全文获取类型
收费全文 | 154073篇 |
免费 | 1977篇 |
国内免费 | 661篇 |
专业分类
电工技术 | 3160篇 |
综合类 | 191篇 |
化学工业 | 24582篇 |
金属工艺 | 5817篇 |
机械仪表 | 5002篇 |
建筑科学 | 4472篇 |
矿业工程 | 378篇 |
能源动力 | 4008篇 |
轻工业 | 17421篇 |
水利工程 | 1147篇 |
石油天然气 | 621篇 |
武器工业 | 5篇 |
无线电 | 20915篇 |
一般工业技术 | 29234篇 |
冶金工业 | 23990篇 |
原子能技术 | 2347篇 |
自动化技术 | 13421篇 |
出版年
2019年 | 863篇 |
2018年 | 1131篇 |
2017年 | 1172篇 |
2016年 | 1317篇 |
2015年 | 1104篇 |
2014年 | 1885篇 |
2013年 | 6757篇 |
2012年 | 3326篇 |
2011年 | 4753篇 |
2010年 | 3698篇 |
2009年 | 4285篇 |
2008年 | 4783篇 |
2007年 | 5031篇 |
2006年 | 4440篇 |
2005年 | 4187篇 |
2004年 | 4066篇 |
2003年 | 3958篇 |
2002年 | 3982篇 |
2001年 | 4020篇 |
2000年 | 3779篇 |
1999年 | 3729篇 |
1998年 | 6730篇 |
1997年 | 5305篇 |
1996年 | 4500篇 |
1995年 | 3741篇 |
1994年 | 3382篇 |
1993年 | 3205篇 |
1992年 | 2811篇 |
1991年 | 2718篇 |
1990年 | 2637篇 |
1989年 | 2619篇 |
1988年 | 2467篇 |
1987年 | 2172篇 |
1986年 | 2121篇 |
1985年 | 2567篇 |
1984年 | 2327篇 |
1983年 | 2200篇 |
1982年 | 2074篇 |
1981年 | 1996篇 |
1980年 | 1864篇 |
1979年 | 1877篇 |
1978年 | 1771篇 |
1977年 | 2092篇 |
1976年 | 2570篇 |
1975年 | 1586篇 |
1974年 | 1431篇 |
1973年 | 1459篇 |
1972年 | 1196篇 |
1971年 | 1116篇 |
1970年 | 949篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
W D Tiner 《International Journal of Project Management》1985,3(1):13-18
In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure. 相似文献
142.
143.
A mathematical model was developed to describe the removal of volatile organic compounds from drinking water in aeration basins. The model was used to simulate removal under a range of expected treatment conditions using the Continuous Systems Modeling Program. Results indicated that temperature and air-to-water ratio are the major factors influencing the removal of chloroform from water in an aeration basin. Bubble diameter was a lesser factor while liquid residence time had the smallest effect of the variables examined. 相似文献
144.
Vibro-fluidized beds are widely used in drying sticky powders and agglomerated materials as milk powder. Using a vibro-fluidized laboratory scale dryer, this work is aiming at analyzing preliminarily the effect of its operational variables on the drying kinetics and characteristics of whole milk powder. The full-factorial design technique with three replications at the central point has been employed to generate data and correlations to quantify the effect of inlet air temperature, air flow rate, and vibration bed amplitude on the drying curves and the milk powder properties related to its faster reconstitution in water (as tapped density, Hausner cohesion ratio, agglomerate size distribution, and internal pore concentration). Results obtained are analyzed and discussed to identify the adequate operation condition for final drying whole milk powder in vibro-fluidized beds, assuring a high product quality. 相似文献
145.
In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study. 相似文献
146.
147.
This paper reports investigations on the techniques and economics of hydrogen storage by means of cryoadsorption. Also a comparison with alternative storage methods is included. The hydrogen storage capacity of several adsorbents in the temperature range 65–150 K has been investigated experimentally. Based on these data, economics and operating conditions for minimum total costs of the system are calculated. Utilization-factor and capacity-factor parameters are shown to be decisive for outlining the favourable ranges of application for competitive hydrogen storage methods. 相似文献
148.
W Holt 《Materials & Design》1985,6(1):42-45
The world-wide sales for silicon integrated circuits totalled some £3,500M in 1980. The high growth rate of the industry is generated by high levels of investment in research, development and capital equipment leading to rapid innovation in design and manufacturing methods. This article concentrates on the increasing use of computers in the design process, new design concepts and the efforts to make the components within the silicon chip even smaller. 相似文献
149.
K.W. Allen S.M. Smith W.C. Wake A.O. van Raalte 《International Journal of Adhesion and Adhesives》1985,5(1):23-32
The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints. 相似文献
150.
Aleph is one of the four large high-energy physics experiments being completed for the LEP (Large Electron Positron) accelerator at CERN. Several hundred thousand detector elements deliver some 500 Mbytes of raw data per second. The author briefly describes the accelerator and the Aleph detector. He then discusses the design and implementation of the multilevel real-time data reduction and acquisition system, covering the requirements, the readout architecture, its implementation, data reduction, aspects of the detector-specific front-end electronics, and Aleph's present status and performance 相似文献