全文获取类型
收费全文 | 836988篇 |
免费 | 9123篇 |
国内免费 | 2453篇 |
专业分类
电工技术 | 14338篇 |
综合类 | 2828篇 |
化学工业 | 126020篇 |
金属工艺 | 37872篇 |
机械仪表 | 27576篇 |
建筑科学 | 18746篇 |
矿业工程 | 6282篇 |
能源动力 | 20084篇 |
轻工业 | 58311篇 |
水利工程 | 10163篇 |
石油天然气 | 19679篇 |
武器工业 | 43篇 |
无线电 | 91540篇 |
一般工业技术 | 173390篇 |
冶金工业 | 136054篇 |
原子能技术 | 19812篇 |
自动化技术 | 85826篇 |
出版年
2021年 | 6747篇 |
2019年 | 6519篇 |
2018年 | 24879篇 |
2017年 | 23941篇 |
2016年 | 21726篇 |
2015年 | 8272篇 |
2014年 | 13117篇 |
2013年 | 34873篇 |
2012年 | 22951篇 |
2011年 | 35374篇 |
2010年 | 29023篇 |
2009年 | 29493篇 |
2008年 | 31197篇 |
2007年 | 31622篇 |
2006年 | 21583篇 |
2005年 | 20475篇 |
2004年 | 19545篇 |
2003年 | 19273篇 |
2002年 | 18097篇 |
2001年 | 17456篇 |
2000年 | 16670篇 |
1999年 | 16693篇 |
1998年 | 40236篇 |
1997年 | 28882篇 |
1996年 | 22239篇 |
1995年 | 16852篇 |
1994年 | 15084篇 |
1993年 | 15060篇 |
1992年 | 11326篇 |
1991年 | 10943篇 |
1990年 | 10885篇 |
1989年 | 10505篇 |
1988年 | 10158篇 |
1987年 | 8977篇 |
1986年 | 8867篇 |
1985年 | 9980篇 |
1984年 | 9379篇 |
1983年 | 8611篇 |
1982年 | 8059篇 |
1981年 | 8200篇 |
1980年 | 7854篇 |
1979年 | 7918篇 |
1978年 | 8067篇 |
1977年 | 8987篇 |
1976年 | 11300篇 |
1975年 | 7124篇 |
1974年 | 6910篇 |
1973年 | 7053篇 |
1972年 | 6106篇 |
1971年 | 5589篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
Conclusions The chemical mutagenesis method is recommended for use in local purification installations for cleaning up of caprolactam-containing wastewater.Use of this method permits one to carry out a biochemical clean-up of wastewater having a caprolactam content up to 600 mg/liter while increasing the oxidative power of the aeration tank by a factor of two.Translated from Khimicheskie Volokna, No. 6, p. 46, November–December, 1985. 相似文献
992.
An assessment is made of the technical contents of flight-vehicle structures curricula at 41 U.S. universities with accredited aerospace engineering programs. The assessment is based on the technical needs for the new and projected aeronautical and space systems as well as on the likely characteristics of the aerospace engineering work environment. A number of deficiencies and areas of concern are identified and recommendations are presented for enhancing the effectiveness of flight-vehicle structures education. A number of government supported programs that can help aerospace engineering education are listed in the appendix. 相似文献
993.
G. H. Palmir 《Journal of the Institute of Brewing》1987,93(4):332-333
The aleurone cells of barley, wheat, rice, rye, oats and triticale contained, comparatively, higher percentages of phosphorus than the aleurone cells of sorghum, maize or millet. The aleurone tissues of barley, wheat and rice had more phosphate than corresponding tissues of sorghum and maize. Phosphate was not detected in the aleurone tissue of maize but was found in trace amounts in the aleurone tissue of sorghum. 相似文献
994.
Z. P. Shul'man B. M. Khusid I. L. Ryklina É. A. Zal'tsgendler O. R. Dornyak É. V. Ivashkevich Z. A. Shabunina 《Journal of Engineering Physics and Thermophysics》1987,53(5):1285-1291
Dynamic processes are studied in media with softly and hardly internal destroyable configurations. A method is examined for the measurement of properties of media with spatial separation of the chemical transformation stages and thermal hydrodynamic measurements.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 781–789, November, 1987. 相似文献
995.
996.
997.
998.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献
999.
M. V. Zagidullin V. D. Nikolaev M. I. Svistun N. A. Khvatov 《Journal of Engineering Physics and Thermophysics》2007,80(3):555-562
The results of parametric tests of a centrifugal bubble singlet-oxygen generator based on the reaction of chlorine with an
alkaline hydrogen peroxide solution have been given. The utilization of chlorine grows with bubble-layer height, whereas the
relative content of O2(1Δ) remains constant. Growth in centrifugal acceleration leads to a more efficient utilization of chlorine. A specific oxygen
output of more than 1 mmole·cm−2·sec−1 from the bubble layer for a degree of chlorine utilization of ∼95% and a singlet-oxygen yield of more than 50% has been attained.
It has been shown that a centrifugal bubble singlet-oxygen generator is an efficient energy source for an oxygen-iodine laser.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 121–128, May–June, 2007. 相似文献
1000.
As feature size of electronic devices decreases, fast and accurate capacitance extraction has become increasingly critical for verification and analysis as regard as electromagnetic compatibility and signal integrity issues. The partial element equivalent circuit method is implemented for three-dimensional capacitance extraction of interconnects and very large-scale integration circuits with multiple dielectrics. The electric field coupling due to free and bound charges are analysed and modelled separately thus allowing to distinguish their contribution. The proposed approach provides physical insight, totally compatible fast methods for accelerating matrix-vector products, allows an easy treatment of lossy and dispersive dielectrics and is well suited for applying model order reduction techniques 相似文献