全文获取类型
收费全文 | 41564篇 |
免费 | 1391篇 |
国内免费 | 67篇 |
专业分类
电工技术 | 428篇 |
综合类 | 31篇 |
化学工业 | 7864篇 |
金属工艺 | 782篇 |
机械仪表 | 880篇 |
建筑科学 | 2154篇 |
矿业工程 | 124篇 |
能源动力 | 1168篇 |
轻工业 | 3235篇 |
水利工程 | 464篇 |
石油天然气 | 140篇 |
武器工业 | 5篇 |
无线电 | 3008篇 |
一般工业技术 | 6901篇 |
冶金工业 | 8409篇 |
原子能技术 | 340篇 |
自动化技术 | 7089篇 |
出版年
2023年 | 223篇 |
2022年 | 457篇 |
2021年 | 734篇 |
2020年 | 503篇 |
2019年 | 672篇 |
2018年 | 827篇 |
2017年 | 747篇 |
2016年 | 882篇 |
2015年 | 794篇 |
2014年 | 1111篇 |
2013年 | 2574篇 |
2012年 | 1769篇 |
2011年 | 2254篇 |
2010年 | 1785篇 |
2009年 | 1663篇 |
2008年 | 1965篇 |
2007年 | 1927篇 |
2006年 | 1723篇 |
2005年 | 1563篇 |
2004年 | 1276篇 |
2003年 | 1227篇 |
2002年 | 1194篇 |
2001年 | 805篇 |
2000年 | 657篇 |
1999年 | 751篇 |
1998年 | 1102篇 |
1997年 | 926篇 |
1996年 | 786篇 |
1995年 | 702篇 |
1994年 | 653篇 |
1993年 | 645篇 |
1992年 | 561篇 |
1991年 | 361篇 |
1990年 | 468篇 |
1989年 | 453篇 |
1988年 | 400篇 |
1987年 | 401篇 |
1986年 | 360篇 |
1985年 | 478篇 |
1984年 | 492篇 |
1983年 | 368篇 |
1982年 | 345篇 |
1981年 | 337篇 |
1980年 | 323篇 |
1979年 | 322篇 |
1978年 | 297篇 |
1977年 | 311篇 |
1976年 | 348篇 |
1975年 | 224篇 |
1974年 | 220篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Predicts the future of behavior therapy, focusing on theoretical development, therapeutic techniques, and empirical research. The importance of cognitive and affective processes in behavior change will attract increasing attention. Already one of the most widely adopted approaches, behavior therapy will be used to treat an expanded range of psychiatric disorders and health problems. Research will focus on comparative outcome studies and provide probes for investigating the nature of specific disorders and the mechanisms of therapeutic change. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
102.
In this paper, the TRNSYS Simulation Program is used to investigate the monthly and annual solar fraction of a Thermosyphon Solar Water Heater and to evaluate its economic viability in terms of its life cycle savings over a conventional water heating system. The results of the simulation indicate that the yearly solar contribution of the system ranges from 63% for a high hot water consumption profile to 89% for a low consumption pattern. The payback period of the system is as low as 3 years when compared to electric water heating systems. As long as the competitor is diesel oil, the payback period increases to 7–9 years, depending on the hot water consumption profile used. 相似文献
103.
Jue Donald; Meador Kimford J.; Zamrini Edward Y.; Allen Martha E.; Feldman Daniel S.; Loring David W. 《Canadian Metallurgical Quarterly》1992,6(4):331
Studied memory for visuospatial arrays in 28 male and 34 female healthy dextral adults (aged 20–90 yrs). 10 abstract figures were presented in each hemispace over a series of learning trials, and then delayed free recall of figure placement was obtained. Figures were misplaced significantly downward and leftward in both hemispaces. Both vertical and horizontal absolute error increased significanty with age, but no age effects on directional errors were observed. The increase in absolute error over age is consistent with decreased anterograde memory and visuospatial skills in the elderly. The directional errors are believed to result from an attentional shift toward proximal peripersonal space, in combination with attentional shifts from differential left vs right cerebral activation. Gender effects were also observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
David Sanborn Scott 《International Journal of Hydrogen Energy》2003,28(12):1303-1306
105.
