全文获取类型
收费全文 | 22578篇 |
免费 | 1911篇 |
国内免费 | 1784篇 |
专业分类
电工技术 | 1763篇 |
技术理论 | 1篇 |
综合类 | 2586篇 |
化学工业 | 732篇 |
金属工艺 | 791篇 |
机械仪表 | 1687篇 |
建筑科学 | 941篇 |
矿业工程 | 659篇 |
能源动力 | 327篇 |
轻工业 | 346篇 |
水利工程 | 430篇 |
石油天然气 | 788篇 |
武器工业 | 292篇 |
无线电 | 3003篇 |
一般工业技术 | 755篇 |
冶金工业 | 520篇 |
原子能技术 | 166篇 |
自动化技术 | 10486篇 |
出版年
2024年 | 59篇 |
2023年 | 138篇 |
2022年 | 299篇 |
2021年 | 392篇 |
2020年 | 456篇 |
2019年 | 350篇 |
2018年 | 321篇 |
2017年 | 478篇 |
2016年 | 569篇 |
2015年 | 776篇 |
2014年 | 1347篇 |
2013年 | 1143篇 |
2012年 | 1588篇 |
2011年 | 1893篇 |
2010年 | 1457篇 |
2009年 | 1428篇 |
2008年 | 1564篇 |
2007年 | 1894篇 |
2006年 | 1635篇 |
2005年 | 1494篇 |
2004年 | 1211篇 |
2003年 | 1197篇 |
2002年 | 936篇 |
2001年 | 791篇 |
2000年 | 618篇 |
1999年 | 441篇 |
1998年 | 344篇 |
1997年 | 294篇 |
1996年 | 258篇 |
1995年 | 200篇 |
1994年 | 156篇 |
1993年 | 130篇 |
1992年 | 82篇 |
1991年 | 61篇 |
1990年 | 34篇 |
1989年 | 44篇 |
1988年 | 29篇 |
1987年 | 27篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 31篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 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.
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
3.
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
4.
5.
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
6.
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
7.
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
8.
9.
基于多相滤波器的信道化接收机及其应用研究 总被引:16,自引:0,他引:16
本文主要研究了应用多相滤波技术的信道化接收机建模问题。在给定信道频谱划分方案下,推导了基于多相 滤波器的信道化接收机数学模型。并由此模型设计了一个四信道模拟系统。最后用仿真实验结果验证了模型的正确性。 相似文献
10.
应用遗传算法设计和开发了针对爱立信GSM900系统的频率规划软件。在设计中,采用了交叉点存储、变异回退以及分割分步降维的方法,从而提高遗传算法的执行速度。 相似文献