全文获取类型
收费全文 | 16007篇 |
免费 | 1701篇 |
国内免费 | 1024篇 |
专业分类
电工技术 | 3249篇 |
技术理论 | 1篇 |
综合类 | 2019篇 |
化学工业 | 262篇 |
金属工艺 | 281篇 |
机械仪表 | 1668篇 |
建筑科学 | 1716篇 |
矿业工程 | 561篇 |
能源动力 | 407篇 |
轻工业 | 153篇 |
水利工程 | 475篇 |
石油天然气 | 364篇 |
武器工业 | 563篇 |
无线电 | 2133篇 |
一般工业技术 | 1758篇 |
冶金工业 | 585篇 |
原子能技术 | 147篇 |
自动化技术 | 2390篇 |
出版年
2024年 | 54篇 |
2023年 | 159篇 |
2022年 | 256篇 |
2021年 | 325篇 |
2020年 | 388篇 |
2019年 | 358篇 |
2018年 | 325篇 |
2017年 | 428篇 |
2016年 | 521篇 |
2015年 | 556篇 |
2014年 | 941篇 |
2013年 | 934篇 |
2012年 | 1103篇 |
2011年 | 1248篇 |
2010年 | 903篇 |
2009年 | 975篇 |
2008年 | 963篇 |
2007年 | 1204篇 |
2006年 | 1070篇 |
2005年 | 891篇 |
2004年 | 801篇 |
2003年 | 717篇 |
2002年 | 560篇 |
2001年 | 528篇 |
2000年 | 478篇 |
1999年 | 346篇 |
1998年 | 276篇 |
1997年 | 239篇 |
1996年 | 200篇 |
1995年 | 179篇 |
1994年 | 163篇 |
1993年 | 95篇 |
1992年 | 98篇 |
1991年 | 52篇 |
1990年 | 67篇 |
1989年 | 44篇 |
1988年 | 53篇 |
1987年 | 42篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 20篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1965年 | 9篇 |
1964年 | 11篇 |
1957年 | 9篇 |
1956年 | 9篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
M. Lipow 《Quality and Reliability Engineering International》1985,1(1):27-35
This paper presents a demonstration of a methodology for fault removal during software development. The methodology encompasses the entire development history, from system and software requirements generation to system test. Thus it considers not only the faults during software testing after formal configuration controls have been invoked, but also the faults discovered prior to that phase: during system and software requirements generation, preliminary design, detailed design and code and unit testing. The agents for fault discovery used in verification and validation are called activities, techniques and tools (AT & Ts) in this paper, each having a certain maximum potential or capability for fault discovery. The AT & Ts considered include the usual specification review activities, and also certain tools not normally applied in ‘standard’ software development, such as automated requirements aids. Application of the methodology yields numbers of residual faults as of each phase of development, including those remaining to be discovered during operations and maintenance. Some previous experience and data on residual faults correspond to these results, indicating that the methodology and choice of parameters are reasonable. The methodology also allows one to calculate a relative loss due to delay in fault discovery, which, as is well known, rises rapidly when faults are not discovered during the phase in which they are generated. 相似文献
24.
张丽 《冶金标准化与质量》2003,41(2):34-36
在广泛参阅了对暂态量保护的研究 ,对各种基于故障时产生暂态量的保护原理和技术特点及应用进行了分析比较 ,并指出了各种新型保护的优缺点及暂态量保护的发展趋势 相似文献
25.
Techniques for improving the reliability and maintainability of both nonrepairable and repairable items can be suggested by failure data analysis. It is shown that a given set of failure numbers leads to very different improvement strategies when the numbers are the times-between-successive-failures of one or more repairable items, rather than the times-to-failure of nonrepairable items. Since this should have been obvious more than 50 years ago, at the onset of formal reliability engineering activities, several reasons are proffered for the widespread and protracted misinterpretation of even the most basic—and simple!—conceptual and practical differences between nonrepairable and repairable items. 相似文献
26.
A method for constructing an approximation of the critical excitation that drives an elastoplastic system from rest to a target threshold at a specified time instant, referred to as the “suboptimal excitation,” is presented in this paper. It is based on the observations gained from study of the critical excitations in the companion paper. Essentially, for the usual case of interest where the failure time is not small compared to the natural period, the duration of the positive and negative pulses of the critical excitation are roughly equal to half of the natural period. This consideration allows for a simple intuitive approximation of the critical excitation. The amplitudes of the positive and negative pulses are obtained in closed forms using energy balance. Numerical investigations show that the critical excitations are well approximated by the suboptimal excitations. 相似文献
27.
Boundary objects are a critical, but understudied, theoretical construct in CSCW. Through a field study of aircraft technical
support, we examined the role of boundary objects in the practical achievement of safety by service engineers. Their resolution
of repair requests was preserved in the organization’s memory via three compound boundary objects. These crystallizations
did not manifest a static interpretation, but instead were continually reinterpreted in light of meta-negotiations. This suggests
design implications for organizational memory systems which can more fluidly represent the meta-negotiations surrounding boundary
objects. 相似文献
28.
29.
CIMS可靠性模型随机研究的突出特点是工作站的并行结构使系统的状态个数呈现指数级增大,同时,并行结构与有限的缓冲库相互交织在一起,这使系统状态呈爆炸趋势,显然,对系统作精确的分析与系统呈现的状态爆炸趋势构成了难以解决的矛盾,如何解决这一矛盾正是CIMS随机理论有待开发的重要课题。我们把扩散近似方法引入到多台并行的CIMS可靠性模型中,以简单的连续过程描述了具有状态爆炸趋势的复杂离散过程,给出了CI 相似文献
30.
施志康 《电子产品可靠性与环境试验》2002,(5):27-30
阐述了试行产中产品质量和可靠性的主要保证方法,由于这些做法来自于工厂的生产实践,所以,对承制方,订购方等各级,各类人员都有借鉴意义。同时对理论工作者也有一定的参考价值。 相似文献