全文获取类型
收费全文 | 201750篇 |
免费 | 4914篇 |
国内免费 | 1923篇 |
专业分类
电工技术 | 4711篇 |
技术理论 | 5篇 |
综合类 | 1947篇 |
化学工业 | 32222篇 |
金属工艺 | 9212篇 |
机械仪表 | 6587篇 |
建筑科学 | 6358篇 |
矿业工程 | 1608篇 |
能源动力 | 5299篇 |
轻工业 | 19135篇 |
水利工程 | 2110篇 |
石油天然气 | 4459篇 |
武器工业 | 174篇 |
无线电 | 22870篇 |
一般工业技术 | 36137篇 |
冶金工业 | 34186篇 |
原子能技术 | 4517篇 |
自动化技术 | 17050篇 |
出版年
2022年 | 1712篇 |
2021年 | 2553篇 |
2020年 | 1810篇 |
2019年 | 2067篇 |
2018年 | 2991篇 |
2017年 | 2986篇 |
2016年 | 3012篇 |
2015年 | 2670篇 |
2014年 | 4077篇 |
2013年 | 9292篇 |
2012年 | 6239篇 |
2011年 | 7957篇 |
2010年 | 6478篇 |
2009年 | 7272篇 |
2008年 | 7173篇 |
2007年 | 7055篇 |
2006年 | 6208篇 |
2005年 | 5641篇 |
2004年 | 5210篇 |
2003年 | 5063篇 |
2002年 | 5264篇 |
2001年 | 5072篇 |
2000年 | 4582篇 |
1999年 | 4636篇 |
1998年 | 10720篇 |
1997年 | 7690篇 |
1996年 | 5933篇 |
1995年 | 4504篇 |
1994年 | 3790篇 |
1993年 | 3699篇 |
1992年 | 2699篇 |
1991年 | 2614篇 |
1990年 | 2486篇 |
1989年 | 2477篇 |
1988年 | 2411篇 |
1987年 | 2142篇 |
1986年 | 2086篇 |
1985年 | 2375篇 |
1984年 | 2191篇 |
1983年 | 2017篇 |
1982年 | 1885篇 |
1981年 | 1949篇 |
1980年 | 1807篇 |
1979年 | 1816篇 |
1978年 | 1776篇 |
1977年 | 2108篇 |
1976年 | 2687篇 |
1975年 | 1557篇 |
1974年 | 1549篇 |
1973年 | 1607篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The main factors that determine the uniformity with which smelting products are tapped from a blast furnace are the rate of accumulation of the products in the hearth and the tapping rate. The first parameter is in turn determined by the stability of the furnace’s operation and can vary significantly even over the course of 24 h. The second parameter is determined mainly by the condition of the iron notch, the maintenance it receives, any changes that occur in the diameter of the channel of the notch, and the quality of the materials used to form the notch. Recommendations are presented to optimize tapping of the smelting products. 相似文献
112.
The Chelyabinsk Metallurgical Combine has periodically used Kachkanar agglomerate to make conversion pig iron since 1972.
Use of this material reached a peak in 1998, when it comprised an average of 27.1% of the charge. In some months, the amount
of this material charged into the furnace reached highs of 45.6 and 74.1% on certain furnaces. The coolers on the iron notches
of furnaces 4 and 5 burned during that year, the quality of the smelting products and the condition of the ladles rapidly
deteriorated, and the smelting rate declined. No Kachkanar agglomerate was used in 2000–2001, but it was again added to the
charge in February 2002. The amount used was smaller than previously, averaging 10.7% for the shop as a whole. It was determined
that using a charge with 15% Kachkanar agglomerate has both positive and negative consequences.
N. N. Gorshkov, A. V. Denisov, and V. Kh. Barinov also participated in this study.
__________
Translated from Metallurg, No. 3, pp. 43–45, March, 2006. 相似文献
113.
Molino A. Vacca F. Masera G. Nguyen T.Q. 《Vision, Image and Signal Processing, IEE Proceedings -》2006,153(6):860-868
To efficiently compute the phase difference (PD) between two complex numbers, two novel approaches are described. The problem of fast PD computation is central in many applications. As a case study, the main focus is on the phase correlation technique that is used for motion estimation. Starting from the problem statement, the system requirements are dealt with showing how PD requires a remarkable amount of computational resources. Reduced complexity techniques are then proposed and specifically tailored to suit the application needs. Each solution is completely implemented both in 0.25 mum as well as 0.13 mum CMOS. The so-called LUT-ROT exhibits noteworthy figures in terms of area occupation, delay and power dissipation, saving nearly 50% in terms of area and power when compared to recent work on this subject 相似文献
114.
Stievano I.S. Maio I.A. Canavero F.G. Siviero C. 《Advanced Packaging, IEEE Transactions on》2006,29(1):31-38
This paper addresses the impact of device macromodels on the accuracy of signal integrity and performance predictions for critical digital interconnecting systems. It exploits nonlinear parametric models for both single-ended and differential devices, including the effects of power supply fluctuations and receiver bit detection. The analysis demonstrates that the use of well-designed macromodels dramatically speeds up the simulation as well it preserves timing accuracy even for long bit sequences. 相似文献
115.
It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38–75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction. 相似文献
116.
The Magnitogorsk Metallurgical Combine has conducted a study of the effect of technological factors on the hydrogen content
of chromium-nickel-molybdenum steel after vacuum degassing. It was established that the most important factor is the hydrogen
content of the steel before the degassing operation. The study also determined the effects of the circulation coefficient,
the duration of the degassing operation, and the vacuum used in the treatment.
__________
Translated from Metallurg, No. 7, pp. 68–69, July, 2006. 相似文献
117.
P. L. Sun E. K. Cerreta G. T. Gray III J. F. Bingert 《Metallurgical and Materials Transactions A》2006,37(10):2983-2994
Commercial purity aluminum AA1050 was subjected to equal channel angular extrusion (ECAE) that resulted in an ultrafine-grained
(UFG) microstructure with an as-received grain size of 0.35 μm. This UFG material was then annealed to obtain microstructures
with grain sizes ranging from 0.47 to 20 μm. Specimens were compressed at quasi-static, intermediate, and dynamic strain rates
at temperatures of 77 and 298 K. The mechanical properties were found to vary significantly with grain size, strain rate,
and temperature. Yield stress was found to increase with decreasing grain size, decreasing temperature, and increasing strain
rate. The work hardening rate was seen to increase with increasing grain size, decreasing temperature, and increasing strain
rate. The influence of strain rate and temperature is most significant in the smallest grain size specimens. The rate of work
hardening is also influenced by strain rate, temperature, and grain size with negative rates of work hardening observed at
298 K and quasi-static strain rates in the smallest grain sizes and increasing rates of work hardening with increasing loading
rate and grain size. Work hardening behavior is correlated with the substructural evolution of these specimens. 相似文献
118.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
119.
120.
炼油达标污水回用处理试验研究 总被引:1,自引:0,他引:1
采用曝气生物滤池、多介质过滤、超滤、反渗透工艺,对炼油达标外排污水进行回用处理中试试验。结果表明,曝气生物滤池对油、COD和浊度去除效果良好,超滤、反渗透膜化学清洗周期达到 2个月以上,脱盐率稳定在98%以上,产水品质达到回用要求。 相似文献