全文获取类型
收费全文 | 17736篇 |
免费 | 2512篇 |
国内免费 | 1594篇 |
专业分类
电工技术 | 1771篇 |
综合类 | 1904篇 |
化学工业 | 2366篇 |
金属工艺 | 1013篇 |
机械仪表 | 1346篇 |
建筑科学 | 1577篇 |
矿业工程 | 501篇 |
能源动力 | 469篇 |
轻工业 | 2007篇 |
水利工程 | 570篇 |
石油天然气 | 388篇 |
武器工业 | 376篇 |
无线电 | 2011篇 |
一般工业技术 | 1572篇 |
冶金工业 | 442篇 |
原子能技术 | 347篇 |
自动化技术 | 3182篇 |
出版年
2024年 | 95篇 |
2023年 | 278篇 |
2022年 | 680篇 |
2021年 | 963篇 |
2020年 | 622篇 |
2019年 | 467篇 |
2018年 | 491篇 |
2017年 | 551篇 |
2016年 | 486篇 |
2015年 | 716篇 |
2014年 | 932篇 |
2013年 | 1186篇 |
2012年 | 1517篇 |
2011年 | 1483篇 |
2010年 | 1435篇 |
2009年 | 1474篇 |
2008年 | 1497篇 |
2007年 | 1486篇 |
2006年 | 1267篇 |
2005年 | 1059篇 |
2004年 | 810篇 |
2003年 | 522篇 |
2002年 | 526篇 |
2001年 | 524篇 |
2000年 | 344篇 |
1999年 | 158篇 |
1998年 | 48篇 |
1997年 | 37篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1959年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
COMPARATIVE STUDY OF CHEMICAL COMPOSITION AND PHYSICOCHEMICAL PROPERTIES OF DEFATTED WHEAT GERM FLOUR AND ITS PROTEIN ISOLATE 总被引:2,自引:0,他引:2
Chemical composition and physicochemical properties of defatted wheat germ (WG) flour (DWGF) and protein isolate (DWGPI) were evaluated to determine their potential as food ingredients. Protein content of DWGF was 31.42% while that of DWGPI was 84.18%. Comparison of the amino acid composition to the Food and Agriculture Organization/World Health Organization reference pattern indicated that DWGF and DWGPI had well‐balanced amino acid profiles. Both of them were relatively rich in lysine, whereas cystine was lacking. The main mineral constituents of DWGF were potassium, magnesium and calcium, while sodium was the dominating element in DWGPI as a result of salt extraction. Concentrations of potassium, magnesium, calcium, manganese and zinc in DWGPI were significantly decreased because of alkaline extraction compared to those in DWGF. The elements copper and iron were higher in DWGPI than in DWGF. Total flavonoid content of DWGF was about 0.35 g rutin equiv/100 g, whereas that of DWGPI was lower (about 0.24 g rutin equiv/100 g). Compared to soybean protein isolate, DWGPI was easily digested by pepsin in vitro, while DWGF was comparatively indigestible. Nonreduced and reduced sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analyses seem to show that interpolypeptide S‐S bonds were absent in the structure of WG proteins. DWGF and DWGPI shared four groups of bands: (1) 85–70 kDa; (2) 55–50 kDa; (3) 47–40 kDa; and (4) below 20 kDa. 相似文献
53.
数字振荡器的实现原理与仿真编程 总被引:1,自引:1,他引:0
鉴于数字信号处理中的实时应用问题,探讨了数字滤波器的实时实现原理,包括离散时间网络结构的作用和离散时间信号处理的特点,重点介绍了实时应用中实现数字滤波器的基本思想,运用MATLAB和所导出的通用数字振荡器的系统函数对一个非正弦数字振荡器进行了仿真编程,还讨论了有关实时处理的几个重要的系统性质,表达了作者对于当前学习和应用数字信号处理方法的观点。 相似文献
54.
骨组织工程PLGA/TCP复合材料的性能研究 总被引:1,自引:0,他引:1
骨组织工程的支架要求有与人骨在功能梯度上相一致的材料结构、几何结构和生理功能。PLGA/TCP复合材料具有适用于骨组织工程支架的综合性能。以快速成形技术低温沉积工艺的成形效果来评价材料的成形性能,以体外降解试验来评价材料的降解性能,以国家标准的方法来评价材料的细胞毒性,对PLGA和TCP不同配比下的性能进行了研究,发现TCP含量的增加有利于降低材料的细胞毒性,加快了材料的降解,但同时降低了材料的成形性能。从骨组织工程的临床应用来看,低的细胞毒性是需要首先得到保证的,成形性能则通过其他方式来改善。 相似文献
55.
56.
1 Introduction Since the world first laser successfully developed by Maiman [1] in 1960, the research activities in this field has never been stopped. With diode laser pumping, it is possible to built higher efficiency, and therefore simpler and more compact laser in an all solid- state device. With recent progress in the development of reliable higher power diode lasers, parallel improvements in diode - pumped solid - state lasers have been made. Diode laser- pumped solid- lasers also offer … 相似文献
57.
A new technology for treating waste plastics (WP) by traditional coking process was introduced. With a thermo-balance and a 10 g atmospheric fixed bed reactor, the thermo-gravimetric behavior and product were studied during co-coking of WP with blended coal. And then, using a coke-oven with capacity of 200 kg, the characteristics of products were assessed. The results showed that there is an overlapping temperature range (200-550℃ ) of decomposition between WP and blended coal, and the pyrolysis synergism index η and synergism strength β proposed could evaluate the synergism between them. 1% of added WP results in the maximum synergism in all series experiments. The increase of added WP decreases the synergism. Tar yield in co-coking is increased with the decrease of water yield for synergism. Moreover, it was also found that the quality indexes of coke, such as M10, M40, CRI and CSR, are degraded with the increase of WP until 4%, though the quality of tar and gas is optimized for WP addition. 相似文献
58.
内陆核电站低放射性废水排放的三维计算 总被引:3,自引:0,他引:3
本研究应用EFDC三维水动力学数学模型,对典型受纳水体富水水库中核电站的低放射性废水排放进行了数值计算。富水水库库容较大、水体较深、水面窄长。先对由排放引起的水库内浓度场的稳定过程和稳定时间进行了预备计算,之后对表层排放、底层排放两种不同的排放方案进行了计算与分析,给出了表、底层排放核素分布的三维结构。模拟结果表明:污染物在环境水域中的运动规律,主要由环境流场决定。水库水深大,水体的稀释能力较强,且有向流速大的水层输移的趋势;不同半衰期物质,其浓度分布因水流输运作用与自衰作用的影响程度不一,同样条件下,半衰期长的核素浓度线包络面积也较大。 相似文献
59.
60.