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   779914篇
  免费   9998篇
  国内免费   1560篇
电工技术   14741篇
综合类   973篇
化学工业   121321篇
金属工艺   30288篇
机械仪表   24302篇
建筑科学   18464篇
矿业工程   4899篇
能源动力   20243篇
轻工业   66598篇
水利工程   8673篇
石油天然气   16699篇
武器工业   43篇
无线电   87230篇
一般工业技术   154875篇
冶金工业   138377篇
原子能技术   17888篇
自动化技术   65858篇
  2021年   6891篇
  2019年   6628篇
  2018年   11409篇
  2017年   11459篇
  2016年   11959篇
  2015年   7703篇
  2014年   12992篇
  2013年   36036篇
  2012年   20380篇
  2011年   27619篇
  2010年   22056篇
  2009年   24677篇
  2008年   25269篇
  2007年   25108篇
  2006年   21830篇
  2005年   19952篇
  2004年   19243篇
  2003年   18760篇
  2002年   18143篇
  2001年   17907篇
  2000年   17182篇
  1999年   17284篇
  1998年   40524篇
  1997年   29353篇
  1996年   22937篇
  1995年   17652篇
  1994年   16038篇
  1993年   15678篇
  1992年   12117篇
  1991年   11597篇
  1990年   11499篇
  1989年   11238篇
  1988年   10839篇
  1987年   9571篇
  1986年   9471篇
  1985年   10893篇
  1984年   9845篇
  1983年   9354篇
  1982年   8438篇
  1981年   8687篇
  1980年   8187篇
  1979年   8273篇
  1978年   8043篇
  1977年   9071篇
  1976年   11505篇
  1975年   7165篇
  1974年   6847篇
  1973年   6989篇
  1972年   5930篇
  1971年   5471篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
81.
Journal of Machinery Manufacture and Reliability - The problem of calculating the reliability and fatigue life of machine parts by the fatigue failure under random changes in the actual and limit...  相似文献   
82.
83.
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.  相似文献   
84.
85.
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   
86.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
87.
88.
89.
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   
90.
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