全文获取类型
收费全文 | 4462篇 |
免费 | 20篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 151篇 |
金属工艺 | 13篇 |
机械仪表 | 38篇 |
建筑科学 | 67篇 |
矿业工程 | 13篇 |
能源动力 | 45篇 |
轻工业 | 109篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 80篇 |
一般工业技术 | 133篇 |
冶金工业 | 3672篇 |
原子能技术 | 6篇 |
自动化技术 | 128篇 |
出版年
2022年 | 8篇 |
2021年 | 8篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 13篇 |
2014年 | 18篇 |
2013年 | 42篇 |
2012年 | 25篇 |
2011年 | 33篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 25篇 |
2007年 | 38篇 |
2006年 | 28篇 |
2005年 | 32篇 |
2004年 | 24篇 |
2003年 | 28篇 |
2002年 | 17篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 137篇 |
1998年 | 1209篇 |
1997年 | 666篇 |
1996年 | 461篇 |
1995年 | 241篇 |
1994年 | 185篇 |
1993年 | 239篇 |
1992年 | 32篇 |
1991年 | 58篇 |
1990年 | 68篇 |
1989年 | 48篇 |
1988年 | 48篇 |
1987年 | 49篇 |
1986年 | 40篇 |
1985年 | 38篇 |
1984年 | 19篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 46篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 81篇 |
1976年 | 149篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 13篇 |
1972年 | 7篇 |
1968年 | 6篇 |
排序方式: 共有4482条查询结果,搜索用时 8 毫秒
81.
Since pneumotachograph masks are commonly used in studies of speech breathing, the purpose of this study was to measure the differences in respiratory volumetric and frequency measures during speech under two conditions: with and without a circumferentially vented pneumotachograph mask coupled to the face. Thus we sought to identify whether changes in breathing patterns occur with the use of a specific face mask, because these patterns are accepted as representative of normal speech breathing. Subjects were 10 normal-speaking women, each of whom produced a syllable train and a connected speech task, both at comfortable intensity levels. Respiratory measures were made using linearized magnetometers during speech production. The measurements included lung volume, rib cage volume, and abdominal volume at utterance initiation and termination, volume excursions during the utterance, and the number of breath groups during the speech task. There were no significant differences between the mask-on and mask-off conditions in volumetric and frequency measures. A significant task difference for abdominal initiation was found. It was concluded that the use of a circumferentially vented pneumotachograph mask does not alter the reliability of respiratory volume and frequency measures for studies of voice. 相似文献
82.
AI Robles ML Rodriguez-Puebla AB Glick C Trempus L Hansen P Sicinski RW Tennant RA Weinberg SH Yuspa CJ Conti 《Canadian Metallurgical Quarterly》1998,12(16):2469-2474
Cyclin D1 is part of a cell cycle control node consistently deregulated in most human cancers. However, studies with cyclin D1-null mice indicate that it is dispensable for normal mouse development as well as cell growth in culture. Here, we provide evidence that ras-mediated tumorigenesis depends on signaling pathways that act preferentially through cyclin D1. Cyclin D1 expression and the activity of its associated kinase are up-regulated in keratinocytes in response to oncogenic ras. Furthermore, cyclin D1 deficiency results in up to an 80% decrease in the development of squamous tumors generated through either grafting of retroviral ras-transduced keratinocytes, phorbol ester treatment of ras transgenic mice, or two-stage carcinogenesis. 相似文献
83.
Six experiments are reported that contrasted the effects of frequency and age of acquisition on written word recognition. Age of acquisition affected word-naming speed when frequency was controlled (Experiment 1), but there was no effect of frequency when age of acquisition was controlled (Experiment 2). Experiments 3 and 4 found an effect of age of acquisition upon immediate but not delayed naming speed, but no frequency effect on either immediate or delayed naming once age of acquisition was controlled. Independent effects of frequency and age of acquisition were observed in the lexical decision task (Experiments 5 and 6). Implications for theoretical accounts of word recognition and the possible roles of age of acquisition and frequency in word recognition are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
The compositions of the fatty acids in the 1, 2 and 3 positions of the principal glycerolipids and their various stereoisomers
were determined. Fatty acids in the 1 and 3 positions of triglycerides were similar in composition and less unsaturated than
those in the 2 position. Fatty acids in the 1,2-, 1,3- and 2,3-diglycerides were distributed in a pattern which indicated
isomerization ofsn-1,2-diacylglycerol. Lysophosphatidyl choline (the principal monoacyl lipid) consisted of about 80% 1-acyl and 20% 2-acyl
isomers. The fatty acid compositions indicated that most of the 2-lysophosphatidyl choline was formed by isomerization of
1-lysophosphatidyl choline. Most of the digly cerides and lysophosphatidyl choline were synthesized in the ripening wheat
grain. However a small proportion of these partial glycerides and all of the other minor partial glycerides (monoglycerides,
digalactosyl monoglycerides) appeared to be the result of limited lipolysis of the corresponding diacyl lipids in the wheat
or in the freshly-milled flour. Fatty acids in the 2 position of all the fully acylated glycerides were very similar in composition,
but there were considerable differences in the 1 position fatty acids. 相似文献
85.
