全文获取类型
收费全文 | 2251篇 |
免费 | 22篇 |
专业分类
电工技术 | 8篇 |
综合类 | 61篇 |
化学工业 | 134篇 |
金属工艺 | 11篇 |
机械仪表 | 10篇 |
建筑科学 | 52篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 43篇 |
水利工程 | 11篇 |
石油天然气 | 7篇 |
无线电 | 93篇 |
一般工业技术 | 85篇 |
冶金工业 | 1588篇 |
原子能技术 | 4篇 |
自动化技术 | 146篇 |
出版年
2023年 | 8篇 |
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 22篇 |
2014年 | 34篇 |
2013年 | 50篇 |
2012年 | 41篇 |
2011年 | 37篇 |
2010年 | 55篇 |
2009年 | 37篇 |
2008年 | 50篇 |
2007年 | 56篇 |
2006年 | 50篇 |
2005年 | 39篇 |
2004年 | 40篇 |
2003年 | 32篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 60篇 |
1998年 | 407篇 |
1997年 | 253篇 |
1996年 | 166篇 |
1995年 | 111篇 |
1994年 | 98篇 |
1993年 | 104篇 |
1992年 | 16篇 |
1991年 | 32篇 |
1990年 | 36篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 34篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 2篇 |
1978年 | 9篇 |
1977年 | 37篇 |
1976年 | 84篇 |
1975年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有2273条查询结果,搜索用时 15 毫秒
81.
Rick RabiserAuthor Vitae Pádraig O’LearyAuthor Vitae Ita RichardsonAuthor Vitae 《Journal of Systems and Software》2011,84(2):285-300
More and more organizations adopt software product lines to leverage extensive reuse and deliver a multitude of benefits such as increased quality and productivity and a decrease in cost and time-to-market of their software development. When compared to the vast amount of research on developing product lines, relatively little work has been dedicated to the actual use of product lines to derive individual products, i.e., the process of product derivation. Existing approaches to product derivation have been developed independently for different aims and purposes. While the definition of a general approach applicable to every domain may not be possible, it would be interesting for researchers and practitioners to know which activities are common in existing approaches, i.e., what are the key activities in product derivation. In this paper we report on how we compared two product derivation approaches developed by the authors in two different, independent research projects. Both approaches independently sought to identify product derivation activities, one through a process reference model and the other through a tool-supported derivation approach. Both approaches have been developed and validated in research industry collaborations with different companies. Through the comparison of the approaches we identify key product derivation activities. We illustrate the activities’ importance with examples from industry collaborations. To further validate the activities, we analyze three existing product derivation approaches for their support for these activities. The validation provides evidence that the identified activities are relevant to product derivation and we thus conclude that they should be considered (e.g., as a checklist) when developing or evaluating a product derivation approach. 相似文献
82.
Comparing the performance of distance learning and on-campus students is a well-studied problem. Results have shown that distance learners can perform as well or better than on-campus students. Few studies, however, have explored how or why traditional on-campus students utilize the technology intended for distance learners. Many universities and corporations provide educational and training content simultaneously to both face-to-face and distance students. Thus, exploring how instructional technology typically designed for distance learning students could benefit traditional students is important to our understanding of present and future learning environments. To this end, a pilot study was undertaken that explored how graduate students – primarily business majors – adopted and used video-streaming technology for a one semester course on Knowledge Management Tools and Techniques. Results indicated that age, previous use of the technology, need for interaction and Internet connectivity all influenced the decisions of the subjects to adopt the technology. Two-thirds of the subjects used the technology, with a self-reported estimate of procuring 16% of the course content asynchronously. Most used video streaming for convenience reasons and to review class material. 相似文献
83.
84.
Pilot studies conducted by the authors seem to indicate that obturation of a root canal system by the lateral condensation of gutta-percha using an electrically heated spreader results in a more homogeneous mass of gutta-percha than standard lateral condensation. This article describes an improved variation which prevents inadvertent dislodgement of the mass of gutta-percha during the obturation. The authors refer to this technique as "zap and tap" and a case report describes its use to obturate a C-shaped canal system of a mandibular second molar. 相似文献
85.