Fault-accommodation with intelligent sensors 总被引:1,自引:0,他引:1
Giacomo Tortora Author Vitae Author Vitae David Clarke Author Vitae 《Automatica》2003,39(7):1227-1233
Optimal sensor fault-accommodation is considered for faults modelled by an increase in measurement noise. This noise is taken to be bounded and its probabilistic properties unknown. It is assumed that intelligent (e.g. self-validating) instrumentation is in use and estimates of the noise bounds are available. The fault-tolerant controller is designed to optimize a noise rejection and a nominal reference tracking index and leads to a mixed norm minimization problem (l1/l2). We exploit known results and a particular feedback configuration to show that it is possible to optimize simultaneously without a trade-off the two performance indices. The results are applied to systems where the presence of auxiliary measurements allows for an optimal fault-accommodation strategy. Using properties of the optimal solution, we define a factorization for the optimal controller alternative to the Youla parametrization, leading to an algorithm which is optimal, transparent and efficient. 相似文献
106.
David Duke 《Network Security》2003,2003(2):4-8
Anti-virus (AV) products and other fingerprint-based systems are typical of the applications used to enforce security. AV products are probably the first step that most organizations take to protect their systems and enhance security. Many small to medium organizations rely almost entirely on AV products. 相似文献
107.
Memorializes John Bissell (Jack) Carroll, an early leader in the development of psycholinguistics and a dominant contributor to psychometrics and the study of individual differences in cognitive abilities. His seminal work in evaluating foreign language proficiencies across multiple cultures combined his expertise in psycholinguistics with that in psychometrics and defined fundamental issues in the study of language acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
Collaborative filtering (CF) involves predicting the preferences of a user for a set of items given partial knowledge of the user's preferences for other items, while leveraging a database of profiles for other users. CF has applications e.g. in predicting Web sites a person will visit and in recommending products. Fundamentally, CF is a pattern recognition task, but a formidable one, often involving a huge feature space, a large data set, and many missing features. Even more daunting is the fact that a CF inference engine must be capable of predicting any (user-selected) items, given any available set of partial knowledge on the user's other preferences. In other words, the model must be designed to solve any of a huge (combinatoric) set of possible inference tasks. CF techniques include memory-based, classification-based, and statistical modelling approaches. Among these, modelling approaches scale best with large data sets and are the most adept at handling missing features. The disadvantage of these methods lies in the statistical assumptions (e.g. feature independence), which may be unjustified. To address this shortcoming we propose a new model-based CF method, based on the maximum entropy principle. For the MS Web application, the new method is demonstrated to outperform a number of CF approaches, including naive Bayes and latent variable (cluster) models, support vector machines (SVMs), and the (Pearson) correlation method. 相似文献
109.
George Owusu David B. Dreisinger Ernest peters 《Metallurgical and Materials Transactions B》1995,26(1):5-12
Liquid sulfur-zinc sulfate solution interfacial tensions and liquid sulfur-zinc sulfate solution-zinc sulfide (marmatite)
contact angles were measured in the absence and presence of surface-active agents. Interfacial tensions measured varied between
54 ± 1 mN/m in the surfactant-free system and 20 ± 1 mN/m in the presence of a surfactant. The liquid sulfur-zinc sulfide
mineral-zinc sulfate solution contact angle varies between 80 ± 5 deg, in the absence of any surfactant, and 148 ± 5 deg,
depending on the surfactant used. The surface-active agents were used as dispersants for sulfur in bench-scale zinc pressure-leaching
experiments. The observed extent of zinc extraction depends on the surfactant and varies from 40 to 96 pct. 相似文献
110.