方法来进行全面的环境冲击评估,以提高评估的经济效益和准确度,并希望能为决策者提供一个可供参考的环境冲击评估的理念和方法。 相似文献
28.
制造业企业竞争情报系统建设浅析 总被引:1,自引:0,他引:1
讨论了制造业企业信息化进程中包含竞争情报系统的必要性。论述了该类企业竞争情报系统的内涵及功能特征。较详细地介绍了相应系统常用外部数据资源内容及各自应用特点;此外本文还简要地说明了该类系统现有开发支持工具软件、开发关键步骤等内容。 相似文献
29.
Wesley W. Chu Ph.D. Ion T. leong Ph.D. Ricky K. Taira Ph.D. 《The VLDB Journal The International Journal on Very Large Data Bases》1994,3(4):445-477
We introduce a semantic data model to capture the hierarchical, spatial, temporal, and evolutionary semantics of images in pictorial databases. This model mimics the user's conceptual view of the image content, providing the framework and guidelines for preprocessing to extract image features. Based on the model constructs, a spatial evolutionary query language (SEQL), which provides direct image object manipulation capabilities, is presented. With semantic information captured in the model, spatial evolutionary queries are answered efficiently. Using an object-oriented platform, a prototype medical-image management system was implemented at UCLA to demonstrate the feasibility of the proposed approach. 相似文献
30.
DNA序列比对分析中的统计特征方法 总被引:1,自引:0,他引:1
提出了一种新的基于统计的序列特征定义,并以此对进化树进行构建.同时对这一方法进行了分类测试和进化树构建测试,发现所得测试结果与同样是用进化树进行构建的基于两序列比对的传统算法比较,其性能和适用性都有明显改善. 相似文献