全文获取类型
收费全文 | 49226篇 |
免费 | 5494篇 |
国内免费 | 3327篇 |
专业分类
电工技术 | 3961篇 |
技术理论 | 2篇 |
综合类 | 4473篇 |
化学工业 | 7185篇 |
金属工艺 | 3021篇 |
机械仪表 | 3240篇 |
建筑科学 | 3455篇 |
矿业工程 | 1543篇 |
能源动力 | 1521篇 |
轻工业 | 4910篇 |
水利工程 | 1400篇 |
石油天然气 | 2095篇 |
武器工业 | 425篇 |
无线电 | 5509篇 |
一般工业技术 | 5285篇 |
冶金工业 | 2164篇 |
原子能技术 | 1097篇 |
自动化技术 | 6761篇 |
出版年
2024年 | 294篇 |
2023年 | 894篇 |
2022年 | 1747篇 |
2021年 | 2221篇 |
2020年 | 1594篇 |
2019年 | 1367篇 |
2018年 | 1470篇 |
2017年 | 1606篇 |
2016年 | 1572篇 |
2015年 | 2126篇 |
2014年 | 2582篇 |
2013年 | 2961篇 |
2012年 | 3389篇 |
2011年 | 3769篇 |
2010年 | 3239篇 |
2009年 | 3299篇 |
2008年 | 3362篇 |
2007年 | 3317篇 |
2006年 | 3088篇 |
2005年 | 2600篇 |
2004年 | 1886篇 |
2003年 | 1650篇 |
2002年 | 1769篇 |
2001年 | 1646篇 |
2000年 | 1181篇 |
1999年 | 794篇 |
1998年 | 441篇 |
1997年 | 407篇 |
1996年 | 386篇 |
1995年 | 315篇 |
1994年 | 210篇 |
1993年 | 176篇 |
1992年 | 154篇 |
1991年 | 103篇 |
1990年 | 77篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 43篇 |
1986年 | 37篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1959年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
一种语音混沌保密通信方案的研究与硬件实现 总被引:7,自引:0,他引:7
在硬件实验研究的基础上,建立一种环形蔡氏电路,提出用环蔡氏电路实现语音混沌保密通信的一种闭环逆系统方案,其特点是利用环形蔡氏电路的单向耦合原理,通过反馈的方法形成一个包括有用信号在内的极联闭合环路,从而实现改善端与接收端之间混沌系统的严格同步而不受有用信息调制的影响。理论分析与硬件实验结果证明,该方案同现有的其它混沌通信方案相比较,具有非线性失真小、保真度高的优点,完全能够满足传送语音信号的要求。 相似文献
33.
A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze trace elements,especially lead,in vehicle exhaust of Shanghai city.The result shows that the chemical composition and its corresponding x-ray relative intensity are different among different vehicle exhausts.There are many kinds of metal elements in particles of vehicle exhaust.most are harmful to people,such as Ti,Cr,Mn,Pb,etc.We found that the lead concentration was 6820μg/g and the bromine concentration was 5300μg/g in the exhaust from Santana using leaded gasoline(SULG).which is higher than any other kinds of vehicle exhausts.We have also detected the minimum lead in the particles of unleaded gasoline and its content varies from one to another.Its mean concentration was 450μg/g and the highest reached 6210μg/g.The unleaded gasoline‘s Pb existed in the whole particle while the leaded gasoline‘s enriched in the surface of the particle and was more harmful to the human beings. 相似文献
34.
35.
We present a new iterative alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method. By recognizing the ADI-FDTD method as a special case of a more general iterative approach to solve the Crank-Nicolson (CN) FDTD scheme, the splitting error in ADI-FDTD can be reduced systematically. Numerical examples are used to illustrate the improved accuracy of this method. 相似文献
36.
为扩大我省工程咨询业在国外的影响,进一步加强工程咨询企业的国际合作,学习和借鉴发达国家在城市规划与建设领域的先进理念和经验,受美国、加拿大相关部门的的邀请,经省发展改革委批准,由江苏省工程咨询协会组织的业内领导及工程咨询专业技术骨干赴美国、加拿大考察团一行9人,于6月15日至27日对美国、加拿大城市规划与建设情况进行了学习考察. 相似文献
37.
Yewang Su Baohua Ji Yonggang Huang Kehchih Hwang 《Journal of Materials Science》2007,42(21):8885-8893
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus
on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the
liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition
from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of
adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like
contact shape has advantages in a hydrophobic environment and on a rough surface. 相似文献
38.
39.
Struts是基于模型视图控制体系(MVC)的Web应用框架。详细介绍了基于MVC体系的Struts工作原理,探讨应用Struts框架构建企业级应用系统的步骤及方法。给出了基于Struts的科研资源计划系(SRRPS)的设计实现,结果表明Struts框架能极大地提高系统的可扩展性、可重用性及可维护性。 相似文献
40.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献