全文获取类型
收费全文 | 44280篇 |
免费 | 3898篇 |
国内免费 | 1781篇 |
专业分类
电工技术 | 5264篇 |
技术理论 | 2篇 |
综合类 | 2941篇 |
化学工业 | 2311篇 |
金属工艺 | 1056篇 |
机械仪表 | 3074篇 |
建筑科学 | 5677篇 |
矿业工程 | 2905篇 |
能源动力 | 1240篇 |
轻工业 | 3082篇 |
水利工程 | 3398篇 |
石油天然气 | 1174篇 |
武器工业 | 216篇 |
无线电 | 3185篇 |
一般工业技术 | 2907篇 |
冶金工业 | 2845篇 |
原子能技术 | 568篇 |
自动化技术 | 8114篇 |
出版年
2024年 | 194篇 |
2023年 | 661篇 |
2022年 | 1298篇 |
2021年 | 1615篇 |
2020年 | 1606篇 |
2019年 | 1178篇 |
2018年 | 1063篇 |
2017年 | 1426篇 |
2016年 | 1653篇 |
2015年 | 1851篇 |
2014年 | 3185篇 |
2013年 | 2920篇 |
2012年 | 3799篇 |
2011年 | 3969篇 |
2010年 | 2707篇 |
2009年 | 2570篇 |
2008年 | 2418篇 |
2007年 | 2632篇 |
2006年 | 2368篇 |
2005年 | 2125篇 |
2004年 | 1810篇 |
2003年 | 1495篇 |
2002年 | 1156篇 |
2001年 | 814篇 |
2000年 | 678篇 |
1999年 | 551篇 |
1998年 | 430篇 |
1997年 | 361篇 |
1996年 | 264篇 |
1995年 | 218篇 |
1994年 | 172篇 |
1993年 | 118篇 |
1992年 | 78篇 |
1991年 | 68篇 |
1990年 | 64篇 |
1989年 | 61篇 |
1988年 | 53篇 |
1987年 | 27篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 32篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1966年 | 9篇 |
1963年 | 12篇 |
1958年 | 9篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Norbert Delatte 《Canadian Metallurgical Quarterly》2004,130(1):37-43
For the last seven years, a summer Research Experiences for Undergraduates site in structural engineering, funded by the National Science Foundation, has operated at the University of Alabama at Birmingham. During this time, 33 students from 22 colleges and universities have participated in the site. Participants are recruited nationally and have come from as far away as California and Puerto Rico. The program is intended to provide students interested in graduate studies with an introduction to research methods, and to provide students who will not continue their studies past a bachelor of science in civil engineering with a better understanding of how research provides the theoretical foundation of engineering practice. Students work individually with faculty on literature reviews, computer modeling, laboratory testing, and field research. Three students have researched structural failure case studies and the technical and ethical lessons to be learned from them. Participants also have the opportunity to tour construction sites and construction material manufacturers’ and fabricators’ facilities. During the past three years, an ethics seminar series has been added. At the end of the program, students prepare research papers and Web pages documenting their work and present their results to faculty, students, and other participants. 相似文献
103.
深基坑施工安全的监测与实例 总被引:1,自引:0,他引:1
从明确深基坑施工安全监测的关键出发,确定了监测内容和相关极限报警值,用工程实例进行了阐述。 相似文献
104.
The current study examined psychological and physical health outcomes of the written disclosure paradigm and the hypothesis that the principles of therapeutic exposure account for the beneficial effects of the paradigm. Participants were randomly assigned to either a written disclosure condition or a control condition. Reactivity to the writing sessions was examined using both subjective and physiological measures. Measures of psychological and physical health were completed before and 1 month after the sessions. Participants assigned to the disclosure condition reported fewer psychological and physical symptoms at follow-up compared with control participants, though reductions were clinically significant for only 1 outcome measure. Physiological activation to the 1st disclosure session was associated with reduced psychological symptoms at follow-up for disclosure participants. Subjective reports of emotional responding corresponded with physiological reactivity. Implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
本文设计了一种应用于油气藏永久性实时动态监测系统。该系统用光纤Bragg光栅(FBG)传感器作为井下永久性传感器,测量目的层的温度、压力等参数的模拟信号;在井口建立数据采集处理系统,将模拟信号解调成数字信号;通过GPRS无线移动通信网络传输到监测中心的数据库服务器上,并以Web形式发布到Internet网络上,同时提供移动用户浏览接口,且当数据异常时可以发送报警短消息。该系统实现了油气藏的远程实时动态监测,可以为油藏管理人员和技术人员及时、准确地做出决策提供可靠依据。 相似文献
106.
The determination of the Young’s modulus and damping coefficient Q−1 by means of non-destructive vibrating techniques has been applied to bulk and coated industrial materials. Extensions of a previous analytic model of composite beam allow to determine accurately the macroscopic modulus of each component of multilayered structural materials as coated superalloys or nitride-hardened steels. Furthermore, the study of glasses and polymers has been investigated. An attempt of normalisation of the modulus versus temperature curves allows to establish master curves depending on the specific structure, from metallic glasses to polymeric glasses. Finally a comparison of dynamical modulus and Q−1 values measured between resonant (>1 kHz) and subresonant techniques (10−3 to 10 Hz) in relation to the loading frequencies applied in real conditions has been under folder. For metallic materials such as forged or rolled titanium alloys, the brittle-to-fragile transition occurs abruptly or smoothly with a shift of 300 K following the range of excitation frequencies. 相似文献
107.
本文介绍了差分光学吸收光谱法(DOAS)测量大气污染气体浓度的基本原理。DOAS方法就是利用氙灯发出的紫外—可见光,经望远镜准直后再经过一段距离的传输,由望远镜来接收.在传输中,由于各种不同的分子在不同的波段对光有不同的吸收特征,使光谱具有了污染物的特征,再通过与光源发出的光进行比较,反演这些气体在大气中浓度.我们将DOAS方法应用在监测有机物上,在分析光谱的过程中,应用多项式拟合和最小二乘法,从而精确地从测量光谱中来反演出大气中污染气体的浓度.文中用DOAS方法测量了苯和甲苯的样品,并分析了结果,结果和理论吻合.可为环境中有机污染物监测提供可靠的方法。 相似文献
108.
Melamed Barbara G.; Matthews Karen A.; Routh Donald K.; Stabler Brian 《Canadian Metallurgical Quarterly》1986,5(3):181
This article introduces the current issue of Health Psychology. The call for early intervention to prevent adulthood health problems and the need to consider each period of children's lives within its developmental perspective are the main emphases in this special issue of the journal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
A statistical method for surveying water quality and analysing the results in terms of quantiles is described. The value of a water quality variable in a grab-sample is taken as a deterministic function of the temporal and spatial coordinates of the sampling point. Quantiles can then be defined for any specified region in time and space as unique, fixed values, and randomly located grab-samples may be used to estimate them for the purposes of describing or regulating water quality. Robust statistical inferences are possible using the binomial distribution. Properties of the quantiles, confidence limits, comparisons with fixed values or between regions, assessment of trends, simultaneous inferences and estimation of sample sizes are discussed. Two examples of water quality surveys, one of Port Phillip Bay, the other of the Maribyrnong River, Victoria, are used to illustrate the theory, paying particular attention to practical problems which arose. The proposed method is compared with others based on stochastic models, and is claimed to be simpler and more reliable. 相似文献
110.