全文获取类型
收费全文 | 36745篇 |
免费 | 3385篇 |
国内免费 | 1790篇 |
专业分类
电工技术 | 2703篇 |
综合类 | 2485篇 |
化学工业 | 8781篇 |
金属工艺 | 6618篇 |
机械仪表 | 1554篇 |
建筑科学 | 3716篇 |
矿业工程 | 1075篇 |
能源动力 | 1242篇 |
轻工业 | 2431篇 |
水利工程 | 800篇 |
石油天然气 | 1205篇 |
武器工业 | 266篇 |
无线电 | 2054篇 |
一般工业技术 | 4254篇 |
冶金工业 | 1771篇 |
原子能技术 | 245篇 |
自动化技术 | 720篇 |
出版年
2024年 | 211篇 |
2023年 | 755篇 |
2022年 | 1489篇 |
2021年 | 1651篇 |
2020年 | 1439篇 |
2019年 | 1124篇 |
2018年 | 1070篇 |
2017年 | 1484篇 |
2016年 | 1383篇 |
2015年 | 1399篇 |
2014年 | 1945篇 |
2013年 | 2013篇 |
2012年 | 2449篇 |
2011年 | 2734篇 |
2010年 | 1884篇 |
2009年 | 2182篇 |
2008年 | 1761篇 |
2007年 | 2104篇 |
2006年 | 2100篇 |
2005年 | 1738篇 |
2004年 | 1442篇 |
2003年 | 1248篇 |
2002年 | 1037篇 |
2001年 | 902篇 |
2000年 | 750篇 |
1999年 | 690篇 |
1998年 | 550篇 |
1997年 | 471篇 |
1996年 | 354篇 |
1995年 | 358篇 |
1994年 | 295篇 |
1993年 | 198篇 |
1992年 | 162篇 |
1991年 | 135篇 |
1990年 | 94篇 |
1989年 | 83篇 |
1988年 | 54篇 |
1987年 | 43篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1961年 | 2篇 |
1960年 | 3篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Yaping KeLU 《材料科学技术学报》2002,18(6):492-496
In this paper,glass transition and thermal stability of the Zr-Al-Cu-Ni metallic glasses were investigated by using electrical resistance measurement(ERM),DSC and X-ray diffraction techniques.The experimental results show that the ERM is capable of detecting the glass transition of the amorphous alloys and can help to distinguish the crystallization products of the Zr-Al-Cu-Ni metallic glasses owing to the difference of the electrical resistivity between the precipitation phases. 相似文献
52.
The objective of the present study is to develop multi-functioned coating to the components, which are made of copper with electroplated Ni and are widely used for steel making industry. In this paper, we report the mechanical and thermal properties of Ni based superalloys with carbide sprayed by high velocity oxygen fuel (HVOF), and the detailed effects of sprayed material, spraying conditions, and initial powder structure on these properties. It was found that, among commercial Ni self-fluxing alloys (without fusing treatment), coating with a carbon content of 0.58 mass% had the most preferable properties, with a good balance of the hardness, strength, and thermal shock resistance. The thermal shock resistance depended not only on the strength of the coating but also on the volume contraction when tested at high temperatures. For the several developed Ni based superalloys with carbide, Ni20Cr8Mo5Fe–WC and Ni16Cr15Mo3–WC demonstrated the prominent adhesion strength and thermal shock resistance with high Galvanic corrosion resistance through optimized spraying condition. Also, 20 mass% NiCr–Cr3C2 coating sprayed by using employed relatively small primary particle succeeded in achieving the multi-superior properties; high adhesion strength, high corrosion resistance and thermal shock resistance. 相似文献
53.
54.
钢铁表面黑色转化膜处理技术 总被引:1,自引:1,他引:0
黑色转化膜技术是目前较为先进的钢铁表面处理技术 ,本文试验研究了一种新工艺 ,提出了TB值的概念 ,通过控制TB值即可控制处理液的质量 ,获得性能优良的转化膜。此工艺性能可靠 ,可操作性强 ,并可应用于激光热处理前的预处理。 相似文献
55.
本文描述用离子束透过钽金属膜进行混合和快速热处理方法来形成钽的硅化物.用溅射方法在P型硅衬底上淀积一层金属钽,然后用砷离子束透过钽金属模进行混合,采用快速热处理后形成了平整的硅化钽薄层.使用厚度为500埃的钽金属膜,得到钽的硅化物薄层电阻为5.5Ω/□.研究了砷离子能量、剂量及钽膜厚度对钽的硅化物薄层电阻的影响.用透射电镜和台阶仪对所形成的硅化钽进行了分析和厚度测量. 相似文献
56.
C R Chakravorty 《Bulletin of Materials Science》1994,17(6):733-745
Magnesium-lithium alloys are among the lowest density metallic materials. Addition of lithium, with a relative density of
0·53, in magnesium reduces the density of the alloy significantly. Furthermore, addition of nearly 11 wt.% lithium converts
hexagonal close packed structure of pure magnesium to a body centered cubic lattice, markedly improving formability of the
alloy. The development of these alloys, however, had been hampered due to the high reactivity of lithium and magnesium in
the molten state and also, due to poor creep resistance and instability of mechanical properties at room temperature. In an
attempt to indigenize these ultra light alloys for possible applications in Indian satellite programme, detailed research
work was initiated in DMRL. The difficulties associated with producing sound cast ingots have been overcome by controlling
melting and casting parameters of these alloys. Extensive work has been done on structure-property correlation of alloys with
varying lithium content and minor alloying additions. Based on these work, advanced magnesium-lithium alloys have been developed
with improved tensile properties, room temperature stability and creep resistance. Wrought products (plates/sheets) of magnesium-lithium
alloy have been supplied to ISAC, Bangalore and are being used in their INSAT-2 programme. This paper describes the systematic
studies carried out in the laboratory to indigenize these ultra light alloys. 相似文献
57.
从分析某高架桥中异形板板底裂缝的特点及成因着手 ,对设计与施工工艺诸方面提出防止裂缝的对策和对裂缝进行加固的全过程。 相似文献
58.
Birthe Mller Jose Luis Molina‐Cano Lars Munck 《Journal of the Institute of Brewing》2002,108(3):294-302
In earlier studies concerning vigour, where subsamples are heat‐treated before germination there was found heat‐sensitive as well as heat‐resistant barley samples. The vigour model developed by Ellis and Roberts and further developed at Carlsberg, could only describe the heat‐sensitive barleys. Seventeen samples of the “Alexis” variety grown widely in Europe were collected from the EBC trials in 1994 in order to see if heat resistance in barley was influenced by different growing conditions. We found both heat‐sensitive samples following the vigour model as well as pronounced heat‐resistant samples, but these were not divided according to growing conditions. The germination curves dependent on heat treatment and germination time were evaluated by Principal Component Analysis (PCA). Heat‐resistant barley samples could be differentiated from heat‐sensitive samples already after ½ h of heat treatment at 68°C (12% moisture) and after 3 days of germination. The barley samples were analysed with regard to malting quality. The PCA evaluation of the data divided the samples according to growing location, mainly due to differences in protein and β‐glucan. However, the malting analyses could not describe the differences in heat resistance and sensitivity of the barleys. The biochemical background of the heat resistance found is discussed on the basis of literature. Our findings should give an experimental basis for exploiting a biochemical principle for heat resistance, which is formed during grain filling and consumed during storage and germination. 相似文献
59.
60.
文章叙述了新型镍基耐蚀哈氏合金G-30在不同介质中的耐蚀性能以及工业应用,综合分析了该合金应用的经济性及前景。 相似文献