全文获取类型
收费全文 | 67574篇 |
免费 | 5830篇 |
国内免费 | 5625篇 |
专业分类
电工技术 | 1484篇 |
综合类 | 3431篇 |
化学工业 | 9987篇 |
金属工艺 | 28229篇 |
机械仪表 | 3495篇 |
建筑科学 | 1013篇 |
矿业工程 | 1490篇 |
能源动力 | 1428篇 |
轻工业 | 1731篇 |
水利工程 | 115篇 |
石油天然气 | 1226篇 |
武器工业 | 906篇 |
无线电 | 2563篇 |
一般工业技术 | 11588篇 |
冶金工业 | 7319篇 |
原子能技术 | 870篇 |
自动化技术 | 2154篇 |
出版年
2024年 | 249篇 |
2023年 | 1115篇 |
2022年 | 1912篇 |
2021年 | 2198篇 |
2020年 | 2275篇 |
2019年 | 1846篇 |
2018年 | 1805篇 |
2017年 | 2354篇 |
2016年 | 2215篇 |
2015年 | 2302篇 |
2014年 | 3316篇 |
2013年 | 3546篇 |
2012年 | 4173篇 |
2011年 | 5145篇 |
2010年 | 3863篇 |
2009年 | 4148篇 |
2008年 | 3441篇 |
2007年 | 4639篇 |
2006年 | 4611篇 |
2005年 | 3639篇 |
2004年 | 3187篇 |
2003年 | 2811篇 |
2002年 | 2360篇 |
2001年 | 2089篇 |
2000年 | 1747篇 |
1999年 | 1468篇 |
1998年 | 1073篇 |
1997年 | 978篇 |
1996年 | 932篇 |
1995年 | 733篇 |
1994年 | 620篇 |
1993年 | 449篇 |
1992年 | 417篇 |
1991年 | 333篇 |
1990年 | 280篇 |
1989年 | 240篇 |
1988年 | 151篇 |
1987年 | 73篇 |
1986年 | 44篇 |
1985年 | 30篇 |
1984年 | 43篇 |
1983年 | 21篇 |
1982年 | 32篇 |
1981年 | 38篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
991.
992.
Electrochemical Ni-Mo alloying of the surface of a nickel substrate was investigated using alternating pulsed electrolysis in an aqueous solution containing only molybdate ions (MoO42−) as a metal ion component. In this electrochemical process, the nickel substrate was slightly dissolved during the anodic pulses, providing nickel ions into the solution in the vicinity of the substrate, while Ni and Mo were both electrodeposited on the substrate surface during the subsequent cathodic pulses. Through the optimization of anodic and cathodic conditions independently based on a set of direct-current electrolysis data, amorphous Ni-Mo alloy layers were found to be formed at the surface of the nickel substrate by the alternating pulsed electrolysis using the MoO42− solution of pH 3.0-5.0. The conditions for Ni-Mo alloy formation were discussed in terms of the dissolving regime of ionic species in the electrolytes determined by an equilibrium calculation. 相似文献
993.
M. F. Gogulya M. N. Makhov M. A. Brazhnikov A. Yu. Dolgoborodov 《Combustion, Explosion, and Shock Waves》2006,42(4):480-485
The effect of the addition of Al on the detonation velocity of bis(2,2,2-trinitroethyl) nitramine (BTNEN) was studied experimentally.
It is shown that the dependence of the detonation velocity of BTNEN on the initial density is nearly linear, and a 75/25 BTNEN/Al
mixture is characterized by an increase in the slope of the dependence with increasing density. The addition of Al decreases
the detonation velocity of BTNEN. The density range characterized by a maximum decrease in the detonation velocity is determined.
A comparison of experimental detonation velocities of BTNEN/Al mixtures with literature data obtained by calculations taking
into account a possible change in the phase state of Al2O3 showed that the thermodynamic model used in the calculations needs to be improved.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 125–130, July–August, 2006. 相似文献
994.
