全文获取类型
收费全文 | 579771篇 |
免费 | 57088篇 |
国内免费 | 30018篇 |
专业分类
电工技术 | 96192篇 |
技术理论 | 55篇 |
综合类 | 56389篇 |
化学工业 | 54142篇 |
金属工艺 | 21759篇 |
机械仪表 | 37009篇 |
建筑科学 | 55253篇 |
矿业工程 | 25337篇 |
能源动力 | 23051篇 |
轻工业 | 28746篇 |
水利工程 | 21002篇 |
石油天然气 | 20338篇 |
武器工业 | 7490篇 |
无线电 | 57074篇 |
一般工业技术 | 37310篇 |
冶金工业 | 22020篇 |
原子能技术 | 6467篇 |
自动化技术 | 97243篇 |
出版年
2024年 | 1285篇 |
2023年 | 6933篇 |
2022年 | 12985篇 |
2021年 | 18582篇 |
2020年 | 16982篇 |
2019年 | 13221篇 |
2018年 | 12628篇 |
2017年 | 17087篇 |
2016年 | 21163篇 |
2015年 | 23788篇 |
2014年 | 39747篇 |
2013年 | 34790篇 |
2012年 | 43217篇 |
2011年 | 45636篇 |
2010年 | 34086篇 |
2009年 | 34363篇 |
2008年 | 33134篇 |
2007年 | 41407篇 |
2006年 | 37662篇 |
2005年 | 32892篇 |
2004年 | 26743篇 |
2003年 | 23525篇 |
2002年 | 18421篇 |
2001年 | 15240篇 |
2000年 | 12745篇 |
1999年 | 9894篇 |
1998年 | 7186篇 |
1997年 | 5976篇 |
1996年 | 5062篇 |
1995年 | 4286篇 |
1994年 | 3609篇 |
1993年 | 2535篇 |
1992年 | 2061篇 |
1991年 | 1494篇 |
1990年 | 1275篇 |
1989年 | 1094篇 |
1988年 | 720篇 |
1987年 | 480篇 |
1986年 | 361篇 |
1985年 | 395篇 |
1984年 | 358篇 |
1983年 | 291篇 |
1982年 | 223篇 |
1981年 | 184篇 |
1980年 | 192篇 |
1979年 | 118篇 |
1978年 | 78篇 |
1977年 | 66篇 |
1962年 | 76篇 |
1959年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 84 毫秒
101.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations. 相似文献
102.
This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations. 相似文献
103.
隐患采空区是目前影响露天开采矿山安全生产的主要危害源之一。随着台阶开采的不断剥离,露天开采境界内各台阶与地下空区群的隔离层厚度越来越薄,随时有可能发生采空区顶板坍塌事故。考虑到露天矿采空区地质赋存条件和围岩稳固性等特征,以弓长岭露天铁矿浅层采空区为工程背景,运用现场监测和数值模拟相结合的手段综合分析了浅层采空区的稳定性。将液体静力水准地表沉降监测系统的监测数据与FLAC数值模拟结果对比,调整蠕变参数使得数值模拟的蠕变速率与现场监测结果一致,而后据此进行未来结果的预测。最终根据地表沉降数据确定的蠕变参数取值为A=1.0×10^-12、m=1.75、n=0.35。研究表明:静力水准测点地表最大沉降位移为-9.8 mm,蠕变计算结果顶板最大垂直位移约20.4 mm,应力最大值约25 MPa,综合分析显示该采空区较稳定。上述研究提供了一种基于采空区现场监测数据的数值模拟蠕变分析方法,可为类似矿山采空区稳定性分析提供借鉴。 相似文献
104.
105.
106.
Ting Cui Ling Xu Feng Ding Ahmed Alsaedi Tasawar Hayat 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1658-1676
Parameter estimation plays an important role in the field of system control. This article is concerned with the parameter estimation methods for multivariable systems in the state-space form. For the sake of solving the identification complexity caused by a large number of parameters in multivariable systems, we decompose the original multivariable system into some subsystems containing fewer parameters and study identification algorithms to estimate the parameters of each subsystem. By taking the maximum likelihood criterion function as the fitness function of the differential evolution algorithm, we present a maximum likelihood-based differential evolution (ML-DE) algorithm for parameter estimation. To improve the parameter estimation accuracy, we introduce the adaptive mutation factor and the adaptive crossover factor into the ML-DE algorithm and propose a maximum likelihood-based adaptive differential evolution algorithm. The simulation study indicates the efficiency of the proposed algorithms. 相似文献
107.
通过河南省渑池地区含锂铝土矿(岩)层工艺矿物学分析,查明铝土矿的物质组成、嵌布特征、伴生锂分布特征和赋存状态,为矿产综合利用提供理论依据。结果显示:该铝土矿Al2O3含量为54.8%,铝硅比值(A/S)为2.6,铝土矿层和粘土岩层中Li2O含量均高于伴生锂边界品位,粘土岩中锂更为富集;矿物组成除一水硬铝石之外,主要是以集合体形态产出的粘土矿物。采用稀酸解析、选矿测试和电子探针分析锂的赋存状态,查明矿石中锂主要是以类质同象置换形式赋存在伊利石和高岭石等粘土矿物中;选矿富锂尾矿中Li2O可富集到0.57%左右,是锂综合回收利用的重点研究对象。 相似文献
108.
针对臂式斗轮取料机运行中抖动现象,进行了故障分析和排除,并对其液压原理和元件选型进行了优化及改进,为相关液压系统的故障分析和设计选型提供参考。 相似文献
109.
AbstractDifferent drying methods (spray drying (SD), vacuum drying (VD), microwave vacuum drying (MVD), and infrared vacuum drying (IFVD)) were applied in order to compare the hygroscopicity behavior of chicken powders. The hygroscopicity curves and glass transition temperature were used to evaluate the influence of ambient humidity and temperature on moisture absorption of powders. The results showed that the chicken powder dried by MVD had the lowest moisture absorption, followed by IFVD, VD, and SD. The hygroscopicity of SD chicken powders was different from other three kinds of chicken powders due to the physical properties of particles and the changes of protein secondary structure as detected by the Fourier transform-infrared spectrometer. For the three vacuum drying methods, the difference of protein secondary structure was the main reason of differences in hygroscopicity. Although MVD chicken powders were slightly inferior to SD chicken powders in taste, MVD chicken powders were the best in terms of smell and color as suggested by instrumental sensory parameter evaluations. It was found that MVD had a positive effect on reducing moisture absorption and maintaining sensory quality of chicken powders. 相似文献
110.
Dushyant Kumar 《分离科学与技术》2020,55(15):2844-2854
ABSTRACT In this study, electrocoagulation (EC) was used to determine the optimum conditions on the basis of maximum chemical oxygen demand (COD) and color removal. At the optimum conditions chlorophenols (CPs), biological oxygen demand and total organic carbon (TOC) were determined. The biodegradability of wastewater was increased significantly with 63% COD, 98% color, 61% TOC and overall 65.51% reductions in CPs. Further, the electro-coagulated sludge was characterized by using different analytical techniques to assist the physicochemical and elemental phases, to find-out better management option, reusability for plant growth and safe disposal. Additionally, aluminum content (70.62%) was successfully recovered from sludge. 相似文献