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   52篇
  免费   0篇
电工技术   1篇
化学工业   7篇
金属工艺   1篇
机械仪表   2篇
建筑科学   2篇
能源动力   4篇
轻工业   13篇
无线电   5篇
一般工业技术   10篇
冶金工业   4篇
自动化技术   3篇
  2023年   1篇
  2022年   1篇
  2020年   3篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2014年   3篇
  2012年   1篇
  2011年   1篇
  2010年   2篇
  2009年   3篇
  2008年   1篇
  2007年   1篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2003年   4篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1998年   5篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1987年   1篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1968年   2篇
  1967年   1篇
  1925年   1篇
排序方式: 共有52条查询结果,搜索用时 15 毫秒
1.
The 2011 AASHTO Roadside Design Guide (RDG) contains perhaps the most widely used procedure for choosing an appropriate length of need (LON) for roadside barriers. However, this procedure has several limitations. The procedure uses a highly simplified model of vehicle departure, and the procedure does not allow designers to specify an explicit level of protection. A new procedure for choosing LON that addresses these limitations is presented in this paper. This new procedure is based on recent, real-world road departure trajectories and uses this departure data in a more realistic way. The new procedure also allows LON to be specified for a precisely known level of protection – a level which can be based on number of crashes, injury outcomes or even estimated crash cost – while still remaining straightforward and quick to use like the 2011 RDG procedure.  相似文献   
2.
The assessment of ionic liquids (ILs) as lubricants in several tribological systems has shown their ability to provide remarkable reduced friction and protection against wear, whether they are used as additives or in the neat form. However, their corrosion and limited solubility in non-polar hydrocarbon oils represent the bottleneck-limiting factors for the use of ILs as lubricants. Therefore, in order to tackle these problems, mixtures of alkylborane–imidazole complexes with one halogen-free IL as additive were used in this study. The knowledge of the additive–surface interactions and hence the understanding of tribological properties are an important issue for lubricant formulations and were also investigated in this work. Thus, combination effects between two ionic liquid additives, a halogenated and a halogen-free one, were evaluated by a ball-on-disc-type tribometer under boundary lubrication conditions. Effective friction reduction and anti-wear properties have been demonstrated in tribological investigations when adding between 0.7 and 3.4 wt% of the halogen-free IL into base fluid composed of alkylborane–imidazole complexes. X-ray photoelectron spectroscopy analyses of the steel specimens were conducted to study the correlation between tribological properties and chemical surface composition of the boundary films formed on the rubbing surface. This work suggests potential applications for using halogen-free ILs as additives for synthetic ionic liquid lubricants.  相似文献   
3.
The adenovirus type 5 (Ad5) early 1B 55-kDa protein (E1B-55kDa) is a multifunctional phosphoprotein that regulates viral DNA replication and nucleocytoplasmic RNA transport in lytically infected cells. In addition, E1B-55kDa provides functions required for complete oncogenic transformation of rodent cells in cooperation with the E1A proteins. Using the far-Western technique, we have isolated human genes encoding E1B-55kDa-associated proteins (E1B-APs). The E1B-AP5 gene encodes a novel nuclear RNA-binding protein of the heterogeneous nuclear ribonucleoprotein (hnRNP) family that is highly related to hnRNP-U/SAF-A. Immunoprecipitation experiments indicate that two distinct segments in the 55-kDa polypeptide which partly overlap regions responsible for p53 binding are required for complex formation with E1B-AP5 in Ad-infected cells and that this protein interaction is modulated by the adenovirus E4orf6 protein. Expression of E1B-AP5 efficiently interferes with Ad5 E1A/E1B-mediated transformation of primary rat cells. Furthermore, stable expression of E1B-AP5 in Ad-infected cells overcomes the E1B-dependent inhibition of cytoplasmic host mRNA accumulation. These data suggest that E1B-AP5 might play a role in RNA transport and that this function is modulated by E1B-55kDa in Ad-infected cells.  相似文献   
4.
5.
6.
The analysis of minor hysteresis loop behavior during partial alternating flux reversal in toroidal cores with a rectangular hysteresis loop is considered. A simple flux-reversal model is proposed on the basis of which, with the aid of dimensionless units, the asymmetry of minor hysteresis loops is derived. The drift of minor hysteresis loops during alternating flux reversal is investigated on the basis of loop asymmetry and by means of a proposed indirect method. The method involves compensation of the minor-loop drift by means of a dc component of the exciting field, the magnitude and sense of which are a measure of the drift. The experimental section deals partly with a qualitative comparison of the character of the actual asymmetry of a minor loop with that derived from the flux reversal model, and partly with comparing the actual minor-loop drift to the drift derived theoretically on the basis of the indirect method. Experimental results indicate that in the case of the 50 percent nickel-iron alloy, cold-rolled at a great reduction, there appear additional factors which affect the instability of the minor loop. This effect is further investigated, and a simplified mechanism is proposed for its stimulation. Finally, the proposed mechanism is verified experimentally.  相似文献   
7.
