全文获取类型
收费全文 | 7958篇 |
免费 | 381篇 |
国内免费 | 244篇 |
专业分类
电工技术 | 228篇 |
技术理论 | 1篇 |
综合类 | 519篇 |
化学工业 | 814篇 |
金属工艺 | 71篇 |
机械仪表 | 125篇 |
建筑科学 | 1781篇 |
矿业工程 | 485篇 |
能源动力 | 429篇 |
轻工业 | 389篇 |
水利工程 | 764篇 |
石油天然气 | 116篇 |
武器工业 | 14篇 |
无线电 | 223篇 |
一般工业技术 | 273篇 |
冶金工业 | 851篇 |
原子能技术 | 16篇 |
自动化技术 | 1484篇 |
出版年
2024年 | 12篇 |
2023年 | 64篇 |
2022年 | 116篇 |
2021年 | 168篇 |
2020年 | 200篇 |
2019年 | 150篇 |
2018年 | 150篇 |
2017年 | 174篇 |
2016年 | 277篇 |
2015年 | 276篇 |
2014年 | 417篇 |
2013年 | 473篇 |
2012年 | 460篇 |
2011年 | 651篇 |
2010年 | 504篇 |
2009年 | 540篇 |
2008年 | 502篇 |
2007年 | 563篇 |
2006年 | 491篇 |
2005年 | 393篇 |
2004年 | 383篇 |
2003年 | 333篇 |
2002年 | 267篇 |
2001年 | 210篇 |
2000年 | 138篇 |
1999年 | 118篇 |
1998年 | 88篇 |
1997年 | 71篇 |
1996年 | 65篇 |
1995年 | 48篇 |
1994年 | 43篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 19篇 |
1990年 | 30篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1964年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有8583条查询结果,搜索用时 0 毫秒
21.
在详细分析220 kV和110 kV变压器的容量不相匹配,以及采用常规保护配置与整定方法可能引发220 kV主变压器110 kV侧后备保护越级跳闸,造成大面积停电事故的基础上,研究并提出220 kV主变保护中的相应后备保护改用距离原理保护而其他保护保留的特殊配置的解决方案。对该解决方案进行了分析和计算,提出在不同情况下对距离保护的整定策略。研制了按阻抗原理配置的220 kV变压器保护装置,进行了静态模拟和动态模拟试验,结果表明,该保护装置是有效和可行的,取得了上下级保护相互配合的预期效果。 相似文献
22.
Tuning in to psychological change: Linguistic markers of psychological traits and emotions over time in popular U.S. song lyrics. 总被引:1,自引:0,他引:1
DeWall C. Nathan; Pond Richard S. Jr.; Campbell W. Keith; Twenge Jean M. 《Canadian Metallurgical Quarterly》2011,5(3):200
American culture is filled with cultural products. Yet few studies have investigated how changes in cultural products correspond to changes in psychological traits and emotions. The current research fills this gap by testing the hypothesis that one cultural product—word use in popular song lyrics—changes over time in harmony with cultural changes in individualistic traits. Linguistic analyses of the most popular songs from 1980–2007 demonstrated changes in word use that mirror psychological change. Over time, use of words related to self-focus and antisocial behavior increased, whereas words related to other-focus, social interactions, and positive emotion decreased. These findings offer novel evidence regarding the need to investigate how changes in the tangible artifacts of the sociocultural environment can provide a window into understanding cultural changes in psychological processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
23.
This paper introduces readers to the concepts of implementation science, implementation theory, and implementation frameworks and models. A wide range of models has been published in the literature related to implementation. The paper will present an overview of the Consolidated Framework for Implementation Research (CFIR), which is a comprehensive typology that unifies and consolidates the array of constructs that influence implementation from the perspective of these models. The CFIR is then used to evaluate implementation models used in studies of substance use disorder (SUD) treatments. Implementation research is scarce, with few prospective studies of theory-driven implementation. We assert that future research in SUD needs to meet three overarching objectives to promote wider implementation of evidence-based practices: (a) differentiation of core versus adaptable components of evidence-based interventions need; (b) development of methods to design implementation strategies, effectively adapted to the broad context; and (c) design and testing of predictive models to assess likelihood of effective implementation and prospects for sustainability while taking into account salient contextual factors. A recommended strategy for accomplishing these objectives is described. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
24.
