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   255篇
  免费   3篇
  国内免费   24篇
电工技术   12篇
综合类   32篇
化学工业   25篇
金属工艺   4篇
机械仪表   8篇
建筑科学   35篇
矿业工程   1篇
能源动力   37篇
轻工业   7篇
水利工程   1篇
石油天然气   3篇
武器工业   1篇
无线电   30篇
一般工业技术   31篇
冶金工业   4篇
原子能技术   2篇
自动化技术   49篇
  2023年   5篇
  2022年   8篇
  2021年   2篇
  2020年   12篇
  2019年   7篇
  2018年   2篇
  2017年   5篇
  2016年   13篇
  2015年   4篇
  2014年   15篇
  2013年   10篇
  2012年   14篇
  2011年   18篇
  2010年   28篇
  2009年   25篇
  2008年   20篇
  2007年   9篇
  2006年   12篇
  2005年   20篇
  2004年   14篇
  2003年   8篇
  2002年   5篇
  2001年   3篇
  2000年   3篇
  1999年   8篇
  1998年   5篇
  1996年   1篇
  1995年   1篇
  1994年   4篇
  1992年   1篇
排序方式: 共有282条查询结果,搜索用时 15 毫秒
41.
针对我厂改性沥青感温性能指数不达标的原因,用SBS聚合物的改性沥青机理和相分离机理进行了分析,提出了改进措施,并在生产中进行了验证,提高了感温性能指数。  相似文献   
42.
Compacted graphite iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 L Audi V8 TDI and the 4.0 L BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount as decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools.  相似文献   
43.
王万祯  徐峰  黄俊伟  王春青 《特种结构》2010,27(5):57-60,76
利用通用软件ANSYS的二次开发功能,将静水应力型广义屈服模型编制成子程序模块。对直角角焊缝进行了基于广义强度模型的数值模拟,以建议的椭球面断裂准则为判据,提出了等效考虑焊接缺陷和残余应力的断裂因子CI的修正系数k。基于修正后的断裂因子CI,对T型钢桁架下弦一般节点进行断裂分析,得出了防止T型钢桁架节点脆断的细部构造。  相似文献   
44.
Many short-run studies point to the potential for direct fueling of compression ignition engines with plant oil fuels. There is a much smaller body of work that examines the potential for these fuels in long-run tests that illuminate engine endurance and longevity issues. Generally, longevity studies involving direct fueling of engines with straight plant oils have shown significant impact to the life of the engine, though test results vary widely depending on the oil, engine type, test conditions, and measurement approach. This study utilizes a previously designed modification kit [1] to investigate the longevity implications of directly fueling straight plant oil in an indirect injection (IDI) listeroid type, slow speed stationary engine common in agro-processing applications in developing countries. Specifically this study focuses on the lubrication oil by developing a model to characterize the engine wear and estimate lube oil change frequency. The model is extended to an analysis of the piston rings. Cylinder liner wear, emissions, engine performance, and a visual investigation of several critical engine components are also studied.  相似文献   
45.
Emerging trends in the area of digital very large scale integration (VLSI) signal processing can lead to a reduction in the cost of the cochlear implant. Digital signal processing algorithms are repetitively used in speech processors for filtering and encoding operations. The critical paths in these algorithms limit the performance of the speech processors. These algorithms must be transformed to accommodate processors designed to be high speed and have less area and low power. This can be realized by basing the design of the auditory filter banks for the processors on digital VLSI signal processing concepts. By applying a folding algorithm to the second‐order digital gammatone filter (GTF), the number of multipliers is reduced from five to one and the number of adders is reduced from three to one, without changing the characteristics of the filter. Folded second‐order filter sections are cascaded with three similar structures to realize the eighth‐order digital GTF whose response is a close match to the human cochlea response. The silicon area is reduced from twenty to four multipliers and from twelve to four adders by using the folding architecture.  相似文献   
46.
Essential changes in cell metabolism and redox signaling occur during the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs). In this paper, using genetic and pharmacological approaches, we have investigated the role of electron transport chain (ETC) complex-I (CI) of mitochondria in the process of cell reprogramming to pluripotency. Knockdown of NADH-ubiquinone oxidoreductase core subunits S1 (Ndufs1) or subunit B10 (Ndufb10) of the CI or inhibition of this complex with rotenone during mouse embryonic fibroblast (MEF) reprogramming resulted in a significantly decreased number of induced pluripotent stem cells (iPSCs). We have found that mitochondria and ROS levels due course of the reprogramming tightly correlate with each other, both reaching peak by day 3 and significantly declining by day 10 of the process. The transient augmentation of mitochondrial reactive oxygen species (ROS) could be attenuated by antioxidant treatment, which ameliorated overall reprogramming. However, ROS scavenging after day 3 or during the entire course of reprogramming was suppressive for iPSC formation. The ROS scavenging within the CI-deficient iPSC-precursors did not improve, but further suppressed the reprogramming. Our data therefore point to distinct modes of mitochondrial ROS action during the early versus mid and late stages of reprogramming. The data further substantiate the paradigm that balanced levels of oxidative phosphorylation have to be maintained on the route to pluripotency.  相似文献   
47.
48.
通过对企业商标和形象识别设计的历史、构成因素、作用以及流程的回顾 ,分析了我国陶瓷企业领域导入该系统的价值 ,并提出了一些建设性的意见。文章强调在世界经济一体化和中国加入WTO这个众多机遇与挑战交汇的历史时刻 ,陶瓷企业重视商标与形象识别设计对我国陶瓷企业发展和改革具有重要意义  相似文献   
49.
通过滨海景观案例,解析景观CI设计工作的步骤与应用,具有实践意义。  相似文献   
50.
S. Swami Nathan 《Fuel》2010,89(2):515-521
In this work, experiments were conducted on a homogeneous charge compression ignition (HCCI) engine with acetylene as the sole fuel at different power outputs. Initially, the intake air was heated to different temperatures in order to determine the optimum level at every output. Charge temperatures needed were in the range of 40-110 °C from no load to a BMEP (Brake Mean Effective Pressure) of 4 bar. Subsequently, exhaust gas re-circulation (EGR) was done at the identified charge temperatures and brake thermal efficiency was found to improve. At high BMEPs, use of EGR led to knocking. Thus, fine control over charge temperature and EGR quantity is needed at these conditions. Nitric oxide and smoke levels were very low. However, HC levels were high at about 1700-2700 ppm. Brake thermal efficiencies were comparable to or even better than the compression ignition mode of operation.  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