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   1579篇
  免费   29篇
  国内免费   3篇
电工技术   84篇
综合类   2篇
化学工业   439篇
金属工艺   46篇
机械仪表   39篇
建筑科学   21篇
能源动力   113篇
轻工业   133篇
水利工程   10篇
石油天然气   1篇
无线电   140篇
一般工业技术   284篇
冶金工业   93篇
原子能技术   48篇
自动化技术   158篇
  2023年   7篇
  2022年   12篇
  2021年   21篇
  2020年   13篇
  2019年   25篇
  2018年   17篇
  2017年   15篇
  2016年   29篇
  2015年   18篇
  2014年   51篇
  2013年   108篇
  2012年   87篇
  2011年   87篇
  2010年   74篇
  2009年   96篇
  2008年   87篇
  2007年   70篇
  2006年   55篇
  2005年   55篇
  2004年   41篇
  2003年   51篇
  2002年   50篇
  2001年   26篇
  2000年   34篇
  1999年   42篇
  1998年   52篇
  1997年   31篇
  1996年   36篇
  1995年   23篇
  1994年   19篇
  1993年   31篇
  1992年   25篇
  1991年   16篇
  1990年   16篇
  1989年   17篇
  1988年   15篇
  1987年   7篇
  1986年   10篇
  1985年   15篇
  1984年   13篇
  1983年   10篇
  1982年   11篇
  1981年   14篇
  1980年   17篇
  1979年   12篇
  1978年   11篇
  1977年   11篇
  1976年   11篇
  1968年   3篇
  1967年   3篇
排序方式: 共有1611条查询结果,搜索用时 218 毫秒
11.
In recent years the requirement for the reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. For example, in the power generation field, as thermal power generation occupied 60% of the power generation demand, considerable improvement of the thermal efficiency is required. This paper describes the pressure drop characteristics of finned tube banks used for heat exchangers in thermal power generation that were clarified by testing serrated finned tube banks with different fin heights for improved heat transfer and conventional spiral finned tube banks with different fin heights, and an equation to predict pressure drop which is necessary for the heat exchanger design is proposed. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 179–193, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20112  相似文献   
12.
Discusses 2 interrelated traditions as they are reflected in contemporary and traditional approaches to psychotherapy in Japan. One uses various meditational and self-focusing instructional sets whose common goal is to facilitate the slowing down, deepening, and clearer focusing of sensory and interpersonal awareness. The 2nd tradition focuses on physical self-regulation and autonomic self-control through exercises that foster enhanced voluntary control over physical states and processes. Eastern psychology offers a set of practices that help the individual overcome the inherent selfishness of his/her isolated experience. The goals of such work include recognition of gratitude to important people in the client's life, rediscovery of the joy of meaningful work, and the experience of a unifying cosmic consciousness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
13.
A series of Mo–TiC alloys were heated in vacuum at 2473 K for 36 ks. First grain growth behavior was observed using a scanning electron microscope. Then effects of TiC addition on the strengths and ductility at low temperature were discussed from the viewpoints of chemical composition and grain structure.

Materials with TiC additions of not larger than 0.1% demonstrated a single-crystalline grain structure. Both yield and maximum strengths increased by TiC addition and consequently ductility was improved.  相似文献   

14.
Electric power systems are expanding in size and complexity, and the requirement for the energy management system (EMS) is becoming more important. In this computer control system, a single control computer is used mainly as the primary computer and its software is very complicated because of its hugh number of small, quick tasks to obtain high response speed. Therefore, much effort is needed to develop and modify the programs, and the responsiveness of this centralized architecture varies greatly when many faults occur in the power system. This paper describes a new distributed architecture for the EMS. Distributed processors execute the functions cooperatively with periodic access to the common bulletin board database in which information about the power system exist. This architecture facilitates the software development and maintenance, and it also enhances the performance by the parallel processing of the distributed functions.  相似文献   
15.
One of the most important issues in avoiding a global water crisis is to solve the confrontation between developed and developing countries. As Japan in the 20th century has experienced the shift from a developing country to a developed country, it should candidly share its precious historical experience, both its merits and demerits, with people throughout Monsoon Asia. Two practical proposals to economize water demand are as follows: to economize toilet water in a way that meets the conditions of each region; and to develop the effective utilization of water for irrigated rice paddies, not only in the Monsoon Asia but throughout the world. In short, new life-styles are necessary if the global water crisis is to be averted.  相似文献   
16.
When a fault occurs on transmission or distribution systems due to lightning or overvoltage, often an arc discharge occurs at the fault point. The arc discharge, which is caused by a fault current, has a high current, high temperature, strong light emission, etc., thus it sometimes causes heavy damages to electric power equipment. The arc discharge is influenced by the conditions around the arcs, i.e., gas, insulation materials, gap length, weather, etc. Also, the arc voltage along the arc column indicates the characteristics of the arc. If the voltage waveforms of the arcs caused by the fault on transmission or distribution systems are classified, it is possible to find the location and the equipment where the fault occurred. In this paper, the arc voltage data in 6-kV class XLPE cables and 6-kV class overhead lines are analyzed and an artificial neural network method is applied to classify the arc voltage waveforms. The results obtained from the six artificial neural networks developed show that the artificial neural network method is effective for classification of arc voltage waveforms if adequate input parameters are selected.  相似文献   
17.
The behaviour of the amorphous chain in vulcanized natural rubber (NR) and styrene-butadiene rubber (SBR) under extension is studied by means of the cylindrical distribution function (CDF) derived from wide angle X-ray scattering (WAXS). In the case of the highly stretched vulcanized NR where the orientation-induced crystallization took place, the observed WAXS intensity was separated into a crystalline peak component and a broad amorphous one from which the CDF was obtained. The CDF calculated from the broad component shows that some of the amorphous segments of the highly stretched vulcanized NR are extended as fully as the crystalline chains and that the fraction of the segments increases with increasing extension. In the case of SBR, such fully stretched segments as in the case of the vulcanized NR show higher degree of an interchain packing order than those in the vulcanized NR.  相似文献   
18.
We prepared La-Sr-Nb-O system samples both in bulk form and as a film, with sharp resistive transitions at temperatures of 228–323 K, depending on the annealing conditions. The sharp resistive transitions might be attributable to superconductivity. Magnetic ordering was observed over a narrow temperature range around 40 K for some of the samples.  相似文献   
19.
20.
The wax esters of sperm whale head oil have been characterized by gas-liquid chromatography on an APOLAR 10C column according to their carbon number and number of double bonds. The novel technique permits the direct quantitative analysis of saturated and unsaturated wax esters.  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