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   356129篇
  免费   34026篇
  国内免费   17583篇
电工技术   24216篇
技术理论   69篇
综合类   44713篇
化学工业   43585篇
金属工艺   12863篇
机械仪表   18595篇
建筑科学   43394篇
矿业工程   21092篇
能源动力   14272篇
轻工业   20930篇
水利工程   15120篇
石油天然气   28999篇
武器工业   3159篇
无线电   22372篇
一般工业技术   26258篇
冶金工业   19390篇
原子能技术   3900篇
自动化技术   44811篇
  2024年   4373篇
  2023年   4964篇
  2022年   7591篇
  2021年   9165篇
  2020年   9819篇
  2019年   8227篇
  2018年   7573篇
  2017年   8894篇
  2016年   10597篇
  2015年   11216篇
  2014年   19941篇
  2013年   18966篇
  2012年   24309篇
  2011年   25193篇
  2010年   19381篇
  2009年   19968篇
  2008年   18671篇
  2007年   24018篇
  2006年   23192篇
  2005年   20058篇
  2004年   17206篇
  2003年   15490篇
  2002年   12930篇
  2001年   11035篇
  2000年   9392篇
  1999年   7800篇
  1998年   5904篇
  1997年   5204篇
  1996年   4687篇
  1995年   3993篇
  1994年   3501篇
  1993年   2626篇
  1992年   2309篇
  1991年   1751篇
  1990年   1510篇
  1989年   1314篇
  1988年   993篇
  1987年   673篇
  1986年   515篇
  1985年   413篇
  1984年   395篇
  1983年   285篇
  1982年   266篇
  1981年   243篇
  1980年   175篇
  1979年   138篇
  1978年   74篇
  1977年   84篇
  1976年   61篇
  1975年   59篇
排序方式: 共有10000条查询结果,搜索用时 142 毫秒
21.
Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known.  相似文献   
22.
What has become known as Community Operational Research has been around in the UK for many years. The election of Jonathan Rosenhead as President of the UK OR Society in 1986–87 was the catalyst for bringing together and expanding activities which had been carried out largely by individuals working in isolation on a voluntary basis. The following five years have seen the establishment of the Community OR Unit at Northern College, the Centre for Community OR at Hull University and the Community OR Network, which supports the activities of volunteer OR workers across the UK. This paper reviews the range and types of work which have been undertaken by various practitioners. An assessment of the success of community OR is made and a number of issues which have arisen are discussed. Finally, given the diverse nature of community OR, its practice and practitioners, there is some discussion about the future of the area.  相似文献   
23.
The hydrolysis of isocyanic acid in the gaseous phase has been investigated at temperatures between 553 and 613 K by mass spectrometry and evaluated to obtain the corresponding kinetic data. The reaction order and reaction constant have been determined. Finally, the influence of water on the catalysed formation of melamine from isocyanic acid under the operating conditions employed has been investigated in order to determine whether there is a need to try the process gas.  相似文献   
24.
Dimensionless material balance equations describing an uninhibited enzyme hydrolysis process in a semi-batch reactor (i.e. fed-batch reactor) are formulated; numerical solution of these equations provided concentration profiles of the enzyme-substrate complex by using published kinetic parameters. The unrestricted values obtained are compared with estimates based separately on the reaction steady state and stationary state assumptions. Results are discussed in terms of the enzyme/substrate inventory used and it is found that the reaction steady state is a satisfactory approximation only when this ratio is sufficiently small. The stationary state may be a better approximation at other values, particularly when enzyme is added to substrate or when an empty tank is being filled. Reaction yields from semi-batch and batch operations are compared. Processing takes longer in the semi-batch operations and complete conversions are only practical in this mode when enzyme is added to substrate.  相似文献   
25.
26.
In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure.  相似文献   
27.
28.
支气管上皮靶细胞形态学参数对计算受氡子体照射的支气管的剂量是很重要的。本文介绍利用奥尔新兰-PAS 染色的外科切除人肺组织切片,测量基底细胞粘液细胞和的胞核深度与数目。结果表明,叶、段和小支气管的粘液细胞核深度分别为相应节段基底细胞的61%、69%和73%;此三节段粘液细胞的数目分别为基底细胞的53%、29%和28%,平均为37%。  相似文献   
29.
30.
论社区服务产业化   总被引:2,自引:0,他引:2  
社区经济作为一种优化的资源配置方式,利用社区服务为载体,将社区内互不相联的各种经济成份变为利益共同体,建立一种新的经济生产方式,从而带动社区乃至更广区域的经济发展。  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