全文获取类型
收费全文 | 42509篇 |
免费 | 3021篇 |
国内免费 | 3031篇 |
专业分类
电工技术 | 2736篇 |
技术理论 | 5篇 |
综合类 | 4165篇 |
化学工业 | 1314篇 |
金属工艺 | 1242篇 |
机械仪表 | 4068篇 |
建筑科学 | 2585篇 |
矿业工程 | 987篇 |
能源动力 | 1061篇 |
轻工业 | 625篇 |
水利工程 | 682篇 |
石油天然气 | 1156篇 |
武器工业 | 466篇 |
无线电 | 5017篇 |
一般工业技术 | 1414篇 |
冶金工业 | 806篇 |
原子能技术 | 394篇 |
自动化技术 | 19838篇 |
出版年
2024年 | 89篇 |
2023年 | 229篇 |
2022年 | 472篇 |
2021年 | 633篇 |
2020年 | 702篇 |
2019年 | 527篇 |
2018年 | 547篇 |
2017年 | 714篇 |
2016年 | 895篇 |
2015年 | 1200篇 |
2014年 | 2388篇 |
2013年 | 2079篇 |
2012年 | 2859篇 |
2011年 | 3578篇 |
2010年 | 2672篇 |
2009年 | 2532篇 |
2008年 | 2813篇 |
2007年 | 3423篇 |
2006年 | 3114篇 |
2005年 | 2866篇 |
2004年 | 2360篇 |
2003年 | 2338篇 |
2002年 | 1936篇 |
2001年 | 1497篇 |
2000年 | 1167篇 |
1999年 | 956篇 |
1998年 | 766篇 |
1997年 | 633篇 |
1996年 | 549篇 |
1995年 | 419篇 |
1994年 | 327篇 |
1993年 | 293篇 |
1992年 | 209篇 |
1991年 | 166篇 |
1990年 | 90篇 |
1989年 | 114篇 |
1988年 | 80篇 |
1987年 | 55篇 |
1986年 | 30篇 |
1985年 | 40篇 |
1984年 | 41篇 |
1983年 | 52篇 |
1982年 | 26篇 |
1981年 | 20篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 16篇 |
1976年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
Software is a central component in the modern world and vastly affects the environment’s sustainability. The demand for energy and resource requirements is rising when producing hardware and software units. Literature study reveals that many studies focused on green hardware; however, limited efforts were made in the greenness of software products. Green software products are necessary to solve the issues and problems related to the long-term use of software, especially from a sustainability perspective. Without a proper mechanism for measuring the greenness of a particular software product executed in a specific environment, the mentioned benefits will not be attained. Currently, there are not enough works to address this problem, and the green status of software products is uncertain and unsure. This paper aims to identify the green measurements based on sustainable dimensions in a software product. The second objective is to reveal the relationships between the elements and measurements through empirical study. The study is conducted in two phases. The first phase is the theoretical phase, where the main components, measurements and practices that influence the sustainability of a software product are identified. The second phase is the empirical study that involved 103 respondents in Malaysia investigating current practices of green software in the industrial environment and further identifying the main sustainability dimensions and measurements and their impact on achieving green software products. This study has revealed seven green measurements of software product: Productivity, Usability, Cost Reduction, Employee Support, Energy Efficiency, Resource Efficiency and Tool Support. The relationships are statistically significant, with a significance level of less than 0.01 (p = 0.000). Thus, the hypothesised relationships were all accepted. The contributions of this study revolve around the research perspectives of the measurements to attain a green software product. 相似文献
2.
针对自动飞行控制系统结构复杂、关联部件众多,发生故障时诊断时间长,从而影响飞机运行效率的问题,提出一种基于飞机通信寻址报告系统(ACARS)的远程实时故障诊断方案。首先,分析自动飞行控制系统的故障特点,设计搭建检测滤波器;然后,利用ACARS数据链实时发送的自动飞行控制系统的关键信息进行相关部件的残差计算,并根据残差决策算法进行故障诊断及定位;最后,针对不同故障部件残差间的差异大、决策门限无法统一的缺点,提出基于二次差值的残差决策改进算法,减缓了检测对象的整体变化趋势,降低了随机噪声和干扰的影响,避免了将瞬态故障诊断为系统故障的情况。实验仿真结果表明,基于二次差值的改进残差决策算法避免了多决策门限的复杂性,在采样时间为0.1 s的情况下,故障检测所需时间大约为2 s,故障检测时间大幅降低,有效故障检测率大于90%。 相似文献
3.
