全文获取类型
收费全文 | 57964篇 |
免费 | 4827篇 |
国内免费 | 2576篇 |
专业分类
电工技术 | 3587篇 |
技术理论 | 3篇 |
综合类 | 3956篇 |
化学工业 | 9623篇 |
金属工艺 | 3342篇 |
机械仪表 | 3831篇 |
建筑科学 | 4563篇 |
矿业工程 | 1825篇 |
能源动力 | 1678篇 |
轻工业 | 3796篇 |
水利工程 | 1042篇 |
石油天然气 | 3933篇 |
武器工业 | 524篇 |
无线电 | 6276篇 |
一般工业技术 | 6962篇 |
冶金工业 | 2627篇 |
原子能技术 | 585篇 |
自动化技术 | 7214篇 |
出版年
2024年 | 262篇 |
2023年 | 1041篇 |
2022年 | 1774篇 |
2021年 | 2419篇 |
2020年 | 1946篇 |
2019年 | 1573篇 |
2018年 | 1734篇 |
2017年 | 1928篇 |
2016年 | 1669篇 |
2015年 | 2284篇 |
2014年 | 2963篇 |
2013年 | 3301篇 |
2012年 | 3591篇 |
2011年 | 4044篇 |
2010年 | 3502篇 |
2009年 | 3279篇 |
2008年 | 3216篇 |
2007年 | 2979篇 |
2006年 | 3071篇 |
2005年 | 2563篇 |
2004年 | 1845篇 |
2003年 | 1631篇 |
2002年 | 1609篇 |
2001年 | 1392篇 |
2000年 | 1294篇 |
1999年 | 1527篇 |
1998年 | 1285篇 |
1997年 | 1120篇 |
1996年 | 1014篇 |
1995年 | 828篇 |
1994年 | 665篇 |
1993年 | 481篇 |
1992年 | 422篇 |
1991年 | 264篇 |
1990年 | 213篇 |
1989年 | 165篇 |
1988年 | 122篇 |
1987年 | 82篇 |
1986年 | 70篇 |
1985年 | 44篇 |
1984年 | 35篇 |
1983年 | 32篇 |
1982年 | 31篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1940年 | 3篇 |
1933年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Wei-Jun Liu Wei-Dong He Xue-Wu Ge Hua-Rong Liu Mo-Zheng Wang Zheng-Qi Chang 《Materials Letters》2007,61(13):2818-2821
Interfacial-initiated polymerization of styrene (St) was carried out in inversed emulsion with cumene hydroperoxide (CHPO) and ferrous sulfate (FeSO4)/disodium ethylenediaminetetraacetate (NaEDTA)/sodium formaldehyde sulfoxylate (SFS) as the redox initiation system. The water-soluble Fe2+-NaEDTA-SFS acted as the reducing component and the oil-soluble CHPO as the oxidant component of the redox initiation system. Therefore, the primary radicals were produced mainly at the oil/water interface to initiate the polymerization of St. Thus, sub-micrometer hollow polystyrene (PSt) spheres were obtained by one-stage polymerization, which was supported by the techniques of transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). 相似文献
102.
《钢结构工程施工质量验收规范》修订简介 总被引:1,自引:1,他引:0
简要介绍《钢结构工程施工质量验收规范》(GB 5 0 2 0 5 - 2 0 0 1)的修订原则、方法以及对原规范进行修订中新增加的内容及要求 ,并进行了详细解释 ,以便于对新规范的理解 相似文献
103.
104.
In this study, nanocrystalline Ni powders and thermally sprayed coatings, containing ultrafine AlN particles, were synthesized
and characterized. The results indicated that the presence of AlN particles in the powders drastically decreased the dimension
of agglomerates formed by cryomilling and increased the surface roughness of the agglomerates. The AlN phase was broken down
into ultrafine particles of approximately 30 nm in size. These particles were dispersed in the Ni matrix and enhanced the
development of a nanocrystalline structure in the Ni matrix during cryomilling. Selected-area diffraction patterns, obtained
from transmission electron microscopy (TEM) and X-ray mapping with scanning electron microscopy (SEM), confirmed the presence
of AlN particles in the coatings. The presence of AlN particles also led to an increase in the amount of NiO phase that was
distributed in the coating, in the form of ultrafine, round particles. AlN particles increased the microhardness of the Ni
coating by approximately 60 pct. Indentation-fracture results also indicated that the fine, dispersed AlN particles raised
the apparent toughness of the Ni coating. The synthesized Ni coatings containing ultrafine AlN particles were characterized
as equiaxed nanocrystalline grains with an average size of 24 nm, in which twins were observed. The increase in microhardness
resulted from both grain refinement and the presence of ultrafine particles. The latter played the primary role in strengthening. 相似文献
105.
Convergence of simultaneous perturbation stochastic approximation for nondifferentiable optimization 总被引:1,自引:0,他引:1
We consider simultaneous perturbation stochastic approximation for function minimization. The standard assumption for convergence is that the function be three times differentiable, although weaker assumptions have been used for special cases. However, all work that we are aware of at least requires differentiability. We relax the differentiability requirement and prove convergence using convex analysis. 相似文献
106.
M. Liu Q. Fang G. He L.Q. Zhu S.S. Pan L.D. Zhang 《Materials Science in Semiconductor Processing》2006,9(6):876
High-k HfOxNy thin films have been grown by radio frequency (rf) reactive sputtering of metal Hf target in N2/Ar/O2 ambient at different substrate temperatures. The chemical compositions of the films have been investigated as a function of substrate temperature by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that nitrogen concentration increases with an increase in substrate temperature. Room-temperature spectroscopic ellipsometry (SE) with photon energy 0.75–6.5 eV was used to investigate the optical properties of the films. SE results demonstrated that refractive index n increases with an increase in substrate temperature. Based on TL parameters which were obtained from the best fit results used in a simulation of the measured spectra, meanwhile, we conclude that the energy band gap (Eg) decreases with an increase in substrate temperature. 相似文献
107.
多排数翅片管空冷器风阻特性的数值模拟 总被引:1,自引:0,他引:1
本文对多排数翅片管空冷器空气侧的风阻特性进行了数值模拟.利用商用软件Fluent进行数值计算,结合经验公式和已有的实验数据,分析了不同入口风速下,阻力的变化规律以及流动阻力和温度变化对模拟计算的影响. 相似文献
108.
109.
阐述了ADSLMODEM远程管理的意义及应遵循的原则,并对远程管理的方案作了简要阐述,最后比较分析了不同方案的优缺点。 相似文献
110.
本文介绍了离子束混合工艺方法。与直接注入相比较,离子束混合所使用的设备造价低1/4—1/2,而生产效率可提高1—2个数量级,因而使生产成本大幅度降低,这无疑对离子束工艺的实际应用将产生巨大的促进作用。 通过对轴承材料(GCr15和Cr4Mo4V)经Cr、N、Ta不同元素的混合处理后,在0.5M H_2SO_4和0.1M NaCl的缓冲溶液中的阳极极化曲线表明经混合处理后的两种材料试样,其抗蚀能力和抗点蚀能力均大大提高,这与直接注入的试样效果是一致的。 通过俄歇谱仪和透射电镜的分析结果表明混合是成功的,且在一定的条件下,形成非晶组织。 本文的结论是,无论是离子的直接注入还是离子束混合,对提高轴承材料的抗腐蚀性能都是有效的方法,特别是离子束混合技术具有更大的应用前景。 相似文献