全文获取类型
收费全文 | 297907篇 |
免费 | 36356篇 |
国内免费 | 25428篇 |
专业分类
电工技术 | 28479篇 |
技术理论 | 1篇 |
综合类 | 30872篇 |
化学工业 | 36392篇 |
金属工艺 | 20592篇 |
机械仪表 | 21861篇 |
建筑科学 | 23402篇 |
矿业工程 | 10642篇 |
能源动力 | 7664篇 |
轻工业 | 33277篇 |
水利工程 | 10569篇 |
石油天然气 | 9722篇 |
武器工业 | 4253篇 |
无线电 | 32587篇 |
一般工业技术 | 26505篇 |
冶金工业 | 10590篇 |
原子能技术 | 5033篇 |
自动化技术 | 47250篇 |
出版年
2024年 | 1240篇 |
2023年 | 5202篇 |
2022年 | 12030篇 |
2021年 | 15693篇 |
2020年 | 11161篇 |
2019年 | 7925篇 |
2018年 | 8144篇 |
2017年 | 9190篇 |
2016年 | 8483篇 |
2015年 | 13104篇 |
2014年 | 16606篇 |
2013年 | 19880篇 |
2012年 | 24703篇 |
2011年 | 25776篇 |
2010年 | 24431篇 |
2009年 | 23591篇 |
2008年 | 24024篇 |
2007年 | 23457篇 |
2006年 | 20487篇 |
2005年 | 16891篇 |
2004年 | 12311篇 |
2003年 | 8203篇 |
2002年 | 7399篇 |
2001年 | 6837篇 |
2000年 | 5508篇 |
1999年 | 2316篇 |
1998年 | 867篇 |
1997年 | 705篇 |
1996年 | 536篇 |
1995年 | 460篇 |
1994年 | 363篇 |
1993年 | 316篇 |
1992年 | 282篇 |
1991年 | 225篇 |
1990年 | 183篇 |
1989年 | 189篇 |
1988年 | 136篇 |
1987年 | 106篇 |
1986年 | 112篇 |
1985年 | 68篇 |
1984年 | 55篇 |
1983年 | 55篇 |
1982年 | 40篇 |
1981年 | 50篇 |
1980年 | 103篇 |
1979年 | 58篇 |
1965年 | 15篇 |
1964年 | 10篇 |
1959年 | 55篇 |
1951年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
Hydrolysis of Milk Fat with Lipase in Reversed Micelles 总被引:5,自引:0,他引:5
Enzymatic hydrolysis of milk fat was studied in a reversed-micelle system consisting of lecithin, water (1% total volume) and butteroil. Candida cylindracea lipase entrapped in the water pools of reversed micelles hydrolyzed surrounding triglycerides. The optimum temperature for enzyme activity was 55°C with an activation energy of 15.4 kcal/mole, while maximum enzyme activity was observed between pH 4 to 6. The molar ratio of water to surfactant (R value) in the system influenced enzyme activity with maximum activity at R = 10. Enzyme activity also increased with increasing surfactant or enzyme concentration. 相似文献
972.
反应器网络综合优化方法的研究进展 总被引:3,自引:0,他引:3
反应器网络综合优化方法在选择反应器类型和反应工艺条件时,比传统的方法表现出了很大的优势。综述了各类反应器网络综合优化方法的基本原理和研究进展,并分析了它们的优缺点。这些方法有基于过程特征的方法,包括可得区法和导数分析法;超结构优化法;目标类方法,包括目标法、构造目标法和构造MINLP法;以及经验推断法和分布参数法等。最后分析了这方面研究的发展趋势。 相似文献
973.
Beyene W.T. Xingchao Yuan Cheng N. Hao Shi 《Advanced Packaging, IEEE Transactions on》2004,27(1):34-44
With the rapid advance of silicon process technology, it is now possible to design input/output (I/O) circuits that operate at multigigabit data rates. As a result, accurate modeling and analysis of high-speed interconnect systems is essential to optimize the performance of the overall system. This paper describes the interconnect design, modeling, simulation, and characterization methodologies that are essential to achieve multigigabit data rates. It focuses on the physical layer verification and hardware correlation of functional systems and silicon to ensure robust system operation over 3.2Gb/s data rate using conventional low-cost packaging and printed circuit board (PCB) technologies. In order to capture conductor and dielectric losses, as well as other high-frequency effects of three-dimensional structures, accurate measurement-based simulation techniques that directly incorporate frequency-domain parameters from measurement or electromagnetic solver parameters into circuit simulation tools using fast Fourier transform (FFT) and bandlimiting windowing techniques are developed. Finally, simulation waveforms are correlated with prototypes at both component and system levels in both time and frequency domains. 相似文献
974.
The influence of the milk fat globule membrane (MFGM) on oxidation of milk fat under various conditions was monitored by fatty acid analysis and oxygen consumption at 50°C. The rate of copper-catalyzed oxidation of cream containing the membrane was faster than when the membrane was removed. In the dry state, the isolated MFGM, membrane lipids (ML) and the nonlipid membrane solids (NLMS) inhibited oxidation at 50°C and 95°C. In the presence of water, however, all membrane components enhanced oxidation at 50°C. The balance between the accelerating effects of membrane components and the inhibiting influence of other factors appeared to depend on processing conditions. 相似文献
975.
The growth time, growth mode and the method of preparing the supported catalysts play an important role in the growth of single-walled nanotubes (SWNTs). Their effects on the chemical vapor deposition (CVD) growth of SWNTs with MgO-supported catalysts were investigated in this study. It is shown that the growth rate of SWNTs was large during the initial few minutes of growth, however the quality of the tubes was low owing to the formation of many defects. Long term growth may favor the formation of tubes with high quality and high yield, but the introduction of other forms of carbon (impurities) is also unavoidable. There was a balance between the increase in yield and quality and sacrifice of the purity during growth of SWNTs. MgO-supported catalysts prepared by the co-precipitation method were found to be more effective for the synthesis of SWNTs than those prepared by the widely used impregnation method. The size and dispersion state of the catalyst were found to be crucial in enhancing the growth of SWNTs. In addition, growth on the surface of SWNTs over nanosized catalyst films was shown to be more favorable for the synthesis of tube products with higher quality, yield and purity. 相似文献
976.
977.
978.
设计研制了一种带模糊控制的新型单回路可编程调节器 ,该调节器不仅适用于一般的线性控制对象 ,也适用于中和滴定、球罐液位控制等非线性对象和复杂的工业对象 ,实现了多种常用的控制算法 ,在工业中有很好的实用价值 相似文献
979.
980.