ContextEnterprise software systems (e.g., enterprise resource planning software) are often deployed in different contexts (e.g., different organizations or different business units or branches of one organization). However, even though organizations, business units or branches have the same or similar business goals, they may differ in how they achieve these goals. Thus, many enterprise software systems are subject to variability and adapted depending on the context in which they are used.ObjectiveOur goal is to provide a snapshot of variability in large scale enterprise software systems. We aim at understanding the types of variability that occur in large industrial enterprise software systems. Furthermore, we aim at identifying how variability is handled in such systems.MethodWe performed an exploratory case study in two large software organizations, involving two large enterprise software systems. Data were collected through interviews and document analysis. Data were analyzed following a grounded theory approach.ResultsWe identified seven types of variability (e.g., functionality, infrastructure) and eight mechanisms to handle variability (e.g., add-ons, code switches).ConclusionsWe provide generic types for classifying variability in enterprise software systems, and reusable mechanisms for handling such variability. Some variability types and handling mechanisms for enterprise software systems found in the real world extend existing concepts and theories. Others confirm findings from previous research literature on variability in software in general and are therefore not specific to enterprise software systems. Our findings also offer a theoretical foundation for describing variability handling in practice. Future work needs to provide more evaluations of the theoretical foundations, and refine variability handling mechanisms into more detailed practices. 相似文献
4.
性能效率是APP软件的重要质量属性,但目前缺乏APP软件性能效率的通用模型。分析了APP软件的性能特征,基于ISO/IEC 25010标准提出了APP软件的性能效率模型,定义了APP软件性能效率的子特性和度量指标。基于提出的APP软件性能效率模型,通过实验对APP软件的性能效率进行了度量及相关分析。 相似文献
5.
1-read/1-write (1R1W) register file (RF) is a popular memory configuration in modern feature rich SoCs requiring significant amount of embedded memory. A memory compiler is constructed using the 8T RF bitcell spanning a range of instances from 32 b to 72 Kb. An 8T low-leakage bitcell of 0.106 μm2 is used in a 14 nm FinFET technology with a 70 nm contacted gate pitch for high-density (HD) two-port (TP) RF memory compiler which achieves 5.66 Mb/mm2 array density for a 72 Kb array which is the highest reported density in 14 nm FinFET technology. The density improvement is achieved by using techniques such as leaf-cell optimization (eliminating transistors), better architectural planning, top level connectivity through leaf-cell abutment and minimizing the number of unique leaf-cells. These techniques are fully compatible with memory compiler usage over the required span. Leakage power is minimized by using power-switches without degrading the density mentioned above. Self-induced supply voltage collapse technique is applied for write and a four stack static keeper is used for read Vmin improvement. Fabricated test chips using 14 nm process have demonstrated 2.33 GHz performance at 1.1 V/25 °C operation. Overall Vmin of 550 mV is achieved with this design at 25 °C. The inbuilt power-switch improves leakage power by 12x in simulation. Approximately 8% die area of a leading 14 nm SoC in commercialization is occupied by these compiled RF instances. 相似文献
6.
7.
Visual FoxPro是小型数据库应用系统开发工具,而报表设计是数据库应用系统开发的一个重要组成部分,直接决定系统的输出是否能够满足用户的需要。为此详细研究了报表设计方法,结合Microsoft的OLE技术,引入面向对象方法,提出了一种新的报表设计方法。实践应用证明,该方法非常适合设计复杂的报表。 相似文献
8.
大型弧形闸门静力特性有限元分析 总被引:5,自引:0,他引:5
以某水电站溢洪道弧形闸门为例,建立了大型弧形闸门的有限元分析模型,应用ANSYS软件对其在各种工况下的支铰反力、闸门应力、位移挠度以及屈曲失稳等静力特性进行了计算分析,为完善闸门结构的设计提供了依据,对同类闸门结构的设计计算有参考意义。 相似文献
9.
为实现电源设备乃至通信机房的少人或无人值守和集中维护,必须建立一套完善的电信局动力环境集中监控系统。文中结合番禺区电信局的实际,讨论了提高系统运行可靠性的几点措施,包括硬件方面与软件方面的手段,关键在于加强系统的运行管理。 相似文献
10.