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   1619133篇
  免费   28342篇
  国内免费   7095篇
电工技术   34900篇
综合类   6562篇
化学工业   277305篇
金属工艺   65962篇
机械仪表   46288篇
建筑科学   48725篇
矿业工程   11655篇
能源动力   50591篇
轻工业   126463篇
水利工程   16623篇
石油天然气   37945篇
武器工业   140篇
无线电   200168篇
一般工业技术   304109篇
冶金工业   217041篇
原子能技术   34329篇
自动化技术   175764篇
  2021年   15796篇
  2020年   12072篇
  2019年   14860篇
  2018年   17860篇
  2017年   17370篇
  2016年   22690篇
  2015年   17786篇
  2014年   29100篇
  2013年   88565篇
  2012年   38869篇
  2011年   53306篇
  2010年   45109篇
  2009年   52850篇
  2008年   48912篇
  2007年   46797篇
  2006年   47325篇
  2005年   42486篇
  2004年   44354篇
  2003年   44052篇
  2002年   42621篇
  2001年   39953篇
  2000年   37941篇
  1999年   37992篇
  1998年   62014篇
  1997年   49439篇
  1996年   42102篇
  1995年   34772篇
  1994年   32203篇
  1993年   31839篇
  1992年   27224篇
  1991年   24518篇
  1990年   24680篇
  1989年   23759篇
  1988年   22319篇
  1987年   20474篇
  1986年   19992篇
  1985年   23323篇
  1984年   23068篇
  1983年   20915篇
  1982年   19675篇
  1981年   19838篇
  1980年   18452篇
  1979年   18935篇
  1978年   18145篇
  1977年   18811篇
  1976年   21367篇
  1975年   16289篇
  1974年   15763篇
  1973年   15886篇
  1972年   13315篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
182.
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing...  相似文献   
183.
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   
184.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
185.
186.
Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self-healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion-based techniques such as emulsion polymerization and solvent evaporation from oil-in-water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the release mechanisms of core material from PMMA capsules were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48039.  相似文献   
187.
188.
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   
189.
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   
190.
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