全文获取类型
收费全文 | 49516篇 |
免费 | 5536篇 |
国内免费 | 2235篇 |
专业分类
电工技术 | 1506篇 |
技术理论 | 9篇 |
综合类 | 2826篇 |
化学工业 | 18646篇 |
金属工艺 | 3152篇 |
机械仪表 | 1039篇 |
建筑科学 | 2856篇 |
矿业工程 | 1013篇 |
能源动力 | 4043篇 |
轻工业 | 2918篇 |
水利工程 | 321篇 |
石油天然气 | 2502篇 |
武器工业 | 169篇 |
无线电 | 2184篇 |
一般工业技术 | 9582篇 |
冶金工业 | 3327篇 |
原子能技术 | 524篇 |
自动化技术 | 670篇 |
出版年
2024年 | 275篇 |
2023年 | 1145篇 |
2022年 | 1618篇 |
2021年 | 1739篇 |
2020年 | 1882篇 |
2019年 | 1733篇 |
2018年 | 1633篇 |
2017年 | 1836篇 |
2016年 | 1927篇 |
2015年 | 1803篇 |
2014年 | 2795篇 |
2013年 | 3058篇 |
2012年 | 3463篇 |
2011年 | 4107篇 |
2010年 | 2990篇 |
2009年 | 3046篇 |
2008年 | 2392篇 |
2007年 | 2975篇 |
2006年 | 2888篇 |
2005年 | 2391篇 |
2004年 | 2054篇 |
2003年 | 1826篇 |
2002年 | 1445篇 |
2001年 | 1088篇 |
2000年 | 983篇 |
1999年 | 764篇 |
1998年 | 676篇 |
1997年 | 487篇 |
1996年 | 437篇 |
1995年 | 339篇 |
1994年 | 306篇 |
1993年 | 218篇 |
1992年 | 173篇 |
1991年 | 155篇 |
1990年 | 131篇 |
1989年 | 76篇 |
1988年 | 57篇 |
1987年 | 58篇 |
1986年 | 41篇 |
1985年 | 67篇 |
1984年 | 57篇 |
1983年 | 50篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1959年 | 5篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
The aim of this research is to investigate how ammonia treatment of the surface can influence the activity of a viscose-based activated carbon cloth (ACC) for the oxidative retention of H2S and SO2 in humid air at 25 °C. Surface basic nitrogen groups were introduced either by treatment with ammonia/air at 300 °C or with ammonia/steam at 800 °C. The pore structure of the samples so prepared was examined by adsorption measurements. Changes in the surface chemistry were assessed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and temperature programmed desorption (TPD). The change of ACC activity could not be merely attributed to surface nitrogen groups but to other changes in the support. Ammonia/steam treatment improved ACC performance the most, not only by introducing nitrogen surface groups, but also by extending the microporosity and by modifying the distribution of surface oxygen groups. Successive adsorption-regeneration cycles showed important differences between oxidative retention of H2S and SO2 and the subsequent catalyst/support regeneration process. 相似文献
52.
孙伟成 《兵器材料科学与工程》2003,26(3):59-62
综述了纳米晶体材料和纳米碳管材料的力学性能研究的最新进展。实验数据表明纳米晶体材料的强度与其晶粒尺寸大小的关系并不遵循Hall-Petch方程。相对于常规晶体材料 ,纳米材料的超塑性发生在更低的温度和更高的应变速率下。理论计算和实验数据表明 :纳米碳管是一种有着高刚性、高强度、高韧性和低密度的材料。纳米晶体材料和纳米碳管的异常的力学性能已经有了一些应用实例 相似文献
53.
Min-Seok Park Vladislav P. Vislovskiy Jong-San Chang Yong-Gun Shul Jin S. Yoo Sang-Eon Park 《Catalysis Today》2003,87(1-4):205-212
Alumina-supported vanadium oxide, VOx/Al2O3, and binary vanadium–antimony oxides, VSbOx/Al2O3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by SBET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO2 pulse methods. VSbOx/Al2O3 exhibited enhanced catalytic activity and especially on-stream stability compared to VOx/Al2O3 catalyst. Incorporation of antimony into VOx/Al2O3 increased dispersion of active VOx species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V0.43Sb0.57Ox/Al2O3 system. 相似文献
54.
55.
56.
57.
Gerald Leach 《Energy Policy》1991,19(10):918-925
The UK differs from may other industrialized nations in that its carbon dioxide (CO2) emissions from energy use have declined in recent years despite relatively rapid economic growth. In all sectors but transport, substantial reductions have already occurred in the level of carbon emissions per unit of GDP output. At the same time, a number of official and unofficial studies have pointed out that the UK has one of the largest remaining potentials amongst comparable industrialized countries for achieving further CO2 reductions through the implementation of cost-effective energy efficiency and fuel switching measures. This paper discusses past and present patterns of energy use and carbons emissions in the UK. The analysis then examines historical trends in UK energy policy and presents policy options for further reducing the UK's energy-use and carbon emissions in the future. 相似文献
58.
Copper phthalocyanine as corrosion inhibitor for ASTM A606-4 steel in 16% hydrochloric acid 总被引:2,自引:0,他引:2
A study based on the corrosion inhibition properties of copper phthalocyanine is described. Coverage degrees of copper phthalocyanine (Cu-phcy) on ASTM-A606-4 steel, obtained by weight loss measurements, were fitted to Langmuir, Frumkin, Temkin and Flory–Huggins adsorption isotherms. A better fit to the Langmuir isotherm was obtained. The polarization curves showed that polarization of both the anodic and cathodic reactions were verified for concentrations higher than 10–4 M, indicating a mixed type action. Only the anodic reactions were polarized for lower concentrations. At high frequencies the Nyquist diagrams showed one capacitive loop attributable to double layer charging and a small one at intermediary frequencies attributable to the faradaic process of hydrogen evolution. The formation of an adsorbed film was characterized by increasing charge transfer resistance values in the low frequency range for increasing inhibitor concentrations. According to the techniques used in this study, copper phthalocyanines showed a high corrosion inhibiting efficiency for all concentrations. 相似文献
59.
C/O测井中采用同步测量技术来分析非弹性γ与俘获γ,但在一些MSI C/O测井中发现非弹性γ的一小部分或一大部分超前于非弹性门而进入俘获门,我们把这一问题叫做“错位”。“错位”使得C/O的CI值不正常,测井曲线不合格。这样的仪器不能用来测井。吉林油田测井公司碳氧比维修班成功地解决了C/O仪器“错位”等技术难题,在该油田所使用的CZF90-94-09发生器已测井88口,累计打靶时间230h,并且至今 相似文献
60.
本文利用可控平均冷却速度的单向凝固实验炉测定了45号钢在不同平均冷却速度下的冷却曲线,由此得到其在凝固期间的平均冷却速度R,相应地测量了不同平均冷却速度下试样的二次枝晶臂间距S2,通过回归,得到了如下关系式:S2=727R-0.41,并将引式成功地应用于实际生产中。 相似文献