全文获取类型
收费全文 | 25518篇 |
免费 | 3538篇 |
国内免费 | 1197篇 |
专业分类
电工技术 | 814篇 |
综合类 | 1471篇 |
化学工业 | 5590篇 |
金属工艺 | 4708篇 |
机械仪表 | 1752篇 |
建筑科学 | 877篇 |
矿业工程 | 1077篇 |
能源动力 | 944篇 |
轻工业 | 1140篇 |
水利工程 | 280篇 |
石油天然气 | 744篇 |
武器工业 | 186篇 |
无线电 | 2253篇 |
一般工业技术 | 4856篇 |
冶金工业 | 2827篇 |
原子能技术 | 292篇 |
自动化技术 | 442篇 |
出版年
2024年 | 137篇 |
2023年 | 824篇 |
2022年 | 770篇 |
2021年 | 1058篇 |
2020年 | 1181篇 |
2019年 | 1135篇 |
2018年 | 903篇 |
2017年 | 1040篇 |
2016年 | 943篇 |
2015年 | 950篇 |
2014年 | 1369篇 |
2013年 | 1547篇 |
2012年 | 1599篇 |
2011年 | 1622篇 |
2010年 | 1164篇 |
2009年 | 1259篇 |
2008年 | 1130篇 |
2007年 | 1476篇 |
2006年 | 1454篇 |
2005年 | 1352篇 |
2004年 | 1064篇 |
2003年 | 1154篇 |
2002年 | 906篇 |
2001年 | 735篇 |
2000年 | 697篇 |
1999年 | 533篇 |
1998年 | 455篇 |
1997年 | 332篇 |
1996年 | 306篇 |
1995年 | 236篇 |
1994年 | 203篇 |
1993年 | 161篇 |
1992年 | 123篇 |
1991年 | 98篇 |
1990年 | 85篇 |
1989年 | 75篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Composition Range of Amorphous Mg-Ni-Y Alloys 总被引:1,自引:0,他引:1
Based on the thermodynamic point of view, a method for predication of the composition range of amorphous ter-nary alloys was proposed. The composition range of amorphous ternary alloys is determined by the comparison of the excess free energy of the amorphous alloy and the free energy of competing crystalline states. The free energy is extrapolated from the data of three binary alloys by using Toop‘s model. The method was applied to predict the composition range of amor-phous Mg-Ni-Y alloys. The theoretical results are in good agreement with the available experimental results. It indicates that the present method can be used to predict the composition range for amorphous ternary alloys. 相似文献
93.
M 2highspeedsteel (M 2steel)isamaterialwidelyusedintoolsanddies[1,2 ] .M 2steelischarac terizedbyalongsolidificationrangeandcomplexeu tecticreactions ,whichresultsinsegregationofalloy ingelementsandformationofseveraldifferenttypesofcarbidesduringsolidification[3,4 ] .Forconventionallyprocessedhigh speedsteels ,itisinevitablethatacoarsecarbidenetworkwillbeformedduringsolidifi cation .Coarseprimarycarbidestendtoresultinun evencarbidebandsdistributionafterasubstantialamountofhotprocessing[5] .Ma… 相似文献
94.
Marina Fomina Geoffrey M Gadd 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(1):23-34
The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Qmax) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association. © 2002 Society of Chemical Industry 相似文献
95.
A generic method has been developed for the synthesis of crystalline metal nanowires or nanotubes (such as bismuth nanotubes, tungsten nanowires) from lamellar structures. In a typical process, lamellar surfactant/inorganic composite precursors are first prepared by reacting cationic or anionic surfactants with inorganic species under appropriate conditions. After treating these precursors by hydrothermal pyrolysis, or other processes, crystalline metallic nanotubes or nanowires are obtained. 相似文献
96.
97.
The physical preconditions are considered for the temperature of a body to influence the force of gravity experienced by it. The results are given of experiments on weighing metal rods heated by ultrasound which confirm a dependence of the weight of the rods on their temperature. 相似文献
98.
The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523-723K for 1h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet. 相似文献
99.
做为一种耐磨性能很好的材料 ,SiC颗粒增强铝基复合材料切削加工表面具有分形特征。实际研究表明SiC颗粒增强铝基复合材料切削加工表面分形维数与抗磨损性能有密切关系 ,本文还分析了表面分形维数越大其抗磨损性能越强的机理。 相似文献
100.
在浸泡、阴极极化、阴极极化同时迭加拉伸变形、添加As2O3毒化剂等常见致氢条件下,通过慢应变速率拉伸试验研究了SiCp/2024复合材料的力学性能,考察了断口形貌.测定了该材料在按几种常用充氢条件充氢后的氢含量.发现虽然强烈阴极极化使材料力学性能下降,但其原因在于阴极极化引起的碱性腐蚀,与氢脆无关.获得了不同于前人研究的新结论:在本文试验条件下SiCp/2024材料不发生氢脆,也不发生不可逆氢损伤,其原因与该材料难以充入氢有关. 相似文献