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   324篇
  免费   16篇
电工技术   4篇
综合类   31篇
化学工业   93篇
金属工艺   16篇
机械仪表   3篇
建筑科学   6篇
能源动力   10篇
轻工业   47篇
水利工程   3篇
无线电   13篇
一般工业技术   54篇
冶金工业   30篇
自动化技术   30篇
  2023年   2篇
  2022年   4篇
  2021年   8篇
  2020年   9篇
  2019年   11篇
  2018年   9篇
  2017年   11篇
  2016年   5篇
  2015年   5篇
  2014年   13篇
  2013年   10篇
  2012年   12篇
  2011年   22篇
  2010年   18篇
  2009年   5篇
  2008年   26篇
  2007年   13篇
  2006年   11篇
  2005年   12篇
  2004年   12篇
  2003年   9篇
  2002年   9篇
  2001年   5篇
  2000年   5篇
  1999年   2篇
  1998年   7篇
  1997年   6篇
  1996年   5篇
  1995年   2篇
  1994年   7篇
  1993年   2篇
  1992年   3篇
  1990年   4篇
  1989年   4篇
  1988年   2篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   6篇
  1982年   2篇
  1981年   4篇
  1980年   2篇
  1978年   2篇
  1977年   5篇
  1976年   2篇
  1975年   4篇
  1974年   5篇
  1925年   1篇
  1924年   1篇
  1920年   1篇
排序方式: 共有340条查询结果,搜索用时 15 毫秒
1.
2.
This research reports age and gender differences in cardiac reactivity and subjective responses to the induction of autobiographical memories related to anger, fear, sadness, and happiness. Heart rate (HR) and subjective state were assessed at baseline and after the induction of each emotion in 113 individuals (61 men, 52 women; 66% European American, 34% African American) ranging in age from 15 to 88 years (M = 50.0; SD = 20.2). Cardiac reactivity was lower in older individuals; however, for anger and fear, these age effects were significantly more pronounced for the women than the men. There were no gender differences in subjective responses, however, suggesting that the lower cardiac reactivity found among older people is dependent on gender and the specific emotion assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Zusammenfassung Die numerische Berechnung von turbulenten Str?mungen, sei es isotherm oder mit chemischer Reaktion und W?rmefreisetzung, kann infolge der st?ndigen Fortschritte auf Seiten der Hardware-Entwicklung, auf immer weiteren Anwendungsgebieten eingesetzt werden. Im vorliegenden Fall handelt es sich um ein Programmpaket (COMPAC-3D), welches für die dreidimensionale Simulation der Str?mung und W?rmefreisetzung in Dampferzeugerfeuerungen konzipiert wurde. Hierbei kommt ein neuer Gleichungsl?sungs-und Bilanzierungsalgorithmus zum Einsatz, welcher es gestattet, Parameterstudient mit wesentlich geringerem Rechenzeitaufwand durchzuführen. Dieser Algorithmus wird im folgenden beschrieben. Anhand eines klassischen Testbeispiels, n?mlich der horizontalen Eindüsung in eine vertikale Hauptstr?mung, werden die Simulationsergebnisse mit Me?werten und Ergebnissen aus Rechenl?ufen mit dem Programmpaket PHOENICS verglichen.  相似文献   
4.
Obliterative or constrictive bronchiolitis is characterized by narrowing of the small airways, due to submucosal and peribronchiolar fibrosis, with chronic obstruction. The vast majority of cases of bronchiolitis obliterans are associated with other diseases and only few cases are idiopathic. We report on the main computed tomography (CT) methods used study obliterative bronchiolitis, the CT findings and the differential diagnosis with other diseases. The dynamic study of alveolar ventilation with CT uses inspiratory and expiratory CT or high-resolution CT (HRCT), spiral dynamic CT or HRCT with advanced image display, ultrafast CT. In abnormal cases HRCT shows direct and indirect signs of small airways disease. The most common (> 80%) sign of obliterative bronchiolitis is the so-called mosaic oligohemia, with low attenuating lobules, caused by air trapping and best seen on expiratory CT, associated with blood flow redistribution to more normal lobules; this finding simulates the ground-glass pattern from infiltrative lung disease. Differential diagnosis is more difficult in the presence of true ground-glass patterns associated with diffuse bronchiolar obstruction and also with mosaic oligohemia due to pulmonary vascular disease and pulmonary emphysema. HRCT can distinguish these diseases and dynamic CT is more sensitive than functional tests in detecting regional abnormalities and air trapping. The combination of HRCT, rapid volumetric scanning and advanced image display is a powerful tool study the normal and abnormal features of bronchiolar function and alveolar ventilation.  相似文献   
5.
For timber the tensile stress perpendicular to the grain is a critical type of stress. The influence of long-term loading, temperature and climate changes upon the tensile strength perpendicular to the grain of timber is shown. The results prove that the greatest loss of strength happened after long-term outdoors loading. While storing under alternating climate conditions, great crepp strains appeared, and it is to be presumed that the damages of wooden components which fail across the grain are less a problem of “tensile stress perpendicular to the grain” than a problem of “strain under tension perpendicular to the grain”.  相似文献   
6.
7.
Summary: The influence of number‐average molecular weight ranging from 1.4 · 104 to 1.2 · 106 g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.

Concentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.  相似文献   

8.
The note presents an output feedback control strategy for Markov jump linear systems with no mode observation. Based on minimizing a finite‐time quadratic cost, we derive an algorithm that generates output feedback gains that satisfy a necessary optimality condition. These gains can be computed off‐line relying only on the initial condition of the system. This result expands a previous one from the literature that considered state‐feedback only. To illustrate the usefulness of the approach, real‐time laboratory experiments were performed to control an automotive electronic throttle valve subject to Markov‐driven voltage fluctuations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
9.
Journal of Intelligent Manufacturing - Remanufacturing includes disassembly and reassembly of used products to save natural resources and reduce emissions. While assembly is widely understood in...  相似文献   
10.
Agroindustrial by-products are an abundant source of biocompounds that contain valuable nutrients, which are not exploited. In this work, lignocellulosic wastes (LW) were used in submerged fermentation (SmF) and solid-state fermentation (SSF) by Aspergillus niger NRRL3 to obtain valuable enzymes required in industries. SmF using soya bean hulls (SH), wheat bran (WB) and a by-product of wheat flour (F) produced the highest activities of endo-1,4-β-xylanase (Xyl) and endo-1,4-β-D-glucanase (EG) being at least 3 times lower than those obtained by SSF. The highest ratio of Xyl to EG was obtained in SmF with F. Xyl obtained by SmF with WB was the most thermally resistant. The enzymatic extract obtained in SmF using SH presented a high power of saccharification. The production of enzymes for further application such as bioethanol generation process revalue these LW and can help offset growing environmental problems.  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