全文获取类型
收费全文 | 10342篇 |
免费 | 1491篇 |
国内免费 | 1001篇 |
专业分类
电工技术 | 331篇 |
技术理论 | 1篇 |
综合类 | 991篇 |
化学工业 | 203篇 |
金属工艺 | 129篇 |
机械仪表 | 493篇 |
建筑科学 | 515篇 |
矿业工程 | 117篇 |
能源动力 | 46篇 |
轻工业 | 201篇 |
水利工程 | 80篇 |
石油天然气 | 85篇 |
武器工业 | 87篇 |
无线电 | 1488篇 |
一般工业技术 | 979篇 |
冶金工业 | 1223篇 |
原子能技术 | 23篇 |
自动化技术 | 5842篇 |
出版年
2024年 | 63篇 |
2023年 | 203篇 |
2022年 | 295篇 |
2021年 | 368篇 |
2020年 | 377篇 |
2019年 | 339篇 |
2018年 | 324篇 |
2017年 | 330篇 |
2016年 | 419篇 |
2015年 | 380篇 |
2014年 | 566篇 |
2013年 | 668篇 |
2012年 | 682篇 |
2011年 | 804篇 |
2010年 | 668篇 |
2009年 | 706篇 |
2008年 | 709篇 |
2007年 | 730篇 |
2006年 | 617篇 |
2005年 | 559篇 |
2004年 | 495篇 |
2003年 | 400篇 |
2002年 | 344篇 |
2001年 | 305篇 |
2000年 | 210篇 |
1999年 | 171篇 |
1998年 | 128篇 |
1997年 | 85篇 |
1996年 | 112篇 |
1995年 | 72篇 |
1994年 | 77篇 |
1993年 | 51篇 |
1992年 | 51篇 |
1991年 | 41篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1985年 | 35篇 |
1984年 | 36篇 |
1983年 | 29篇 |
1982年 | 27篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 33篇 |
1978年 | 12篇 |
1976年 | 12篇 |
1964年 | 20篇 |
1958年 | 10篇 |
1956年 | 10篇 |
1955年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.
Perkins Kenneth A.; Ciccocioppo Melinda; Jacobs Lynette; Doyle Todd; Caggiula Anthony 《Canadian Metallurgical Quarterly》2003,11(4):269
Nonpharmacological cues associated with drug intake may influence subjective and reinforcing effects of those drugs. Social drinkers (N = 80) participated in 2 sessions in which they rated and then consumed ad lib their preferred beer (with participants blind to brand). Visual and olfactory stimuli were obscured during 1 session (blocked) and not obscured during the other (unblocked). Dependent measures included ratings of "liking", "want another", and "desire to drink"; subjective mood; and ad lib beer consumption (reinforcement). Most ratings and ad lib consumption were lower during the blocked versus the unblocked condition. There were no interactions of blockade condition with sex and no effect of blockade on mood. These findings show that nonpharmacological stimuli associated with alcohol consumption influence alcohol's subjective and reinforcing effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
52.
53.
The present article reports the investigation of the effects of surrounding brightness on a visual search for three safety colors: red, orange, and yellow. Images of visual stimuli consisting of an array of colored circles placed on a large visual field (a visual angle of 40°) were displayed on an 80‐in. screen with a DLP projector. Experiment I examined the search efficiency under three levels of background luminance that were equivalent to the three target luminances. The results showed that the search efficiency for the orange target decreased as the number of distractors increased, under each of the background luminance levels, whereas the efficiency scarcely decreased for the red and yellow targets. Although a reduction in background luminance increased the search efficiency for the orange target, it is suggested that the effect of background luminance is smaller than the effect of the target color in search efficiency. Experiment II examined the search efficiency under three conditions of low levels of incident illuminance, which were matched with a linear regression to the luminance of color chips of safety colors measured twilight conditions. The results showed that the search efficiency for the orange target decreased as the number of distractors increased under each of the different illuminance conditions, whereas the efficiency scarcely decreased for red and yellow targets. Furthermore, as illuminance decreased, the search time for the orange target was more greatly impacted than for red or yellow. These results imply that the recognition of orange tends to be influenced by the surrounding brightness. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 400–409, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20152 相似文献
54.
