全文获取类型
收费全文 | 23181篇 |
免费 | 2746篇 |
国内免费 | 2157篇 |
专业分类
电工技术 | 3561篇 |
综合类 | 3284篇 |
化学工业 | 961篇 |
金属工艺 | 425篇 |
机械仪表 | 1327篇 |
建筑科学 | 1645篇 |
矿业工程 | 474篇 |
能源动力 | 721篇 |
轻工业 | 630篇 |
水利工程 | 352篇 |
石油天然气 | 435篇 |
武器工业 | 239篇 |
无线电 | 3460篇 |
一般工业技术 | 1152篇 |
冶金工业 | 1171篇 |
原子能技术 | 234篇 |
自动化技术 | 8013篇 |
出版年
2024年 | 114篇 |
2023年 | 300篇 |
2022年 | 417篇 |
2021年 | 507篇 |
2020年 | 635篇 |
2019年 | 652篇 |
2018年 | 577篇 |
2017年 | 822篇 |
2016年 | 956篇 |
2015年 | 946篇 |
2014年 | 1422篇 |
2013年 | 1619篇 |
2012年 | 1567篇 |
2011年 | 1739篇 |
2010年 | 1396篇 |
2009年 | 1442篇 |
2008年 | 1495篇 |
2007年 | 1709篇 |
2006年 | 1424篇 |
2005年 | 1276篇 |
2004年 | 1136篇 |
2003年 | 1014篇 |
2002年 | 809篇 |
2001年 | 741篇 |
2000年 | 659篇 |
1999年 | 474篇 |
1998年 | 341篇 |
1997年 | 346篇 |
1996年 | 258篇 |
1995年 | 219篇 |
1994年 | 204篇 |
1993年 | 148篇 |
1992年 | 145篇 |
1991年 | 113篇 |
1990年 | 93篇 |
1989年 | 58篇 |
1988年 | 51篇 |
1987年 | 33篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 27篇 |
1983年 | 26篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1977年 | 7篇 |
1964年 | 10篇 |
1959年 | 7篇 |
1958年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
A discrete-time, model-based output feedback control structure for nonlinear processes is developed in the present work. The structure makes use of a closed-loop observer, while at the same time it guarantees that the overall feedback controller possesses integral action. An algebraic transformation is applied on the observer states to insure that the input/output gain of the observer matches the model upon which the static state feedback control law is based. The resulting control algorithm is a two-degree-of-freedom control law, in the sense that the output and the set point are processed in different ways. The control structure is shown not only to have the same properties as the standard model-state feedback structure, but also that it emerges from a model algorithmic control framework. Finally, a simulation example using an exothermic CSTR operating at an open-loop unstable steady state is used to evaluate the closed-loop performance of the proposed method. 相似文献
52.
本文就房地产中介服务业在政府机构管理、行业经营方面存在的问题进行了总结,同时提出一些改进建议,对于房地产中介服务业规范经营、健康发展具有很好的指导意义。 相似文献
53.
54.
The modality effect in immediate recall refers to superior recall of the last few items within lists presented in spoken as opposed to printed form. The locus of this well-known effect has been unclear. N. Cowan, J. S. Saults, E. M. Elliott, and M. Moreno (2002) introduced a new method to distinguish between the effects of input serial position, output serial position, and the number of items yet to be recalled and found that large modality effects occurred only in conditions in which delay and interference at output (from items already recalled) was high. The authors replicated that finding, even when the response period included output interference acoustically similar to the spoken stimuli to be recalled. However, the authors found that output delay and interference act only by lowering the level of performance to a more sensitive range. The modality effect thus originates during encoding of the list to be recalled, not during output. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
论工艺参数对烧结产质量的影响及分析 总被引:7,自引:0,他引:7
本文论述了正确认识烧结工艺参数对搞好烧结生产的意义,介绍了烧结工艺参数其及相互关系,详述了烧结主要工艺参数对其产质量的影响,提出了烧结工艺参数认识的几点结论性意见。 相似文献
56.
Five studies examined the hypotheses that when people experience positive affect, those low in self-esteem are especially likely to dampen that affect, whereas those high in self-esteem are especially likely to savor it. Undergraduate participants' memories for a positive event (Study 1) and their reported reactions to a success (Study 2) supported the dampening prediction. Results also suggest that dampening was associated with worse mood the day after a success (Study 2), that positive and negative affect regulation are distinct, that self-esteem is associated with affect regulation even when Neuroticism and Extraversion are controlled (Studies 3 and 4), and that self-esteem may be especially important for certain types of positive events and positive affect regulation (Study 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Chronis Andrea M.; Lahey Benjamin B.; Pelham William E. Jr.; Williams Stephanie Hall; Baumann Barbara L.; Kipp Heidi; Jones Heather A.; Rathouz Paul J. 《Canadian Metallurgical Quarterly》2007,43(1):70
Children with attention-deficit/hyperactivity disorder (ADHD) are at risk for adverse outcomes such as substance abuse and criminality, particularly if they develop conduct problems. Little is known about early predictors of the developmental course of conduct problems among children with ADHD, however. Parental psychopathology and parenting were assessed in 108 children who first met Diagnostic and Statistical Manual of Mental Disorders (4th ed.) criteria for ADHD at 4-7 years old. When demographic variables and baseline ADHD and conduct problems were controlled, maternal depression predicted conduct problems 2-8 years following the initial assessment, whereas positive parenting during the structured parent- child interaction task predicted fewer future conduct problems. These findings suggest that maternal depression is a risk factor, whereas early positive parenting is a protective factor, for the developmental course of conduct problems among children with ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
Qi Gong 《Automatica》2007,43(1):184-189
In this paper we address the practical tracking problem for a class of nonlinear systems by dynamic output feedback control. Unlike most of the existing results where the unmeasurable states in the nonlinear vector field can only grow linearly, we allow higher-order growth of unmeasurable states. The proposed controller makes the tracking error arbitrarily small and demonstrates nice properties such as robustness to disturbances and universal property to reference signals. 相似文献
59.
设计一条钢筋网自动化焊接生产线,包括经料送料平台、纬料自动分料及上料机构、多点电阻点焊机、接料平台、卸料机械手。从上料到出料依靠电机、汽缸之间的协调工作来实现。并由单片机和PLC实现控制功能,上位机用MCGS组态软件在整个过程监视现场,采集工作状态及参数,起到监控作用。 相似文献
60.
房地产投资的主要风险与防范策略 总被引:2,自引:2,他引:0
对房地产投资的风险进行了分析研究,并针对各个风险因素提出了具体的应对措施,同时就房地产投资风险的防范策略进行了深入探讨,以提高房地产投资的经济效益。 相似文献