全文获取类型
收费全文 | 314184篇 |
免费 | 45233篇 |
国内免费 | 35327篇 |
专业分类
电工技术 | 22686篇 |
技术理论 | 141篇 |
综合类 | 22146篇 |
化学工业 | 41357篇 |
金属工艺 | 20551篇 |
机械仪表 | 15584篇 |
建筑科学 | 19841篇 |
矿业工程 | 12991篇 |
能源动力 | 15119篇 |
轻工业 | 18313篇 |
水利工程 | 7744篇 |
石油天然气 | 23388篇 |
武器工业 | 5876篇 |
无线电 | 43059篇 |
一般工业技术 | 39069篇 |
冶金工业 | 17818篇 |
原子能技术 | 8442篇 |
自动化技术 | 60619篇 |
出版年
2024年 | 1508篇 |
2023年 | 7507篇 |
2022年 | 12724篇 |
2021年 | 14812篇 |
2020年 | 15295篇 |
2019年 | 12019篇 |
2018年 | 12364篇 |
2017年 | 13671篇 |
2016年 | 14128篇 |
2015年 | 14637篇 |
2014年 | 22346篇 |
2013年 | 26717篇 |
2012年 | 35650篇 |
2011年 | 32667篇 |
2010年 | 24296篇 |
2009年 | 24313篇 |
2008年 | 15847篇 |
2007年 | 22229篇 |
2006年 | 20111篇 |
2005年 | 9540篇 |
2004年 | 4805篇 |
2003年 | 3990篇 |
2002年 | 4002篇 |
2001年 | 3507篇 |
2000年 | 3529篇 |
1999年 | 2860篇 |
1998年 | 2234篇 |
1997年 | 1956篇 |
1996年 | 2040篇 |
1995年 | 1628篇 |
1994年 | 1312篇 |
1993年 | 1302篇 |
1992年 | 1040篇 |
1991年 | 853篇 |
1990年 | 779篇 |
1989年 | 708篇 |
1988年 | 898篇 |
1987年 | 1457篇 |
1986年 | 1392篇 |
1985年 | 400篇 |
1984年 | 345篇 |
1983年 | 204篇 |
1982年 | 229篇 |
1981年 | 197篇 |
1980年 | 194篇 |
1979年 | 137篇 |
1978年 | 72篇 |
1976年 | 64篇 |
1959年 | 125篇 |
1951年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
科技期刊编辑专业化和学者化是保证期刊学术质量的关键 总被引:1,自引:0,他引:1
一般科技期刊刊载的论文内容都具有很强的专业性,这就要求科技期刊编辑必须具有丰富的专业知识和较高的学术水平才能胜任编辑工作.从编辑过程的选题组稿、论文初审、选择审稿专家和编辑加工四个方面对此进行了阐述,指出了提高科技期刊编辑的相关专业知识和学术水平的措施. 相似文献
63.
Cz. Woźniak 《Acta Mechanica》1989,78(1-2):81-94
Summary In this paper a new high efficiency C-O grid coupled with the potential flow solver based on the finite volume technique is given. It significantly reduces the CPU time and increases the computational efficiency. In order to improve the accuracy of traditional potential method a shock point operator is used to account for entropy correction. Some calculated results of 2D inviscid, viscous/inviscid interaction and 3D inviscid flow indicate that nonisentropic potential method produces results closer to Euler solution as well as experimental data, while its computational efforts are nearly the same as the usual isentropic potential method.With 9 Figures 相似文献
64.
High speedsteel (HSS) ,ischaracterizedbyex cellenthardness ,wearresistance ,and goodredhardness .Recently ,HSSisappliedtomanufacturehotrollingrollstoproducestripsofgoodshapeandsmallcrownwithextendedrollservicelife[1,2 ] .TheHSSisappliedtomanufacturerollcollarfor… 相似文献
65.