Through two experiments, the study sought to emphasize the usefulness of the visual and kinesthetic imagery in mental practice. In Experiment 1, it was hypothesized that when the task to be learned through mental practice necessitates the reproduction of a form by drawing, the visual image, which provides a wide span of apprehension, is more suitable than the kinesthetic image. On the other hand, the kinesthetic image that supplies inputs from the muscles' positions and movements should be more appropriate for the acquisition of the duration of the drawing. In Experiment 2, it was hypothesized that the task, transformed into a motor task necessitating minute coordination of the two hands, would benefit more from kinesthetic imagery. To have optimal control over what was actually experienced during mental practice, the participants' imagery skills were measured. The participants also benefited from prior imagery training. The results demonstrate that when using mental practice to initially acquire a task, visual imagery is better for tasks that emphasize form while kinesthetic imagery is better for those tasks that emphasize timing or minute coordination of the two hands. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
The primary visual sources of depth and size information are binocular cues and motion parallax. Here, the authors determine the efficacy of these cues to control prehension by presenting them in isolation from other visual cues. When only binocular cues were available, reaches showed normal scaling of the transport and grasp components with object distance and size. However, when only motion parallax was available, only the transpont component scaled reliably. No additional increase in scaling was found when both cues were available simultaneously. Therefore, although equivalent information is available from binocular and motion parallax information, the latter may be of relatively limited use for the control of the grasp. Binocular disparity appears selectively important for the control of the grasp. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
PAC-learnability of probabilistic deterministic finite state automata in terms of variation distance
We consider the problem of PAC-learning distributions over strings, represented by probabilistic deterministic finite automata (PDFAs). PDFAs are a probabilistic model for the generation of strings of symbols, that have been used in the context of speech and handwriting recognition, and bioinformatics. Recent work on learning PDFAs from random examples has used the KL-divergence as the error measure; here we use the variation distance. We build on recent work by Clark and Thollard, and show that the use of the variation distance allows simplifications to be made to the algorithms, and also a strengthening of the results; in particular that using the variation distance, we obtain polynomial sample size bounds that are independent of the expected length of strings. 相似文献
57.
The constraint satisfaction problem is known to be NP-hard in general, but a number of restrictions of the problem have been identified over the years which ensure tractability. This paper introduces two simple methods of combining two or more tractable classes over disjoint domains, in order to synthesise larger, more expressive tractable classes. We demonstrate that the classes so obtained are genuinely novel, and have not been previously identified. In addition, we use algebraic techniques to extend the tractable classes which we identify, and to show that the algorithms for solving these extended classes can be less than obvious. 相似文献
58.
No authorship indicated 《Canadian Metallurgical Quarterly》1993,48(4):346
Recognizes Martha J. Farah for rigorous empirical and theoretical analysis of visual cognition, in which understanding of normal function and analysis of neurological deficits illuminate and strengthen one another. Applying diverse experimental techniques within an integrated approach to the study of mind and brain, she has sharpened and helped to answer fundamental questions about how humans generate and manipulate visual images, recognize objects, and attend to positions in space. Along with a citation, a biography is presented for Farah, as well as a bibliography of her works. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Reviews the book, Basic Processes in Reading Visual Word Recognition by Derek Besner and Glyn W. Humphreys (see record 1990-99017-000). While there has been an increase in the amount of work on many different aspects of reading, as Besner and Humphreys point out in the overview to their book, the vast majority of the research on the topic of reading in the past twenty years has been concerned with the processes involved in word recognition. For this reason, Besner and Humphreys have attempted to bring together studies on topics which are both relevant to current debates in the field of word recognition, and which are likely to be important for future developments in the field. They have compiled an edited volume consisting of their overview and eight additional chapters. The editors have attempted to span the continuum of processes involved in word recognition and thus have included chapters which cover topics ranging from the visual analysis of words, to those on the influence of semantic factors on word recognition. The authors of these chapters comprise an impressive list of researchers in the field of word recognition, with the majority of chapters being authored by leading researchers on the topic. Given the stature of the authors and the range of topics covered, in theory this volume should provide a very thorough overview of current theory and research on reading. There is no question that each of the chapters is interesting and important in its own right. However, in practice the volume as a whole fell somewhat short of my expectations. The different tacts taken by different authors has resulted in a very uneven coverage of the current debates in the field. Notwithstanding these criticisms, I am sure that the majority of researchers in this field will consider this volume to be an important contribution. The book would provide a very useful addition to graduate courses in cognitive sciences and as a supplemental text for an undergraduate course on the psychology of reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
60.
Participants' usage of informational variables in learning visual relative-mass discrimination in collisions was tracked by means of PROBIT correlations. Four groups received feedback that was true or accorded with either of three nonspecificational cue variables. A majority in each group adopted the feedback, but several participants defied the false feedback. Unlike in previous research, the fit to data of the relative-mass invariant could not be bettered by post hoc linear combinations of the cues. Discriminability was lower in the use of the invariant. Analytic complexity was rejected as an explanation for discriminability differences. A "smart mechanism" for pickup of the relative-mass invariant was developed as an extension of G. Johansson's (1950/1994) vector model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献