全文获取类型
收费全文 | 12367篇 |
免费 | 1456篇 |
国内免费 | 406篇 |
专业分类
电工技术 | 969篇 |
综合类 | 480篇 |
化学工业 | 2338篇 |
金属工艺 | 574篇 |
机械仪表 | 852篇 |
建筑科学 | 1111篇 |
矿业工程 | 477篇 |
能源动力 | 467篇 |
轻工业 | 899篇 |
水利工程 | 229篇 |
石油天然气 | 650篇 |
武器工业 | 74篇 |
无线电 | 1232篇 |
一般工业技术 | 1600篇 |
冶金工业 | 496篇 |
原子能技术 | 107篇 |
自动化技术 | 1674篇 |
出版年
2024年 | 118篇 |
2023年 | 363篇 |
2022年 | 607篇 |
2021年 | 881篇 |
2020年 | 580篇 |
2019年 | 524篇 |
2018年 | 588篇 |
2017年 | 619篇 |
2016年 | 476篇 |
2015年 | 617篇 |
2014年 | 819篇 |
2013年 | 959篇 |
2012年 | 1034篇 |
2011年 | 1034篇 |
2010年 | 888篇 |
2009年 | 748篇 |
2008年 | 693篇 |
2007年 | 602篇 |
2006年 | 640篇 |
2005年 | 481篇 |
2004年 | 252篇 |
2003年 | 161篇 |
2002年 | 125篇 |
2001年 | 76篇 |
2000年 | 81篇 |
1999年 | 66篇 |
1998年 | 29篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Highly densified W2B5/C composites with W2B5 content from 30 to 70 vol% were fabricated by reaction hot pressing of the powder mixture of B4C, WC and carbon black. The reaction products were identified by XRD analysis to consist of only W2B5 and carbon, regardless of carbon content. The reaction formed composites have excellent mechanical properties (the maximum flexural strength and fracture toughness of 786 MPa and 8.9 MPa m1/2 respectively), electrical conductivity (the highest electrical conductivity of 1.64 × 106 Ω−1 m−1), and resistance to both wear and oxidation because of the presence of the plate-like W2B5 grains. In this paper, the preparation, microstructure and properties of this new composite are investigated, and the strengthening, toughening, conduction mechanisms are discussed. 相似文献
62.
影视动画产业是当今社会的朝阳产业,是传统经济发展和延伸的一种新方式,政府对影视动画产业十分重视.而影视文化产业具有浓厚文化色彩和广阔的自由发展空间,有利于影视动画的进一步发展与建设.影视动画产业发展对象可以是影视基地,也可以是影视剧本,产业发展对象丰富,所以此产业的发展前景非常明朗,并且还具有高度的研究价值. 相似文献
63.
如今的世界已经是一个信息化和数字化交织的庞大体系,人们对数据安全和保密的重要性认识不断提高,为确保数据的安全多种加密技术被广泛使用。然而数据的非法复制,解密和盗版问题日益严重,数据加密技术依旧是很重要的环节,本文仅对目前常用的加密算法加以比较研究提出较好的加密方法。 相似文献
64.
王俊杰 《重庆科技学院学报(社会科学版)》2010,(8):134-136
花瑶挑花是首批公布的国家级非物质文化遗产代表作。研究花瑶挑花文化空间,保护原生态地,传承濒危的挑花艺术;认为独特的自然地理环境与民族生活方式孕育和滋养花瑶人独特而又精湛的挑花工艺,美仑美奂的挑花服饰亦深深融入花瑶文化空间中。 相似文献
65.
讨论了核为︱x-s︱~(-1)ln︱x-s︱的一种强奇异积分∫baln︱x-s︱/︱x-s︱f(xdx),给出了它的Hadamard有限部分积分的定义,并利用Lagrange线性插值构造了函数这类强奇异积分的数值算法,最后分析和讨论了算法的误差估计。 相似文献
66.
Liguo Huang Jidong Ge Barry Boehm Jian Lv 《International Journal of Software and Informatics》2010,4(1):101-119
Commercial organizations increasingly need software processes sensitive to busi-
ness value, quick to apply, supportive of multi-stakeholder collaboration, and capable of early
analysis for subprocess consistency and compatibility. This paper and a companion paper
\Applying Value-Based Software Process: An ERP Example" present our experience in ap-
plying a lightweight synthesis of a Value-Based Software Quality Achievement (VBSQA)
process and an Object-Petri-Net (OPN) based process model to achieve a stakeholder win-
win outcome for software quality achievement in an ERP software project in China. We
attempt to answer such questions as (1) whether it is possible to model various project
stakeholder perspectives using formal process modeling languages in a real-world project?
(2) how to make stakeholders synchronize and stabilize their value propositions, activities
and commitments as needed. The companion paper presents the VBSQA process and its
application to the ERP project; this paper presents the OPN-based process modeling and its
application. The application results of OPN process modeling conˉrmed that (1) the OPN-
based process model provided project managers with a synchronization and stabilization
framework for process activities, success-critical stakeholders and their value propositions;
(2) process visualization and simulation tools signiˉcantly increased management visibility
and controllability for the success of the software project. 相似文献
67.
Oxygen consumption is an important index of coal oxidation.In order to explore the coal-oxygen reaction,we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures.The size of coal samples ranged from 0.18~0.42 mm and the system heat-rate was 0.8℃/min.The results show that,for high ranked coals,oxygen consumption rises with coal temperature as a piecewise non-linear process.The critical coal temperature is about 50%.Below this temperature,oxygen consumption decreases with rising coal temperatures and reached a minimum at 50℃,approximately.Subsequently,it begins to increase and the rate of growth clearly increased with temperature.For low ranked coals,this characteristic is inconspicuous or even non-existent.The difference in oxygen consumption at the same temperatures varies for differently ranked coals.The results show the difference in oxygen consumption of the coals tested in our study reached 78.6% at 100 ℃.Based on the theory of coal-oxygen reaction,these phenomena were analyzed from the point of view of physical and chemical characteristics,as well as the appearance of the coal-oxygen complex.From theoretical analyses and our experiments,we conclude that the oxygen consumption at programmed temperatures reflects the oxidation ability of coals perfectly. 相似文献
68.
69.
同步发电机与电网大系统进行并列是一项非常复杂关键的任务,阐述了同步发电机并列的条件及传统手动并列验证装置及方法。为了使同步发电机在实验室条件下,准确、快速地与电网大系统并列,介绍了一种以AT89C51单片机为核心的同步发电机自动并列装置。分析了该系统的硬件组成及软件设计,该并列装置并网时具有快速、准确等优点。 相似文献
70.
建立重力坝坝基深层抗滑稳定极限状态函数是进行可靠度研究的第一步,对已有4种极限状态函数进行比较研究,探讨其合理性.研究结果表明:根据剩余推力法、被动抗力法及等K法表达式建立的极限状态函数计算得到的可靠指标是一致的,3种极限状态函数可统一表达为安全系数极限状态函数,而以上、下游块等可靠指标为约束条件的等β法高估了双滑块模型的失效概率,以此来评价坝基深层抗滑稳定的安全度并不合理. 相似文献