全文获取类型
收费全文 | 6572篇 |
免费 | 717篇 |
国内免费 | 546篇 |
专业分类
电工技术 | 412篇 |
综合类 | 786篇 |
化学工业 | 507篇 |
金属工艺 | 178篇 |
机械仪表 | 573篇 |
建筑科学 | 714篇 |
矿业工程 | 695篇 |
能源动力 | 186篇 |
轻工业 | 336篇 |
水利工程 | 321篇 |
石油天然气 | 444篇 |
武器工业 | 94篇 |
无线电 | 459篇 |
一般工业技术 | 476篇 |
冶金工业 | 400篇 |
原子能技术 | 81篇 |
自动化技术 | 1173篇 |
出版年
2024年 | 23篇 |
2023年 | 92篇 |
2022年 | 148篇 |
2021年 | 218篇 |
2020年 | 237篇 |
2019年 | 201篇 |
2018年 | 164篇 |
2017年 | 205篇 |
2016年 | 251篇 |
2015年 | 260篇 |
2014年 | 379篇 |
2013年 | 342篇 |
2012年 | 510篇 |
2011年 | 519篇 |
2010年 | 401篇 |
2009年 | 385篇 |
2008年 | 334篇 |
2007年 | 457篇 |
2006年 | 415篇 |
2005年 | 338篇 |
2004年 | 325篇 |
2003年 | 300篇 |
2002年 | 204篇 |
2001年 | 188篇 |
2000年 | 153篇 |
1999年 | 124篇 |
1998年 | 111篇 |
1997年 | 97篇 |
1996年 | 76篇 |
1995年 | 75篇 |
1994年 | 70篇 |
1993年 | 40篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1984年 | 6篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1964年 | 4篇 |
1961年 | 2篇 |
1959年 | 4篇 |
1958年 | 3篇 |
1956年 | 4篇 |
1955年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有7835条查询结果,搜索用时 31 毫秒
1.
Lauren Folk Kiara Gonzales John Gales Michael Kinsey Elisabetta Carattin Tim Young 《火与材料》2020,44(4):585-606
Practitioners are continuing to develop egress modelling software for the design of the built environment. These models require data about human behaviour and factors for calibration, validation and verification. This study aims to address the specific data and knowledge gap: emergency egress of the elderly. Such data are difficult to collect given privacy and consent concerns, with strong relationships generally being required between residences and researchers. Through the observation of nine fire drills at six Canadian long-term care (LTC) and retirement homes, specific evacuation actions and behaviour were observed for 37 staff members and information about the evacuation of 56 residents was collected. These drills demonstrated that emergency egress in LTC and retirement homes is highly staff dependent with 72% of residents recorded requiring full assistance at all stages of movement in evacuation, and that the type of announced/unannounced drill and level of resident care will affect the type of data collected. The development of travel speed and pre-movement is discussed subject to limitation with qualitative behavioural insights of residents that were observed. This study provides valuable methodological discussion on how to conduct behavioural studies in similar highly restricted research environments. Specific attention is given to understanding the considerations that must be made when using fire drills as data sources, and the impact that these can have on using such data for modelling. This study may inform the initial setup and programming of evacuation models from an actions and behavioural perspectives of staff members and residents. 相似文献
2.
Amir Abdolmaleki Mohammad Reza Molavian 《Polymer-Plastics Technology and Engineering》2015,54(12):1241-1250
2,6-Bis(5-amino-1H-benzimidazol-2-yl)pyridine was prepared and characterized by Fourier transform infrared spectroscopy, elemental analysis, 1H-NMR, and 13C-NMR spectroscopic methods. Then a new poly(benzimidazole-amide) was synthesized by polymerization of the corresponding diamine and isophthalic acid. The obtained poly(benzimidazole-amide) exhibited good yield and high thermal stability. Due to the existence of benzimidazole moieties in polymer’s structure, it has the tendency to form complexes with metal ions. So, a new poly(benzimidazole-amide)/Co nanocomposite was prepared. Morphological studies revealed that metal nanoparticles were dispersed in the polymer matrix without any aggregation. poly(benzimidazole-amide)/Co nanocomposite was used as a catalyst in the oxidation of ethyl benzene to acetophenone with tert-butyl hydroperoxide. 相似文献
3.
Paul Geoerg Florian Berchtold Steven Gwynne Karen Boyce Stefan Holl Anja Hofmann 《火与材料》2019,43(7):759-781
To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design. 相似文献
4.
针对跨数据中心的资源调度问题,提出了一种基于组合双向拍卖(PCDA)的资源调度方案。首先,将云资源拍卖分为三个部分:云用户代理报价、云资源提供商要价、拍卖代理组织拍卖;其次,在定义用户的优先级及任务紧迫度的基础上,在拍卖过程中估算每一个工作发生的服务等级协议(SLA)违规并以此计算云提供商的收益,同时每轮竞拍允许成交多项交易;最终达到根据用户等级合理分配云资源调度的效果。仿真实验结果表明该算法保证了竞拍成功率,与传统一次拍卖成交一项的组合双向拍卖方案相比,PCDA在竞拍时间段产生的能耗降低了35.00%,拍卖云提供商的利润提高了约38.84%。 相似文献
5.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
6.
7.
为了研究Furuta摆在倒立点附近的稳定控制问题,采用基于T-S模糊模型的一类连续模糊动态系统控制方法,首次进行Furuta摆的模糊状态空间建模,并采用模糊切换的思想,设计了Furuta摆在倒立点附近的稳定控制器,进而分析了系统稳定性。与已有的方法相比,该方法的优点是稳定区域大、调节时间短。数字仿真结果验证了方法的有效性。 相似文献
8.
本文叙述了反应堆保护系统停棒与汽轮机降功率子系统的系统功能、保护参数和秦山核电站控制棒组插入监测器的设计与参数选择,确定了控制棒提升上极限值和在不同工况下棒插入低位、低-低位整定值,并在热态零功率条件下加以验证。试验证明参数选择是合理的,为功率运行阶段提供了数据。 相似文献
9.
基于运动的摄像机定标方法的综述 总被引:3,自引:0,他引:3
该文从运动方式角度将摄像机定标方式分为非限定运动方式和限定运动方式两大类,分别对摄像机各种运动方式对定标技术的影响进行了系统的研究,在应用中应该根据具体情况选择合适的摄像机的运动方式,以满足实际问题的需要。 相似文献
10.