全文获取类型
收费全文 | 72673篇 |
免费 | 6323篇 |
国内免费 | 3263篇 |
专业分类
电工技术 | 4033篇 |
技术理论 | 7篇 |
综合类 | 4929篇 |
化学工业 | 12233篇 |
金属工艺 | 4406篇 |
机械仪表 | 4440篇 |
建筑科学 | 5612篇 |
矿业工程 | 2581篇 |
能源动力 | 2188篇 |
轻工业 | 4707篇 |
水利工程 | 1318篇 |
石油天然气 | 5056篇 |
武器工业 | 568篇 |
无线电 | 7696篇 |
一般工业技术 | 8514篇 |
冶金工业 | 3799篇 |
原子能技术 | 840篇 |
自动化技术 | 9332篇 |
出版年
2024年 | 316篇 |
2023年 | 1247篇 |
2022年 | 2211篇 |
2021年 | 3056篇 |
2020年 | 2304篇 |
2019年 | 1997篇 |
2018年 | 2209篇 |
2017年 | 2481篇 |
2016年 | 2222篇 |
2015年 | 2939篇 |
2014年 | 3653篇 |
2013年 | 4201篇 |
2012年 | 4466篇 |
2011年 | 4888篇 |
2010年 | 4447篇 |
2009年 | 3963篇 |
2008年 | 3931篇 |
2007年 | 3808篇 |
2006年 | 3819篇 |
2005年 | 3255篇 |
2004年 | 2338篇 |
2003年 | 2393篇 |
2002年 | 2685篇 |
2001年 | 2255篇 |
2000年 | 1789篇 |
1999年 | 1876篇 |
1998年 | 1390篇 |
1997年 | 1172篇 |
1996年 | 1196篇 |
1995年 | 914篇 |
1994年 | 684篇 |
1993年 | 511篇 |
1992年 | 408篇 |
1991年 | 296篇 |
1990年 | 227篇 |
1989年 | 180篇 |
1988年 | 163篇 |
1987年 | 96篇 |
1986年 | 72篇 |
1985年 | 42篇 |
1984年 | 47篇 |
1983年 | 29篇 |
1982年 | 30篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Neural Processing Letters - This paper discusses the global exponential stability for a class of hybrid non-autonomous neural networks (HNNNs) with Markovian switching, which includes the factors... 相似文献
62.
63.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
64.
Natural Computing - The fiber stretching process plays the key role in the process of fiber production and its effects is measured by the stretching ratio. The stretching ratio is determined by the... 相似文献
65.
66.
气烟囱效应——礁滩相岩性气藏的典型地震响应特征 总被引:14,自引:0,他引:14
品质良好的地震剖面上出现的地震模糊带称为气烟囱,发现和识别气烟囱是寻找大型气藏的有效方法。四川盆地东北部长兴组气藏是礁滩相岩性气藏,礁、滩作为一个独立的岩性体,与周围的地层、岩性结构差异较大,由此在构造应力场中形成力学尖点,从而产生气烟囱效应。已知的黄龙场、普光等气田,其气烟囱普遍存在。点礁通常形成下方的气烟囱,台缘礁通常在上方形成气烟囱;礁滩相在构造运动中控制了断层的发育过程,凸起的礁滩相上方可能发育对冲断层;斜坡较陡的台缘礁可能发育叠置的逆冲断层;礁、滩两侧边缘的断层一般都比较发育。断层发育加强了气烟囱效应。模拟试验验证了地震剖面解释结果。根据气烟囱地震相特征,预测黑池梁存在一个大型气藏。 相似文献
67.
We extend the definition of the classical Jacobi polynomials withindexes α, β>−1 to allow α and/or β to be negative integers. We show that the generalized Jacobi polynomials, with indexes corresponding to the number of boundary conditions in a given partial differential equation, are the natural basis functions for the spectral approximation of this partial differential equation. Moreover, the use of generalized Jacobi polynomials leads to much simplified analysis, more precise error estimates and well conditioned algorithms.Mathematics subject classification 1991. 65N35, 65N22, 65F05, 35J05 相似文献
68.
Feng Juanni Guo Xuefeng Xu Chunjie Zhang Zhongming 《中国稀土学报(英文版)》2006,24(1):120-120
As-east mierostruetures and their distribution of Mg-Zn-Y ternary alloy with high magnesium, low zinc and yttrium were examined using Nikon Epiphot optical microscopy (OM), RigakuD/max-3C X- ray diffraetion (XRD), and JEOL JSM-6700F scanning electron microscopy (SEM) equipped with an energydispersive X-ray spectroscopy (EDS). In the as-east mierostructures, Yttrium and zinc tend to segregate at grain boundaries, 相似文献
69.
Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(t, γ), shows a decreasing trend with step strain. The experimental results indicate that G(t, γ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(t, γ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(t, γ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior. 相似文献
70.
水工混凝土修补技术应用 总被引:1,自引:0,他引:1
针对水工混凝土的老化病害,介绍了不同类型修补材料的特点、性能、适用范围,以及修补技术应用中的一些实例和经验。 相似文献