全文获取类型
收费全文 | 44619篇 |
免费 | 5639篇 |
国内免费 | 3321篇 |
专业分类
电工技术 | 5602篇 |
综合类 | 4892篇 |
化学工业 | 4186篇 |
金属工艺 | 1202篇 |
机械仪表 | 2425篇 |
建筑科学 | 2832篇 |
矿业工程 | 1098篇 |
能源动力 | 1275篇 |
轻工业 | 2038篇 |
水利工程 | 975篇 |
石油天然气 | 1885篇 |
武器工业 | 680篇 |
无线电 | 5871篇 |
一般工业技术 | 4145篇 |
冶金工业 | 1708篇 |
原子能技术 | 625篇 |
自动化技术 | 12140篇 |
出版年
2024年 | 170篇 |
2023年 | 521篇 |
2022年 | 1034篇 |
2021年 | 1227篇 |
2020年 | 1513篇 |
2019年 | 1446篇 |
2018年 | 1244篇 |
2017年 | 1697篇 |
2016年 | 1879篇 |
2015年 | 1989篇 |
2014年 | 2704篇 |
2013年 | 3113篇 |
2012年 | 3195篇 |
2011年 | 3390篇 |
2010年 | 2514篇 |
2009年 | 2663篇 |
2008年 | 2543篇 |
2007年 | 3031篇 |
2006年 | 2756篇 |
2005年 | 2290篇 |
2004年 | 1893篇 |
2003年 | 1754篇 |
2002年 | 1531篇 |
2001年 | 1313篇 |
2000年 | 1144篇 |
1999年 | 903篇 |
1998年 | 724篇 |
1997年 | 622篇 |
1996年 | 482篇 |
1995年 | 414篇 |
1994年 | 334篇 |
1993年 | 279篇 |
1992年 | 190篇 |
1991年 | 184篇 |
1990年 | 128篇 |
1989年 | 126篇 |
1988年 | 85篇 |
1987年 | 86篇 |
1986年 | 58篇 |
1985年 | 58篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 37篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1964年 | 12篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
131.
This paper presents a robustness analysis of the optimal solution of the step tracking problem in a one-degree of freedom control architecture, for the discrete-time multivariable (MIMO) case. It is shown that the resulting closed loop becomes arbitrarily fragile, i.e. the sensitivity peak becomes arbitrarily large, for certain reference directions. The cause of this problem is that the optimal controller depends on the reference direction. The paper shows that this dependence can be eliminated with an alternative formulation of the optimal problem where the cost is averaged over all reference directions. 相似文献
132.
A detection-theoretic analysis of the auditory localization of dual-impulse stimuli is described, and a model for the processing of spatial cues in the echo pulse is developed. Although for over 50 years "echo suppression" has been the topic of intense theoretical and empirical study within the hearing sciences, only a rudimentary understanding of its mechanisms has emerged. In this article, psychometric functions and results from matching studies are used in developing a model that specifies the perceived position of the echo pulse as a normal deviate, with an expectation that is a logistic function of the echo delay and a variance that depends on interaural time difference. Loss of information in the echo event is quantified as a decline in the efficiency with which the binaural system receives information from the lag impulse. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
133.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
135.
复杂不规则刚体转动惯量的测试原理和方法 总被引:6,自引:0,他引:6
为了测量复杂不规则刚体转动惯量,采用时间常数法,通过A/D卡PS2129的定时/计数器8253高精度测速、计时,能较好地应用于测量转动惯量。 相似文献
136.
Docherty Nancy M.; Cohen Alex S.; Nienow Tasha M.; Dinzeo Thomas J.; Dangelmaier Ruth E. 《Canadian Metallurgical Quarterly》2003,112(3):469
This study examined the degree to which different types of communication disturbances in the speech of 48 schizophrenia patients and 28 controls were variable and state related versus stable and traitlike. Clinically rated formal thought disorder and 5 types of referential disturbance showed substantial stability within participants over time. The sixth type of referential disturbance, the vague reference, was not stable over time. Formal thought disorder was associated with the severity of core psychotic symptoms in patients, whereas referential disturbances showed little or no association with positive or negative symptom severity. Furthermore, changes in psychotic symptoms over time were accompanied by corresponding changes in formal thought disorder but not referential disturbances. These results support the idea that some types of referential disturbances are traitlike and may be reflective of vulnerability as well as manifest illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
137.
在鱼罐喷粉预处理水模实验数据的基础上,进一步利用线性回归确定各工艺操作参数对喷吹基本参数(均混时间、粉剂穿透比和粉剂停留时间)的影响,得出各传输动力学基本参数的函数关系式。 相似文献
138.
139.
Din Xue-dong Shanghai University of Technology Shanghai Institute of Applied Mathematics & Mechanics Shanghai P.R.ChinaXu Xue-zi Zhejiang University Hangzhou P.R.China 《水动力学研究与进展(B辑)》1992,(1)
To the flow produced in particle-suspension by a rotating disk of infinite extent,the asymptotic behavior at infinity is analyzed.A corresponding series solution is presented.It isshown that this approach yields widely valid solutions of high accuracy for all the cases in whichthat suction or weak injection at the disk surface exists.For the cases that strong injection or par-ticle-free band exists,the series method fails. 相似文献
140.
一、概述核电厂压水堆的初始过剩反应性是通过控制捧、固体可燃毒物和溶解在主回路冷却剂中的硼酸等三种方式联合控制的。随着反应堆的燃耗和裂变毒物的积累,堆的过剩反应性不断减少,需要通过化容系统,控制硼酸的浓度来进行补偿。如果化容系统发生故障或操作员误操作,就会给回路注入无硼或低于规定浓度的补给水,给反应堆引入正反应性,造成硼稀释事故。按核安全法规的要求,应对换料、冷停堆、热停堆和启动等工况进行计算,并要求在这些 相似文献