全文获取类型
收费全文 | 1012篇 |
免费 | 23篇 |
专业分类
电工技术 | 107篇 |
综合类 | 1篇 |
化学工业 | 388篇 |
金属工艺 | 8篇 |
机械仪表 | 13篇 |
建筑科学 | 23篇 |
能源动力 | 46篇 |
轻工业 | 105篇 |
水利工程 | 1篇 |
无线电 | 57篇 |
一般工业技术 | 149篇 |
冶金工业 | 44篇 |
原子能技术 | 31篇 |
自动化技术 | 62篇 |
出版年
2022年 | 8篇 |
2021年 | 25篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 37篇 |
2012年 | 45篇 |
2011年 | 45篇 |
2010年 | 41篇 |
2009年 | 34篇 |
2008年 | 52篇 |
2007年 | 50篇 |
2006年 | 38篇 |
2005年 | 32篇 |
2004年 | 30篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 23篇 |
1998年 | 39篇 |
1997年 | 24篇 |
1996年 | 34篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 22篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有1035条查询结果,搜索用时 31 毫秒
991.
This paper reports a promising approach for reducing the density of threading dislocations in GaAs on Si. In
x
Ga1-x
As/GaAs strained-layer superlattices (SLSs) grown by migration-enhanced epitaxy at 300° C on GaAs/Si acted as barriers to
threading dislocations. Unlike conventional high-temperature-grown SLSs, the low-temperature-grown SLSs were hardly relaxed
by the formation of misfit dislocations at GaAs/SLS interfaces, and this allowed them to accumulate considerable strain. New
threading dislocation generation due to the misfit dislocation was also suppressed. These factors caused effective bending
of threading dislocations and significantly reduced the dislocation density. For the samples that had an SLS withx = 0.3, the average etch-pit density was 7 × 104 cm-2, which is comparable to that of GaAs substrates. 相似文献
992.
Akiyama H Isuzugawa K Harikai N Watanabe H Iijima K Yamakawa H Mizuguchi Y Yoshikawa R Yamamoto M Sato H Watai M Arakawa F Ogasawara T Nishihara R Kato H Yamauchi A Takahata Y Morimatsu F Mamegoshi S Muraoka S Honjoh T Watanabe T Wakui C Imamura T Toyoda M Maitani T 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2003,44(5):213-219
Inter-laboratory evaluation studies were conducted for the notified ELISA methods for allergic substances (Egg). Standard extracts of egg spiked in extracts of sausage, sauce, cookie, bread and cereal at a level of 5-20 ng/mL as the sample solution were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of all three ELISA methods using an Egg Protein ovalbumin ELISA Kit (ovalbumin kit), an Egg Protein ovomucoid ELISA Kit (ovomucoid kit) and a FASTKIT Egg ELISA kit (Egg ELISA kit) were mostly less than 10%. Mean recoveries of the standard extract of egg were over 40% in the three ELISA methods. Repeatability relative standard deviations of egg standard solution in five food extracts were in the ranges of 18.7-25.5%, 18.6-41.8%, 21.3-43.3% for the ovalbumin kit, the ovomucoid kit and the Egg ELISA kit, respectively. Reproducibility relative standard deviations of egg standard solution in five food extracts were 16.8-35.1%, 19.6-35.8%, 24.7-51.1% for the ovalbumin kit, the ovomucoid kit and the Egg ELISA kit, respectively. The detection limits of all the ELISA methods were 4-5 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of egg protein levels in extracts of sausage, sauce, cookie, bread and cereal. 相似文献
993.
Polymer-coated fibrous materials as the stationary phase in packed capillary gas chromatography 总被引:1,自引:0,他引:1
Synthetic polymer filaments have been introduced as the support material in packed capillary gas chromatography (GC). The filaments of the heat-resistant polymers, Zylon, Kevlar, Nomex, and Technora, were longitudinally packed into a short fused-silica capillary, followed by the conventional coating process for open-tubular GC columns. The separation of several test mixtures such as n-alkylbenzenes and n-alkanes was carried out with these polymer-coated fiber-packed capillary columns. With the coating by various polymeric materials on the surface of these filaments, the retentivity was significantly improved over the parent fiber-packed column (without polymer coating) as well as a conventional open-tubular capillary of the same length. The results demonstrated a good combination of Zylon as the support and poly(dimethylsiloxane)-based materials as the coating liquid-phase for the successful GC separation of n-alkanes and polycyclic aromatic hydrocarbons (PAHs), while successful applications for other separations such as poly(ethylene glycol) coating for the separation of alcohols were also obtained. From the results it has been suggested that the selectivity of the fiber-packed column could be tuned by selecting different coating materials, indicating the promising possibility for a novel usage of fine fibrous polymers as the support material that can be combined with newly synthesized coating materials specially designed for particular separations. Taking advantage of good thermal stability of the fibers, the column temperature could be elevated to higher than 350 degrees C with the combination of a short metallic capillary. 相似文献
994.
As is well known, due to the existence of unstable limiting zeros and/or the minimum phase property of continuous-time systems, there are many cases that the discretized systems are of non-minimum phase. In this case, it is impossible to construct a stable digital inverse by usual methods. However, in this paper, we will show that if the inter-sample output is used in the design, one can always construct a stable digital inverse system. 相似文献
995.
Shoichi Okamoto Akira Kawai Kenkichiro Kobayashi Masasuke Takata Tsutomu Yamashita Shiro Yamashita 《Journal of the American Ceramic Society》1983,66(5):78-C-
Boron ions were implanted at room temperature in Ti films at a high dose (7.1 × 10I7 and 2.3 × 1018 ions/cm2 ), The formation of TiB2 films was confirmed by X-ray diffraction. Boron concentration profiles in implanted films were studied by secondary-ion mass spectrometry. 相似文献
996.
997.
Adsorption and anodic oxidation of methanol on palladium electrode in 0·5 N NaOH was studied by measuring current—potential (i-E) and reflectivity—potential (R/R0-E) curves. Presence of methanol retarded the formation of the oxide layer of Pd, giving rise to an anodic shift of the potential. A linear relation was found between the potential retarded and the logarithm of methanol concentration, the slope being about 30 mV/decade. The form of adsorbed entities was discussed based on the slope. The cathodic charge consumed by the reduction of Pd-oxide was smaller in the presence of methanol than in the absence. This was explained by three causes; the less amount of oxide layer formed during the anodic sweep owing to the adsorption of oxidation product of methanol, the reduction of formed oxide layer by a chemical reaction with methanol, and a compensation effect due to the anodic oxidation of methanol during the cathodic sweep. Plottings of the total charge in the anodic region vs — ΔR/R0 in the absence and the presence of methanol suggested that electro-oxidation of methanol proceeds only at the bare portion of Pd. 相似文献
998.
Kozo Tanabe Hideshi Hattori Tsutomu Yamaguchi Susumu Yokoyama Junichi Umematsu Yuzo Sanada 《Fuel》1982,61(4):389-390
The catalytic activity of Fe2O3for the hydrocracking of a bituminous coal at 673K increases when a small amount of SO42? is included in the catalyst. The effect of SO42? is marked in the formation of resins, stronger polar compounds and asphaltenes. 相似文献
999.
1000.