全文获取类型
收费全文 | 32720篇 |
免费 | 3909篇 |
国内免费 | 2260篇 |
专业分类
电工技术 | 2284篇 |
技术理论 | 7篇 |
综合类 | 4148篇 |
化学工业 | 2309篇 |
金属工艺 | 337篇 |
机械仪表 | 1425篇 |
建筑科学 | 8791篇 |
矿业工程 | 389篇 |
能源动力 | 364篇 |
轻工业 | 2930篇 |
水利工程 | 215篇 |
石油天然气 | 507篇 |
武器工业 | 265篇 |
无线电 | 3773篇 |
一般工业技术 | 2479篇 |
冶金工业 | 503篇 |
原子能技术 | 179篇 |
自动化技术 | 7984篇 |
出版年
2024年 | 55篇 |
2023年 | 389篇 |
2022年 | 734篇 |
2021年 | 842篇 |
2020年 | 970篇 |
2019年 | 829篇 |
2018年 | 786篇 |
2017年 | 982篇 |
2016年 | 1099篇 |
2015年 | 1284篇 |
2014年 | 2321篇 |
2013年 | 1956篇 |
2012年 | 2581篇 |
2011年 | 2725篇 |
2010年 | 2437篇 |
2009年 | 2372篇 |
2008年 | 2277篇 |
2007年 | 2602篇 |
2006年 | 2208篇 |
2005年 | 1780篇 |
2004年 | 1411篇 |
2003年 | 1175篇 |
2002年 | 938篇 |
2001年 | 784篇 |
2000年 | 653篇 |
1999年 | 518篇 |
1998年 | 377篇 |
1997年 | 289篇 |
1996年 | 259篇 |
1995年 | 257篇 |
1994年 | 213篇 |
1993年 | 167篇 |
1992年 | 154篇 |
1991年 | 74篇 |
1990年 | 67篇 |
1989年 | 63篇 |
1988年 | 49篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 25篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1964年 | 6篇 |
1959年 | 9篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
51.
This research shows the effect of simultaneous contrast on a design solution that generates it, and it also shows how its manifestation affects the shift of perception attributes of the observer's color. In the conducted research, 55 subjects had to harmonize the primary stimuli from the reproduction obtained with the help of digital printing technology, with the primary stimuli presented on two computer screens. As a visual harmonization technique, simultaneous binocular harmonization was used. The primary stimuli were made achromatic, with a 50% Raster Tone value (RTV), and are surrounded by achromatic secondary stimuli whose values increase in steps from 10% RTV up to 100% RTV. A shift in the perceptual attributes of color has been shown with the help of the CIEDE2000 system. Using ANOVA with repeated-measures and Fisher's post hoc analysis, statistically significant differences were found between the perceived means of shift in the ΔC00 chroma and ΔL00 lightness on defined samples on both computer screens, while in the case of the ΔH00 hue, no statistically significant differences were observed. The research also determined colorimetric differences in the ΔE00 color difference. Moreover, the student's t test was used to determine that the effect is stronger when manifested on the Lenovo computer than on the Asus computer screen (P < .05). 相似文献
52.
介绍了通过初级颜料的润湿、研磨与分散、稳定处理技术,使助剂和树脂均匀地包裹在颜料表面,并通过特殊工艺制得水性和油性色浆粉,并赋予了很好的速溶性和分散性。 相似文献
53.
54.
Large confined space has high incidence of fires, which seriously threatens the safety of people working there. Understanding the distribution of smoke in such large space is critical to fire development prediction and smoke control. Three improved methods for the stratification interface prediction of fire smoke are developed, including of improved intra-variance, integral ratio and N-percentage methods. In these methods, the interface height is determined by the vertical temperature distribution based on a three-layer smoke zone model, which is an improvement of a two-layer zone model. Thereafter, the three improved methods are applied to several typical fire cases simulated CFD to predict the smoke interface, and their applicability and reliability are verified by comparison of the smoke stratification results with the filed simulation results. Results show that the three improved methods can effectively determine the location of the three-layer zone model's interface, and they have the ability to predict smoke interface for fires with different fire source types and ventilation conditions. 相似文献
55.
Recently, permutation based indexes have attracted interest in the area of similarity search. The basic idea of permutation based indexes is that data objects are represented as appropriately generated permutations of a set of pivots (or reference objects). Similarity queries are executed by searching for data objects whose permutation representation is similar to that of the query, following the assumption that similar objects are represented by similar permutations of the pivots. In the context of permutation-based indexing, most authors propose to select pivots randomly from the data set, given that traditional pivot selection techniques do not reveal better performance. However, to the best of our knowledge, no rigorous comparison has been performed yet. In this paper we compare five pivot selection techniques on three permutation-based similarity access methods. Among those, we propose a novel technique specifically designed for permutations. Two significant observations emerge from our tests. First, random selection is always outperformed by at least one of the tested techniques. Second, there is no technique that is universally the best for all permutation-based access methods; rather different techniques are optimal for different methods. This indicates that the pivot selection technique should be considered as an integrating and relevant part of any permutation-based access method. 相似文献
56.
57.
Boundary colors are observed when light from a scene is dispersed by a prism or diffraction grating. We discovered that patterns with repeating black and white stripes can produce repeating bands of boundary colors with two hues. These hues are virtually constant as measured by chromaticity or CIELAB. We found seven cases of this kind using a new appearance model for boundary colors. The model correctly predicts that green and magenta bands recur as stripe widths and dispersion strength vary. The first green/magenta case in the sequence traces out an accurate ellipse in XYZ color space. Green and magenta bands are prominent in supernumerary rainbows and interference rings, and we explain why that might be the case. The explanation is based on an interesting property of the visible spectrum. In addition to the green/magenta cases, the other cases are orange/cyan, yellowish‐green/purple, and yellow/violet. The success of the boundary color appearance model implies that bands are perceived as if the wavelength responses of the cones were essentially independent, which contradicts the actual behavior of cones. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 135–146, 2015 相似文献
58.
Siting facilities in continuous space to maximize coverage of regional demand is an important planning problem. It is challenging to solve because demand is continuously distributed in a region and facilities may be sited anywhere in the region, suggesting that an infinite number of locations must be considered both as demand for service as well as a potential facility. An ingenious approach for solving continuous space coverage problems is abstracting continuously distributed demand as discrete spatial objects (points, lines or polygons), generating a finite dominating set from continuous space as candidate facility sites, and applying a discrete location coverage model. However, abstracting continuous demand and potential facility sites often introduces errors and uncertainties in coverage of regional demand, rendering findings (service and optimal facility locations) less than definitive. In this paper we examine the continuous space maximal coverage problem. Studies focused on locating antennas in Paradise Valley, Arizona and emergency warning sirens in Dublin, Ohio, are used to highlight issues and challenges in continuous space modeling. Potential paths forward are suggested based on empirical insights. 相似文献
59.
Human skin detection in images is desirable in many practical applications, e.g., human–computer interaction and adult-content filtering. However, existing methods are mainly suffer from confusing backgrounds in real-world images. In this paper, we try to address this issue by exploring and combining several human skin properties, i.e. color property, texture property and region property. First, images are divided into superpixels, and robust skin seeds and background seeds are acquired through color property and texture property of skin. Then we combining color, region and texture properties of skin by proposing a novel skin color and texture based graph cuts (SCTGC) to acquire the final skin detection results. Comprehensive and comparative experiments show that the proposed method achieves promising performance and outperforms many state-of-the-art methods over publicly available challenging datasets with a great part of hard images. 相似文献
60.