全文获取类型
收费全文 | 1887427篇 |
免费 | 51266篇 |
国内免费 | 22178篇 |
专业分类
电工技术 | 54885篇 |
技术理论 | 45篇 |
综合类 | 31220篇 |
化学工业 | 329613篇 |
金属工艺 | 84467篇 |
机械仪表 | 66133篇 |
建筑科学 | 73858篇 |
矿业工程 | 23108篇 |
能源动力 | 59322篇 |
轻工业 | 139796篇 |
水利工程 | 22389篇 |
石油天然气 | 59675篇 |
武器工业 | 2918篇 |
无线电 | 233478篇 |
一般工业技术 | 327023篇 |
冶金工业 | 200246篇 |
原子能技术 | 37682篇 |
自动化技术 | 215013篇 |
出版年
2022年 | 19809篇 |
2021年 | 28978篇 |
2020年 | 21899篇 |
2019年 | 22710篇 |
2018年 | 26365篇 |
2017年 | 27188篇 |
2016年 | 31474篇 |
2015年 | 30775篇 |
2014年 | 45484篇 |
2013年 | 107352篇 |
2012年 | 58616篇 |
2011年 | 74240篇 |
2010年 | 65126篇 |
2009年 | 72017篇 |
2008年 | 66002篇 |
2007年 | 62753篇 |
2006年 | 64496篇 |
2005年 | 57399篇 |
2004年 | 53443篇 |
2003年 | 52162篇 |
2002年 | 50220篇 |
2001年 | 46274篇 |
2000年 | 44525篇 |
1999年 | 44639篇 |
1998年 | 57773篇 |
1997年 | 48312篇 |
1996年 | 43035篇 |
1995年 | 36558篇 |
1994年 | 33496篇 |
1993年 | 32031篇 |
1992年 | 28339篇 |
1991年 | 25109篇 |
1990年 | 25169篇 |
1989年 | 23997篇 |
1988年 | 22439篇 |
1987年 | 20380篇 |
1986年 | 19674篇 |
1985年 | 22855篇 |
1984年 | 22800篇 |
1983年 | 20633篇 |
1982年 | 19510篇 |
1981年 | 19577篇 |
1980年 | 18201篇 |
1979年 | 18694篇 |
1978年 | 17897篇 |
1977年 | 17942篇 |
1976年 | 19480篇 |
1975年 | 16112篇 |
1974年 | 15611篇 |
1973年 | 15730篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
N.C. Knowles 《Nuclear Engineering and Design》1989,116(1)
Geomechanical aspects of the storage of radioactive waste in salt formations have been studied extensively using finite element methods over the last 20 years. In consequence a range of computer programs and associated modelling techniques have been assembled. The paper is based on a benchmark exercise to compare the predictive abilities of a number of these programs and highlights the difficulties of making reliable a-priori estimates of long term behaviour. 相似文献
992.
Intensive fertilizer use has led to nitrate contamination of groundwater in many areas. This article examines the possibility of removing nitrates through the construction of artificial wetlands. A pilot study conducted in Denmark has found that the method is effective and economical, at least for small waterworks, though further treatment is necessary before an acceptable microbiological water quality is attained. 相似文献
993.
Experiments showing the frequency and amplitude of the flow induced motion of the gate for a 2- and a 4-in. swing check valve have been performed. The gate motion is due to turbulence in approach flow. We have found the dominant turbulent frequency of the approach flow is about half the natural frequency of the valves. The valves appear to be almost critically damped. Because of this, the valves respond almost as they would to a static force of the magnitude characteristic of the turbulent fluctuation in the flow. Both the dimensionless exciting force and the damping ratio have been found to be independent of valve size so the above statements are true for larger valves also. The recommended valve oscillation amplitudes and frequencies are used to calculate the wear at the shaft and at the stop. For an unpegged check valve, such as one of the 10-in. valves which was used at the San Onofre Nuclear Generation Station, it was found that shaft bearing wear would amount to 0.27 in.3/year and stop wear to 0.03 in.3/year. 相似文献
994.
V. I. Kusov A. K. Gruznov V. I. Kulichkov N. P. Kusova A. V. Dyubchenko 《Metallurgist》1989,33(11):224-225
Institute of Ferrous Metallurgy. Novolipetsk Metallurgical Combine. Translated from Metallurg, No. 11, pp. 32–33, November, 1989. 相似文献
995.
996.
997.
The evaluation of microcomputer programs: an area of debate 总被引:1,自引:0,他引:1
V. M. Johnston 《Journal of Computer Assisted Learning》1987,3(1):40-50
998.
999.
James W. Conard 《Information Systems Management》1987,4(1):8-17
The concept of the integrated services digital network (ISDN) could revolutionize information management. The purpose of the ISDN is to provide a worldwide network that offers end-to-end digital connectivity supporting a wide variety of communications services. ISDN subscribers will have direct access to a high-speed digital pipeline capable of supporting simultaneous voice, data, facsimile, and various other services and calling features. 相似文献
1000.
R.C. Whiting 《Journal of food science》1987,52(5):1126-1129
Blends of lard with eight separate fats or oils (70:30 w/w) were prepared and used as the fat component of meat batters. After cooking, the batters were analyzed for water and fat exudation and gel strength. None differed significantly from the control of 100% lard. Positive correlation coefficients, however, were significant between percent monounsaturated triglycerides and water exudation, polyunsaturated triglycerides and fat exudation and saturated triglycerides and gel strength. Addition of lecithin, cholesterol or methyl palmitate to the lard increased fat exudation and decreased gel strength. Sodium laurate had the opposite effect whether added to the lard or to the aqueous phase. 相似文献