全文获取类型
收费全文 | 10171篇 |
免费 | 1351篇 |
国内免费 | 672篇 |
专业分类
电工技术 | 845篇 |
综合类 | 803篇 |
化学工业 | 1591篇 |
金属工艺 | 487篇 |
机械仪表 | 563篇 |
建筑科学 | 966篇 |
矿业工程 | 294篇 |
能源动力 | 298篇 |
轻工业 | 1073篇 |
水利工程 | 291篇 |
石油天然气 | 431篇 |
武器工业 | 107篇 |
无线电 | 1226篇 |
一般工业技术 | 1113篇 |
冶金工业 | 345篇 |
原子能技术 | 118篇 |
自动化技术 | 1643篇 |
出版年
2024年 | 104篇 |
2023年 | 279篇 |
2022年 | 547篇 |
2021年 | 698篇 |
2020年 | 486篇 |
2019年 | 424篇 |
2018年 | 444篇 |
2017年 | 447篇 |
2016年 | 407篇 |
2015年 | 552篇 |
2014年 | 677篇 |
2013年 | 673篇 |
2012年 | 738篇 |
2011年 | 800篇 |
2010年 | 701篇 |
2009年 | 648篇 |
2008年 | 586篇 |
2007年 | 511篇 |
2006年 | 485篇 |
2005年 | 367篇 |
2004年 | 285篇 |
2003年 | 219篇 |
2002年 | 223篇 |
2001年 | 211篇 |
2000年 | 116篇 |
1999年 | 142篇 |
1998年 | 75篇 |
1997年 | 76篇 |
1996年 | 66篇 |
1995年 | 51篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1959年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A new type of modified bismaleimide resin was obtained by copolymerization between tris(allylphenoxy)triazine monomer (TAPT) and an aromatic diamine‐chain‐extension bismaleimide [e.g., 4,4′‐diaminodiphenylmethane (DADPM)‐chain‐extension 4,4′‐bismaleimidodiphenylmethane (BMDPM)]. The new three‐component‐polymer system had good processibility and mechanical properties. Better results were obtained when the weight ratio of TAPT to the DADPM‐chain‐extension BMDPM resin was 30%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 475–480, 2004 相似文献
42.
Association Link Network (ALN) is a kind of Semantic Link Network built by mining the association relations among multimedia Web resources for effectively supporting Web intelligent application such as Web-based learning, and semantic search. This paper explores the Small-World properties of ALN to provide theoretical support for association learning (i.e., a simple idea of “learning from Web resources”). First, a filtering algorithm of ALN is proposed to generate the filtered status of ALN, aiming to observe the Small-World properties of ALN at given network size and filtering parameter. Comparison of the Small-World properties between ALN and random graph shows that ALN reveals prominent Small-World characteristic. Then, we investigate the evolution of Small-World properties over time at several incremental network sizes. The average path length of ALN scales with the network size, while clustering coefficient of ALN is independent of the network size. And we find that ALN has smaller average path length and higher clustering coefficient than WWW at the same network size and network average degree. After that, based on the Small-World characteristic of ALN, we present an Association Learning Model (ALM), which can efficiently provide association learning of Web resources in breadth or depth for learners. 相似文献
43.
Xuan Wang 《Asian journal of control》2014,16(6):1713-1725
Fault occurrence can be embodied by the physical parameter variations of the hydraulic servo system. Faults can, therefore, be diagnosed according to the model coefficient variations of the hydraulic servo system. This paper proposes an approach for fault diagnosis based on the unscented Kalman filter (UKF) with a mathematical model of the hydraulic servo system. The mathematical model is established using the dynamic equations of the hydraulic servo system. Based on the fault mechanism analysis results, several important system model parameters that can separately represent different faults in different components of the hydraulic servo system are chosen. Discrete state space equations are derived from the dynamic equations. The UKF algorithm is used to estimate the important system model parameters of the hydraulic servo system by utilizing the discretized state space model. According to the variations of these model parameters, the fault modes and locations of the hydraulic servo system can be diagnosed and isolated. Two types of faults, namely, abrupt fault in servovalve gain and slow wear fault in hydraulic cylinder piston, which cannot be directly detected from the system output, are introduced individually to the hydraulic servo system in this work. By comparing with the extended Kalman Filter, three different experimental cases are used to validate the effectiveness of the UKF for hydraulic servo system fault diagnosis. 相似文献
44.
45.
Jianying Yu Lin Wang Xuan Zeng Shaopeng Wu Bin Li 《Polymer Engineering and Science》2007,47(9):1289-1295
Clay/styrene–butadiene–styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na‐MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na‐MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na‐MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high‐temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289–1295, 2007. © 2007 Society of Plastics Engineers 相似文献
46.
47.
IPv6/IPv4共存环境下多址同源识别是共存网络管理与拓扑发现的一个关键问题。现有研究主要集中于子网内部的双栈发现及单一IP协议栈中的别名解析,难以识别远程IPv6/IPv4共存网络中的多址同源。通过分析同源地址间的本质联系,提出一种IPv6/IPv4多址同源识别模型(SSI),该模型综合利用特殊地址格式匹配、TCP时钟指纹比对和上层协议短时致瘫等多种方式来提高同源地址的识别能力。实验结果表明,上述方法均可有效识别IPv6/IPv4多址同源;SSI模型具有较理想的识别率和正确率。 相似文献
48.
49.
Nianxue Song Zhengqian Xuan Jonathan K. Bartley Stuart H. Taylor David Chadwick Graham J. Hutchings 《Catalysis Letters》2006,106(3-4):127-131
The use of a periodic flow reactor is described for the oxidation of butane to maleic anhydride to compare the catalytic performance
of vanadium phosphate catalysts operating under aerobic and anaerobic conditions. It is found that for the catalyst prepared
via a standard VPO method, operation in the absence of oxygen leads to a very small enhancement in selectivity when butane
concentrations in the range 0.9–2.9% are used. Operation in the absence of oxygen leads to very small differences in conversion
such that the overall yield is enhanced and this effect is maximised for reactor feeds containing 1.5% butane. However, the
enhancement is negligible when the catalyst is operated at high conversion required for commercial operation, indicating that
reactors operating with continuous flow with aerobic conditions are preferred. Similar experiments are conducted for a catalyst
prepared by the VPD method and, in contrast, this catalyst gives lower butane conversion and maleic anhydride selectivity
when operated in the absence of oxygen. 相似文献
50.