全文获取类型
收费全文 | 20130篇 |
免费 | 2146篇 |
国内免费 | 1430篇 |
专业分类
电工技术 | 852篇 |
技术理论 | 1篇 |
综合类 | 2170篇 |
化学工业 | 1558篇 |
金属工艺 | 1763篇 |
机械仪表 | 1124篇 |
建筑科学 | 2224篇 |
矿业工程 | 592篇 |
能源动力 | 293篇 |
轻工业 | 817篇 |
水利工程 | 298篇 |
石油天然气 | 588篇 |
武器工业 | 128篇 |
无线电 | 1529篇 |
一般工业技术 | 1374篇 |
冶金工业 | 3609篇 |
原子能技术 | 103篇 |
自动化技术 | 4683篇 |
出版年
2024年 | 100篇 |
2023年 | 247篇 |
2022年 | 528篇 |
2021年 | 523篇 |
2020年 | 618篇 |
2019年 | 462篇 |
2018年 | 392篇 |
2017年 | 568篇 |
2016年 | 698篇 |
2015年 | 751篇 |
2014年 | 1225篇 |
2013年 | 1130篇 |
2012年 | 1467篇 |
2011年 | 1531篇 |
2010年 | 1349篇 |
2009年 | 1290篇 |
2008年 | 1138篇 |
2007年 | 1456篇 |
2006年 | 1273篇 |
2005年 | 1000篇 |
2004年 | 862篇 |
2003年 | 792篇 |
2002年 | 650篇 |
2001年 | 625篇 |
2000年 | 588篇 |
1999年 | 485篇 |
1998年 | 384篇 |
1997年 | 323篇 |
1996年 | 267篇 |
1995年 | 207篇 |
1994年 | 175篇 |
1993年 | 123篇 |
1992年 | 112篇 |
1991年 | 80篇 |
1990年 | 65篇 |
1989年 | 63篇 |
1988年 | 30篇 |
1987年 | 31篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1964年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In this article, we are combining minimization criteria in the colorant separation process for spectral color reproduction. The colorant separation is performed by inverting a spectral printer model: the spectral Yule‐Nielsen modified Neugebauer model. The inversion of the spectral printer model is an optimization operation in which a criterion is minimized at each iteration. The approach we proposed minimizes a criterion defined by the weighted sum of a spectral difference and a perceptual color difference. The weights can be tuned with a parameter α ∞ [0, 1]. Our goal is to decrease the spectral difference between the original data and its reproduction and also to consider perceptual color difference under different illuminant conditions. In order to find the best α value, we initially compare a pure colorimetric criterion and a pure spectral criterion for the reproduction, then we combine them. We perform four colorant separations: the first separation will minimize the 1976 CIELAB color difference where four illuminants are tested, the second separation will minimize an equally weighted summation of 1976 CIELAB color difference with the four illuminants tested independently, the third colorant separation will minimize a spectral difference, and the fourth colorant separation will combine a weighted sum of a spectral difference and one of the two first colorimetric differences previously introduced. This last colorant separation can be tuned with a parameter in order to emphasize on spectral or colorimetric difference. We use a six colorants printer with artificial inks for our experiments. The prints are simulated by the spectral Yule‐Nielsen modified Neugebauer model. Two groups of data are used for our experiments. The first group describes the data printed by our printing system, which is represented by a regular grid in colorant space of the printer and the second group describes the data which is not originally produced by our printing system but mapped to the spectral printer gamut. The Esser test chart and the Macbeth Color Checker test chart have been selected for the second group. Spectral gamut mapping of this data is carried out before performing colorant separation. Our results show improvement for the colorant separations combining a sum of 1976 CIELAB color difference for a set of illuminants and for the colorant separation combining a sum of 1976 CIELAB color difference and spectral difference, especially in the case of spectral data originally produced by the printer. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 494–504, 2008 相似文献
102.
The recommendation of the CIE has been followed as closely as possible to evaluate the accuracy of five color gamut mapping algorithms (GMAs)—two nonspatial and three spatial algorithms—by psychophysical experiments with 20 test images, 20 observers, one test done on paper and a second one on display. Even though the results do not show any overall “winner,” one GMA is definitely perceived as not accurate. The importance of a high number of test images to obtain robust evaluation is underlined by the high variability of the results depending on the test images. Significant correlations between the percentage of out‐of‐gamut pixels, the number of distinguishable pairs of GMAs, and the perceived difficulty to distinguish them have been found. The type of observers is also important. The experts, who prefer a spatial GMA, show a stronger consensus and look especially for a good rendering of details, whereas the nonexperts hardly make a difference between the GMAs. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 470–476, 2008 相似文献
103.
104.
105.
Preference mapping with 10 pears identified 3 segments among New Zealand consumers. While 1 segment preferred ripe European cultivars, another rejected only the seedling with strong off‐flavors. A 3rd segment combined the 2 former segments, but also rejected 2 hybrid samples. Survey responses to the question “To me, the ideal pear is ?” from a 2nd consumer sample confirmed the general preference for juicy and sweet pears, the key characteristics of ripeness. A separate appearance evaluation revealed 4 segments based on color and shape. Combining information from several sources resulted in suggestions for new breeding directions for pears, while highlighting the importance of appearance and the need for more extensive measurements. 相似文献
106.
107.
文东油田连续气举优化配气数学模型建立及应用 总被引:1,自引:0,他引:1
针对连续气举在开发过程中出现的注入气利用效率低、综合效益差的问题,建立了供气能力有限时的优化配气数学模型,给出了解析法求解过程。文东油田现场试验表明,应用该技术可以实现连续气举井的合理配气,并提高油井产量,适合在油田推广应用。 相似文献
108.
Nalavany Blace A.; Ryan Scott D.; Gomory Tomi; Lacasse Jeffrey R. 《Canadian Metallurgical Quarterly》2005,14(1):27
In this pilot study, concept mapping, a methodological approach combining qualitative and quantitative analytic strategies, was used to identify the therapist qualities, competencies, and skills necessary for effective play therapy outcomes as perceived by a sub-sample of 28 experienced play therapists who are members of the Association for Play Therapy (APT). The clusters associated with the therapeutic relationship and facilitative skills (e.g., empathy, warmth, and genuineness) were rated as the most essential skills to possess and also as the most difficult to develop. In contrast, the clusters associated with play therapy interventions and theories were rated as the least important skills to possess but as the easiest to acquire. The findings are discussed, with implications for therapeutic practice, research, and policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
基于Legendre多项式的随机连续系统的Markov参数估计 总被引:3,自引:3,他引:0
本文在讨论连续Wisenr过程的Legendre多项式逼近值的相关性和Wiener过程扰动下连续线性系统基于该正交多项的最小二乘估计有偏性后,提出了无偏一致的且数估计误差方差最小的Markov估计(最小方差估计)算法,并给出本文方法的仿真结果。 相似文献
110.
本文采用伪线性化变换将船舶操纵非线性系统近似地化为线性可控正则型,并对线性化系统设计了一种连续的变结构以提高整个闭环系统的鲁棒性。该方案用于限制水域中船舶的航向航迹纠编控制中,取得了预期的结果。 相似文献