首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   100篇
  免费   0篇
化学工业   2篇
机械仪表   2篇
建筑科学   5篇
轻工业   1篇
石油天然气   4篇
无线电   9篇
一般工业技术   7篇
冶金工业   66篇
自动化技术   4篇
  2023年   1篇
  2021年   1篇
  2017年   1篇
  2015年   3篇
  2014年   2篇
  2013年   2篇
  2009年   1篇
  2008年   2篇
  2007年   2篇
  2005年   1篇
  2003年   3篇
  2002年   3篇
  2001年   2篇
  2000年   1篇
  1999年   3篇
  1998年   13篇
  1997年   14篇
  1996年   7篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   2篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1985年   4篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1976年   6篇
  1974年   1篇
  1972年   3篇
  1971年   1篇
  1970年   1篇
  1966年   1篇
排序方式: 共有100条查询结果,搜索用时 46 毫秒
1.
American visceral leishmaniasis is a main public health matter in Brazil. Since dogs have been incriminated as the main urban reservoir of AVL agent Leishmania chagasi, a cohort study aimed at understanding the dynamics of the canine infection was carried out in Jequié--an endemic community in the Northeast of Brazil. The inhabited urban and periurban areas of Jequié were divided into 140 clusters of 0.25 km2. All 1681 dogs domiciled in 34 randomly selected clusters were screened for Leishmania antibodies in an enzyme-linked immunosorbent assay. After the seropositive dogs were painlessly eliminated, a cohort of 1286 seronegative dogs was followed up for 18 months, yielding a total of 1739.7 dog-years. The overall incidence of Leishmania infection, as assessed by the detection of Leishmania antibodies in blood samples collected every six months, was 6.55 cases/100 dog-years (95% confidence interval; CI 6.04-7.26). Two subsets of clusters, with 0.70 and 1.35 relative risks of infection, were identified. The annual emigration rate was 2.26 cases/100 dog-years (95% CI 1.86-2.66). The implications of these findings for the control of American visceral leishmaniasis are discussed.  相似文献   
2.
3.
Platforming has become an important means of cost-sharing among industrial products. However, many firms face systemic downward pressure on commonality, with the result that many platforms realize less commonality than intended. Past research has hypothesized that divergence is the result of conflicting tensions between product customization/optimization and cost control. This article investigates the control and incentive levers available to platform managers to shape the behavior of the organization when divergence opportunities arise. Management levers are drawn from a series of 12 industrial case studies, stemming from investigations of the causes of divergences. These management levers are categorized as technical levers, financial levers, and organizational levers. This article illustrates each of the management levers with examples from the case studies.  相似文献   
4.
5.
6.
A low-IF fully integrated tuner for DBS satellite TV applications has been realized in 0.13-mum CMOS. A wideband ring oscillator-based frequency synthesizer having a large frequency step was used to downconvert a cluster of channels to a sliding low-IF frequency, while the second downconversion to baseband was performed in the digital domain. Eliminating the inductors and using a small-area oscillator has reduced both the parasitic magnetic and substrate coupling, allowing single-chip integration of the sensitive tuner and the noisy digital demodulator. A significant reduction in die area was achieved by using a single oscillator to cover the entire satellite TV spectrum, while a noise attenuator was cascaded with the PLL passive loop filter to reduce the equivalent VCO tuning gain. This improves PLL noise and spur performance and allows the on-chip integration of the loop filter. The digital low-IF tuner allows the use of a discrete step AGC loop that results in lower noise figure and higher linearity. Automatic signal path gain and bandwidth digital calibration was realized using replica ring oscillators. Tuner specifications include: 90 dB gain range, 10 dB noise figure at max gain, +25dBm IIP3 at min gain, 1.3deg rms integrated phase noise, <-50dBc spurs, 0.5-W power consumption from dual 1.8/3.3-V supplies, and 1.8times1.2 mm2 die area  相似文献   
7.
The construction and property sector has seen the development of a number of methods for evaluating the 'greenness' of buildings in the 1990s - both for new designs and existing buildings. These range from very detailed life cycle assessment methods, which account for all the embodied and operational environmental impacts of building materials, to higher level environmental impact assessment methods, which evaluate the broader implications of the building's impact on the environment. In between these two are environmental assessment methods such as BREEAM, BEPAC, LEED, and GBA. In this paper, we discuss the potential market applications of these systems and compare and contrast several of the major environmental assessment methods. Le secteur de la construction et de l'immobilier a ete le temoin du developpement d'un certain nombre de methodes permettant d'evaluer les performances ecologiques des batiments dans les annees 1990, tant sur le plan des nouveaux concepts que des batiments existants. Ces methodes vont de l'evaluation tres detailee du cycle de vie, qui tient compte de l'impact specifique et des incidences operationnelles des materiaux de construction sur l'environnement, jusqu'a une evaluation de l'impact environnemental a un niveau plus eleve. Entre ces deux extremes, on trouve des methodes d'evaluation environnementale telles que BREEAM, BEPAC, LEED et GBA. Dans cet article, nous examinons les applications commerciales potentielles des ces systemes; nous comparons, en les opposant, plusieurs methodes majeures d'evaluation environnementale.  相似文献   
8.
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号