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   137736篇
  免费   8154篇
  国内免费   4146篇
电工技术   6318篇
技术理论   8篇
综合类   12705篇
化学工业   9294篇
金属工艺   5296篇
机械仪表   14231篇
建筑科学   33039篇
矿业工程   4430篇
能源动力   3122篇
轻工业   5101篇
水利工程   4100篇
石油天然气   7967篇
武器工业   1465篇
无线电   7756篇
一般工业技术   14211篇
冶金工业   3229篇
原子能技术   747篇
自动化技术   17017篇
  2024年   496篇
  2023年   1365篇
  2022年   2392篇
  2021年   3022篇
  2020年   3379篇
  2019年   2603篇
  2018年   2583篇
  2017年   3107篇
  2016年   3602篇
  2015年   3866篇
  2014年   9751篇
  2013年   7789篇
  2012年   9821篇
  2011年   10525篇
  2010年   8760篇
  2009年   9073篇
  2008年   8138篇
  2007年   9697篇
  2006年   8171篇
  2005年   7243篇
  2004年   5810篇
  2003年   5471篇
  2002年   4330篇
  2001年   3672篇
  2000年   2963篇
  1999年   2346篇
  1998年   1934篇
  1997年   1612篇
  1996年   1353篇
  1995年   1073篇
  1994年   905篇
  1993年   619篇
  1992年   502篇
  1991年   424篇
  1990年   286篇
  1989年   268篇
  1988年   195篇
  1987年   143篇
  1986年   86篇
  1985年   98篇
  1984年   129篇
  1983年   82篇
  1982年   94篇
  1981年   32篇
  1980年   61篇
  1979年   37篇
  1978年   14篇
  1977年   12篇
  1964年   9篇
  1959年   18篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Utilizing the existing properties of steel, a modern technological society has been constructed. While there are over 25,000 worldwide equivalent steels based on manipulating the eutectoid transformation, there exist only a handful of commercial nanostructured steel alloys based on manipulating the more complex glass devitrification transformation. Thus, research on nanostructured steels is in its infancy, and many further developments are expected with the demonstrated promise of developing new combinations of superior properties. In this article, seven enabling metallurgical factors are presented that ultimately allow a variety of nanostructured steel products to be produced in an ever-increasing array of industrial processing techniques. Additionally, a case example of the formation of nanostructured steel are given showing how these factors can be harnessed on an industrial scale.  相似文献   
42.
郑银环  张仲甫 《机床与液压》2005,(3):107-108,51
讨论了渐变刚度钢板弹簧的载荷、变形量、刚度和应力的计算,建立了少片渐变刚度钢板弹簧的优化数学模型,利用MATLAB优化工具箱进行优化,并给出了计算实例。  相似文献   
43.
水性聚氨酯材料配方设计技巧   总被引:1,自引:1,他引:1  
介绍了优选法的0.618法和分数法,对其进行改进创新和原理证明,并应用于生产涂料配方设计中。  相似文献   
44.
阐述了设计院拥有技术和开发技术的重要性及获取技术的途径,并详细介绍了设计人员能够开展的技术开发工作。  相似文献   
45.
We present a simple and fast algorithm to test the thermodynamic stability and determine the necessary chemical environment for the production of a multiternary material, relative to competing phases and compounds formed from the constituent elements. If the material is found to be stable, the region of stability, in terms of the constituent elemental chemical potentials, is determined from the intersection points of hypersurfaces in an (n−1)(n1)-dimensional chemical potential space, where nn is the number of atomic species in the material. The input required is the free energy of formation of the material itself, and that of all competing phases. Output consists of the result of the test of stability, the intersection points in the chemical potential space and the competing phase to which they relate, and, for two- and three-dimensional spaces, a file which may be used for visualization of the stability region. We specify the use of the program by applying it both to a ternary system and to a quaternary system. The algorithm automates essential analysis of the thermodynamic stability of a material. This analysis consists of a process which is lengthy for ternary materials, and becomes much more complicated when studying materials of four or more constituent elements, which have become of increased interest in recent years for technological applications such as energy harvesting and optoelectronics. The algorithm will therefore be of great benefit to the theoretical and computational study of such materials.  相似文献   
46.
Despite the apparent maturity of the learning design field, and the variety of tooling available to support it, adoption among the teacher community (one of its alleged main targets) is still low. There is a lack of research on teachers' perception and use of different technological learning design tools, as existing evaluations are often restricted to a single tool. In order to explore whether there are common factors hampering teacher adoption, and which tool features might appeal to different teachers, more studies involving multiple authoring tools are needed. This paper provides a first step in this direction, describing a mixed methods study performed around a professional development workshop with 18 university teachers from multiple disciplines. This workshop exposed teachers to two different authoring tools (WebCollage and EDIT2), as they learned to create computer-supported collaborative learning (CSCL) designs and implement them. The findings of our interpretive study (which included questionnaires, observations, or group discussion recordings) support the idea that there is no single tool or set of features that are globally perceived as better, although our evidence also highlights certain factors as important for participant teachers – amongst others, the integration of learning designs with the ICT platforms for enactment, as well as with other tools that they already use in their everyday practice.  相似文献   
47.
Defining appropriate pricing strategy for smart environment is important and complex task at the same time. It holds the primal fraction in Demand Response (DR) program. In our work, we devise an incentive based smart dynamic pricing scheme for consumers facilitating a multi-layered scoring rule. The proposed strategy characterizes both incentive based DR and price based DR programs facilities. This mechanism is applied between consumer agents (CA) to electricity provider agent (EP) and EP to Generation Company (GENCO). Based on the Continuous Ranked Probability Score (CRPS), a hierarchical scoring system is formed among these entities, CA–EP–GENCO. As CA receives the dynamic day-ahead pricing signal from EP, it will schedule the household appliances to lower price period and report the prediction in a form of a probability distribution function to EP. EP, in similar way reports the aggregated demand prediction to GENCO. Finally, GENCO computes the base discount after running a cost-optimization problem. GENCO will reward EP with a fraction of discount based on their prediction accuracy. EP will do the same to CA based on how truthful they were reporting their intentions on device scheduling. The method is tested on real data provided by Ontario Power Company and we show that this scheme is capable to reduce energy consumption and consumers’ payment.  相似文献   
48.
多降液管筛板塔的设计计算   总被引:2,自引:0,他引:2  
李汉 《化工设计》2002,12(1):21-23,48
简要介绍多降液管筛板塔的特点及塔板参数的设计计算方法。  相似文献   
49.
The HUB-CI model is investigated in a telerobotic system in a client/server network to manage the lifecycle of engineering design and prototyping. The purpose of this platform is to support collaborative engineering design and proof of concept to enhance distributed team collaboration and resource utilization. The suggested platform is exemplified in two collaboration support tools and a physical prototyping platform. Structured Co-Insight Management is developed to support innovative idea exchanges and the consensus decision-making during the design process. Conflict/error detection management helps preventing conflicts and errors during the lifecycle of design and development. Physical collaboration over the network occurs when a team controls the telerobot operation during prototyping and testing in design cycles. A pilot system is implemented with a group project for the design of an electronic circuit (including both hardware and software designs). The functional assessment method is used to compare this platform to other collaborative design tools. The system presented offers unique qualitative advantages as an integrated collaboration support system.  相似文献   
50.
介绍了氟化氢吸收原理、流程 ,国内外氟化氢吸收设备的选型 ,满足工艺要求的穿流栅板塔的设计计算及应用。  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