BACKGROUND AND PURPOSE: Activated leukocytes appear to potentiate central nervous system reperfusion injury, and agents that block leukocyte adhesion have shown neuroprotective efficacy in experimental models. Doxycycline, a tetracycline antibiotic, inhibits leukocyte function in vitro, presumably through divalent cation binding. We used a model of focal central nervous system reperfusion injury to determine the efficacy of doxycycline treatment in preserving neurological function. METHODS: Rabbits randomly received 10 mg/kg i.v. doxycycline 30 minutes before ischemia (pretreatment group) or 45 minutes after ischemia (posttreatment group) or received phosphate-buffered saline vehicle (control group) followed by 10 mg/kg q 8 hours times two. The average length of reversible spinal cord ischemia required to produce paraplegia (P50) at 18 hours was calculated for each group. RESULTS: For the control group (n = 13), the P50 was 22.8 +/- 2.2 minutes; for the pretreatment group (n = 14), 35.5 +/- 2.4 minutes (P < .01; t = 3.8); and for the posttreatment group (n = 13), 31.4 +/- 4.2 minutes (not significant; t = 1.6). Doxycycline also attenuated postischemic decreases in vivo leukocyte counts and inhibited in vitro leukocyte adhesion. Therapeutic doxycycline levels at 24 hours were confirmed in the plasma and spinal cord. CONCLUSIONS: This significant protective effect suggests that doxycycline, a safe and readily available agent, may play a role in reducing clinical central nervous system reperfusion injury.  相似文献   
8.
To improve protein digestibility of aqueously extracted soy proteins, an effective chemical treatment under mild conditions is needed. Soy proteins, including storage protein glycinin and antinutritional factors such as trypsin inhibitors, are rich in disulfide bonds. Reduction of these disulfide bonds by incubating soy proteins with sodium sulfite and sodium metabisulfite at 55 °C showed no net increase of free sulfhydryl groups after dialysis to remove the residual reducing agent. However, the in vitro digestibility measured by trypsin hydrolysis using the pH-Stat method was significantly increased. Sodium metabisulfite (SMBS) was more effective in increasing in vitro digestibility than sodium sulfite at the same molar concentration. The digestibility of soy protein treated by 0.5 mmol SMBS/g soy flour at 55 °C was more than doubled compared to that of the control without reduction treatment. Large-scale testing of soy proteins treated with SMBS for an in vivo animal feeding study showed similar in vitro digestibility by trypsin, e.g., the degree of hydrolysis of the treated sample was 8.5% compared to 1.6% of the control. These soy proteins were further evaluated using a chick growth model. The protein efficiency ratio (PER) increased by 57% when the chicks fed SMBS-treated soy were compared to the chicks fed raw soy flour. SMBS-fed chicks did not display any pancreatic hypertrophy compared to those fed with raw soy control. These results indicate that there is great potential to use safe chemicals and mild temperature to inactivate the antinutritional factors in soybeans and thus improve digestibility of soy proteins that are extracted with low-temperature aqueous process.  相似文献   
9.
In Friedberg (Hessen) wurde im Juli 2008 erstmals in Deutschland eine Straßenbrücke unter Verwendung von glasfaserverstärktem Kunststoff (GFK) fertig gestellt. Das Bauwerk überspannt mit 27 m die Bundesstraße B 3a bei der Stadt Friedberg (Hessen) und wurde in Stahl‐GFK‐Verbundbauweise realisiert. Die hohe Dauerhaftigkeit des neuen Werkstoffs und die zügige Montage der Brücke waren die entscheidenden Gründe pro GFK. In den letzten Jahren wurden in den USA, Japan und auch in Europa einige Leichtbaubrücken mit faserverstärkten Kunststoffen realisiert. Dabei konnten wertvolle Erfahrungen zum Bau und Betrieb gesammelt und die Leistungsfähigkeit von Verbundwerkstoffen unter Beweis gestellt werden. Die Brücke in Friedberg geht über diese Vorbilder hinaus, indem hier erstmals die Verbundwirkung zwischen der GFK‐Fahrbahn und dem Haupttragwerk aus Stahl berücksichtigt wird. Außerdem wurde konsequent der Ansatz eines wartungsarmen und langlebigen Bauwerks verfolgt, indem auf Lager und Fahrbahnübergänge verzichtet wurde. Bridges with Glass Fibre Reinforced Polymers (GFRP) decks – The new Road Bridge in Friedberg (Hessen, Germany). In July 2008 the first road bridge in Germany using glass fibre reinforced polymers (GFRP) was finished in Friedberg (Hessen). The structure has a span of 27 m and acts as overfly of the federal road B 3 near Friedberg (Hessen). The high durability of the new construction material and the fast assembly of the bridge were decisive factors in favour of GFRP. Within the last years several light weight bridges using FRP were realised in USA, Japan and also in Europe. Through this valuable experiences could be gathered regarding construction, the use and performance of composites could be demonstrated. The bridge in Friedberg extends this experience with the approach of considering the composite action of the FRP deck and the steel girders. It also follows consequently the approach of durable bridge construction by omitting any bearings or expansion joints.  相似文献   
10.
Comparison of roadside crash injury metrics using event data recorders   总被引:1,自引:0,他引:1  
The occupant impact velocity (OIV) and acceleration severity index (ASI) are competing measures of crash severity used to assess occupant injury risk in full-scale crash tests involving roadside safety hardware, e.g. guardrail. Delta-V, or the maximum change in vehicle velocity, is the traditional metric of crash severity for real world crashes. This study compares the ability of the OIV, ASI, and delta-V to discriminate between serious and non-serious occupant injury in real world frontal collisions. Vehicle kinematics data from event data recorders (EDRs) were matched with detailed occupant injury information for 180 real world crashes. Cumulative probability of injury risk curves were generated using binary logistic regression for belted and unbelted data subsets. By comparing the available fit statistics and performing a separate ROC curve analysis, the more computationally intensive OIV and ASI were found to offer no significant predictive advantage over the simpler delta-V.  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