全文获取类型
收费全文 | 171941篇 |
免费 | 23366篇 |
国内免费 | 16981篇 |
专业分类
电工技术 | 22327篇 |
技术理论 | 20篇 |
综合类 | 21826篇 |
化学工业 | 7305篇 |
金属工艺 | 3949篇 |
机械仪表 | 10786篇 |
建筑科学 | 11397篇 |
矿业工程 | 5164篇 |
能源动力 | 3666篇 |
轻工业 | 2774篇 |
水利工程 | 4588篇 |
石油天然气 | 3526篇 |
武器工业 | 2757篇 |
无线电 | 29015篇 |
一般工业技术 | 10590篇 |
冶金工业 | 4069篇 |
原子能技术 | 524篇 |
自动化技术 | 68005篇 |
出版年
2024年 | 1259篇 |
2023年 | 3258篇 |
2022年 | 6051篇 |
2021年 | 6688篇 |
2020年 | 6983篇 |
2019年 | 5177篇 |
2018年 | 4640篇 |
2017年 | 5601篇 |
2016年 | 6263篇 |
2015年 | 6935篇 |
2014年 | 11489篇 |
2013年 | 10504篇 |
2012年 | 13441篇 |
2011年 | 13642篇 |
2010年 | 10653篇 |
2009年 | 11141篇 |
2008年 | 11551篇 |
2007年 | 13062篇 |
2006年 | 11199篇 |
2005年 | 9819篇 |
2004年 | 8164篇 |
2003年 | 7137篇 |
2002年 | 5468篇 |
2001年 | 4720篇 |
2000年 | 3852篇 |
1999年 | 3000篇 |
1998年 | 2200篇 |
1997年 | 1832篇 |
1996年 | 1481篇 |
1995年 | 1178篇 |
1994年 | 961篇 |
1993年 | 675篇 |
1992年 | 468篇 |
1991年 | 355篇 |
1990年 | 271篇 |
1989年 | 273篇 |
1988年 | 181篇 |
1987年 | 96篇 |
1986年 | 73篇 |
1985年 | 84篇 |
1984年 | 88篇 |
1983年 | 68篇 |
1982年 | 62篇 |
1981年 | 29篇 |
1980年 | 40篇 |
1979年 | 41篇 |
1977年 | 13篇 |
1965年 | 11篇 |
1964年 | 11篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
阐述了会计信息失真的表现形式及其危害性,从会计自身、内控制度、外部审计、道德观念、执法等方面分析了会计信息失真的原因,并从完善法规制度、实行会计委派制、健全会计监督体系、加强立法和执法力度、更新观念、提高素质等方面提出了治理会计信息失真的办法,从根本上杜绝会计信息失真的现象。 相似文献
42.
温熙华 《电信工程技术与标准化》2002,(5):36-39
本主要介绍基于CDMA智能网平台的一种增值业务——“位置服务”,阐述这个业务的网络结构、涉及到的技术问题和解决方案,并将这个整体思路投入到开发业务中去。 相似文献
43.
