全文获取类型
收费全文 | 65124篇 |
免费 | 7208篇 |
国内免费 | 4125篇 |
专业分类
电工技术 | 5211篇 |
技术理论 | 2篇 |
综合类 | 5882篇 |
化学工业 | 9489篇 |
金属工艺 | 3750篇 |
机械仪表 | 4378篇 |
建筑科学 | 5221篇 |
矿业工程 | 2063篇 |
能源动力 | 1677篇 |
轻工业 | 6651篇 |
水利工程 | 1703篇 |
石油天然气 | 2473篇 |
武器工业 | 782篇 |
无线电 | 7283篇 |
一般工业技术 | 6458篇 |
冶金工业 | 2615篇 |
原子能技术 | 965篇 |
自动化技术 | 9854篇 |
出版年
2024年 | 412篇 |
2023年 | 1255篇 |
2022年 | 2571篇 |
2021年 | 3304篇 |
2020年 | 2500篇 |
2019年 | 1874篇 |
2018年 | 2112篇 |
2017年 | 2414篇 |
2016年 | 2068篇 |
2015年 | 3030篇 |
2014年 | 3994篇 |
2013年 | 4573篇 |
2012年 | 5289篇 |
2011年 | 5409篇 |
2010年 | 5098篇 |
2009年 | 4666篇 |
2008年 | 4538篇 |
2007年 | 4378篇 |
2006年 | 3730篇 |
2005年 | 3012篇 |
2004年 | 2154篇 |
2003年 | 1530篇 |
2002年 | 1421篇 |
2001年 | 1134篇 |
2000年 | 1039篇 |
1999年 | 769篇 |
1998年 | 396篇 |
1997年 | 366篇 |
1996年 | 332篇 |
1995年 | 263篇 |
1994年 | 191篇 |
1993年 | 150篇 |
1992年 | 108篇 |
1991年 | 87篇 |
1990年 | 52篇 |
1989年 | 62篇 |
1988年 | 46篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 7篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1959年 | 8篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Vacuum treatment and ion-beam bombardment are two major processes in the low energy ion-beam implantation. To accurately study the contributions of these two major factors to the bioeffects separately, the M1 generation variation of Arabidopsis thaliana with ion-beam implantation and vacuum treatment were compared through a series of key plant development parameters including morphological observation, biochemical assay and RAPD (random amplified polymorphic DNA) analysis. The results showed that ion-beam implantation had obvious effect on almost all of these parameters, and the vacuum treatment had some impacts on several morphological parameters such as the bolting time and the length of the primary stem. Taking the results together, the indication is that vacuum treatment has some slight contributions to the bioeffects of ion-beam implantation while ion-beam bombardment itself is the major creator of the bioeffects. 相似文献
42.
43.
44.
45.
介绍了新型环保钢制散热器的设计、结构特点及主要制造工艺和性能特点。通过实际运行 ,证明该新型环保钢制散热器在室内供暖方面具有广泛的应用推广价值 相似文献
46.
47.
织物-树脂复合材料层压板的准静态侵彻机理 总被引:4,自引:1,他引:3
本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。 相似文献
48.
The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene. 相似文献
49.
应用色谱—质谱(GC-MS)及裂解色谱-质谱(PGC-MS)测定了乙烯基三甲基硅烷等离子体聚合反应中的气体冷凝物及聚合物,研究推导了等离子体聚合反应历程。单体在气相中被电子撞击,然后扩散到基底,在基底发生链增长和链终止反应。 相似文献
50.
This paper reports a new, highly integrated modular design approach for pulsewidth-modulation AC-AC converters based on a modular phase-bank structure. Novel high-power 3-in-1 integrated bi-directional power modules (IBPM) rated at 1200-V AC and 150 A and the 3-to-1 phase bank circuits have been successfully developed, fabricated and tested. This enables the modularity design of the multiphase converter systems and reduces the critical parasitic inductance. A theoretical analysis of the IBPM's silicon utilization for this new breed of direct power converters has been outlined. A lab prototype at medium power level has been successfully designed, implemented, and tested with good results. A nearly 460-VRMS out voltage at a 1:0.955 voltage transfer ratio, which, perhaps, is the highest performance reported so far in the literature, has been achieved by the novel two-side modulation control system. The converter-fed AC motor system is able to operate over the 0-240 Hz range with inherent regenerative capability and four-quadrant operation. Potential industrial applications are also briefly highlighted in this paper 相似文献