全文获取类型
收费全文 | 164968篇 |
免费 | 25191篇 |
国内免费 | 8162篇 |
专业分类
电工技术 | 10393篇 |
技术理论 | 8篇 |
综合类 | 11582篇 |
化学工业 | 34563篇 |
金属工艺 | 7619篇 |
机械仪表 | 8947篇 |
建筑科学 | 11844篇 |
矿业工程 | 3823篇 |
能源动力 | 4245篇 |
轻工业 | 19565篇 |
水利工程 | 3624篇 |
石油天然气 | 5675篇 |
武器工业 | 1383篇 |
无线电 | 20936篇 |
一般工业技术 | 23262篇 |
冶金工业 | 5461篇 |
原子能技术 | 1586篇 |
自动化技术 | 23805篇 |
出版年
2024年 | 670篇 |
2023年 | 2065篇 |
2022年 | 4225篇 |
2021年 | 5766篇 |
2020年 | 5708篇 |
2019年 | 6243篇 |
2018年 | 6590篇 |
2017年 | 7447篇 |
2016年 | 7438篇 |
2015年 | 9456篇 |
2014年 | 11174篇 |
2013年 | 13431篇 |
2012年 | 12653篇 |
2011年 | 13050篇 |
2010年 | 12318篇 |
2009年 | 11498篇 |
2008年 | 11110篇 |
2007年 | 10436篇 |
2006年 | 9404篇 |
2005年 | 7815篇 |
2004年 | 5923篇 |
2003年 | 4853篇 |
2002年 | 4788篇 |
2001年 | 4083篇 |
2000年 | 3263篇 |
1999年 | 2100篇 |
1998年 | 1011篇 |
1997年 | 812篇 |
1996年 | 722篇 |
1995年 | 479篇 |
1994年 | 418篇 |
1993年 | 281篇 |
1992年 | 264篇 |
1991年 | 184篇 |
1990年 | 138篇 |
1989年 | 118篇 |
1988年 | 75篇 |
1987年 | 54篇 |
1986年 | 52篇 |
1985年 | 18篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 37篇 |
1979年 | 21篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1959年 | 9篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
RM Martín‐Aranda E Ortega‐Cantero ML Rojas‐Cervantes MA Vicente‐Rodríguez MA Baares‐Muoz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(2):234-238
α,β‐Unsaturated nitriles have been synthesized by Knoevenagel condensation of a carbonylic compound with malononitrile, assisted by sonochemical irradiation. Two alkaline‐promoted clays (Li+‐ and Cs+‐exchanged saponites) have been employed as catalysts. The influence of the carbonylic compound (benzaldehyde or cyclohexanone) and the use of a solvent on the catalytic activity have been studied. Remarkable increase in the conversion values has been found when the reaction is activated by ultrasound, as compared with the thermal activation. In this green, solvent‐free procedure, α,β‐unsaturated nitriles have been produced in very high yields (97%) when the Cs+‐saponite is used as catalyst. Copyright © 2004 Society of Chemical Industry 相似文献
102.
The texture effect on visual colour difference evaluation was investigated in this study. Five colour centers were selected and textured colour pairs were generated using scanned textile woven fabrics and colour‐mapping technique. The textured and solid colour pairs were then displayed on a characterized cathode ray tube (CRT) monitor for colour difference evaluation. The colour difference values for the pairs with texture patterns are equal to 5.0 CIELAB units in lightness direction. The texture level was represented by the half‐width of histogram, which is called texture strength in this study. High correlation was found between texture strength and visual colour difference for textured colour pairs, which indicates that an increasing of 10 units of texture strength in luminance would cause a decreasing of 0.25 units visual difference for the five colour centers. The ratio of visual difference between textured and solid colour pairs also indicates a high parametric effect of texture. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 341–347, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 相似文献
103.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
104.
105.
Gang Chen Zhonghua Yang Chor Ping Low 《Industrial Informatics, IEEE Transactions on》2006,2(4):269-280
In this paper, we address agent coordination from a dynamic systems perspective and propose a dynamic coordination model, which is inspired by biological metabolic systems. A new coordination mechanism through dynamic local adjustment (CDLA) is presented, and coordination is achieved when every agent utilizes explicitly the global system dynamics and performs iteratively a dynamic local adjustment procedure. The CDLA mechanism is investigated in an example multiagent shop floor system. The results show that the example manufacturing process is well-coordinated and the coordination approach is practically applicable and effective 相似文献
106.
结合海河流域防汛会商系统的开发情况,对防汛会商系统的功能、技术进行了详细的说明,对今后防汛会商系统开发及改进具有借鉴意义. 相似文献
107.
108.
109.
Wenhui MA Gang XIE Hua WANGFaculty of Materials Metallurgical Engineering Kunming University of Science Technology Kunming China Manuscript received January in revised form May 《材料科学技术学报》2002,18(3):286-287
The thermal expansion behavior of La1-xSrxMn1-yCoyO3-δ (x=0.2-0.4, y=0.1-0.3) perovskites in air has been investigated. The average linear thermal expansion coefficients increased with increasing Sr content up to 40 mole fraction or Co content up to 30 mole fraction. The expansion is generally attributed to an increase in the average cation radius as some of the cations in the perovskite are reduced in valence when oxygen ions are removed from the structure. 相似文献
110.