全文获取类型
收费全文 | 89611篇 |
免费 | 10396篇 |
国内免费 | 7245篇 |
专业分类
电工技术 | 7032篇 |
技术理论 | 1篇 |
综合类 | 9372篇 |
化学工业 | 9879篇 |
金属工艺 | 4398篇 |
机械仪表 | 8438篇 |
建筑科学 | 10503篇 |
矿业工程 | 6090篇 |
能源动力 | 4075篇 |
轻工业 | 4115篇 |
水利工程 | 3619篇 |
石油天然气 | 8307篇 |
武器工业 | 1500篇 |
无线电 | 4824篇 |
一般工业技术 | 8985篇 |
冶金工业 | 3204篇 |
原子能技术 | 977篇 |
自动化技术 | 11933篇 |
出版年
2024年 | 453篇 |
2023年 | 1289篇 |
2022年 | 2466篇 |
2021年 | 2866篇 |
2020年 | 3129篇 |
2019年 | 2527篇 |
2018年 | 2490篇 |
2017年 | 3092篇 |
2016年 | 3500篇 |
2015年 | 3609篇 |
2014年 | 5658篇 |
2013年 | 5694篇 |
2012年 | 7188篇 |
2011年 | 7284篇 |
2010年 | 5399篇 |
2009年 | 5291篇 |
2008年 | 4894篇 |
2007年 | 6122篇 |
2006年 | 5588篇 |
2005年 | 4674篇 |
2004年 | 3987篇 |
2003年 | 3295篇 |
2002年 | 2788篇 |
2001年 | 2491篇 |
2000年 | 2157篇 |
1999年 | 1708篇 |
1998年 | 1420篇 |
1997年 | 1230篇 |
1996年 | 978篇 |
1995年 | 856篇 |
1994年 | 744篇 |
1993年 | 464篇 |
1992年 | 386篇 |
1991年 | 327篇 |
1990年 | 257篇 |
1989年 | 247篇 |
1988年 | 158篇 |
1987年 | 105篇 |
1986年 | 67篇 |
1985年 | 75篇 |
1984年 | 49篇 |
1983年 | 37篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 37篇 |
1979年 | 37篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1959年 | 17篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
G. N. Churilov R. B. Weisman N. V. Bulina N. G. Vnukova A. P. Puzir L. A. Solovyov S. M. Bachilo D. A. Tsyboulski G. A. Glushenko 《Fullerenes, Nanotubes and Carbon Nanostructures》2003,11(4):371-382
The addition of metallic Ir and Pt to a fullerene-forming, atmospheric-pressure plasma reactor was found to influence the generation of carbonaceous products. It was observed that the added metals were efficiently dispersed into the plasma and that their presence increased the yield of fullerenes. The addition of Ir led to a noticeable shift in the fullerene distribution towards C60, whereas the addition of Pt increased the proportion of C60 oxides and decreased the proportion of higher fullerenes. Addition of Ir also caused a reduction of the soot particle size and the formation of a considerable quantity of carbon nanotubes. 相似文献
22.
Specific interactions in blends containing Chitosan and functionalized polymers. Molecular dynamics simulations 总被引:2,自引:0,他引:2
Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH2OH or -NH2, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases. 相似文献
23.
本文主要介绍了在动态汽车衡的试验过程中不确定度来源,并以动态试验为例重点介绍了计算各分量的标准不确定度、合成标准不确定度以及扩展不确定度的方法. 相似文献
24.
26.
N. A. Kochetov B. S. Seplyarskii S. G. Vadchenko 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(3):206-209
Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N2-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed
to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.
相似文献
27.
28.
储层压力与天然气分布关系——以鄂北塔巴庙地区上古生界储层为例 总被引:2,自引:0,他引:2
通过分析塔巴庙地区储层压力的分布特征,建立了研究区泥岩压实曲线,并对影响和控制该区储层压力的主要因素和机理进行了探讨,对“欠压实”剩余压力、生气增压、抬升引起的降压进行了定量计算。分析结果表明,晚三叠-早白垩世末“欠压实”作用和晚侏罗-早白垩世末烃源岩大量生烃作用使塔巴庙地区上古生界形成异常高压;晚白垩系构造抬升降压,使得现今储层为正常-低异常压力。同时证实了“欠压实”对天然气有压力封盖作用,天然气都分布在最大“欠压实”幅度以下的储层当中。烃源岩生气高峰为晚侏罗-早白垩世末,但天然气大规模运移是在晚白垩世,方向以沿过剩压力梯度降低较快的方向(太原-山西组至下石盒子组)垂向运移,通道主要为裂缝,运移的动力主要为异常高压。由于储层致密,聚集成藏能量有限,造成天然气充注不足、气水分异不好、含气饱和度低。 相似文献
29.
从控制和保证压力容器类焊接产品质量角度出发,通过分析其在制造过程中每道工序可能出现的质量问题,总结出这类产品在制造过程质量分析的要领及内容,提出了质量控制的关键,为制定焊接检验方案提供依据。 相似文献
30.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献