全文获取类型
收费全文 | 19992篇 |
免费 | 2046篇 |
国内免费 | 1342篇 |
专业分类
电工技术 | 1409篇 |
综合类 | 1756篇 |
化学工业 | 2184篇 |
金属工艺 | 1956篇 |
机械仪表 | 1888篇 |
建筑科学 | 1194篇 |
矿业工程 | 1362篇 |
能源动力 | 729篇 |
轻工业 | 1727篇 |
水利工程 | 608篇 |
石油天然气 | 810篇 |
武器工业 | 215篇 |
无线电 | 1567篇 |
一般工业技术 | 2122篇 |
冶金工业 | 601篇 |
原子能技术 | 211篇 |
自动化技术 | 3041篇 |
出版年
2024年 | 45篇 |
2023年 | 275篇 |
2022年 | 514篇 |
2021年 | 596篇 |
2020年 | 650篇 |
2019年 | 540篇 |
2018年 | 568篇 |
2017年 | 693篇 |
2016年 | 779篇 |
2015年 | 837篇 |
2014年 | 1229篇 |
2013年 | 1303篇 |
2012年 | 1495篇 |
2011年 | 1637篇 |
2010年 | 1235篇 |
2009年 | 1180篇 |
2008年 | 996篇 |
2007年 | 1406篇 |
2006年 | 1221篇 |
2005年 | 933篇 |
2004年 | 806篇 |
2003年 | 706篇 |
2002年 | 594篇 |
2001年 | 500篇 |
2000年 | 448篇 |
1999年 | 406篇 |
1998年 | 274篇 |
1997年 | 281篇 |
1996年 | 239篇 |
1995年 | 181篇 |
1994年 | 167篇 |
1993年 | 126篇 |
1992年 | 107篇 |
1991年 | 71篇 |
1990年 | 74篇 |
1989年 | 57篇 |
1988年 | 42篇 |
1987年 | 24篇 |
1986年 | 26篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
941.
In this study, a synthesis method for a non-integer periodic function generator of a four-bar mechanism using a Haar wavelet is presented. Using wavelet theory, the mathematical model for the output of a four-bar mechanism is established. Next, the characteristics of the four-bar mechanism output variable are described by the wavelet feature parameters; the relationship of the wavelet feature parameters between the output and its translation or dilation is also investigated. Based on this finding, three numerical atlas databases comprising of 203,500 groups of basic dimensional types of planar four-bar mechanisms, 148,995 groups of basic dimensional types of spherical four-bar mechanism and 11,175 groups of basic dimensional types of planar slider–crank mechanism are compiled. According to the internal relationship between the wavelet feature parameters, the sizes of the objective mechanism can be obtained using fuzzy recognition. Based on a genetic algorithm, optimization of the link parameters can be realized. Three examples are presented to demonstrate the efficacy and practicality of the proposed theory. 相似文献
942.
943.
Automatic photo enhancement is one of the long‐standing goals in image processing and computational photography. While a variety of methods have been proposed for manipulating tone and colour, most automatic methods used in practice, operate on the entire image without attempting to take the content of the image into account. In this paper, we present a new framework for automatic photo enhancement that attempts to take local and global image semantics into account. Specifically, our content‐aware scheme attempts to detect and enhance the appearance of human faces, blue skies with or without clouds and underexposed salient regions. A user study was conducted that demonstrates the effectiveness of the proposed approach compared to existing auto‐enhancement tools. 相似文献
944.
An T. Nguyen Wei-Cheng Lai Van Viet Tran Duc Dung Nguyen Hung-Chih Kan 《Energy Materials: Materials Science and Engineering for Energy Systems》2016,11(2):23-29
Specific graphene architectures at the macroscopic scale are paramount for exploring new functions and practical uses of graphene. In this study, macroscopic, freestanding, and tubular graphene (TG) architectures were successfully fabricated through a versatile and robust process based on the annealing of cellulose acetate (CA) on Ni templates. These TG architectures can be obtained as woven tubes with diameters of approximately 50 μm; they possess high graphitic crystallinity, strong electrical conductivity, and favorable corrosion resistance. The effects of processing parameters, such as annealing temperature, annealing time, and amount of CA, on the graphene properties of these architectures were investigated and are discussed in this paper. The graphene properties were characterized through field emission scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, Raman spectroscopy, four-point probe resistivity, and electrochemical measurements. 相似文献
945.
