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   756030篇
  免费   10392篇
  国内免费   1675篇
电工技术   13730篇
综合类   610篇
化学工业   119555篇
金属工艺   30710篇
机械仪表   23683篇
建筑科学   17921篇
矿业工程   5271篇
能源动力   19366篇
轻工业   64073篇
水利工程   8807篇
石油天然气   18176篇
武器工业   48篇
无线电   81102篇
一般工业技术   152596篇
冶金工业   131065篇
原子能技术   18244篇
自动化技术   63140篇
  2021年   6966篇
  2019年   6603篇
  2018年   11532篇
  2017年   11618篇
  2016年   12355篇
  2015年   7887篇
  2014年   13135篇
  2013年   34970篇
  2012年   20578篇
  2011年   27304篇
  2010年   21988篇
  2009年   24474篇
  2008年   24960篇
  2007年   24559篇
  2006年   21356篇
  2005年   19524篇
  2004年   18511篇
  2003年   18017篇
  2002年   17621篇
  2001年   17078篇
  2000年   16314篇
  1999年   16165篇
  1998年   37824篇
  1997年   27647篇
  1996年   21536篇
  1995年   16540篇
  1994年   14973篇
  1993年   14598篇
  1992年   11274篇
  1991年   10994篇
  1990年   10796篇
  1989年   10593篇
  1988年   10187篇
  1987年   9081篇
  1986年   8865篇
  1985年   10153篇
  1984年   9377篇
  1983年   8912篇
  1982年   8048篇
  1981年   8299篇
  1980年   7882篇
  1979年   7950篇
  1978年   7827篇
  1977年   8873篇
  1976年   11247篇
  1975年   7085篇
  1974年   6797篇
  1973年   6887篇
  1972年   5904篇
  1971年   5527篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
82.
In this paper, we present an aero‐structural model of a tethered swept wing for airborne wind energy generation. The carbon composite wing has neither fuselage nor actuated aerodynamic control surfaces and is controlled entirely from the ground using three separate tethers. The computational model is efficient enough to be used for weight optimisation at the initial design stage. The main load‐bearing wing component is a nontypical “D”‐shaped wing‐box, which is represented as a slender carbon composite shell and further idealised as a stack of two‐dimensional cross section models arranged along an anisotropic one‐dimensional beam model. This reduced 2+1D finite element model is then combined with a nonlinear vortex step method that determines the aerodynamic load. A bridle model is utilised to calculate the individual forces as a function of the aerodynamic load in the bridle lines that connect the main tether to the wing. The entire computational model is used to explore the influence of the bride on the D‐box structure. Considering a reference D‐box design along with a reference aerodynamic load case, the structural response is analysed for typical bridle configurations. Subsequently, an optimisation of the internal geometry and laminate fibre orientations is carried out using the structural computation models, for a fixed aerodynamic and bridle configuration. Aiming at a minimal weight of the wing structure, we find that for the typical load case of the system, an overall weight savings of approximately 20% can be achieved compared with the initial reference design.  相似文献   
83.
84.
85.
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance.  相似文献   
86.
87.
88.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
89.
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils.  相似文献   
90.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  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