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   126609篇
  免费   7230篇
  国内免费   3554篇
电工技术   6229篇
技术理论   7篇
综合类   11065篇
化学工业   9197篇
金属工艺   5283篇
机械仪表   14135篇
建筑科学   28960篇
矿业工程   3927篇
能源动力   2988篇
轻工业   5096篇
水利工程   3649篇
石油天然气   4086篇
武器工业   1439篇
无线电   7739篇
一般工业技术   13290篇
冶金工业   3030篇
原子能技术   661篇
自动化技术   16612篇
  2024年   455篇
  2023年   1239篇
  2022年   2071篇
  2021年   2633篇
  2020年   2902篇
  2019年   2208篇
  2018年   2179篇
  2017年   2746篇
  2016年   3197篇
  2015年   3456篇
  2014年   9066篇
  2013年   7117篇
  2012年   8899篇
  2011年   9532篇
  2010年   8105篇
  2009年   8388篇
  2008年   7606篇
  2007年   9298篇
  2006年   7573篇
  2005年   6677篇
  2004年   5375篇
  2003年   5089篇
  2002年   4048篇
  2001年   3392篇
  2000年   2779篇
  1999年   2169篇
  1998年   1784篇
  1997年   1499篇
  1996年   1264篇
  1995年   995篇
  1994年   811篇
  1993年   563篇
  1992年   442篇
  1991年   374篇
  1990年   238篇
  1989年   240篇
  1988年   184篇
  1987年   139篇
  1986年   82篇
  1985年   93篇
  1984年   123篇
  1983年   81篇
  1982年   92篇
  1981年   31篇
  1980年   35篇
  1979年   28篇
  1978年   13篇
  1977年   11篇
  1959年   11篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
吴金虎 《液晶与显示》2004,19(2):143-147
介绍了研制出其性能达国际先进公司同类产品水平的塑封双列直插式光耦合器的工作原理和提高绝缘耐压的技术难点,从引线框架设计、加工精度控制、内包封材料选型、理想内包封形状控制、塑封气密性的实现、环境条件的完善等方面讨论了提高绝缘耐压的设计和工艺要点。  相似文献   
92.
IPv6和基于IPv6的网络设计   总被引:2,自引:0,他引:2  
对IPv6协议的主要内容进行了简要介绍,并针对IPv6的特点对基于IPv6的网络设计进行了探讨。  相似文献   
93.
By contrast to design meetings, design evaluation meetings (DEMs) have generally been considered as situations in which, according to DEM methodologies, design activities are quite marginal. In a study of DEMs in software development, i.e. in technical review meetings following a particular review methodology, we showed: (i) the occurrence of design activities as part of an argumentation process; (ii) the relative importance of cognitive synchronisation as a prerequisite for evaluation; (iii) the important role played in evaluation by argumentation that makes explicit the underlying design rationale (DR). On the basis of our results, we discuss the potential for using DR methodologies in this kind of meetings.  相似文献   
94.
The literature provides little information on high-speed, high-normal-load, plain linear bearings, although the case for two rigid surfaces in relative linear motion can readily be solved by assuming squeeze action resistance. A new genus of internal combustion engines based on the Stiller-Smith mechanism incorporates connecting rods constrained by linear bearings, with the central normal load on the rod restricted by an oil film. A general analysis takes into account the bending of the rod, when the distributed oil film pressure resists the distributed load on the elastic rod. Design charts result that yield the dimensionless velocity at which the rod sinks in the oil as a function of the dimensionless load and the bearing clearance, and predict the deflection of the beam. The rod clearance history simulations for the Stiller-Smith engine compare favourably with computations for the rigid beam, confirming the analysis technique.  相似文献   
95.
The nave of Santa Maria Novella, a Dominican church in Florence Italy is representative of a Florentine Gothic system of construction. This system, consisting of domical rib vaults on square nave bays, high side aisles, and crypto-buttressing, differs substantially from the French high Gothic system of even-level-crown rib vaults on rectangular bays, with flying buttresses over relatively low aisles. An investigation into the structural aspects of the Florentine Gothic construction system reveals that the domical vaults increase the longitudinal thrust and reduce the transverse thrust, which may require additional precautions to be taken during construction, but entails a less elaborate buttressing system. The domical vaults are found to perform well structurally, with an absence of tensile stresses, and are more suitable for a square bay. In general, the structural system of the nave of Santa Maria Novella is found to be the product of carefully considered structural design, which may be accepted as an alternative to the French Gothic construction system.  相似文献   
96.
In these times of global change, many facility emphases are competing for limited resources. Competing factors include, but are not limited to, sustainable design or green buildings; security, hardening or force protection; accessibility; historic preservation; aesthetics; and functionality. Yet, unlimited resources are seldom, if ever, available to fulfill all of these competing requirements in private or public construction. The Georgia Institute of Technology designed a decision matrix to allow owners and planners to balance these competing requirements on a project-by-project basis and to document the rationale.  相似文献   
97.
Steam generator replacement at nuclear power plants requires large construction openings in nuclear containment structures. This study examines the effects of such openings placed in a 61?cm (2?ft) thick dome of a shield building. The dome is cast in two layers, and the limiting cases of the two layers acting as one and the lower layer carrying the entire load are considered. Without openings, the stresses due to dead load in the structure are very low when compared to the material strength. With openings, the loads are easily redistributed around the opening, and the maximum stresses for the conservative case are between three and four and one-half times larger than in the original structure with no openings. The extent of the affected area around the holes is relatively small. Smooth corners in the openings are necessary to avoid high local stress concentrations.  相似文献   
98.
简述初步设计概算重要性,结合冬瓜山铜矿概算编制的实例,总结了编制初步设计概算的几点体会。  相似文献   
99.
李生云 《山西建筑》2003,29(2):124-125
分析了当前家装存在的破坏结构,一味追求奢华,施工质量差等种种误区,提出了搞好家庭装修的关键环节,对促进家装行业健康发展有积极的意义。  相似文献   
100.
该文结合工程实例介绍了地下室人防及通风设计的方法及实际运用中的注意事项.  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