PD Dr. med. Friedrich Heubel 《Ethik in der Medizin》2012,24(2):125-135
Definition of the problem
Hospitals serve the general purpose to improve the health of patients. Health care professionals are a necessary means to achieve that end but have their own more specific professional ends. What is the due relationship between those kinds of ends with respect to the organisation of hospitals?Arguments
Individual health care in hospitals is delivered by professionals who are dependent upon the hospital??s human, administrative and technical facilities. As organised social entities, hospitals use professionals as the means to an end we normally call health of patients. More precisely, the professional task consists in a specific, namely, therapeutic interaction, an asymmetric relationship between morally equals. Professionals have to explore, interpret and pursue patients?? interests according to their consent. From a moral perspective, this interaction should be kept free from distortion through external incentives which divert the professional??s intrinsic motivation. Although a professional responsibility, the individual professional would be overcharged with this organisational task.Conclusion
The profession has a responsibility to protect and foster professional behaviour of its members including participation in organising hospitals and the individual professional should engage in organising the profession as a collective agent. 相似文献86.
Haixue Yan Hongtao Zhang Rick Ubic Mike Reece Jing Liu Zhijian Shen 《Journal of Materials Science: Materials in Electronics》2006,17(9):657-661
Grain-oriented Aurivillius phase BaBi2Nb2 O9 ceramics were fabricated using Spark Plasma Sintering (SPS). Their relaxor behaviour was confirmed by a strong frequency
dispersion of the dielectric response. The dielectric behaviour has been fitted using different relaxor models. The relaxor
parameters are isotropic, while the dielectric constants are highly anisotropic. The piezoelectric constant d
33 is zero perpendicular and parallel to the hot pressing direction, and the P–E response is dominated by losses. The inability to pole the samples at room temperature is consistent with the T
f temperature (∼
∼115 K) estimated from fitting the experimental data to the Vogel–Fulcher model. This suggests that it may be possible to
observe piezoelectric and ferroelectric properties at very low temperatures. 相似文献
87.
David Katz Rick Gentile 《电子产品世界》2006,(7):119-121
当今许多复杂的嵌入式系统要求信号处理和信号控制两种功能.过去这两种功能一直属于DSP和微控制器(MCU)两种独立的器件.然而,汇聚处理器的推出改变了这种现状,将DSP和MCU两种功能集成到一种灵活体系结构中,典型的代表有ADI公司的B1ackfin处理器系列. 相似文献
88.
89.
Eiden Rina D.; Leonard Kenneth E.; Hoyle Rick H.; Chavez Felipa 《Canadian Metallurgical Quarterly》2004,18(4):350
This study examined the transactional nature of parent-infant interactions over time among alcoholic and nonalcoholic families. The sample consisted of 222 families assessed at 12, 18, and 24 months of child age. Results indicated that infant behavior did not influence parental behavior across time, but parental behavior was longitudinally predictive of infant behavior during play interactions. Higher paternal alcohol consumption at 12 months was longitudinally predictive of negative parental behavior at 24 months. Other significant risk factors included marital conflict, fathers' depression, and fathers' education. Results highlight the nested nature of risk in alcoholic families and the direction of influence from parent to child during interactions and suggest that 1 pathway to risk among these children is through negative parent-infant interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
90.
We have developed a decision support application for the Dutch Aviation Police and Air Support unit for routing their helicopters in anticipation of unknown future incidents. These incidents are not known in advance, yet do require a swift response. A response might include the dispatch of a police helicopter to support the police on the ground. If a helicopter takes too long to arrive at the crime scene, it might be too late to assist. Hence, helicopters have to be proximate when an incident happens to increase the likelihood of being able to support the police on the ground in apprehending suspects. We propose the use of a forecasting technique, followed by a routing heuristic to maximize the number of incidents where a helicopter provides a successful assist. We have implemented these techniques in a decision support application in collaboration with the Dutch Aviation Police and Air Support. Using numerical experiments, we show that our application has the potential to improve the success rate with a factor nine. The Dutch Air Support and Aviation Police are now using the application. 相似文献