全文获取类型
收费全文 | 37077篇 |
免费 | 4070篇 |
国内免费 | 2562篇 |
专业分类
电工技术 | 868篇 |
综合类 | 1924篇 |
化学工业 | 8227篇 |
金属工艺 | 3404篇 |
机械仪表 | 1192篇 |
建筑科学 | 2423篇 |
矿业工程 | 745篇 |
能源动力 | 1386篇 |
轻工业 | 1474篇 |
水利工程 | 275篇 |
石油天然气 | 318篇 |
武器工业 | 493篇 |
无线电 | 4069篇 |
一般工业技术 | 13891篇 |
冶金工业 | 2066篇 |
原子能技术 | 349篇 |
自动化技术 | 605篇 |
出版年
2024年 | 167篇 |
2023年 | 894篇 |
2022年 | 944篇 |
2021年 | 1368篇 |
2020年 | 1629篇 |
2019年 | 1405篇 |
2018年 | 1279篇 |
2017年 | 1394篇 |
2016年 | 1351篇 |
2015年 | 1390篇 |
2014年 | 1971篇 |
2013年 | 2164篇 |
2012年 | 2355篇 |
2011年 | 3109篇 |
2010年 | 2197篇 |
2009年 | 2381篇 |
2008年 | 2133篇 |
2007年 | 2461篇 |
2006年 | 2157篇 |
2005年 | 2024篇 |
2004年 | 1617篇 |
2003年 | 1441篇 |
2002年 | 1162篇 |
2001年 | 862篇 |
2000年 | 782篇 |
1999年 | 532篇 |
1998年 | 512篇 |
1997年 | 353篇 |
1996年 | 291篇 |
1995年 | 227篇 |
1994年 | 238篇 |
1993年 | 168篇 |
1992年 | 135篇 |
1991年 | 135篇 |
1990年 | 121篇 |
1989年 | 103篇 |
1988年 | 47篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 22篇 |
1984年 | 35篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1976年 | 3篇 |
1963年 | 2篇 |
1955年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Christos C. Agrafiotis Chrysoula Pagkoura Souzana Lorentzou Margaritis Kostoglou Athanasios G. Konstandopoulos 《Catalysis Today》2007,127(1-4):265-277
The present work summarizes the recent activities of our laboratory in the field of solar-aided hydrogen production with structured monolithic solar reactors. This reactor concept, “transferred” from the well-known automobile exhaust catalytic after-treatment systems, employs ceramic supports optimized to absorb effectively solar radiation and develop sufficiently high temperatures, that are coated with active materials capable to perform/catalyze a variety of “solar-aided” reactions for the production of hydrogen such as water splitting or natural gas reforming. Our work evolves in an integrated approach starting from the synthesis of active powders tailored to particular hydrogen production reactions, their deposition upon porous absorbers, testing of relevant properties of merit such as thermomechanical stability and hydrogen yield and finally to the design, operation simulation and performance optimization of structured monolithic solar hydrogen production reactors. This approach, among other things, has culminated to the world's first closed, solar-thermochemical cycle in operation that is capable of continuous hydrogen production employing entirely renewable and abundant energy sources and raw materials – solar energy and water, respectively – without any CO2 emissions and holds, thus, a significant potential for large-scale, emissions-free hydrogen production, particularly for regions of the world that lack indigenous resources but are endowed with ample solar energy. 相似文献
52.
53.
54.
Fresh niobium hydroxide was first precipitated from NbF5 solution using an aqueous ammonium hydroxide under basic conditions. Then a simple procedure of mixing lithium and niobium hydroxides together and heating at a low temperature (400 °C) produced pure ultrafine single phase LiNbO3 (LN). In the literature, this is the lowest temperature so far reported on the formation of LN. The phase content and lattice parameters are determined by X-ray diffraction (XRD). The average particle size and morphology were studied by transmission electron microscopy (TEM). 相似文献
55.
56.
57.
Magnesiumandmagnesiumalloyshavebeenin vestigatedashydrogenstoragematerialsforseveralde cadesbecausefarmorehydrogenbyweightcanbestoredinthemthaninmostoftheothercurrentlyknownhydrogenstoragealloys .Moreover ,thehighnaturalabundanceofMg ,itslightmassandenviron mentalcompatibilitypotentiallymakemagnesiumoneofthemostprospectivecandidatesforfuturehydrogenstoragematerials .Unfortunately ,thepracticalappli cationofMganditsalloyshasbeenlimitedonlytocertainstoragedevicebecauseoftheirpoorhydriding dehydr… 相似文献
58.
59.
Y.X. Li 《Materials Letters》2007,61(22):4366-4369
TiC/Al composite was successfully synthesized utilizing laser ignited self-propagating high-temperature synthesis (SHS) of Al-C-Ti system with the different C/Ti molar ratio. When the molar ratio of C to Ti is below 1:1 in the starting materials, in addition to fine TiC particulates, a large amount of Al3Ti phase was found in the composites; however, when the molar ratio of C to Ti is 1:1 in the starting materials, the Al3Ti phase was almost completely eliminated and the distribution of TiC particulates generally appeared to be more homogeneous throughout the products synthesized. 相似文献
60.
超支化聚合物,具有多端基的“缺陷核壳”空间结构,化学反应性活泼,易于改性,与相应的线型聚合物相比,拥有特殊的性能,在多领域展现出广阔的应用前景。随着合成技术的进步,它们的应用研究,尤其是功能化的应用研究,成为多年来的研究热点。主要介绍超支化聚合物的结构、性能、合成及其功能化应用研究概况。 相似文献