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   119篇
  免费   11篇
电工技术   4篇
化学工业   26篇
金属工艺   3篇
机械仪表   6篇
建筑科学   4篇
轻工业   3篇
无线电   10篇
一般工业技术   38篇
冶金工业   18篇
原子能技术   13篇
自动化技术   5篇
  2022年   2篇
  2021年   2篇
  2020年   1篇
  2018年   3篇
  2017年   6篇
  2016年   4篇
  2015年   2篇
  2013年   3篇
  2012年   3篇
  2011年   9篇
  2010年   6篇
  2009年   6篇
  2008年   8篇
  2007年   2篇
  2006年   4篇
  2003年   1篇
  2002年   6篇
  2001年   4篇
  2000年   3篇
  1999年   7篇
  1998年   11篇
  1997年   8篇
  1996年   3篇
  1995年   6篇
  1994年   3篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
排序方式: 共有130条查询结果,搜索用时 0 毫秒
1.
2.
Conventional adaptive driving beam headlamps are limited in achieving still higher quantities of switchable pixels by the number of LEDs and movable elements needed. In this paper, it is shown that by integrating an active matrix liquid crystal display module, it is possible to realize fully adaptive high‐resolution headlights without mechanical elements and a finite number of LED with 30 k switchable pixels.  相似文献   
3.
4.
5.
A subpopulation of neurons is less vulnerable against iron-induced oxidative stress and neurodegeneration. A key feature of these neurons is a special extracellular matrix composition that forms a perineuronal net (PN). The PN has a high affinity to iron, which suggests an adapted iron sequestration and metabolism of the ensheathed neurons. Highly active, fast-firing neurons—which are often ensheathed by a PN—have a particular high metabolic demand, and therefore may have a higher need in iron. We hypothesize that PN-ensheathed neurons have a higher intracellular iron concentration and increased levels of iron proteins. Thus, analyses of cellular and regional iron and the iron proteins transferrin (Tf), Tf receptor 1 (TfR), ferritin H/L (FtH/FtL), metal transport protein 1 (MTP1 aka ferroportin), and divalent metal transporter 1 (DMT1) were performed on Wistar rats in the parietal cortex (PC), subiculum (SUB), red nucleus (RN), and substantia nigra (SNpr/SNpc). Neurons with a PN (PN+) have higher iron concentrations than neurons without a PN: PC 0.69 mM vs. 0.51 mM, SUB 0.84 mM vs. 0.69 mM, SN 0.71 mM vs. 0.63 mM (SNpr)/0.45 mM (SNpc). Intracellular Tf, TfR and MTP1 contents of PN+ neurons were consistently increased. The iron concentration of the PN itself is not increased. We also determined the percentage of PN+ neurons: PC 4%, SUB 5%, SNpr 45%, RN 86%. We conclude that PN+ neurons constitute a subpopulation of resilient pacemaker neurons characterized by a bustling iron metabolism and outstanding iron handling capabilities. These properties could contribute to the low vulnerability of PN+ neurons against iron-induced oxidative stress and degeneration.  相似文献   
6.
Chemical Synthesis of the Oligonucleotides dpG-A-T-A-T-C, dpG-A-T-C-T-T-T-T and dpT-T-T-C-A-T-C-A-T For studies of some sequence dependent structural factors the oligonucleotides dpG-A-T-A-T-C, dpG-A-T-C-T-T-T-T and dpT-T-T-C-A-T-C-A-T were required. Their chemical synthesis is reported according to the diester method.  相似文献   
7.
8.
The poor state of Aboriginal and Torres Strait Islander health has been documented in many ways, most obviously by comparing the relatively higher age-specific mortality and morbidity rates. This paper demonstrates the use of acute hospital separation data as a way to identify potential deficiencies in providing appropriate primary health care services for Aboriginal and Torres Strait Islander populations. It does so by using 'ambulatory sensitive conditions': those conditions (and procedures) for which high-quality appropriate primary health services deliverable under ideal circumstances are though to potentially reduce or eliminate the need for hospitalisation. Potential or realised access to primary care is not analysed directly using primary health service data. In this study, 1993-94 acute hospital separation data from NSW, Queensland, South Australia, Western Australia and the Northern Territory were used to calculate separation rates and odds ratios for Aboriginal and Torres Strait Islander and non-Aboriginal and Torres Strait Islander populations. Age-specific acute hospital separation rates for ambulatory sensitive conditions were 1.7 to 11 times higher for the Aboriginal and Torres Strait Islander populations studied. This supports clinical contentions that much Aboriginal and Torres Strait Islander morbidity and mortality is preventable and that further consideration is needed to service delivery reform at all levels in the health system and the distribution of funding.  相似文献   
9.
Vanadium oxides, such as V2O5, are promising for lithium-ion batteries, catalysis, electrochromic devices and sensors. Vanadium oxides were proposed more than a decade ago for another redox-dependent application: the direct conversion of electrical energy to mechanical energy in actuators (artificial muscles). Although related conducting polymer and carbon nanotube actuators have been demonstrated, electromechanical actuators based on vanadium oxides have not be realized. V2O5 nanofibres and nanotubes provide the potential advantages of low-cost synthesis by sol-gel routes and high charging capacity and long cycle life. Here, we demonstrate electromechanical actuation for obtained high modulus V2O5 sheets comprising entangled V2O5 nanofibres. The high surface area of these V2O5 sheets facilitates electrochemical charge injection and intercalation that causes the electromechanical actuation. We show that the V2O5 sheets provide high Young's modulus, high actuator-generated stress, and high actuator stroke at low applied voltage.  相似文献   
10.
This paper discusses the influence of nonsinusoidal flux waveforms on the remagnetization losses in ferro- and ferrimagnetic materials of inductors, transformers, and electrical machines used in power electronic applications. The nonsinusoidal changes of flux originate from driving these devices by nonsinusoidal voltages and currents at different switching frequencies. A detailed examination of a dynamic hysteresis model shows that the physical origin of losses in magnetic material is the average rate of remagnetization rather than the remagnetization frequency. This principle leads to a modification of the most common calculation rule for magnetic core losses, i.e., to the “modified Steinmetz equation” (MSE). In the MSE, the remagnetization frequency is replaced by an equivalent frequency which is calculated from the average remagnetization rate. This approach allows, for the first time, the calculation of the losses in the time domain for arbitrary waveforms of flux while using the available set of parameters of the classical Steinmetz equation. DC premagnetization of the material, having a substantial influence on the losses, can also be included. Extensive measurements verify the MSE presented in this paper  相似文献   
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