全文获取类型
收费全文 | 7348篇 |
免费 | 799篇 |
国内免费 | 515篇 |
专业分类
电工技术 | 341篇 |
技术理论 | 3篇 |
综合类 | 1387篇 |
化学工业 | 535篇 |
金属工艺 | 222篇 |
机械仪表 | 292篇 |
建筑科学 | 860篇 |
矿业工程 | 797篇 |
能源动力 | 349篇 |
轻工业 | 214篇 |
水利工程 | 428篇 |
石油天然气 | 483篇 |
武器工业 | 274篇 |
无线电 | 327篇 |
一般工业技术 | 741篇 |
冶金工业 | 323篇 |
原子能技术 | 68篇 |
自动化技术 | 1018篇 |
出版年
2024年 | 29篇 |
2023年 | 85篇 |
2022年 | 221篇 |
2021年 | 252篇 |
2020年 | 291篇 |
2019年 | 237篇 |
2018年 | 194篇 |
2017年 | 250篇 |
2016年 | 277篇 |
2015年 | 263篇 |
2014年 | 434篇 |
2013年 | 491篇 |
2012年 | 534篇 |
2011年 | 537篇 |
2010年 | 416篇 |
2009年 | 478篇 |
2008年 | 421篇 |
2007年 | 469篇 |
2006年 | 449篇 |
2005年 | 389篇 |
2004年 | 316篇 |
2003年 | 244篇 |
2002年 | 228篇 |
2001年 | 176篇 |
2000年 | 174篇 |
1999年 | 142篇 |
1998年 | 92篇 |
1997年 | 92篇 |
1996年 | 80篇 |
1995年 | 77篇 |
1994年 | 57篇 |
1993年 | 41篇 |
1992年 | 40篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1966年 | 4篇 |
1963年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有8662条查询结果,搜索用时 15 毫秒
91.
Manish Roy 《Journal of Thermal Spray Technology》2002,11(3):393-399
The objective of the present work was to determine the dynamic hardness of WC-Co coatings from the dynamic hardness of the
coating substrate system. It was also the purpose of this work to evaluate the influence of coating composition, coating thickness,
and substrate materials on the dynamic hardness of the coating. To achieve the above-mentioned objectives, WC-12%Co and WC-17%Co
coatings were deposited by detonation spraying on three different substrate materials: mild steel, commercially pure (CP)
aluminum, and CP titanium. The dynamic hardness of the coating/substrate composite was evaluated by a drop weight system.
The dynamic hardness of the coating independent of the substrate was determined from the dynamic hardness of the coating/substrate
composite. 相似文献
92.
张鉴 《中国有色金属学会会刊》2004,14(2):345-350
Application of equations of mixing thermodynamic parameters formulated on the basis of the coexistence theory of metallic melts in Ba-Al, Mg-Al, Sr-Al and Cu-Al melts leads to fruitful results that not only the evaluated mass action concentrations agree well with the measured activities, but also the calculated mixing thermodynamic parameters are quite coincident with the experimental values. Moreover, the calculated mass action concentrations strictly obey the mass action law. The evaluated mixing thermodynamic parameters have very fine regularity: the mixing free energy is composed of standard free formation energies of all compounds and chemical potentials of all structural units at equilibrium; the mixing enthalpy consists of standard formation enthalpies of all compounds; the mixing entropy is composed of standard entropies of all compounds and configuration entropies of all structural units at equilibrium. As the equations of mixing thermodynamic parameters formulated are widely applicable to metallic melts involving compound formation, they can be used as the second practical criterion to determine whether thermodynamic models of metallic melts are correctly formulated. 相似文献
93.
94.
95.
粉末锻造是一种新型高性能的精密塑性成形技术,但其成形时的特殊性导致目前缺乏完善的、普遍适应的粉末锻造成形理论。通过对还原铁粉烧结多孔体预成形坯锻造镦粗成形致密实验,研究了不同初始相对密度、不同高径比、不同摩擦条件对预成形坯锻造镦粗成形、致密的影响规律。得到了粉末锻造镦粗的断裂极限准则,绘制出了断裂极限应变迹线,并着重分析了初始相对密度、高径比和摩擦因子对镦粗断裂极限的影响,确定了镦粗成形极限工艺参数曲线。实验研究结果为粉末锻造预成形坯与模具的设计、工艺参数的优化奠定了理论基础,并提供了有价值的实验数据。 相似文献
96.
提出了一种新颖的风能转换系统滑模主动容错控制策略.针对风能转换系统执行器故障,运用预测控制思想和迭代算法,设计了一种故障观测器.在设定的优化时域长度内,利用实际系统与故障观测器的输出差值,通过反复迭代运算,不断地对虚拟故障信号进行调整,使其能有效地拟合实际系统执行器故障,并根据故障观测值实时调整滑模容错控制器结构.未发生故障时,故障观测值为零,系统在滑模控制器控制下稳定运行;执行器发生故障时,运用故障观测值实时调整滑模容错控制项,并用双曲正切函数代替符号函数,消除抖动.仿真实验结果表明,滑模容错控制器下的系统具有良好的容错能力,提高了风能转换系统最大风能捕获效率. 相似文献
97.
In 1980s, Robert Metcalfe, the inventor of Ethernet, proposed a formulation of network value in terms of the network size (the number of nodes of the network), which was later named as Metcalfe’s law. ... 相似文献
98.
99.
In this paper, a novel reaching law for discrete‐time variable structure systems is proposed. It ensures that the representative point (state) of the controlled plant approaches the switching plane in finite time and then crosses it in every subsequent step. Moreover, the proposed reaching law ensures that for the nominal plant the absolute value of the sliding variable asymptotically decreases to zero, and for the perturbed plant, it converges to a smaller interval around zero than with the application of previously proposed reaching laws. The control method proposed in this paper guarantees asymptotic stability of the nominal system and uniform ultimate boundedness of the perturbed one. Furthermore, the method ensures that the sliding variable rate of change (i.e. the difference between its values at any two subsequent sampling instants) is bounded by design parameters, which do not depend on the system initial conditions. This is a highly desirable property, as it results in a priori specified, ‘almost’ constant convergence rate of the sliding variable when the system state is far off the switching plane and helps enforce state constraints in the system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
100.
Jong‐Ju Hong Seungjun Shin Woo‐Jin Song Kyung Joon Kwon Seong Gyun Kim 《Journal of the Society for Information Display》2016,24(1):44-56
The impression of quality of images can be enhanced on a high dynamic range (HDR) displays. Generally, a conventional 8‐bit image can be processed to an HDR image by inverse tone mapping operators. Among the operators, brightness discrimination mapping by applying brightness adaptation model attempted to mimic the human visual system. In this paper, we use a brightness adaptation model to derive a brightness discrimination mapping algorithm for HDR displays. The proposed algorithm maximizes a function, which represents the local and global brightness discrimination range by exploiting characteristics of the human visual system. Enhancement of details is verified by visualizing HDR images from dark to bright regions. Improvement of dynamic range is quantified by measuring increased discrimination ratio. 相似文献