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   236571篇
  免费   4185篇
  国内免费   639篇
电工技术   3739篇
综合类   180篇
化学工业   35785篇
金属工艺   8696篇
机械仪表   6738篇
建筑科学   5995篇
矿业工程   1374篇
能源动力   5859篇
轻工业   22140篇
水利工程   2633篇
石油天然气   4199篇
武器工业   12篇
无线电   25210篇
一般工业技术   46624篇
冶金工业   45947篇
原子能技术   5252篇
自动化技术   21012篇
  2021年   2526篇
  2020年   1934篇
  2019年   2198篇
  2018年   3970篇
  2017年   4042篇
  2016年   4228篇
  2015年   2818篇
  2014年   4386篇
  2013年   11453篇
  2012年   7227篇
  2011年   8991篇
  2010年   7165篇
  2009年   7748篇
  2008年   8059篇
  2007年   7932篇
  2006年   6645篇
  2005年   6126篇
  2004年   5836篇
  2003年   5621篇
  2002年   5180篇
  2001年   5069篇
  2000年   4974篇
  1999年   5248篇
  1998年   14122篇
  1997年   9745篇
  1996年   7487篇
  1995年   5308篇
  1994年   4816篇
  1993年   4603篇
  1992年   3408篇
  1991年   3258篇
  1990年   3072篇
  1989年   3134篇
  1988年   2997篇
  1987年   2547篇
  1986年   2470篇
  1985年   2896篇
  1984年   2666篇
  1983年   2456篇
  1982年   2230篇
  1981年   2347篇
  1980年   2160篇
  1979年   2241篇
  1978年   2225篇
  1977年   2534篇
  1976年   3554篇
  1975年   1913篇
  1974年   1829篇
  1973年   1847篇
  1972年   1482篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ABSTRACT

Occupancy patterns are necessary to estimate energy demand and evaluate thermal comfort in households. Because of this, many European countries are developing representative domestic schedules to replace outdated criteria. This paper evaluates the state of knowledge of UK domestic occupancy patterns and develops new domestic occupancy profiles for England. The presented research (1) characterizes methods for collecting occupancy data and inferring patterns; (2) identifies and assesses the quality of categories of occupancy patterns used in building simulation; and (3) develops updated occupancy profiles. A systematic scoping review identified social and monitoring surveys as the most deployed data-collection methods. A systematic literature review also established that the occupancy categories most frequently used in UK building simulation are (a) a family with dependent children where the parents work full time; and (b) a retired elderly couple who spend most of their time indoors. The interview sample from the English Housing Survey 2014–15 was used to map household typologies. Results show that categories (a) and (b) combined amount to only 19% of England’s households, which suggest models are over-reliant on these groups. Considering this result, the paper develops occupancy patterns for England derived from 2015 UK Time Use Survey diaries for each household typology previously identified.  相似文献   
2.
During approximate 773 K aging treatment of 100Mn13 steel, degenerate pearlite will occur and evolve into lamellar pearlite during growth process. The microstructures of degenerate pearlite and its evolutionary lamellar pearlite are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that after 748 K, 773 K and 798 K aging, degenerate pearlites occur at grain boundary. At growth front of degenerate pearlite forming at 773 K and 798 K, pearlite presents a morphology of short lamellae of carbide and ferrite, indicating a trend of developing into lamellar pearlite. The higher the temperature is, the more obvious the trend is, and even a conventional lamellar pearlite has developed. However, there is no morphological evolution for degenerate pearlite forming at 748 K aging. Besides, the constituents of degenerate pearlite is identified as M23C6 and ferrite, and Kurdjumov-Sachs orientation relationship exists between them, (01 )α//( 1 )M23C6, [111]α//[110]M23C6. This orientation relationship maintains in morphological evolution from degenerate pearlite to lamellar pearlite.  相似文献   
3.
Abstract

An efficient 4-noded membrane element tolerant and insensitive to mesh distortion is developed using kinematically coupling the in-plane displacements which satisfy the equilibrium equations in Cartesian coordinates and results in material-dependent coupled field interpolation functions making the element free from volumetric and shear locking. The proposed formulation provides a preliminary concept for the satisfaction of natural boundary conditions which is used to satisfy the strong patch test. The proposed element, passed several benchmark problems from the literature, compared well with elasticity solutions, passed the weak patch test and the inf-sup test for both compressible and incompressible cases.  相似文献   
4.
5.
6.
Foundation of a university research cluster — Co-operation along the value creation chain from raw materials to components — Evidence of joint performance offers — Utilization of synergies — Integration of Christian Doppler Laboratories — Flexible arrangement of co-operations and networks  相似文献   
7.
8.
9.
10.
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