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   91篇
  免费   4篇
化学工业   22篇
金属工艺   3篇
机械仪表   2篇
能源动力   1篇
轻工业   8篇
水利工程   3篇
无线电   3篇
一般工业技术   26篇
冶金工业   23篇
自动化技术   4篇
  2023年   2篇
  2022年   2篇
  2021年   3篇
  2020年   2篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2014年   4篇
  2013年   3篇
  2012年   2篇
  2011年   5篇
  2010年   3篇
  2009年   2篇
  2008年   2篇
  2007年   9篇
  2006年   4篇
  2005年   2篇
  2004年   6篇
  2002年   3篇
  1998年   4篇
  1997年   6篇
  1996年   4篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1981年   1篇
  1978年   1篇
  1976年   3篇
  1973年   1篇
  1966年   1篇
  1956年   1篇
  1954年   2篇
排序方式: 共有95条查询结果,搜索用时 0 毫秒
71.
We report the case of a 62-year-old man with massive pulmonary embolism and severe hemodynamic impairment. Transthoracic Doppler echocardiography was fundamental in confirming the diagnosis by direct visualization of intra-atrial thrombus and signs of right chamber overload. It allowed prompt administration of thrombolytic drug and follow-up monitoring. Doppler echocardiography is a non-invasive, available technique and its early application should be considered in the evaluation of patients with suspected massive pulmonary embolism.  相似文献   
72.
The slip and twinning behavior in extended titanium crystals were studied in some detail. The formation and appearance of coarse kink bands are discussed. Their crystallographic geometry was determined by X-ray analysis. A phenomenological interpretation of the complexities in kink band development is also presented. The critical resolved shear stress, coefficient of shear hardening, and plane of fracture were determined for several crystals extended at room temperature.  相似文献   
73.
74.
The plastic properties at room temperature of extended copper crystals alloyed with aluminium, germanium and silicon were examined as a function of crystal orientation, alloy concentration and nature of solute. A strong orientation dependence was observed on the gross shape of the shear stress/shear strain diagram in all of the alloy crystals examined. In those crystals exhibiting a well-defined two-stage hardening curve, the extent of shear associated with stage I and the shear hardening coefficients of stages I and II are significantly dependent on orientation, nature and concentration of solute. On the other hand, the shear stress defining the onset of stage II is constant and independent of crystal orientation. Variations in the gross shape of the shear stress/shear diagram and in the parameters defining the two-stage hardening curve are correlated with changes in slip line development. No evidence of Lüders band propagation, kink band development or twinning, was observed.  相似文献   
75.
The assemblage of stream habitat types can drive biofilm composition and activity in headwater streams, thereby influencing rates of ecosystem function. However, the influence of human‐induced alterations to the distribution of benthic habitat such as construction, land‐use changes and restoration on biofilm‐mediated processes has not been well studied. We measured nutrient uptake of ammonium, nitrate and phosphate, as well as gross primary production and community respiration in three streams in Michigan, USA, each with an upstream reference and a downstream restored reach. The restoration included a 10‐m sediment trap, paired with 40–60 m of gravel and boulder added downstream and designed to retain sediment, stabilize banks and provide spawning habitat for trout. We sampled four times in the six stream reaches from May 2006 to September 2007. Across streams, restored reaches reflected the structural manipulation with increased predominance of coarse inorganic sediments, higher gas exchange rate and increased transient storage. However, nutrient uptake and community respiration rates were different between reaches at only one site. The ecosystem response by this stream was driven by the large differences in coarse inorganic habitat between reference and restored reaches. We conclude that restorations of benthic habitat which are visually conspicuous, such as creation of settling pools and gravel‐filled reaches, did not universally affect stream ecosystem function. Initial conditions and magnitude of change may be key factors to consider in explaining functional responses, and predicting the influence of habitat restoration on ecosystem function remains a challenge. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
76.
The present paper describes the use of a functional analysis in attempting to make sense of symptomatic delusional statements and behaviors that people diagnosed with schizophrenia present. The three categories that are used to classify symptoms are: (1) positive reinforcement function, (2) negative reinforcement function, and (3) mislabeling of private events. The paper presents a number of clinical cases whose symptoms are representative of each category. Each case is then functionally treated as a result of its "category" characteristics, thus basing treatment on the hypothesized function (or reason) for the symptom.  相似文献   
77.
Among the many metrics used to compute the colour rendition of a light source which have been investigated in recent years, most consider only the spectral power distribution of the light source being tested. To highlight aspects not usually considered in the development of colour rendition metrics, and to propose future directions for alternative approaches consistent with human visual perception, an experiment was conducted to examine colour appearance variations on certain spatial visual content configurations, in other words the effects of illusions under different light sources. Results indicate that stronger simultaneous contrast configurations have a more unpredictable variation in appearance. Therefore, it is proposed that colour spatial distribution should be considered for the future generation of rendering metrics.  相似文献   
78.
In-phantom dosimetry studies have been carried out at the thermal columns of a thermal- and a fast-nuclear reactor for investigating: (a) the spatial distribution of the gamma dose and the thermal neutron fluence and (b) the accuracy at which the boron concentration should be estimated in an explanted organ of a boron neutron capture therapy patient. The phantom was a cylinder (11 cm in diameter and 12 cm in height) of tissue-equivalent gel. Dose images were acquired with gel dosemeters across the axial section of the phantom. The thermal neutron fluence rate was measured with activation foils in a few positions of this phantom. Dose and fluence rate profiles were also calculated with Monte Carlo simulations. The trend of these profiles do not show significant differences for the thermal columns considered in this work.  相似文献   
79.
In order to increase the release of cell wall polysaccharides during alcoholic fermentation, a wine strain of Saccharomyces cerevisiae was subjected to UV mutagenesis to obtain thermosensitive autolytic mutants affected in cell wall integrity. Five mutants and the parental strain were utilized in fermentation trials conducted at 28, 32 and 34 degrees C. Results showed that at all temperatures the mutant strains released into the medium a higher polysaccharide quantity than the parental strain. In particular, at 28 degrees C there was a doubling of these macromolecules. At the end of alcoholic fermentation, all strains showed at 28 degrees C elevated and similar levels of viable cells; at 32 degrees C this parameter remained high for mutant strains ts16 and ts39 and the parental strain; at 34 degrees C all strains underwent a drop in cell viability, which was less intense in the case of strain ts16. As a relationship between cell viability and the quantity of polysaccharides released by the yeast strain was not found, it can be assumed that the mutation led to cells with a less stable wall and thus an easier release of macromolecules into the medium.  相似文献   
80.
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