全文获取类型
收费全文 | 26018篇 |
免费 | 4299篇 |
国内免费 | 3457篇 |
专业分类
电工技术 | 2194篇 |
技术理论 | 2篇 |
综合类 | 2677篇 |
化学工业 | 785篇 |
金属工艺 | 1003篇 |
机械仪表 | 2313篇 |
建筑科学 | 629篇 |
矿业工程 | 628篇 |
能源动力 | 814篇 |
轻工业 | 357篇 |
水利工程 | 534篇 |
石油天然气 | 313篇 |
武器工业 | 346篇 |
无线电 | 2706篇 |
一般工业技术 | 1550篇 |
冶金工业 | 350篇 |
原子能技术 | 80篇 |
自动化技术 | 16493篇 |
出版年
2024年 | 158篇 |
2023年 | 503篇 |
2022年 | 907篇 |
2021年 | 1019篇 |
2020年 | 1093篇 |
2019年 | 990篇 |
2018年 | 921篇 |
2017年 | 1095篇 |
2016年 | 1188篇 |
2015年 | 1378篇 |
2014年 | 1729篇 |
2013年 | 1714篇 |
2012年 | 2018篇 |
2011年 | 2184篇 |
2010年 | 1778篇 |
2009年 | 1890篇 |
2008年 | 1948篇 |
2007年 | 2095篇 |
2006年 | 1720篇 |
2005年 | 1418篇 |
2004年 | 1106篇 |
2003年 | 988篇 |
2002年 | 697篇 |
2001年 | 562篇 |
2000年 | 491篇 |
1999年 | 462篇 |
1998年 | 364篇 |
1997年 | 283篇 |
1996年 | 234篇 |
1995年 | 181篇 |
1994年 | 149篇 |
1993年 | 99篇 |
1992年 | 71篇 |
1991年 | 54篇 |
1990年 | 52篇 |
1989年 | 54篇 |
1988年 | 31篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1974年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
References: 《计算技术与自动化》2003,22(Z1):54-57
In order to avoid unnecessary damage of electrical equipments and installations,high quality power should be delivered to the end user and strict control on frequency should be made, Therefore, it is important to estimate the power system's harmonic components with higher accuracy. This paper presents a new approach for estimating harmonic component in a power system using secant - fuzzy linear regression method. In this approach the non - sinusoidal voltage or current waveform is written as I linear function. The coefficient of this function is assumed to be fuzzy number with a membership function that has center and spread value. The time dependent quantity is written as Taylor series with two different time dependent quantities. The objective is to use the sample obtained from the transmission line to find the power system harmonic components and frequencies. We used an experimental voltage signal from a sub power station as a numerical test. 相似文献
62.
It seems clear that, for whatever reasons, the dementia of the Alzheimer type patient group (as well as other patient groups) exhibits behavior that is different from the normal control group. G. Storms, T. Dirikx, J. Saerens, S. Verstraeten, and P. P. De Deyn (2003) rightfully argue that the observed behavior (similarity judgments) does not tell us the source (cause) of the differences between the 2 groups. Rather, the focus of the study should be placed more on finding the ways the 2 groups are different. They also point out various methodological problems in some of the previous attempts to characterize the nature of the differences. Further methodological issues in G. Storms et al.'s study are examined. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
63.
介绍了集团变分法的集团概率变量、配置熵等统计分析的理论基础及Helmholtz自由能的描述模型.提出了巨势及相对化学势的几何分析理论.讨论了应用集团变分法和巨势分析理论进行相平衡计算的过程,并分析了同结构平衡相图计算的若干实例. 相似文献
64.
65.
Chenn-Jung Huang Wei-Kuang Lai Sheng-Yu Hsiao Hao-Yu Liu Rui-Lin Luo 《International Journal of Wireless Information Networks》2004,11(3):131-146
In this paper, a routing protocol which utilizes the characteristics of Bluetooth technology is proposed for Bluetooth-based mobile ad hoc networks. The routing tables are maintained in the master devices and the routing zone radius for each table is adjusted dynamically by using evolving fuzzy neural networks. Observing there exists some useless routing packets which are helpless to build the routing path and increase the network loads in the existing ad hoc routing protocols, we selectively use multiple unicasts or one broadcast when the destination device is out of the routing zone radius coverage of the routing table. The simulation results show that the dynamic adjustment of the routing table size in each master device results in much less reply time of routing request, fewer request packets and useless packets compared with two representative protocols, Zone Routing Protocol and Dynamic Source Routing. 相似文献
66.
Sipra Mahapatra Turaga P. Prasad 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(2):201-203
Hydrolysis of Fe(OH)SO4 was carried out in the presence of metallic iron in order to prevent the formation of iron(III) oxides with strongly bonded sulphate. Under the conditions of the experiment, the products were found to be mixtures of ?-Fe2O3 and α-FeOOH. The occluded sulphate, if any, could be easily washed out with water. The hydrolysis reaction passes through an equilibrium state before coming to completion. The entropy with enthalpy of the hydrolysis corresponding to the equilibrium state were found to be 4 e.u. and 0·5 kJ/mol, respectively. The activation energy of the hydrolysis reaction was found to be 21 kJ/mol. 相似文献
67.
68.
本文分析了模糊字符串几种类型和它的表示方法,并给出模糊匹配的算法及C语言的源程序,同时也指出了在文枉编辑器的应用例子。 相似文献
69.
用基函数神经网络实现多阈值图象分割 总被引:1,自引:0,他引:1
本文介绍了一种用基函数神经网络实现多阈值图象分割的新方法。它从函数逼近的角度研究基于灰度直方图的多阈值分割问题,提出了一种模糊反向传播学习算法,采用该算法的高斯基函数网络能够准确检测直方图中包含的子区域和它们的分布函数,而且速度很快。实验表明本文的方法在实际图象分割中是有效的。 相似文献
70.
Ibrahim H. Osman Nicos Christofides 《International Transactions in Operational Research》1994,1(3):317-336
The capacitated clustering problem (CCP) is the problem in which a given set of weighted objects is to be partitioned into clusters so that the total weight of objects in each cluster is less than a given value (cluster ‘capacity’). The objective is to minimize the total scatter of objects from the ‘centre’ of the cluster to which they have been allocated. A simple constructive heuristic, a R-interchange generation mechanism, a hybrid simulated annealing (SA) and tabu search (TS) algorithm which has computationally desirable features using a new non-monotonic cooling schedule, are developed. A classification of the existing SA cooling schedules is presented. The effects on the final solution quality of the initial solutions, the cooling schedule parameters and the neighbourhood search strategies are investigated. Computational results on randomly generated problems with size ranging from 50 to 100 customers indicate that the hybrid SA/TS algorithm out-performs previous simulated annealing algorithms, a simple tabu search and local descent algorithms. 相似文献