全文获取类型
收费全文 | 445篇 |
免费 | 23篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 102篇 |
金属工艺 | 4篇 |
机械仪表 | 10篇 |
建筑科学 | 8篇 |
能源动力 | 9篇 |
轻工业 | 43篇 |
水利工程 | 3篇 |
无线电 | 47篇 |
一般工业技术 | 64篇 |
冶金工业 | 69篇 |
原子能技术 | 1篇 |
自动化技术 | 105篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 27篇 |
2011年 | 22篇 |
2010年 | 15篇 |
2009年 | 31篇 |
2008年 | 21篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有468条查询结果,搜索用时 38 毫秒
91.
The effects of hydrogen incorporation in dilute nitride semiconductors, specifically GaAs1‐xNx, are discussed. The remarkable consequences of hydrogen irradiation include tuneable and reversible changes in the electronic, optical, structural, and electrical properties of these materials. The highly trapping‐limited diffusion of H atoms in dilute nitrides results in the formation of extremely sharp heterointerfaces between H‐containing and H‐free regions of the crystals. This, in turn, offers an unprecedented possibility to tailor the physical properties of a semiconductor chip in its growth plane with nanometer precision. A number of examples are presented and discussed. 相似文献
92.
Carmen Lizette Del-Toro-Sánchez Francisco Rodríguez-Félix Francisco Javier Cinco-Moroyoqui Josué Juárez Saúl Ruiz-Cruz Francisco Javier Wong-Corral Jesús Borboa-Flores Daniela Denisse Castro-Enríquez Carlos Gregorio Barreras-Urbina José Agustín Tapia-Hernández 《Journal of Food Processing and Preservation》2021,45(9):e15765
93.
94.
F??bio da Silva Lisboa Gregorio Guadalupe Carbajal Ar??zaga Fernando Wypych 《Topics in Catalysis》2011,54(8-9):474-481
Layered lanthanum and copper(II) laurates were tested as catalysts for methanolic esterification of lauric acid (C12). Factorial design evidenced a positive effect of reaction temperature and amount of catalyst on ester conversion, while the acid:alcohol molar ratio (MR) had a negative effect. With lanthanum laurate, 90.5% conversion was reached at 140???C with 10% catalyst and MR of 6:1. Although the highest conversion with copper(II) laurate converted 81.5% under the same conditions, results were better with a lower amount of catalyst (78% ester at 140???C with 2% catalyst and MR of 6:1). A calcium hydroxide succinate was also investigated showing better catalytic performance than the well-known CaO, under mild reaction conditions (120???C with 1% catalyst and MR of 3:1). Although layered carboxylates can be successively reused, the layered calcium hydroxide salt transformed into inactive CaCO3 in the second reuse reaction. 相似文献
95.
John T. Hofmann Gregorio M. Vlez‐Garcia Donald G. Baird Abby R. Whittington 《Polymer Composites》2013,34(3):390-398
The method of ellipses (MoE) is a common experimental technique utilized to quantitatively determine the orientation state of a population of rigid fibers within a fiber–polymer composite. In this research, the validity of applying the MoE to long, semi‐flexible fiber systems in which the majority of fibers are flexible is discussed. The components of the orientation tensor were first determined for a composite formed by a homogenous, simple shear field. The minimum acceptable image analysis width, or bin width, for the selected geometry was found to be ∼5.5 mm, or 1.4 times the average fiber length. This modified bin width was then used to determine the orientation at multiple percentages of flow within an injection‐molded, center‐gated disc, and compared to orientation values obtained utilizing the traditional, 0.7‐mm bin width. The results show that the traditional, 0.7‐mm bin width is sufficient for analysis of the center‐gated geometry. This fortuitous result is attributed to the axisymmetric nature of the center‐gated geometry, and the highly transverse fiber alignment seen within the samples, especially at moderate to high percentages of flow. In more complex flows, it is expected that the conventional bin width will not apply. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers 相似文献
96.
Jonas Gregorio de Souza Francisco Silva Noelli Marco Madella 《Journal of the Royal Society Interface》2021,18(183)
The expansion of forest farmers across tropical lowland South America during the Late Holocene has long been connected to climate change. The more humid conditions established during the Late Holocene are assumed to have driven the expansion of forests, which would have facilitated the dispersal of cultures that practised agroforestry. The Tupi, a language family of widespread distribution in South America, occupies a central place in the debate. Not only are they one of the largest families in the continent, but their expansion from an Amazonian homeland has long been hypothesized to have followed forested environments wherever they settled. Here, we assess that hypothesis using a simulation approach. We employ equation-based and cellular automaton models, simulating demic-diffusion processes under two different scenarios: a null model in which all land cells can be equally settled, and an alternative model in which non-forested cells cannot be settled or delay the expansion. We show that including land cover as a constraint to movement results in a better approximation of the Tupi expansion as reconstructed by archaeology and linguistics. 相似文献
97.
98.
Scientometrics - Bibliometrics, and more generally all metric indicators, are increasingly used as research tools as well as for managing and evaluating research activities. This study analyzes the... 相似文献
99.
100.
Hybrid chloroperoxidase‐magnetic nanoparticle clusters: effect of functionalization on biocatalyst performance
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)