全文获取类型
收费全文 | 135038篇 |
免费 | 10931篇 |
国内免费 | 6295篇 |
专业分类
电工技术 | 8257篇 |
技术理论 | 8篇 |
综合类 | 10304篇 |
化学工业 | 22685篇 |
金属工艺 | 8572篇 |
机械仪表 | 8659篇 |
建筑科学 | 10890篇 |
矿业工程 | 4028篇 |
能源动力 | 3542篇 |
轻工业 | 9645篇 |
水利工程 | 2740篇 |
石油天然气 | 7472篇 |
武器工业 | 1198篇 |
无线电 | 13978篇 |
一般工业技术 | 14862篇 |
冶金工业 | 6608篇 |
原子能技术 | 1636篇 |
自动化技术 | 17180篇 |
出版年
2024年 | 510篇 |
2023年 | 1931篇 |
2022年 | 3457篇 |
2021年 | 4733篇 |
2020年 | 3654篇 |
2019年 | 3087篇 |
2018年 | 3568篇 |
2017年 | 4021篇 |
2016年 | 3552篇 |
2015年 | 4975篇 |
2014年 | 6295篇 |
2013年 | 7809篇 |
2012年 | 8911篇 |
2011年 | 9521篇 |
2010年 | 8509篇 |
2009年 | 8385篇 |
2008年 | 8395篇 |
2007年 | 8181篇 |
2006年 | 8237篇 |
2005年 | 7109篇 |
2004年 | 4998篇 |
2003年 | 4029篇 |
2002年 | 3727篇 |
2001年 | 3263篇 |
2000年 | 3320篇 |
1999年 | 3395篇 |
1998年 | 2658篇 |
1997年 | 2193篇 |
1996年 | 2175篇 |
1995年 | 1786篇 |
1994年 | 1489篇 |
1993年 | 1025篇 |
1992年 | 843篇 |
1991年 | 642篇 |
1990年 | 458篇 |
1989年 | 403篇 |
1988年 | 318篇 |
1987年 | 217篇 |
1986年 | 144篇 |
1985年 | 92篇 |
1984年 | 63篇 |
1983年 | 42篇 |
1982年 | 46篇 |
1981年 | 40篇 |
1980年 | 28篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
应用功率控制、波束赋形和多用户检测可以有效地消除和减少CDMA系统中的干扰。本文结合波束赋形和多用户检测的特性,提出一种应用波束赋形增益和多用户相关矩阵的解相关算法。基于算法的复杂性,提出一种区分聚集用户进行多用户检测的的算法。由于波束赋形能够消减主瓣波束之外的多用户干扰,对聚集移动台采用解相关检测达到减少运算量和消除多用户干扰的目的。对算法进行了仿真分析,证明了本算法的优越性。 相似文献
64.
65.
Longjie Zhou A. Zimmermann Yu-Ping Zeng F. Aldinger 《Journal of Materials Science》2004,39(8):2675-2681
The bipolar electric fatigue behaviour of antiferroelectric ceramics with the composition of Pb0.88Ba0.10La0.02(Zr0.55Sn0.35Ti0.10)O3 was investigated under various cycling fields. The material exhibits a degradation in the maximum field induced strain, a diffuse AFE-FE phase transition and an enhancement in the diffusion character of the FE-AFE phase transition due to electric cycling. Those variations increase with cycle number, indicating a logarithmic fatigue up to 108 cycles. There is no indication for the variations to be recovered, and the symmetry of the negative and positive parts of the strain hysteresis loops still remains. Higher cycling field results in a stronger deterioration of the maximum field induced strain and a larger extent of diffusion in AFE-FE and FE-AFE phase transitions. The normalized maximum strain shows nearly the same scale of degradation when the materials are cycled at various electric fields. After a heat treatment at 500°C for 1 h, the variations in the AFE-FE and FE-AFE phase transition due to cycling disappear, whereas the maximum strain resumes almost to its original value. Electrochemical variations are considered to contribute to the main fatigue mechanism for the material under investigation. 相似文献
66.
以工业偏钛酸、硫酸锌、氨水为主要原料,用直接沉淀法并进行热处理得到钛酸锌粉体,并用XRD对产物成分进行了检测。结果表明,不同的锌钛比对钛酸锌(ZnO-TiO2)体系的成分有较大影响。 相似文献
67.
Web服务在信用信息工程中的应用 总被引:2,自引:2,他引:0
目前的社会信用信息工程中,许多的政府部门都建立了自己的信用信息数据库,但在政府各级部门数据库之间进行数据交流和共享存在着许多的问题,在许多地方,数据共享还是一片空白。Web服务技术是应用程序通过内联网或者因特网发布和利用软件服务的一种标准机制。利用WEB服务可以方便地实现不同系统之间的数据交换和集成。该文提出利用web服务技术来解决信用信息工程中的信息数据共享问题。并在此基础上提出利用WEB服务工作流技术将信用评估整合到电子商务过程,以实现可信用电子商务 相似文献
68.
69.
Chor Ping Low 《Communications Letters, IEEE》2005,9(11):1012-1014
One of the main issues to be addressed in topological design of centralized networks is that of assigning terminals to concentrators in such a way that each terminal is assigned to one (and only one) concentrator and the total number of terminals assigned to any concentrator (which is referred to as load in this paper) does not overload that concentrator, i.e. is within the concentrator's capacity. Under these constraints, an assignment with the lowest possible cost is sought. An assignment of terminals to concentrators which minimizes the maximum load among the concentrators (which qualitatively represents congestion at some hot spots in a network service area) is referred to as a min-max load assignment. In this paper, we consider the problem of finding a min-max load assignment with the-lowest cost. We call this problem the Minimum Cost Min-Max Load Terminal Assignment Problem (MCMLTAP). We present an algorithm for MCMLTAP and prove that the problem is optimally solvable in polynomial time using our proposed algorithm. 相似文献
70.
A. Carpinteri S. Valente F. P. Zhou G. Ferrara G. Melchiorri 《Materials and Structures》1997,30(5):269-276
Three series of novel tensile and flexural creep tests on partially-damaged concrete specimens were carried out in order to gain some insight into creep crack growth and failure of strain-softening materials. In the tests, each specimen was initially loaded to a given point in the descending branch and thus had a lower load-carrying capacity than that at the peak-point. Then, the specimen was unloaded and reloaded to sustain a load which was from 70% to 95% of its current load-carrying capacity. Experimental creep curves display a three-stage process, consisting of primary, secondary and tertiary stages, with a decreasing, constant and increasing creep rate, respectively. The secondary stage dominates the whole failure lifetime, whereas both the secondary and tertiary stages are important in terms of creep deformation. Failure life-time seems to be more sensitive to the change of load level in flexural tests rather than in tensile tests. The decrease in load-carrying capacity due to damage tends to result in a shorter failure lifetime and a lower critical load level for creep rupture. The descending branch of the static load-deflection or load-CMOD curve may be used as an envelope criterion for creep fracture. 相似文献