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   130359篇
  免费   7290篇
  国内免费   3583篇
电工技术   6211篇
技术理论   7篇
综合类   11022篇
化学工业   9805篇
金属工艺   5355篇
机械仪表   14280篇
建筑科学   28832篇
矿业工程   3940篇
能源动力   3290篇
轻工业   5129篇
水利工程   3666篇
石油天然气   4093篇
武器工业   1449篇
无线电   7838篇
一般工业技术   13672篇
冶金工业   3070篇
原子能技术   710篇
自动化技术   18863篇
  2024年   464篇
  2023年   1278篇
  2022年   2132篇
  2021年   2696篇
  2020年   3011篇
  2019年   2332篇
  2018年   2276篇
  2017年   2916篇
  2016年   3361篇
  2015年   3668篇
  2014年   9315篇
  2013年   7350篇
  2012年   9059篇
  2011年   9882篇
  2010年   8330篇
  2009年   8705篇
  2008年   7809篇
  2007年   9247篇
  2006年   7760篇
  2005年   6818篇
  2004年   5474篇
  2003年   5206篇
  2002年   4115篇
  2001年   3406篇
  2000年   2796篇
  1999年   2210篇
  1998年   1848篇
  1997年   1538篇
  1996年   1297篇
  1995年   1023篇
  1994年   856篇
  1993年   589篇
  1992年   467篇
  1991年   397篇
  1990年   250篇
  1989年   252篇
  1988年   202篇
  1987年   146篇
  1986年   96篇
  1985年   112篇
  1984年   129篇
  1983年   90篇
  1982年   102篇
  1981年   36篇
  1980年   45篇
  1979年   35篇
  1978年   18篇
  1977年   15篇
  1976年   9篇
  1959年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
The aim of this study was to design a modified atmosphere package for a mixed vegetable salad consisting of 75 g of cut carrot, 55 g of cut cucumber, 20 g of sliced garlic and 50 g of whole green pepper. Respiration data of all the components were combined with film permeability data to predict package atmospheres and design optimal packages for experimental testing for improved shelf-life of the produce. The optimal package avoided minimum O2 and maximum CO2 tolerance limits, and chilling injury temperatures for any component. A pouch form package made of 27 mm low density polyethylene developed a modified atmosphere of 2.0–2.1% O2 and 5.5–5.7% CO2, which was beneficial for all components and provided better quality retention than other test packages.  相似文献   
12.
13.
张杰  熊玮 《世界建筑》2004,(11):90-95
本文通过量化分析探索了清代皇家园林规划设计的控制规律及相关理论。  相似文献   
14.
《Drying Technology》2007,25(6):971-983
This article reviews developments in the simulations of spray dryer behavior, including the challenges in modeling the complex flow patterns inside the equipment, which are often highly transient and three-dimensional in nature. There appears to be considerable scope for using CFD simulations for investigating methods to reduce the rates of wall deposition and of thermal degradation for particles by modifying the air flow patterns in the chamber through small changes in the air inlet geometry. Challenges include building particle drying kinetics and reaction processes, as well as agglomeration behavior, into these simulations. The numerical simulations should be valuable supplements to pilot-scale testing, enabling more extensive and accurate optimization to be carried out than hitherto possible. New understanding of reaction processes and materials science, in combination with recent knowledge of the application of CFD to these problems, may enable new engineered powder products to be developed from the one-step spray-drying process.  相似文献   
15.
宣钢l260m^3高炉大修改造时将炉容扩大到l350m^3,对高炉本体系统设备及冷却系统、自动控制及检测系统进行了全面的改造更新,在炉腹、炉腰及炉身下部高热负荷区域采用铜冷却壁,取消炉身中上部铸铁冷却壁凸台,并采用薄内衬等先进、适用、可靠、成熟的技术。  相似文献   
16.
The introduction of multiple, independent production lines has helped many firms to increase their production flexibility, provide for redundancy when equipment breaks down, reduce idle time and labor costs, and achieve many other benefits. This paper introduces and formalizes the multiple U-line balancing problem. Optimal solution methodologies are provided for Type I (minimize the number of stations for a given cycle time), Type II (minimize the cycle time for a given number of stations), and cost-minimization line-balancing problems. A branch-and-bound algorithm is also developed for the situation in which equipment requirements are dependent on the line configuration and the task assignment to stations. Computational results indicate that the greatest benefit of exploiting multiple lines occurs for smaller cycle-time problems that require higher output.  相似文献   
17.
C60F48 has been known to exist in two isomeric forms of D3 and S6 symmetries. However, the quantum-chemical calculations have not agreed on their stability order though a near-isoenergetic picture is otherwise always encountered. In order to clarify the situation, the entropy effects are evaluated for synthetic temperatures of about 500K. The entropy evaluations suggest that the D3 isomer should be more stable in the potential energy by 2.05-2.55 kcal/mol (to which term the ab initio data are closer than the semiempirical ones).  相似文献   
18.
室内设计中绿色设计的功效   总被引:1,自引:0,他引:1  
唐浩 《包装工程》2003,24(4):118-120
绿色设计是一种将功能主义与可持续发展思想相结合的设计。文中就其形成的背景、设计原理及在室内设计领域中的应用进行一些探讨。  相似文献   
19.
This paper reports the findings of a detailed study of Web-based systems design (WBSD) practices in Ireland based on data collected over a 3-year period (2002–2005), the objectives of which were to (1) contribute towards a richer understanding of the current “real-world” context of WBSD by characterising the profile of a typical project (team size, timeframe, nature of requirements, etc.) and identifying the key challenges, constraints, and imperatives (i.e. “mediating factors”) faced by Web-based system designers, and (2) understand how those contextual parameters and mediating factors influence the activity of WBSD as regards the selection and enactment of whatever design practices are therefore engaged (i.e. the use of methods, procedures, etc.). Data was gathered through a survey which yielded 165 usable responses, and later through a series of semi-structured qualitative interviews. Using grounded theory, an explanatory conceptual framework is derived, based on an extension of the “method-in-action” model, the application of which to WBSD has not been previously investigated in depth. It is proposed that this framework of WBSD issues is valuable in a number of ways to educators, researchers, practitioners, and method engineers.  相似文献   
20.
利用均匀设计法通过SPSS10.0计算机软件研究了反应条件对安息香缩合的影响。从而获得优化的工艺条件,与正交试验相比,该法试验次数少。工作效率高,并且便于分析各种因素的影响。  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