全文获取类型
收费全文 | 1295篇 |
免费 | 60篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
综合类 | 2篇 |
化学工业 | 295篇 |
金属工艺 | 3篇 |
机械仪表 | 18篇 |
建筑科学 | 97篇 |
矿业工程 | 3篇 |
能源动力 | 16篇 |
轻工业 | 225篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 99篇 |
一般工业技术 | 222篇 |
冶金工业 | 183篇 |
原子能技术 | 4篇 |
自动化技术 | 171篇 |
出版年
2023年 | 8篇 |
2022年 | 21篇 |
2021年 | 49篇 |
2020年 | 20篇 |
2019年 | 39篇 |
2018年 | 39篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 22篇 |
2014年 | 43篇 |
2013年 | 64篇 |
2012年 | 72篇 |
2011年 | 87篇 |
2010年 | 70篇 |
2009年 | 43篇 |
2008年 | 71篇 |
2007年 | 53篇 |
2006年 | 50篇 |
2005年 | 34篇 |
2004年 | 56篇 |
2003年 | 35篇 |
2002年 | 24篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 46篇 |
1997年 | 43篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有1356条查询结果,搜索用时 31 毫秒
21.
Tariq Benamara Piotr Breitkopf Ingrid Lepot Caroline Sainvitu 《Structural and Multidisciplinary Optimization》2016,54(4):843-855
This paper presents a reformulation of the “Gappy Proper Orthogonal Decomposition” (Gappy-POD) multi-fidelity modeling approach and proposes an enrichment criterion associated with an adaptive infill algorithm. The latter is here applied to the study of the flight domain of the RAE-2822 transonic airfoil at two different levels of accuracy to demonstrate its ability to detect areas in a two-dimensional design space where the surrogate model needs improvement to better drive the optimization process. 相似文献
22.
Lili Wang Yan Tu Li Chen Panpan Zhang Kees Teunissen Ingrid Heynderickx 《Journal of the Society for Information Display》2010,18(6):405-414
Abstract— One of the most annoying distortions in (auto)stereoscopic displays is probably cross‐talk, visible as double edges, which is mainly caused by an imperfect separation of left‐ and right‐eye images. For different types of three‐dimensional (3‐D) displays, cross‐talk is caused by different origins, which could result in different levels of perceived image distortion. To evaluate the influence of (auto)stereoscopic display technology on cross‐talk perception, optical measurements and subjective assessments were performed with three different types of 3‐D displays. It is shown with natural still images that the 3‐D display technology with the lowest luminance and contrast level tolerates the highest level of cross‐talk, while still maintaining an acceptable image‐quality level. 相似文献
23.
Falk Hüffner Christian Komusiewicz Hannes Moser Rolf Niedermeier 《Theory of Computing Systems》2010,47(1):196-217
We initiate the first systematic study of the NP-hard Cluster Vertex Deletion (CVD) problem (unweighted and weighted) in terms of fixed-parameter algorithmics. In the unweighted case, one searches for a minimum
number of vertex deletions to transform a graph into a collection of disjoint cliques. The parameter is the number of vertex
deletions. We present efficient fixed-parameter algorithms for CVD applying the fairly new iterative compression technique.
Moreover, we study the variant of CVD where the maximum number of cliques to be generated is prespecified. Here, we exploit
connections to fixed-parameter algorithms for (weighted) Vertex Cover. 相似文献
24.
Falk T.H. Wai-Yip Chan 《IEEE transactions on audio, speech, and language processing》2010,18(1):90-100
In this paper, auditory inspired modulation spectral features are used to improve automatic speaker identification (ASI) performance in the presence of room reverberation. The modulation spectral signal representation is obtained by first filtering the speech signal with a 23-channel gammatone filterbank. An eight-channel modulation filterbank is then applied to the temporal envelope of each gammatone filter output. Features are extracted from modulation frequency bands ranging from 3-15 H z and are shown to be robust to mismatch between training and testing conditions and to increasing reverberation levels. To demonstrate the gains obtained with the proposed features, experiments are performed with clean speech, artificially generated reverberant speech, and reverberant speech recorded in a meeting room. Simulation results show that a Gaussian mixture model based ASI system, trained on the proposed features, consistently outperforms a baseline system trained on mel-frequency cepstral coefficients. For multimicrophone ASI applications, three multichannel score combination and adaptive channel selection techniques are investigated and shown to further improve ASI performance. 相似文献
25.
Ingrid A.E. Spanjers Pieter WoutersTamara van Gog Jeroen J.G. van Merriënboer 《Computers in human behavior》2011,27(1):46-52
Many animations impose a high cognitive load due to the transience of information, which often hampers learning. Segmentation, that is presenting animations in pieces (i.e., segments), has been proposed as a means to reduce this high cognitive load. The expertise reversal effect shows, however, that design measures that have a positive effect on cognitive load and learning for students with lower levels of prior knowledge, might not be effective, or might even have a negative effect on cognitive load and learning for students with higher levels of prior knowledge. This experiment with animated worked-out examples showed an expertise reversal effect of segmentation: segmented animations were more efficient than continuous animations (i.e., equal test performance with lower investment of mental effort during learning) for students with lower levels of prior knowledge, but not for students with higher levels of prior knowledge. 相似文献
26.
