全文获取类型
收费全文 | 196308篇 |
免费 | 16325篇 |
国内免费 | 12510篇 |
专业分类
电工技术 | 30689篇 |
技术理论 | 8篇 |
综合类 | 18199篇 |
化学工业 | 11398篇 |
金属工艺 | 7819篇 |
机械仪表 | 17230篇 |
建筑科学 | 17649篇 |
矿业工程 | 7991篇 |
能源动力 | 5284篇 |
轻工业 | 6068篇 |
水利工程 | 6215篇 |
石油天然气 | 7046篇 |
武器工业 | 3167篇 |
无线电 | 16858篇 |
一般工业技术 | 10019篇 |
冶金工业 | 8934篇 |
原子能技术 | 1486篇 |
自动化技术 | 49083篇 |
出版年
2024年 | 739篇 |
2023年 | 2079篇 |
2022年 | 3335篇 |
2021年 | 4140篇 |
2020年 | 4992篇 |
2019年 | 3986篇 |
2018年 | 3598篇 |
2017年 | 5292篇 |
2016年 | 5892篇 |
2015年 | 6490篇 |
2014年 | 12502篇 |
2013年 | 10848篇 |
2012年 | 13964篇 |
2011年 | 15016篇 |
2010年 | 11452篇 |
2009年 | 11809篇 |
2008年 | 12090篇 |
2007年 | 14997篇 |
2006年 | 13484篇 |
2005年 | 11785篇 |
2004年 | 9850篇 |
2003年 | 8679篇 |
2002年 | 6905篇 |
2001年 | 5828篇 |
2000年 | 4971篇 |
1999年 | 3987篇 |
1998年 | 3069篇 |
1997年 | 2676篇 |
1996年 | 2162篇 |
1995年 | 1770篇 |
1994年 | 1495篇 |
1993年 | 1082篇 |
1992年 | 881篇 |
1991年 | 666篇 |
1990年 | 512篇 |
1989年 | 444篇 |
1988年 | 327篇 |
1987年 | 191篇 |
1986年 | 153篇 |
1985年 | 129篇 |
1984年 | 162篇 |
1983年 | 127篇 |
1982年 | 121篇 |
1981年 | 85篇 |
1980年 | 65篇 |
1979年 | 68篇 |
1978年 | 48篇 |
1977年 | 49篇 |
1964年 | 17篇 |
1955年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
本文利用最优回归设计“310”方案,研究了黑土地甜菜 Zn、K_2O、B的效果及合理施用问题。得出甜菜块根产量、含糖、产糖量、灰分 K 和有害 N 与 ZnK_2O、B 肥回归关系显著的回归模型,分析了 Zn、K_2O、B 对上述五个指标的效应,明确了 Zn 是影响各项指标的主要因子,并采用频率筛选法,提出了兼顾上述五项指标的优质高产施肥措施。 相似文献
62.
63.
64.
D. Grant Fisher 《加拿大化工杂志》1991,69(1):5-26
This paper presents an overview and personnal perspective on recent developments and current practice in computer process model. The basic concepts behind conventional process control are reviewed to provide a starting point for the non-control specialist and process engineer. The ensuing sections on Internal Model Control (IMC), Model Predictive Control (MPC) and adaptive control illustrate the evolution of control technology from the traditional multiloop strategies to the modern, multivariable, model-based, computer control systems now being used in industry. The paper does not provide a complete, critical review of process control. However, the discussion and the recommended references should provide a good starting point for anyone wanting to become familiar with current practice and some of the new directions of process control. 相似文献
65.
凌礼富 《武汉化工学院学报》1991,(4)
本文通过对SIMATIC S5—115U可编程控制器性能的简介,简述国外PC技术的现状和发展,并提出对PC国产化的看法. 相似文献
66.
Grantham K. H. Pang 《International Journal of Adaptive Control and Signal Processing》1991,5(1):63-86
A multivariable control system design approach in the frequency domain is presented. The issue of control system redesign in an adaptive control scheme is discussed. Expert system techniques have been used for the automated design of controllers for multivariable systems. Design knowledge has been represented using rules, facts and objects. The design process consists of a sequence of operations obtained by heuristics and experience in the the design techniques. An automated design session of a multivariable plant using the expert system demonstrates that the expert system appears to work well in its prototype implementation. 相似文献
67.
The ring-opening polymerization of hexamethylcyclodisilazane (D2NMe), initiated by methyl triflate in 1,2-dichloroethane, forms in the first, fast kinetic step both linear polymer and cyclic dimer (D4NMe). Subsequently a slow depolymerization process occurs leading to exclusively cyclotrisilazane (D3NMe). On the basis of kinetic measurements carried out using an adiabatic calorimetric technique and complementary experiments, mechanisms of both propagation, cyclization and back-biting reactions are proposed. The influence of the reaction temperature was also studied; it is demonstrated that, at low temperature, polymerization does not lead to cyclic oligomer formation. In such conditions, the polymerization presents a ‘living’ character. 相似文献
68.
Leiba Rodman 《Systems & Control Letters》1992,19(6):475-480
Pole shifting of multivariable control system
over finite dimensional real algebras is studied. The main results are expressed in terms of the minimal polynomial of A + BF, where F is a feedback. 相似文献
69.
P. J. M. Sonnemans P. M. W. Krvers A. C. Brombacher P. C. van Beek J. E. A. Reinders 《Quality and Reliability Engineering International》2003,19(3):183-196
Often companies in the (petro‐) chemical industry claim that all possible countermeasures against potential accidents have been taken and therefore accidents are unforeseeable. In this paper we question this statement by analysing the pre‐warning signals (precursors) preceding a number of industrial accidents. 17 accidents that occurred in the (petro‐) chemical industry have been investigated by exploring FACTS, an accident database containing information about industrial accidents worldwide. This paper will demonstrate that the existence of precursor information could have been used to foresee and even prevent these accidents if a proper control action had been initiated. The accidents are analysed further, according to a control model, which was adapted from that of C. Argyris. It demonstrates the ineffectiveness of several elements of business process control loops and that the so‐called ‘double‐loop learning’ cycle is more important than the ‘single‐loop learning’ cycle if one considers safety improvement. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
70.