全文获取类型
收费全文 | 3579篇 |
免费 | 625篇 |
国内免费 | 427篇 |
专业分类
电工技术 | 203篇 |
综合类 | 362篇 |
化学工业 | 287篇 |
金属工艺 | 38篇 |
机械仪表 | 128篇 |
建筑科学 | 206篇 |
矿业工程 | 39篇 |
能源动力 | 43篇 |
轻工业 | 469篇 |
水利工程 | 77篇 |
石油天然气 | 63篇 |
武器工业 | 45篇 |
无线电 | 278篇 |
一般工业技术 | 268篇 |
冶金工业 | 323篇 |
原子能技术 | 5篇 |
自动化技术 | 1797篇 |
出版年
2024年 | 8篇 |
2023年 | 63篇 |
2022年 | 141篇 |
2021年 | 181篇 |
2020年 | 198篇 |
2019年 | 162篇 |
2018年 | 139篇 |
2017年 | 168篇 |
2016年 | 185篇 |
2015年 | 182篇 |
2014年 | 251篇 |
2013年 | 251篇 |
2012年 | 256篇 |
2011年 | 243篇 |
2010年 | 196篇 |
2009年 | 205篇 |
2008年 | 250篇 |
2007年 | 224篇 |
2006年 | 195篇 |
2005年 | 164篇 |
2004年 | 171篇 |
2003年 | 124篇 |
2002年 | 120篇 |
2001年 | 80篇 |
2000年 | 58篇 |
1999年 | 50篇 |
1998年 | 53篇 |
1997年 | 44篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1964年 | 5篇 |
1963年 | 3篇 |
1959年 | 4篇 |
1958年 | 6篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1955年 | 6篇 |
排序方式: 共有4631条查询结果,搜索用时 15 毫秒
1.
《中国稀土学报(英文版)》2022,40(11):1691-1698
White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ with spectral distribution covering whole visible region. Blue light emission originates from Ce3+ ions occupying preferentially Ba2+ site by controlling synthesis conditions. Green and red lights are obtained from Eu2+ occupying Ba2+ (and Ca2+) site and Mn2+ occupying Ca2+ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn2+ is realized by the efficient energy transfer from Ce3+ and Eu2+ to Mn2+. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce3+(K+)/Eu2+/Mn2+ based on efficient simultaneous energy transfer. The results indicate that Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ is a promising white light-emitting phosphor in WLEDs application. 相似文献
2.
ABSTRACTTo ensure the reasonable application and perfect the theory of decision making with interval multiplicative preference relations (IMPRs), this paper continues to discuss decision making with IMPRs. After reviewing previous consistency concepts for IMPRs, we find that Krej?í’s consistency concept is more flexible and natural than others. However, it is insufficient to address IMPRs only using this concept. Considering this fact, this paper researches inconsistent and incomplete IMPRs that are usually encountered. First, programming models for addressing inconsistent and incomplete IMPRs are constructed. Then, this paper studies the consensus of individual IMPRs and defines a consensus index using the defined correlation coefficient. When the consensus requirement does not satisfy requirement, a programming model for improving consensus level is built, which can ensure the consistency. Subsequently, a procedure for group decision making with IMPRs is offered, and associated examples are provided to specifically show the application of main theoretical results. 相似文献
3.
4.
为了解18~45岁女性消费者在购买运动文胸时的情感偏好,以消费者在穿着体验中的评价为依据进行问卷调研,衡量消费者的情感偏好。通过探索性因子分析和验证性因子分析,构建5个一级指标和21个二级指标的消费者情感偏好评价指标模型,采用非线性主成分分析法确定影响消费者情感偏好设计要素的权重值。结果表明:一级指标权重值从大到小依次为面料(0.274)、色彩(0.191)、背部结构(0.188)、肩带形式(0.184)、罩杯形式(0.163),说明面料是消费者购买运动文胸时考虑的主要因素。 相似文献
5.
针对MooseFS元数据节点的单点故障问题,对MooseFS源码进行改造,为其增加一个热备的备元数据节点,并通过主备之间同步元数据,备节点回放操作日志等技术使得备元数据节点内存中的元数据时刻跟主元数据节点保持一致。当主元数据节点发生故障切换到备元数据节点后,备元数据节点无需从本地加载元数据即可快速接替主元数据节点对外提供服务。测试结果表明,备元数据节点本地和内存中的元数据均与主元数据节点保持一致,且故障恢复时间小于1 s。 相似文献
6.
针对时域不确定信息的融合难题,为充分体现时域信息融合的动态性特点和时间因素对融合的影响,在证据理论的基础上,提出一种考虑决策者时序偏好的时域证据融合方法。首先将决策者对时序的偏好融入时域证据融合,通过分析时域证据序列的特点,在定义时序记忆因子的基础上,对决策者的时序偏好进行度量;然后通过构建优化模型求解时序权重,再结合证据信任度的概念,对证据源进行修正;最后利用Dempster组合规则对修正后的证据进行融合。数值算例表明,与没有考虑时间因素的融合方法相比,考虑决策者时序偏好的证据融合方法可以有效处理时域信息序列中的冲突信息,得到合理的融合结果;同时,所提方法充分考虑了时域证据序列的信任度和决策者的主观偏好,可以反映决策者主观因素对时域证据融合的影响,较好地体现了时域证据融合的动态性特点。 相似文献
7.
8.
9.
针对智慧制造评估时专家的决策信息具有犹豫模糊不确定性问题,提出了一种关于准则具有犹豫模糊偏好关系的改进交互式多准则决策(TODIM)方法。首先提出了准则间的犹豫模糊偏好关系概念,并证明了其基本性质。在TODIM方法优势度的计算过程中,将准则权重犹豫模糊偏好关系替代原有的精确值权重,使信息的准确性最大化。将该方法用于智能制造的评估上,实例分析结果表明所提方法是可行和有效的。 相似文献
10.
Customer-involved design concept evaluation (DCE) allows customers to take part in evaluating the design alternatives to get more popular design concept. Traditional customer-involved DCE methods still focus on the collection of customer responses and only consider cost and benefit characteristics of design criteria in multi-criteria decision-making (MCDM) based evaluation process. Few studies have customized the decision-making algorithms specifically aimed at customers’ preferences. This paper further explores the customers’ influences in the early stages of the product design development, and proposes a new rough number based MCDM model (i.e., VIKOR) incorporating customers’ preferences for design specifications along with designers’ perceptions for the characteristics of design criteria (cost and benefit) to perform concept evaluation under subjective environment, and this proposed method is named as integrated rough VIKOR (IR-VIKOR). The objective of this study is to identify the best design concept which maximizes the satisfactions of expectations from most customers as well as conforms to the characteristics of design criteria. Firstly, Shannon entropy is used to obtain the weightings and relative importance ratings of design criteria from the customers’ preferences. Secondly, the customers’ preferences for design attribute values, the importance ratings of design criteria and the characteristics of design criteria are combined together to define the ideal solutions to calculate the rough evaluation index of each design alternative in IR-VIKOR, and finally the ranking result is provided by IR-VIKOR to determine the best design concept. A practical design example is introduced to illustrate the evaluation process of this proposed method, and the empirical comparisons are further carried out to validate its superiority for DCE. Through the sensitivity analysis experiments including i) inside IR-VIKOR, and ii) between IR-VIKOR and other classical MCDM methods, the proposed method is proved to be a reliable and feasible customer-involved DCE approach. 相似文献