Sofia Cassel Falk Howar Bengt Jonsson Bernhard Steffen 《Formal Aspects of Computing》2016,28(2):233-263
We present a black-box active learning algorithm for inferring extended finite state machines (EFSM)s by dynamic black-box analysis. EFSMs can be used to model both data flow and control behavior of software and hardware components. Different dialects of EFSMs are widely used in tools for model-based software development, verification, and testing. Our algorithm infers a class of EFSMs called register automata. Register automata have a finite control structure, extended with variables (registers), assignments, and guards. Our algorithm is parameterized on a particular theory, i.e., a set of operations and tests on the data domain that can be used in guards.Key to our learning technique is a novel learning model based on so-called tree queries. The learning algorithm uses tree queries to infer symbolic data constraints on parameters, e.g., sequence numbers, time stamps, identifiers, or even simple arithmetic. We describe sufficient conditions for the properties that the symbolic constraints provided by a tree query in general must have to be usable in our learning model. We also show that, under these conditions, our framework induces a generalization of the classical Nerode equivalence and canonical automata construction to the symbolic setting. We have evaluated our algorithm in a black-box scenario, where tree queries are realized through (black-box) testing. Our case studies include connection establishment in TCP and a priority queue from the Java Class Library. 相似文献
27.
The antioxidant -tocopherol (vitamin E), applied in a basal trunk band to the green ash tree,Fraxinus pennsylvanica var.subintergerrinia, elicited an alteration of foliar feeding byMalacosoma disstria larvae (Lepidoptera: Lasiocampidae). The bioassayed effects were dependent on the dosage of elicitor, the time after elicitation, and the position in the tree. Leaves for chemical analysis were collected from trees receiving two dosages and at two intervals after elicitation. Compounds in the ethyl acetate extractables from the ash tree leaves were separated by TLC and HPLC. TLC separations showed differences in the nonhydrolyzed extractables attributable to elicitor dosage and time after elicitation. TLC-resolved differences were also evident among acid-hydrolyzed samples. HPLC-resolved profiles revealed eight peaks in the nonhydrolyzed extractables that were quantitatively negatively correlated with larval feeding preference between elicited versus control foliage on at least one of the two sampling dates. Results from this study and other investigations reported in the literature indicate that the antioxidant-tocopherol (vitamin E) can function as an environmental-stress elicitor of alterable defensive chemistry in green ash and other plants. 相似文献
28.
Olson Ingrid R.; Jiang Yuhong; Moore Katherine Sledge 《Canadian Metallurgical Quarterly》2005,31(5):889
The ability to remember visual stimuli over a short delay period is limited by the small capacity of visual working memory (VWM). Here the authors investigate the role of learning in enhancing VWM. Participants saw 2 spatial arrays separated by a 1-s interval. The 2 arrays were identical except for 1 location. Participants had to detect the difference. Unknown to the participants, some spatial arrays would repeat once every dozen trials or so for up to 32 repetitions. Spatial VWM performance increased significantly when the same location changed across display repetitions, but not at all when different locations changed from one display repetition to another. The authors suggest that a major role of learning in VWM is to mediate which information gets retained, rather than to directly increase VWM capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Lu Liu Jun Xia Ingrid Heynderickx Hanchun Yin 《Journal of the Society for Information Display》2004,12(4):509-515
Abstract— The influence of regional background on the visibility of sharpness differences has been investigated by blurring various still images to different extents. The assessment of sharpness has been performed both in China by Chinese people and in the Netherlands by European people. The results showed that both Chinese characters and Roman text were clearly more critical image material for judging sharpness than natural images. Independent on whether the image contained Chinese characters or Roman text, the visibility threshold for a difference in sharpness was the same for both the Chinese and European people. When related to a diagonal step response, the threshold on average equaled an angular resolution of 5 arcsec. 相似文献
30.
G. Schmidl G. Andrä J. Bergmann A. Gawlik I. Höger S. Anders F. Schmidl V. Tympel F. Falk 《Journal of Materials Science》2013,48(12):4177-4182
CW-diode laser crystallization of amorphous silicon (a-Si) deposited by sputtering or by electron beam evaporation onto different substrates (glass without or with SiNx or SiO2 intermediate layers) is investigated. The resulting grain sizes and orientations are characterized by electron backscatter diffraction, optical microscopy, and x-ray diffraction. We demonstrate that 200 nm thick sputtered a-Si layers can be crystallized on all of the used substrates to result in grains from 1 up to 100 μm in size, depending on the laser irradiation parameters (intensity, exposure time). Electron beam evaporated a-Si films can be crystallized only on sputtered SiNx intermediate layers to result in grains of 100 μm in size. Similar crystallographic film properties follow from laser treatment if the product of laser peak intensity and square root of exposure time is kept constant, independent of the scan velocity used. A high fraction of preferred (100)-oriented silicon grains can only be observed for samples with crystallites less than 10 μm in size. 相似文献