《Journal of the European Ceramic Society》2017,37(15):5057-5064
Confidence limits (at selected levels of 68.27%, 90%, 95% and 99%) for unbiased estimation of Weibull parameters obtained using linear least squares (LLS) analysis were investigated in this paper. A Monte Carlo procedure was used to obtain probability distributions for unbiased estimates of Weibull modulus, m, and Weibull scale parameter, So, as a function of total specimen number, N (10 ≤ N ≤ 200), and m (1 ≤ m ≤ 25). Inspection of the probability distributions indicated that confidence limits for m depended only on N whereas those for So depended on both N and m. Whilst the determination of confidence limits for m proved to be relatively straightforward, the respective values for So were obtained by fitting an empirical equation to the So probability distributions approximated by a Gaussian curve. Example values of m and So confidence limits for selected N have been presented in this work. 相似文献
946.
Passenger thermal comfort and behavior: a field investigation in commercial aircraft cabins 下载免费PDF全文
Passengers' behavioral adjustments warrant greater attention in thermal comfort research in aircraft cabins. Thus, a field investigation on 10 commercial aircrafts was conducted. Environment measurements were made and a questionnaire survey was performed. In the questionnaire, passengers were asked to evaluate their thermal comfort and record their adjustments regarding the usage of blankets and ventilation nozzles. The results indicate that behavioral adjustments in the cabin and the use of blankets or nozzle adjustments were employed by 2/3 of the passengers. However, the thermal comfort evaluations by these passengers were not as good as the evaluations by passengers who did not perform any adjustments. Possible causes such as differences in metabolic rate, clothing insulation and radiation asymmetry are discussed. The individual difference seems to be the most probable contributor, suggesting possibly that passengers who made adjustments had a narrower acceptance threshold or a higher expectancy regarding the cabin environment. Local thermal comfort was closely related to the adjustments and significantly influenced overall thermal comfort. Frequent flying was associated with lower ratings for the cabin environment. 相似文献
947.
948.
本文介绍了采用PVD处理方法获得的DLC涂层,针对DLC涂层应用于活塞环,提高活塞环耐磨、减摩性能做了重点介绍,并叙述了该领域的发展现状及趋势。 相似文献
949.
Raúl E. Cian Silvina R. Drago Rolando J. González 《International Journal of Food Science & Technology》2012,47(7):1348-1353
The effect of pH on colour and iron content (Fe) of peptide fractions obtained from bovine haemoglobin concentrate (BHC) hydrolysates was studied. Four hydrolysates were obtained using three enzymes: Protex‐6‐L (P), Fungal–Protease–Concetrate (FC) and Flavourzyme (F). BHC and its hydrolysates (P, FC, P + F, FC + F) were fractioned at pH 4.5, 7.0 and 9.5. Solubility and Fe from different fractions were measured. Correlations between CIELAB colour parameters and Fe from different fractions were analysed. The colour from different fractions varied from red to yellow (a* and b* positives). Lightness values (L*) ranged from twenty‐four to seventy. FC4.5 and FC + F4.5 fractions were the clearest and yellow (higher L*, b*, h), while BHC9.5 and P + F9.5 fractions had the lowest values of L*, b* and h. There was an inverse linear relationship between b* and L* parameters and Fe from fractions. This relationship could be associated with the pH of extraction. As pH increases Fe significantly increases and lower b* and L* values were obtained. 相似文献
950.
P.F. Gao H. YangX.G. Fan S.L. Yan 《Journal of Materials Processing Technology》2012,212(11):2520-2528
In this paper, the microstructure evolution and processing–microstructure relationship in the non-isothermal local loading forming of TA15 titanium alloy were studied through an analog experiment. Some new microstructural mechanisms are found, which are different from those under isothermal local loading forming. In the non-isothermal local loading forming, the tri-modal microstructure consisted of equiaxed primary α, lamellar α and β transformed matrix is achieved. The lamellar α, not produced under isothermal condition, is generated by β → α transformation due to the decrease of component temperature. With the same processing parameters, the volume fraction and grain size of primary α are both greater than those processed isothermally. The content of lamellar α decreases with heating temperature decreasing and little lamellar α can be found when the heating temperature drops to 930 °C. Under small deformation degree, the lamellar α distributes randomly in each feature region. As deformation increases, the lamellar α in transitional region and second-loading region present a preferred orientation perpendicular to the compression direction. The primary α content almost decreases linearly with heating temperature, which is different from the regular that under isothermal condition. Non-isothermal local loading forming with a higher heating temperature (near-β region) offers a cost-efficient way for the manufacture of TA15 titanium alloy large-scale integral components. 相似文献