林明德 《现代塑料加工应用》2002,14(2):1-4
介绍了日本三菱油化公司(现为三菱化学公司)BC-8嵌段聚丙烯的开发经过及实际结构。近年结构分析结果发现BC-8嵌段聚丙烯并非嵌段物,而是由均聚聚丙烯、EPR(乙丙橡胶)以及聚乙烯(链上有少量丙烯单元但并非嵌段物)三者组成的高分子合金。 相似文献
995.
介绍一种用尿素生产高氮磷肥的新工艺 ,分析该工艺的技术参数和影响因素。新工艺克服了过磷酸钙和尿素直接相混时会释放出结晶水的局限性 ,所得产品不仅可以作为复肥生产的原料 ,而且可以直接喷浆造粒生产NP复肥 ,因而具有良好的实用性 相似文献
996.
The paper presents a new method to synthesize β-Sialon bonded corundum brick(β-SBCB) from Al-Si alloy directly and easily under 1430℃,the volume expansion of reaction between Al powder and Nitrogen can help to establish the fast diffusion channel in Al-Si alloy;the suitable crystal seed of Si3N4 is helpful to the fast synthesis of β-Sialon. 相似文献
997.
Surface‐modified polypropylene (PP) films with thermally and photochemically sensitive copolymers consisting of N‐(2‐hydroxypropyl)methacrylamide (HPMA) and 4‐(4‐methoxyphenylazo)phenyl methacrylate (MPAP), poly(HPMA‐co‐MPAP)‐g‐PP (abbreviated g‐PP) film, were prepared by graft copolymerization with an Ar‐plasma postpolymerization technique. The surfaces of the g‐PP films were characterized by means of X‐ray photoelectron spectroscopy; the percentage grafting of poly(HPMA‐co‐MPAP) with a number‐average molecular weight of 3.28 × 104 was 7.12%, and the molar ratio of HPMA–MPAH in the copolymer was 0.75:0.25. The stimuli‐sensitive adsorption of albumin and polystyrene microspheres on the g‐PP film was also measured. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 143–148, 2003 相似文献
998.
999.
The different melting temperatures of N‐methyl morpholine N‐oxide (NMMO) hydrates in the cellulose–NMMO hydrate solution may be explained by the rather different crystal structures of NMMO hydrates, which are determined by the amount of the hydrates. The preparative process of cellulose–NMMO hydrate solution may result in cellulose structural change from cellulose I to cellulose II, depending on the amount of the hydrate. Mixtures of cellulose and NMMO hydrate in a blender was changed from the granules to slurry with increasing mixing time at 60–70°C, which is below the melting point of the NMMO hydrate. In the case of 15 wt % cellulose–NMMO hydrate granules, which were made by mixing for 20 min, the melting points of various NMMO hydrates were obtained as 77.8°C (n = 0.83), 70.2°C (n = 0.97), and 69.7°C (n = 1.23), respectively, depending on the hydrate number. However, the melting points of cellulose–NMMO hydrate slurry and solution were shifted lower than those of cellulose granules, while the mixing time of slurry and solution are 25 and 35 min, respectively. These melting behaviors indicate instantaneous liquefaction of the NMMO hydrate and the diffusion of the NMMO hydrate into cellulose during mixing in a blender. When cellulose was completely dissolved in NMMO hydrate, the crystal structure of cellulose showed only cellulose II structure. In the cellulose–NMMO products of granules or slurry obtained by high‐speed mixing, which is a new preparation method, they still retained the original cellulose I structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1687–1697, 2004 相似文献
1000.
氮化硅陶瓷高温摩擦学性能 总被引:1,自引:0,他引:1
本文研究热压氮化硅陶瓷与3Cr2W8V钢组成的销-盘摩擦副,在空气中非润滑条件下,400~800℃不同载荷(49~343N)的摩擦磨损性能;测定了磨擦系数和Si3N4销的磨损因子;通过对Si3N4磨损面的SEM形貌观察、X射线相结构分析,探讨了陶瓷销的磨损机理 相似文献