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   556895篇
  免费   66237篇
  国内免费   45971篇
电工技术   50837篇
技术理论   3篇
综合类   62017篇
化学工业   68430篇
金属工艺   38874篇
机械仪表   40405篇
建筑科学   43629篇
矿业工程   24367篇
能源动力   14607篇
轻工业   59586篇
水利工程   19237篇
石油天然气   19782篇
武器工业   9280篇
无线电   58659篇
一般工业技术   44821篇
冶金工业   21348篇
原子能技术   8857篇
自动化技术   84364篇
  2024年   2372篇
  2023年   8868篇
  2022年   22013篇
  2021年   28198篇
  2020年   20196篇
  2019年   14111篇
  2018年   14983篇
  2017年   17022篇
  2016年   15222篇
  2015年   24884篇
  2014年   31546篇
  2013年   36623篇
  2012年   47109篇
  2011年   49136篇
  2010年   46828篇
  2009年   44486篇
  2008年   45961篇
  2007年   44789篇
  2006年   38093篇
  2005年   31050篇
  2004年   22461篇
  2003年   15103篇
  2002年   14392篇
  2001年   13015篇
  2000年   9919篇
  1999年   3822篇
  1998年   1181篇
  1997年   924篇
  1996年   718篇
  1995年   633篇
  1994年   454篇
  1993年   467篇
  1992年   392篇
  1991年   247篇
  1990年   243篇
  1989年   266篇
  1988年   175篇
  1987年   119篇
  1986年   117篇
  1985年   59篇
  1984年   73篇
  1983年   63篇
  1982年   66篇
  1981年   93篇
  1980年   182篇
  1979年   115篇
  1965年   16篇
  1964年   10篇
  1959年   106篇
  1951年   117篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
介绍装配式建筑电气设计中的管线分离SI体系、模块化机电设计、集成机电部品、装配式建筑防雷接地系统等关键技术,并进行简要分析.  相似文献   
32.
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications.  相似文献   
33.
本文通过对各项治理技术比选,提出了生态封场技术在非正规垃圾堆放场治理中的应用,并结合实际案例给出了详细治理方案.  相似文献   
34.
我国城市水系统管理职能条块分割、规划协调不足、精细程度不够等现象突出."全周期管理"可以从全要素、全过程、全场景等角度,以系统化思维解决城市水系统综合管理,增强城市水系统韧性和弹性.基于政策工具视角建立了包含战略面、供给面、需求面、环境面和评估面政策的城市水系统全周期管理整体性框架,并从机构统筹、规划引领、智慧监管等方面提出实施机制建议,为实现城市水系统的全要素管控、全流程监督、跨区域协同、分层次治理提供理论依据.  相似文献   
35.
36.
铸造车间生产的N330飞轮在加工Ф1025处M20螺栓孔时会出现一处或多处缩松缺陷,造成了该品种废品率的增加,为解决此缩松问题对飞轮进行了跟踪研究,分析并改进了飞轮的造型、冒口补缩和浇注工艺,通过试制验证了工艺改进的合理性。  相似文献   
37.
Bulletin of Engineering Geology and the Environment - Bio-cementation is currently applied to solidify sandy soils, but only few studies use it to cement loess soil particles. In this study, the...  相似文献   
38.
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased.  相似文献   
39.
The in situ axial X-ray diffraction patterns of four ceramic powder samples (MgO, Al2O3, AlN, and cBN) that were compressed in a diamond anvil cell under uniaxial non-hydrostatic conditions were recorded. The microscopic deviatoric stress as a function of the pressure was determined from the X-ray diffraction peak broadening analysis: the curves increased approximately linearly with the pressure at the initial compression stage and then levelled off under further compression. Pressure-induced transparency was observed in all of the samples under compression, and the pressure at the turning point on the curves of the microscopic deviatoric stress versus pressure corresponded to the pressure at which the samples became transparent. Analysis of the microstructural features of the pressure-induced transparent samples indicated that the compression caused the grains to fracture, and the broken grains bonded with each other. We demonstrated that the ceramics’ pressure-induced transparency was a process during which the grains were squeezed and broken, the pores were close between the grains, and the broken grains were re-bonded under compression.  相似文献   
40.
针对锁紧机构保持架在恶略环境下,反复振动过程中保持架上钢球脱落问题,提出了一种新型防脱落保持架设计方案,重点介绍了锁紧机构中保持架的工作形式,通过ANSYS进行有限元仿真分析,得出新型保持架结构满足刚强度要求以及热变形要求,且在随机振动6.06 g条件位移小,能有效免锁紧机构直线运动时钢球从外部脱落的可能,提高了锁紧机构工作过程中的可靠性与安全性.  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