全文获取类型
收费全文 | 171459篇 |
免费 | 15298篇 |
国内免费 | 11094篇 |
专业分类
电工技术 | 29580篇 |
技术理论 | 7篇 |
综合类 | 16308篇 |
化学工业 | 8947篇 |
金属工艺 | 6579篇 |
机械仪表 | 16013篇 |
建筑科学 | 14956篇 |
矿业工程 | 6903篇 |
能源动力 | 4632篇 |
轻工业 | 4486篇 |
水利工程 | 5437篇 |
石油天然气 | 5593篇 |
武器工业 | 2638篇 |
无线电 | 12889篇 |
一般工业技术 | 7877篇 |
冶金工业 | 7465篇 |
原子能技术 | 1196篇 |
自动化技术 | 46345篇 |
出版年
2024年 | 252篇 |
2023年 | 1849篇 |
2022年 | 3042篇 |
2021年 | 3843篇 |
2020年 | 4609篇 |
2019年 | 3639篇 |
2018年 | 3246篇 |
2017年 | 4825篇 |
2016年 | 5393篇 |
2015年 | 6024篇 |
2014年 | 11542篇 |
2013年 | 9916篇 |
2012年 | 12597篇 |
2011年 | 13529篇 |
2010年 | 10237篇 |
2009年 | 10518篇 |
2008年 | 10504篇 |
2007年 | 12936篇 |
2006年 | 11585篇 |
2005年 | 10128篇 |
2004年 | 8387篇 |
2003年 | 7401篇 |
2002年 | 5925篇 |
2001年 | 4891篇 |
2000年 | 4151篇 |
1999年 | 3316篇 |
1998年 | 2524篇 |
1997年 | 2184篇 |
1996年 | 1761篇 |
1995年 | 1477篇 |
1994年 | 1262篇 |
1993年 | 900篇 |
1992年 | 723篇 |
1991年 | 545篇 |
1990年 | 415篇 |
1989年 | 366篇 |
1988年 | 258篇 |
1987年 | 152篇 |
1986年 | 111篇 |
1985年 | 109篇 |
1984年 | 154篇 |
1983年 | 118篇 |
1982年 | 113篇 |
1981年 | 79篇 |
1980年 | 53篇 |
1979年 | 64篇 |
1978年 | 48篇 |
1977年 | 48篇 |
1964年 | 13篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
91.
M.A. Santanna W.T. Menezes Y.V.B. Santana M.M. Ferrer A.F. Gouveia A.D. Faceto A.J. Terezo A.J.A. Oliveira E. Longo R.G. Freitas E.C. Pereira 《International Journal of Hydrogen Energy》2018,43(14):6838-6850
Ordered arrays of TiO2 nanotubes with smooth and rippled morphologies were prepared by one-step titanium oxidation in NH4F and ethylene glycol solution. The samples were then decorated with ZnS using a microwave-assisted solvothermal method. The experiments under constant or pulsed applied voltage resulted in smooth and rippled TiO2material morphologies, respectively. Field emission scanning electron microscopy, incident photon-to-current efficiency, linear sweep voltammetry and electrochemical impedance spectroscopy were used to investigate the structure and morphology of the TiO2 nanotubes, along with their photoelectrochemical activity in the water splitting reaction. An envelope function was proposed to correlate the anisotropic morphologies and broad distribution of mobility due to the random nature of charge carrier transport. The smooth and rippled morphologies were evaluated using the transmission line model. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level are conducted to obtain a better understanding of optical properties of TiO2. 相似文献
92.
Henrik Szentes 《Construction Management & Economics》2018,36(3):125-140
In recent years, scholars have shown a growing interest in combining control and flexibility when organizing and managing large construction projects, in contrast with the traditional focus on control. Prior research recognizes that there is a paradoxical tension between control and flexibility, meaning that, while both approaches make sense individually, they appear impossible to combine. Large construction projects are interorganizational, which means that tensions between interorganizational control/flexibility coexist with tensions between intraorganizational direction/empowerment, but the interplay and possible reinforcing cycles involving the two tensions have rarely been investigated in prior research. A multiple case study of four large construction projects with three rounds of interviews show how intraorganizational direction/empowerment can influence interorganizational control/flexibility and vice versa, and demonstrate both vicious and virtuous reinforcing cycles that involve the two types of tensions. Therefore, contributing to the project management and construction management literature, it is argued that employing a systemic approach when studying interorganizational projects is essential. A systemic paradox perspective can reveal interdependencies between tensions at different organizational interfaces, improve the understanding of how individuals in all managerial positions interplay, and explain how reinforcing cycles emerge and develop; this is important to recognize when organizing, staffing and managing large construction projects. 相似文献
93.
94.
针对无人机控制站难以与多型无人机互联互通的问题,从通用控制软件的角度开展研究,分析了设计需求,提出了一种采用平台+插件的软件架构,并分析了软件架构、基于XML技术的帧格式信号和参数信息描述、动态报文解析和组包、软件界面定制等关键技术。在车载控制站和便携控制站的工程验证表明,所提解决方案实现了对多型无人机的控制,具有良好的通用性、扩展性,并支持用户自定义对外通信协议和人机交互功能、界面。 相似文献
95.
焦炉生产是典型的大惯性、非线性、时变快的复杂系统,以“火落温度”为基础的焦炉前反馈热工控制系统,通过立火道温度自动测量与人工测温相关性分析、粗煤气温度测量与火落判断、标准温度的优化等运行实践,达到了自动火落时间判断、标准温度指导、加热和燃烧优化、高低温炉号判别等目的,对于稳定炉温、降低回炉煤气消耗、提高焦炭质量以及推进焦化企业技术进步具有重要意义。 相似文献
96.
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
97.
98.
99.
Rui
Zhang Junmin Li Jianmin Jiao 《International Journal of Adaptive Control and Signal Processing》2020,34(7):919-936
This article investigates an adaptive fuzzy tracking control problem for a class of nontriangular form systems with asymmetric time-varying full state constraints. Unknown functions are approximated by the fuzzy logic systems. A domination approach is employed to tackle the nontriangular form structure. Time-varying asymmetric barrier Lyapunov functions (ABLFs) are adopted to ensure full-state constraints satisfaction. Based on the backstepping technique and time-varying ABLFs, an adaptive controller is proposed and guarantees that all the signals in the closed-loop system are ultimately bounded and the time-varying full state constraints are met. Simulation examples are presented to further demonstrate the effectiveness of the proposed approach. 相似文献
100.
由于新能源出力以及终端负荷需求的不确定性,电力零售商在日前市场的竞标电量与实时市场的购买电量之间存在不平衡而产生惩罚成本风险。引入用户侧可控负荷作为平衡资源参与市场交易,提出了一种风险规避程度指标,以此来度量交易前后电量偏差程度,以信息熵度量残差序列离散程度计算风险规避程度指标。以电力零售商运行收益、用户需求响应满意度以及风险规避程度最大为目标建立多目标风险规避模型,采用自适应权重粒子群算法进行模型求解。通过算例表明,所提出的模型从电网-电力零售商-用户多个角度去考虑电力零售商参与平衡市场交易策略,能够有效提高电力零售商的运行效益以及用户满意度,同时可以提高电力市场管理的可靠性与安全性。 相似文献