A novel stylus based profiling instrument has been developed for rapid measurement of small surface areas. Outlined in the following paper are some of the key features of the prototype system including the wideband stylus pick-up and the dedicated scanning traverse mechanism. In addition, some preliminary results obtained by scanning the instrument over several different surfaces are presented. 相似文献
86.
Ben W. Morrison Mark W. Wiggins Glenn Porter 《International journal of human-computer interaction》2013,29(4):297-316
This study examined trainee crime-scene investigators' preference for, and accuracy in using, four different computer-based decision support interface designs, each of which incorporated a different reduced processing information acquisition strategy. The interfaces differed on the basis of the number of options that could be considered simultaneously and the level of control that could be exercised over the number and sequence in which feature values were accessed. Forty trainee investigators completed six decision scenarios in which they were asked to acquire information and formulate a decision by selecting one of three options. The study comprised two phases, the first of which involved familiarizing participants with each of the four interface designs and collecting performance and subjective data. The second phase involved trainees selecting one of the four interfaces to engage in a fifth and sixth decision scenario involving high or low levels of time-pressure. The results indicated that the “all options, full control” interface was the preferred option in the low time-pressure condition. Although the strategy remained the most frequently selected in the high time-pressure condition, this preference was not significant. It was concluded that the perceptions of difficulty and the degree of user control over information acquisition were more important than perceived efficiency in the selection of computer-based interface designs. The outcomes have implications for the design of decision support systems. 相似文献
87.
Andrew Morrison Geska Helena Andersson Robert Brečević Synne Skjulstad 《Digital Creativity》2013,24(1-2):3-20
The metaphor of plasma is taken up to present and discuss movement and engagement by participants in mixed reality installation arts. Two works involving full body video portraits exhibited through large plasma screens in a variety of public settings are covered. Machinic mediations of video realism are considered in terms of embodied interaction in which viewer-participants contribute to the ‘disquiet’ of gendered figuring. Processural, proximal and personal aspects of responsive engagement are discussed. This is extended to performativity that may lead us to critical reflection of our own actions and responses in mixed reality arts. 相似文献
88.
89.
Tip diameter and transmission efficiency of a visible-wavelength near-field optic probe determine both the lateral spatial resolution and experimental utility of the near-field scanning optical microscope. The commonly used tip fabrication technique, laser-heated pulling of fused-silica optical fiber followed by aperture formation through aluminization, is a complex process governed by a large number of parameters. An extensive study of the pulling parameter space has revealed a time-dependent functionality between the various pulling parameters dominated by a photon-based heating mechanism. The photon-based heat source results in a temperature and viscosity dependence that is a complex function of time and fiber diameter. Changing the taper of the optical probe can affect transmission efficiency by an order of magnitude or more. 相似文献
90.
We describe the origins of fuzzy-trace theory, including Piagetian, interference, information-processing, and judgment and decision-making influences. The contrasting properties of gist and verbatim memory serve as its foundation and, in recent models of spontaneous and implanted false memories, explain seemingly contradictory developmental trends, such as reverse developmental findings, differential time courses for true and false memories, and conflicting effects of trace strength. However, approaches that integrate fuzzy-trace theory with neurological, social, emotional, and motivational perspectives are needed. A method for accomplishing this integration, using the recent models, is introduced and new research that spans these perspectives is discussed. Relations to other contemporary theories, especially source-monitoring and dual-process theories, are also explained. We conclude by rejecting the notion that spontaneous false memories are actually "true" and distinguish gist and verbatim senses of the term "true" that have different consequences in real life. 相似文献