《Ergonomics》2012,55(2):178-191
The study investigated the natural work–pause pattern of computer users and the possible effects of imposing pause regimes on this pattern. Hereto, the precise timing of computer events was recorded across a large number of days. It was found that the distribution of the pause durations was extremely skewed and that pauses with twice the duration are twice less likely to occur. The effects of imposing pause regimes were studied by performing a simulation of commercially available pause software. It was found that depending on the duration of the introduced pause, the software added 25–57% of the pauses taken naturally. Analysis of the timing of the introduced pauses revealed that a large number of spontaneous pauses were taken close to the inserted pause. Considering the disappointing results of studies investigating the effects of introducing (active) pauses during computer work, this study has cast doubt on the usefulness of introducing short duration pauses. 相似文献
25.
针对现有利用遥感影像进行土地利用状况调查的需求,从统计模式识别的角度出发,在分析ISODATA算法基本原理的基础上,通过visual C++语言编程实现,并将其运用于武汉市某地区的土地利用调查工作中,同时对照ER—DASIMAGINE软件处理结果对分类结果进行分析,提出了改进意见,证明了该方法的可行性与实用性。 相似文献
26.
分析了国内外电动自行车(简称EB)的市场现状与发展前景;综述了国产EB“摩托化”的隐患和智能助力型EB的优越性;研究了EB电池市场的发展趋势,将由目前的铅蓄电池占主导逐步向MH-Ni、锂离子、燃料电池等新型高能电池发展;详细分析了影响EB电池性能的因素和延长EB电池使用寿命的可能性及可行性。 相似文献
27.
28.
基于统一建模语言(UML)用例图和序列图在描述系统的功能及完成相应功能方面的特点,结合风险分析技术,提出了以用例的使用概率为基础,按照完成用例功能的场景即序列图中所涉及到的组件使用概率和风险程度,从中选出使用概率最高的和风险程度最高的组件为核心,依照三明治的软件集成方式逐个将其他的组件集成进来从而完成整个系统的集成测试.这种测试方式对系统的风险进行控制,实现了部分的可靠性测试. 相似文献
29.
介绍利用WCDMA3G无线通信网络和视频监控技术进行国土资源监控的解决方案,该方案主要用于解决传统卫星遥感成像技术不能及时发现问题的弊端,为耕地保护工作提供一种新型、高效、可行的技术手段。 相似文献
30.
In the digital information era, dealing with privacy issues is problematic in related research since online activities have become an inevitable trend. Following the privacy paradox, which occurs when online services are increasingly accepted or used despite raising the level of privacy concerns of individuals, there is no need to alleviate individual privacy concerns regarding online services. Accordingly, this study aims to empirically analyze the effect of online privacy concerns, when interacting with individual innovativeness, on individual online service use behavior. For the empirical analysis, a Heckman two-step analysis is performed using South Korean data from the 2019 Korea Media Panel Survey conducted by the Korea Information Society Development Institute. The results provide evidence in contradiction of the privacy paradox. Specifically, the main findings of this study are as follows. First, use of online services and privacy concerns are not a contradictory phenomenon both in principle and behavior but can act as a negative influence or constraint. Second, individuals with high levels of innovativeness actively use online services owing to differences in their acceptance and use of innovation. Third, as online activities become more common, privacy concerns are likely to affect the level of online service use by interacting with other personality traits. As a result, privacy concerns are more likely to act as an influencing variable that moderates the degree or intensity of an individual's use of an online service rather than an independent variable for the use of an online service. The impact of privacy concerns of individuals on the use of online services identified in this study suggests there is a need for an adequate governing mechanism for privacy protection to realize service provision through e-government. 相似文献