全文获取类型
收费全文 | 69153篇 |
免费 | 6898篇 |
国内免费 | 3689篇 |
专业分类
电工技术 | 4642篇 |
技术理论 | 2篇 |
综合类 | 4982篇 |
化学工业 | 10888篇 |
金属工艺 | 4105篇 |
机械仪表 | 4717篇 |
建筑科学 | 5618篇 |
矿业工程 | 2060篇 |
能源动力 | 1967篇 |
轻工业 | 5027篇 |
水利工程 | 1529篇 |
石油天然气 | 3462篇 |
武器工业 | 683篇 |
无线电 | 8633篇 |
一般工业技术 | 7932篇 |
冶金工业 | 3010篇 |
原子能技术 | 827篇 |
自动化技术 | 9656篇 |
出版年
2024年 | 318篇 |
2023年 | 1246篇 |
2022年 | 2427篇 |
2021年 | 3247篇 |
2020年 | 2479篇 |
2019年 | 1994篇 |
2018年 | 2068篇 |
2017年 | 2471篇 |
2016年 | 2234篇 |
2015年 | 3153篇 |
2014年 | 3970篇 |
2013年 | 4663篇 |
2012年 | 4943篇 |
2011年 | 5540篇 |
2010年 | 4862篇 |
2009年 | 4656篇 |
2008年 | 4566篇 |
2007年 | 4056篇 |
2006年 | 3688篇 |
2005年 | 3059篇 |
2004年 | 1967篇 |
2003年 | 1618篇 |
2002年 | 1559篇 |
2001年 | 1426篇 |
2000年 | 1168篇 |
1999年 | 1134篇 |
1998年 | 917篇 |
1997年 | 763篇 |
1996年 | 686篇 |
1995年 | 639篇 |
1994年 | 506篇 |
1993年 | 404篇 |
1992年 | 282篇 |
1991年 | 240篇 |
1990年 | 168篇 |
1989年 | 138篇 |
1988年 | 108篇 |
1987年 | 64篇 |
1986年 | 56篇 |
1985年 | 37篇 |
1984年 | 33篇 |
1983年 | 36篇 |
1982年 | 28篇 |
1981年 | 28篇 |
1980年 | 26篇 |
1979年 | 14篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1972年 | 5篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
D. C. Peets R. Liang C. Stock W. J. L. Buyers Z. Tun L. Taillefer R. J. Birgeneau D. A. Bonn W. N. Hardy 《Journal of Superconductivity and Novel Magnetism》2002,15(6):531-534
We have grown cubic centimeter-size crystals of YBa2Cu3O x suitable for neutron studies, by a top-seeded melt-growth technique. Growth conditions were optimized with an eye toward maximizing phase purity. It was found that the addition of 2% Y2BaCuO5 and 0.5% Pt (by mass) were required to prevent melt loss and to obtain the highest crystallinity. A neutron diffraction study on a mosaic of six such crystals found that the final Y2BaCuO5 concentration was 5%, while other impurity phases comprised less than 1% by volume. The oxygen content was set to x = 6.5, the crystals were detwinned, and then carefully annealed to give the well-ordered ortho-II phase. The neutron study determined that 70% of the mosaic's volume was in the majority orthorhomic domain. The neutron (006) and (110) rocking curve widths were ~1° per crystal and ~2.2° for the mosaic, and the oxygen chain correlation lengths were >100 Å in the a- and b-directions and ~50 Å in the c-direction. 相似文献
22.
23.
24.
Triton polymers are commercial surfactants whose molecular weight distributions are conventionally determined by means of high-performance liquid chromatography (HPLC). However, in the case of the important octylphenol ethoxylates [p-C8H17-C6H4-O-(CH2CH2O)n-H], HPLC cannot resolve individual oligomers of high molecular weight Triton surfactants (e.g., greater than 2000 u or so; u = unified atomic mass unit). In this paper, we show that laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD/FT/ICR/MS) provides a simple and accurate measure of such Triton surfactant molecular weight distributions up to at least 3500 u, based on a single-shot laser pulse measurement of a few seconds duration. Comparison of LD/FT/ICR/MS and HPLC molecular weight distributions of low molecular weight surfactants shows that laser desorption/ionization produces minimal fragmentation and thus offers an accurate measure of the relative abundances of the neutral oligomers, without the need for prior chromatographic separation of the components. Moreover, for all Triton polymer molecular weight distributions (700-3000 u), LD/FT/ICR/MS provides much more highly resolved profiles of oligomer relative abundances. Finally, LD/FT/ICR/MS reveals the presence of poly(ethylene oxide) side products of the polymerization process, which are not observed by HPLC with conventional ultraviolet absorption detection. 相似文献
25.
The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry 相似文献
26.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
27.
28.
29.
30.
Hsing-Chung Liang Wen-Chin Ho Ming-Chieh Cheng 《Reliability, IEEE Transactions on》2005,54(2):358-365
In this paper, we discuss some strategies for identifying unrepairable memories, and from that to introduce a novel theorem that can make more precise identification. A new algorithm for searching repair solutions is also proposed, which characterizes the rows, and columns of defective memory cells with revised effective coefficients. We have simulated it on many generated example maps, and compared it with the previous algorithms to verify its efficiency. It's combined with those arranged strategies of judging unrepairability to generate a complete flow. The complete algorithm has also been run on many examples with various memory sizes, defect numbers, and distribution types. The simulation results further show that identifying unrepairability in advance can help the reconfiguration procedure run much faster than searching solutions directly. 相似文献