全文获取类型
收费全文 | 1576篇 |
免费 | 142篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 14篇 |
综合类 | 68篇 |
化学工业 | 554篇 |
金属工艺 | 352篇 |
机械仪表 | 34篇 |
建筑科学 | 13篇 |
矿业工程 | 39篇 |
能源动力 | 30篇 |
轻工业 | 28篇 |
水利工程 | 2篇 |
石油天然气 | 79篇 |
武器工业 | 15篇 |
无线电 | 40篇 |
一般工业技术 | 194篇 |
冶金工业 | 179篇 |
原子能技术 | 154篇 |
自动化技术 | 34篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 44篇 |
2021年 | 61篇 |
2020年 | 60篇 |
2019年 | 55篇 |
2018年 | 61篇 |
2017年 | 65篇 |
2016年 | 47篇 |
2015年 | 64篇 |
2014年 | 73篇 |
2013年 | 167篇 |
2012年 | 119篇 |
2011年 | 101篇 |
2010年 | 65篇 |
2009年 | 90篇 |
2008年 | 61篇 |
2007年 | 100篇 |
2006年 | 77篇 |
2005年 | 72篇 |
2004年 | 65篇 |
2003年 | 47篇 |
2002年 | 59篇 |
2001年 | 46篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1976年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有1829条查询结果,搜索用时 15 毫秒
51.
Dmitri V. Besedin Leila Yu. Ustynyuk Yuri A. Ustynyuk Valerij V. Lunin 《Topics in Catalysis》2005,32(1-2):47-60
The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes (propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (Si–O)3ZrIVH, (Si–O)2ZrIVH2, and (Si–O)2ZrIIIH were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (Si–O)3ZrH, and dihydrides, (Si–O)2ZrH2. Cleavage of linear alkanes on the monohydrides (Si–O)3ZrH is thermodynamically unfavorable; however, the dihydrides (Si–O)2ZrH2 can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (Si–O)2ZrIIIH, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes. 相似文献
52.
53.
一种酸性压裂液研制及其性能评价 总被引:2,自引:0,他引:2
针对低渗透、碱敏性储层,研制了一种以有机锆为交联剂,羧甲基羟丙基胍胶为增稠剂的酸性压裂液体系,并对压裂液相关性能进行了系统评价。实验结果表明,当增稠剂溶液浓度为0.4%,交联比为100∶2,破胶剂加量为0.06%时,与压裂液助剂粘土稳定剂、缓蚀剂、助排剂等配制的压裂液破胶液粘度为1.013 mPa.s,残渣含量为261 mg/L,防膨率为90.5%,表面张力为27.6 mN/m,平均缓蚀速率为0.826 g/(h.m2),在90℃下滤失速率为0.575×10-5 m/min0.5,对储层的伤害率小于15%。 相似文献
54.
55.
56.
Novel and Ideal Zirconium-Based Dense Membrane Reactors for Partial Oxidation of Methane to Syngas 总被引:5,自引:0,他引:5
A novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo0.4Fe0.4Zr0.2O3– and the catalyst of LiLaNiO/-Al2O3. The POM reaction was performed successfully. Not only was a short induction period of 2 h obtained, but also a high catalytic performance of 96–98% CH4 conversion, 98–99% CO selectivity and an oxygen permeation flux of 5.4–5.8 mlcm–2min–1 (1.9–2.0 molm–2S–1Pa–1) at 850°C were achieved. Moreover, the reaction has been steadily carried out for more than 2200 h, and no interaction between the membrane material and the catalyst took place. 相似文献
57.
水热法制备ZrO_2纳米微晶及对乙醇和丁烷气敏性研究 总被引:6,自引:0,他引:6
用水热法制备 Zr O2 纳米微晶的平均尺寸为直径 5 nm,长 7.5 nm。由 X射线衍射确认晶相为单斜相。并对其形状和大小进行了透射电镜和激光散射分析 ,结果表明 Zr O2 纳米粒子在水溶液中存在软团聚 ,团聚体平均尺寸约 90 nm。着重研究了 Zr O2 纳米微晶对乙醇及丁烷的气敏性能 ,结果表明用纳米级 Zr O2 粒子制备的气敏元件对乙醇和丁烷有好的气敏性。并且随着纳米粒子尺寸降低 ,对气体敏感性增强 相似文献
58.
59.
本文介绍了一种测定锆英石中锆铪合量的EDTA络合滴定法,分析了标准样品及实际样品,并验证了该方法的可行性。结果表明,该方法准确、简单、可行性较强。 相似文献
60.
A. F. Y. Al-Shammary I. T. Caga A. Y. Tata J. M. Winterbottom I. R. Harris 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,55(4):361-367
Alloys of the general formula Zr50NixCO50-x, where 0 ≦x≧ 50, have been prepared and used in the temperature range 300–400°C, in the pressure range 1–9 barg in a microtubular reactor for the reaction of hydrogen with carbon monoxide to give hydrocarbons. The alloys or intermetallic materials were prepared by argon arc melting, powdered by hydrogen decrepitation and characterised by means of optical microscopy (metallography), scanning electron microscopy with surface analysis and magnetic susceptibility measurements. The selectivity towards higher hydrocarbons increased with (i) increase in the total pressure and (ii) decrease in hydrogen content of the feed gases. The kinetics were found to be of the form: where m = 1.0 ± 0.2 and n = 0. The apparent energy of activation (Ea) lay in the range of 80–130 kJ mole?1 and there appeared to be a compensation effect between Ea and the pre-exponential factor A. The turnover numbers for the reaction exhibited an activity maximum for alloys of composition around Zr50Ni40Co20 and Zr50Ni30Co20. Magnetic susceptibility measurements indicated that alloys changed their nature from moderately paramagnetic to strongly paramagnetic or even ferromagnetic after use and this is attributed to the conversion of zirconium to zirconium oxide during reaction with the attendant production of free 3d-transition metals. Derived catalysts prepared by air treatment of the hydrogen-decrepitated intermetallics behaved almost identically to the latter materials and gave similar magnetic susceptibility values to used hydrided materials. 相似文献