Paul J. Flory 《Polymer International》1985,17(2):96-102
The earliest investigations on rubber elasticity, commencing in the 19th century, were necessarily limited to phenomenological interpretations. The realisation that polymers consist of very long molecular chains. commencing c. 1930, gave impetus to the molecular theory of rubber elasticity (1932-). according to which the high deformability of an elastomer, and the elastic force generated by deformation, stem from the configurations accessible to long molecular chains. Theories of rubber elasticity put forward from 1934-1946 relied on the assumption that the junctions of the rubber network undergo displacements that are affine in macroscopic strain. The theory of James and Guth (1947) dispensed with this premise, and demonstrated instead that the mean positions of the junctions of a ‘phantom’ network consisting of Gaussian chains devoid of material properties are affine in the strain. The vital significance of the distinction between the actual distribution of chain vectors in a network and their distribution if the junctions would be fixed at their mean positions went unnoticed for nearly 30 years. Experimental investigations, commencing with the incisive work of Gee in 1946. revealed large departures from the relationship of stress to strain predicted by the theories cited. This discrepancy prompted extensive studies, theoretical and experimental, during succeeding years. Inquiry into the fundamentals of polymer networks, formed for example by interlinking very long polymer molecules, exposed the need to take account of network imperfections, typically consisting of chains attached at only one end to a network junction. Various means were advocated to make corrections for these imperfections. The cycle rank ζ of the network has been shown (1976) to be the fundamental measure of its connectivity, regardless of the junction functionality and pattern of imperfections. Often overlooked is the copious interpenetration of the chains comprising typical elastomeric networks. Theories that attempt to represent such networks on a lattice are incompatible with this universal feature. Moreover, the dense interpenetration of chains may limit the ability of junctions in real networks to accommodate the fluctuations envisaged in the theory of phantom networks. It was suggested in 1975 that departures from the form predicted for the elastic equation of state are due to constraints on the fluctuations of junctions whose effect diminishes with deformation and with dilation. Formulation of a self-consistent theory based on this suggestion required recognition of the non-affine connection between the chain vector distribution function and the macroscopic strain in a real network, which may partake of characteristics of a phantom network in some degree. Implementation of the idea was achieved through postulation of domains of constraint affecting the equilibrium distribution of fluctuations of network junctions from their mean positions. This led in due course to a theory that accounts for the relationship of stress to strain virtually throughout the ranges of strain accessible to measurement. The theory establishes connections between structure and elastic properties. This is achieved with utmost frugality in arbitrary parameters. 相似文献
44.
This paper presents a method to compensate voltage sags with minimum energy injection for a series‐connected voltage restorer using a micro‐SMES. A circuit for extracting the fundamental symmetrical components from sag voltages and a minimum energy injection algorithm is described. Simulations of voltage sag compensation have been carried out using PSCAD/EMTDC for various faults. The simulation results confirm the validity of the proposed method and show the possibility of reducing the size of energy storage devices. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 70–80, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10047 相似文献
45.
图书馆图书管理系统分析与设计 总被引:4,自引:0,他引:4
图书馆作为一个专门收集、整理、保存、传播文献 ,并提供利用的科学、文化、教育机构 ,是人们获取知识的主要来源之一。发展至今已有数千年的历史。然而 ,在信息技术迅速普及的今天 ,越来越多的读者希望通过网络更方便、更快捷地进行图书的查阅、借阅 ,获取自己的所需 ,因此图书馆的信息化建设尤为重要 相似文献
46.
条件概率关系数据库模型 总被引:1,自引:0,他引:1
现实世界中大量存在着的不确定性信息,关系数据库模型仅视它们为空值,有必要增强其处理这类信息的能力,文章在总结前人工作的基础上推广关系数据库模型,创建有效处理随机型不确定性信息的条件概念关系数据库模型,该模型通过在关系模式中增加一个条件概率测度属性,为每条记录指定适当的条件概率的途径,来表示不确定性信息。文中以对象码为基本工具,创建了条件概率关系结构;以特征函数为基本工具,定义了一套基于该结构的代数运算规则。条件概率的语意比概率的语意广泛,灵活,因而该模型能有效克服概率关系模型的许多不足。 相似文献
47.
WLAN网管系统的现状和发展 总被引:2,自引:0,他引:2
2001年以来,全球WLAN(无线局域网)市场应用的瓶颈被打破,中国也迎来了WLAN商业化运作和服务的春天,WLAN为我们带来了一种全新的、灵活的工作方式,同时也带来了新的挑战,本文将对WLAN网络管理的主要内容和具体指标进行阐述,并对各大厂商的WLAN网管产品进行简单介绍和比较。 相似文献
48.
NBR/PP热塑性弹性体研究进展 总被引:12,自引:0,他引:12
阐述了NBR/PP共混热塑性弹性体动态硫化胶的国内外研究进展、微观相态结构、性能、应用及展望。 相似文献
49.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献
50.
宽带建设低潮期实际上是一次优胜劣汰的过程,宽带运营竞争的手段将由低价竞争转向服务质量和特色的竞争。应在重视宽带接入建设的同时,也要重视业务运营管理平台的建设。应从长远考虑,不应仅为了节省投资而降低对设备的要求。由于降低成本的主要方向是在线缆部分,因此EVDSL技术应用的速度将大大超过人们的预期。在网络建设上,IPDSLAM虽有优势但也有不足,还需要进一步的成熟、稳定和实践的检验。 相似文献