《Fuel Processing Technology》2007,88(3):215-220
The fly ash (high carbon content and high unreacted CaO) recirculation in CFB is a typical method to improve the carbon burnout efficiency and the calcium utilization ratio. While the effectiveness of it is limited by the resident time and the reactivity of the re-injected fly ash particles. In the present research, an improved fly ash recirculation method is suggested in which the CFB fly ash is mixed with water or the mixtures of additives (such as waste water of paper mill, cement, sodium silicate, and carbide slag) and water in a blender. Then, this mixture is re-injected into the combustion chamber of CFB by a sludge pump. Because the temperature in CFB is higher, the fly ash was flash hydrated. At the same time, it was dehydrated and agglomerated. The size of agglomerates is bigger than that of original particle and their attrition rate is lower. Therefore the resident time of agglomerates is much longer than that of fine fly ash particles. The absorption of SO2 is higher than that of original particles, too. This results in high carbon burnout efficiency. The hydrated lime also improves the calcium utilization. 相似文献
66.
67.
68.
Wenwei He Wuping Liao Weiwei Wang Deqian Li Chunji Niu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1314-1320
BACKGROUND: Thermodynamics and kinetics data are both important to explain the extraction property. In order to develop a novel separation technology superior to current extraction systems, many promising extractants have been developed including calixarene carboxylic acids. The extraction thermodynamics behavior of calix[4]arene carboxylic acids has been reported extensively. In this study, the mass transfer kinetics of neodymium(III) and the interfacial behavior of calix[4]arene carboxylic acid were investigated. RESULTS: The rate constant (Kao) becomes constant when the stirring speed was controlled between 250 rpm and 400 rpm. The activation energy (Ea) was calculated to be 21·41 kJ mol?1 or 88·17 kJ mol?1 (dependent on temperature) from the slope of log Kao against 1000/T. The linear relationship between the specific area and the extraction rate is the characteristic of an interfacial reaction control. The minimum bulk concentration of the extractant necessary to saturate the interface (Cmin) is lower than 4·19 × 10?4 mol L?1. CONCLUSION: The effect of stirring speed, temperature, and species concentration on the extraction rate demonstrates that the extraction regime depends on the extraction conditions. The chemical reaction control governs the extraction regime at temperatures below 303 K and a mixed control regime occurs when the temperature is between 303 K and 318 K. The probable locale for the chemical reaction is at the liquid–liquid interface and the rate equation is deduced to be: ? d[Nd3+](a)/dt = kf[Nd3+](a)[H4A](o)0·727[H+](a)?0·978. The rate‐controlling step was suggested by the analysis of the experimental results. Copyright © 2008 Society of Chemical Industry 相似文献
69.
《Composites Science and Technology》2007,67(7-8):1330-1339
In order to analyze the effect of an epoxidized natural rubber (ENR) and filler treatment on the morphology and behavior of natural rubber (NR) nanocomposites, blends of these polymers have been prepared. The nature and extent of the clay dispersions in the filled samples were evaluated by X-ray diffraction. In the presence of ENR, an exfoliated structure was obtained which suggests that enough rubbery polymer was incorporated into the interlayer spacing. The effect of clay in rubber compounds was analyzed through rheological, mechanical and swelling characterization. A sensible improvement in the nanocomposite properties was observed by the addition of organoclay. It has been deduced that the properties of the compounds strongly depend on the extent of the silicate nanolayers dispersion into the rubber matrices as well as on the organoclay type and elastomer compatibility. 相似文献
70.
Squeeze-film effects of perforated plates for small amplitude vibration are analyzed through modified Reynolds equation (MRE).
The analytical analysis reckons in most important influential factors: compressibility of the air, border effects, and the
resistance caused by vertical air flow passing through perforated holes. It is found that consideration of air compressibility
is necessary for high operating frequency and small ratio of the plate width to the attenuation length. The analytical results
presented in this paper agree with ANSYS simulation results better than that under the air incompressibility assumption. The
analytical analysis can be used to estimate the squeeze-film effects causing damping and stiffness added to the system. Since
the value of Reynolds number involved in this paper is low (< 1), inertial effects are neglected. 相似文献