全文获取类型
收费全文 | 7869篇 |
免费 | 394篇 |
国内免费 | 234篇 |
学科分类
工业技术 | 8497篇 |
出版年
2024年 | 15篇 |
2023年 | 93篇 |
2022年 | 140篇 |
2021年 | 200篇 |
2020年 | 199篇 |
2019年 | 171篇 |
2018年 | 129篇 |
2017年 | 228篇 |
2016年 | 255篇 |
2015年 | 226篇 |
2014年 | 418篇 |
2013年 | 333篇 |
2012年 | 389篇 |
2011年 | 513篇 |
2010年 | 332篇 |
2009年 | 417篇 |
2008年 | 373篇 |
2007年 | 516篇 |
2006年 | 510篇 |
2005年 | 484篇 |
2004年 | 412篇 |
2003年 | 393篇 |
2002年 | 295篇 |
2001年 | 223篇 |
2000年 | 224篇 |
1999年 | 214篇 |
1998年 | 168篇 |
1997年 | 151篇 |
1996年 | 112篇 |
1995年 | 101篇 |
1994年 | 66篇 |
1993年 | 45篇 |
1992年 | 42篇 |
1991年 | 32篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有8497条查询结果,搜索用时 0 毫秒
991.
随着专家系统技术的广泛应用,传统的知识表示方法的缺陷越来越明显。本文在研究典型故障诊断专家系统知识表示基础上,介绍了采用面向对象知识表示的专家系统的设计思路,并对涉及到的关键技术做了阐述。 相似文献
992.
本文在板桥凹陷的埋藏史、热演化史恢复基础上,应用平面二维达西渗流定律及连续流动质量守恒方程模拟计算储层中各时期油、气、水的势场。在古流体势模拟计算过程中,考虑到储层毛细管力和断层连通性的影响。根据各时期流体势的展布特征预测了该区油气分布的有利地区。 相似文献
993.
This paper quantitatively presents the results of a case study which examines the fault tree analysis framework of the safety of digital systems. The case study is performed for the digital reactor protection system of nuclear power plants. The broader usage of digital equipment in nuclear power plants gives rise to the need for assessing safety and reliability because it plays an important role in proving the safety of a designed system in the nuclear industry. We quantitatively explain the relationship between the important characteristics of digital systems and the PSA result using mathematical expressions. We also demonstrate the effect of critical factors on the system safety by sensitivity study and the result which is quantified using the fault tree method shows that some factors remarkably affect the system safety. They are the common cause failure, the coverage of fault tolerant mechanisms and software failure probability. 相似文献
994.
An online fault detection and isolation (FDI) technique for nonlinear systems based on neurofuzzy networks (NFN) is proposed in this paper. Two NFNs are used. The first one trained by data obtained under normal operating condition models the system and the second one trained online models the residuals. Fuzzy rules that are activated under fault free and faulty conditions are extracted from the second NFN and stored in the symptom vectors using a binary code. A fault database is then formed from these symptom vectors. When applying the proposed FDI technique, the NFN that models the residuals is updated recursively online, from which the symptom vector is obtained. By comparing this symptom vector with those in the fault database, faults are isolated. Further, the fuzzy rules obtained from the symptom vector can also provide linguistic information to experienced operators for identifying the faults. The implementation and performance of the proposed FDI technique is illustrated by simulation examples involving a two-tank water level control system under faulty conditions. 相似文献
995.
一种基于动态数据库的电网接线实时显示系统 总被引:2,自引:0,他引:2
介绍了一种用于地区电网调度中心警报处理及故障定位专家系统中 ,基于动态数据库的实时显示信息自动生成系统 ,讨论了它的基本原理及实现方法 ,并对它在该系统中的优点进行了分析 相似文献
996.
松辽盆地徐家围子断陷断裂变形特征及控藏机理 总被引:1,自引:0,他引:1
徐家围子断陷为“西断东超”的箕状断陷,伸展断裂和走滑断裂这2种性质断裂对天然气成藏具有明显的控制作用。伸展断裂系统在控盆同时控制有效烃灶分布,近SN向张扭断裂即徐西断裂与NNE向断裂共同控制了沙河子组煤层分布,形成有效烃源灶。走滑断层为火山喷发的通道,徐中断裂和徐东断裂控制营一段和营三段火山分布,与之相交的北北东向断裂有诱导火山喷发作用,交点位置火山规模最大。徐中断裂在泉头组沉积晚期到青山口组沉积早期再次强烈活动,右旋走滑变形使火山岩产生大量裂缝,特别是在断层交点处最发育,形成优质储层。徐东断裂此时无明显活动,优质储层不受裂缝控制。与此同时断裂强烈活动配合沙河子组气源岩大量生排气,成为气源断层,徐中断裂是最主要的气源断裂,由于岩性对接封闭作用,天然气主要分布在气源断裂下盘,因此,天然气围绕倾向变化的徐中断裂两盘呈“正弦曲线”状分布。反转断层和盖层控制天然气富集层位,火山岩顶面的“混岩”盖层品质好,在反转断层不发育区使天然气富集在火山岩储层中。反转断层发育区,易将火山岩中天然气调整到青山口组区域性盖层下的扶杨油层中聚集,调整期为明水组沉积末期。走滑断裂是天然气成藏的主控因素,明水末期没发生强烈反转是保存的关键。 相似文献
997.
Fault detection for discrete event systems using Petri nets with unobservable transitions 总被引:1,自引:0,他引:1
Maria Paola Cabasino Author Vitae Alessandro Giua Author Vitae Author Vitae 《Automatica》2010,46(9):1531-1539
In this paper we present a fault detection approach for discrete event systems using Petri nets. We assume that some of the transitions of the net are unobservable, including all those transitions that model faulty behaviors. Our diagnosis approach is based on the notions of basis marking and justification, that allow us to characterize the set of markings that are consistent with the actual observation, and the set of unobservable transitions whose firing enable it. This approach applies to all net systems whose unobservable subnet is acyclic. If the net system is also bounded the proposed approach may be significantly simplified by moving the most burdensome part of the procedure off-line, thanks to the construction of a graph, called the basis reachability graph. 相似文献
998.
999.
1000.
Alexander P. Rotshtein Morton Posner Hanna B. Rakytyanska 《Reliability Engineering & System Safety》2006,91(9):1095-1101
This paper proposes using a genetic algorithm as a tool to solve the fault diagnosis problem. The fault diagnosis problem is based on a cause and effect analysis which is formally described by fuzzy relations. Fuzzy relations are formed on the basis of expert assessments. Application of expert fuzzy relations to restore and identify the causes through the observed effects requires the solution to a system of fuzzy relational equations. In this study this search for a solution amounts to solving a corresponding optimization problem. An optimization algorithm is based on the application of genetic operations of crossover, mutation and selection. The genetic algorithm suggested here represents an application in expert systems of fault diagnosis and quality control. 相似文献