全文获取类型
收费全文 | 1414篇 |
免费 | 87篇 |
国内免费 | 116篇 |
专业分类
电工技术 | 41篇 |
综合类 | 85篇 |
化学工业 | 287篇 |
金属工艺 | 307篇 |
机械仪表 | 25篇 |
建筑科学 | 87篇 |
矿业工程 | 24篇 |
能源动力 | 56篇 |
轻工业 | 21篇 |
水利工程 | 6篇 |
石油天然气 | 38篇 |
武器工业 | 8篇 |
无线电 | 89篇 |
一般工业技术 | 242篇 |
冶金工业 | 253篇 |
原子能技术 | 26篇 |
自动化技术 | 22篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 37篇 |
2021年 | 42篇 |
2020年 | 45篇 |
2019年 | 44篇 |
2018年 | 29篇 |
2017年 | 35篇 |
2016年 | 42篇 |
2015年 | 37篇 |
2014年 | 67篇 |
2013年 | 83篇 |
2012年 | 85篇 |
2011年 | 118篇 |
2010年 | 96篇 |
2009年 | 88篇 |
2008年 | 95篇 |
2007年 | 133篇 |
2006年 | 88篇 |
2005年 | 62篇 |
2004年 | 58篇 |
2003年 | 60篇 |
2002年 | 57篇 |
2001年 | 36篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 13篇 |
1997年 | 18篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有1617条查询结果,搜索用时 15 毫秒
1.
Leszek Markowski 《Vacuum》2004,74(2):247-251
In the time-of-flight spectrum of positive ions produced by electron bombardment of NaCl surface a delayed signal of Na+ is detected. This observation is attributed to production of core-excited autoionizing metastable Na** atoms which have their characteristic lifetimes in the 100 ns range. Moreover, it is noticed that the populations of the various metastable Na** states depend on the NaCl layer thickness. The lifetimes of some quartet metastable Na** states have been determined as well. 相似文献
2.
Magnesiumandmagnesiumalloyshavebeenin vestigatedashydrogenstoragematerialsforseveralde cadesbecausefarmorehydrogenbyweightcanbestoredinthemthaninmostoftheothercurrentlyknownhydrogenstoragealloys .Moreover ,thehighnaturalabundanceofMg ,itslightmassandenviron mentalcompatibilitypotentiallymakemagnesiumoneofthemostprospectivecandidatesforfuturehydrogenstoragematerials .Unfortunately ,thepracticalappli cationofMganditsalloyshasbeenlimitedonlytocertainstoragedevicebecauseoftheirpoorhydriding dehydr… 相似文献
3.
Alleviation Effect of Lanthanum on Cadmium Stress in Seedling Hydroponic Culture of Kidney Bean and Corn 总被引:4,自引:0,他引:4
Since1970s,rare earths(RE)have been exten-sively used as micro-fertilizers for crops in China.Ithas already been proved that REcani mprove the pro-duction and quality of crops.However,there havebeen a fewinvestigations about using RE as regulatorin pollution ecology.For example,An et al[1]studiedthe effects of O3on wheat growth and the protectiveeffect of RE.Yan and Zhou et al[2,3]discussed theprotective effect of RE on plants under acid rainstress.Jia et al[4]and Hu et al[5]reported th… 相似文献
4.
We explain why the methods in Langridge, Hart and Crampin [Comput. Phys. Commun. 134 (2001) 78] suffice for the evaluation of the lattice sums entering the Madelung matrix describing multipole interactions in systems with one-dimensional translational periodicity. 相似文献
5.
Measurements of saturated liquid viscosities and densities were performed on environmentally acceptable hydrochlorofluorocarbons (HCFCs), CH3CCl2F (HCFC-141b), CH3CClF2 (HCFC-142b; only for viscosity), CF3CF2CHCl2 (HCFC-225ca), and CClF2CF2CHClF (HCFC-225cb), using a capillary viscometer and a glass pycnometer in the temperature range from 273 to 353 K. The uncertainty in the measurement of viscosity is estimated to be 5% based on the comparison of the present data with those in the literature for HCFC-141b. An equation is given to represent our saturated liquid viscosity data as a function of temperature. 相似文献
6.
SynthesisandCrystalStructureofRE[CH2(CH2)4CONC4H9]3(NO3)3(RE=Dy,La)WangHanzhang(王汉章),XuQingfeng(徐庆锋),QianPu(钱朴)SunJianping(孙建... 相似文献
7.
The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calcu-lation, thermal analysis and in-situ X-ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La2O3 in the La2O3-Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG-DTA were taken. The experimental results show that the chemical state of lanthanum changes during heat-ing. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature. 相似文献
8.
9.
La改性的Ag/TS-1催化剂上丙烯选择氧化制环氧丙烷 总被引:1,自引:0,他引:1
在H2 和O2 混合气体存在下 ,在常压固定床、石英反应器上考察了La改性的Ag/TS - 1催化剂催化丙烯环氧化反应。研究结果表明 ,Ag和La负载在TS - 1上的先后顺序对丙烯环氧化反应有影响。H2 在丙烯气相氧化反应体系中起着重要的作用。 相似文献
10.
本文研究了用金属有机物热发解法制备PLT8薄膜的工艺过程和基片对薄膜结构的影响,并且给出了铁电性能的测量结果。 相似文献