全文获取类型
收费全文 | 321321篇 |
免费 | 38738篇 |
国内免费 | 29103篇 |
专业分类
电工技术 | 29295篇 |
技术理论 | 10篇 |
综合类 | 31242篇 |
化学工业 | 50781篇 |
金属工艺 | 13299篇 |
机械仪表 | 20749篇 |
建筑科学 | 25564篇 |
矿业工程 | 8635篇 |
能源动力 | 10503篇 |
轻工业 | 20609篇 |
水利工程 | 9073篇 |
石油天然气 | 10736篇 |
武器工业 | 3992篇 |
无线电 | 38044篇 |
一般工业技术 | 37047篇 |
冶金工业 | 9408篇 |
原子能技术 | 5510篇 |
自动化技术 | 64665篇 |
出版年
2024年 | 336篇 |
2023年 | 4584篇 |
2022年 | 8234篇 |
2021年 | 10244篇 |
2020年 | 10817篇 |
2019年 | 9121篇 |
2018年 | 8370篇 |
2017年 | 11210篇 |
2016年 | 11661篇 |
2015年 | 13712篇 |
2014年 | 17055篇 |
2013年 | 19905篇 |
2012年 | 24933篇 |
2011年 | 26946篇 |
2010年 | 19811篇 |
2009年 | 20251篇 |
2008年 | 20768篇 |
2007年 | 24311篇 |
2006年 | 22373篇 |
2005年 | 19049篇 |
2004年 | 15981篇 |
2003年 | 12959篇 |
2002年 | 10244篇 |
2001年 | 8018篇 |
2000年 | 6578篇 |
1999年 | 5568篇 |
1998年 | 4418篇 |
1997年 | 3736篇 |
1996年 | 3186篇 |
1995年 | 2902篇 |
1994年 | 2499篇 |
1993年 | 1815篇 |
1992年 | 1538篇 |
1991年 | 1175篇 |
1990年 | 993篇 |
1989年 | 836篇 |
1988年 | 629篇 |
1987年 | 371篇 |
1986年 | 320篇 |
1985年 | 305篇 |
1984年 | 270篇 |
1983年 | 188篇 |
1982年 | 238篇 |
1981年 | 155篇 |
1980年 | 138篇 |
1979年 | 64篇 |
1978年 | 39篇 |
1977年 | 39篇 |
1976年 | 29篇 |
1959年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
蒙特卡洛法需使用大量电网抽样数据,花费的风险评估时间长,提出一种改进蒙特卡洛法实现高效智能电网实时运行风险评估。从多方面考虑,构建智能电网风险评价指标体系,明确蒙特卡洛法存在抽样次数多及方差系数大的问题;将交叉熵重要抽样法与分散抽样法相结合,构建近似函数,令原本电网中微小概率事件转换为大概率事件,减少算法抽样次数和方差系数,提高算法的计算效率。实验表明,所提方法能够有效识别正常状态下及元件失效条件下的电网实时运行风险,并通过失效线路负荷转移的方式有效降低了智能电网实时运行风险。 相似文献
2.
《Advanced Powder Technology》2022,33(8):103664
Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems. 相似文献
3.
《Advanced Powder Technology》2022,33(9):103722
Through a facile hydrothermal method, we have successfully prepared Ti3C2/Bi2.15WO6 (TC/BWO) composite, and systematically investigated their reactivity for the photocatalytic reduction of Cr(VI) under visible light. X-ray diffraction and Raman analysis confirm the formation of heterostructure between Bi2.15WO6 and Ti3C2. The resultant 7TC/BWO composite exhibits enhanced photoactivity toward Cr(VI) reduction. After 120 min irradiation, the conversion of Cr(VI) reaches 92.5% with the quasi-first-order kinetic constant of k = 0.0145 min?1, which is higher than that of pure BWO (30% and k = 0.0005 min?1). The electrochemical and photoluminescent characterization confirm that the introduction of Ti3C2 is conducive to the separation of carriers, thus significantly improves the photocatalytic performance of TC/BWO. Furthermore, the radical capture experiments verify that the electrons are important for enhancing reduction of Cr(VI) to Cr(III). As a result, this research provides a comprehensive understanding of the reduction of Cr(VI) by TC/BWO composite under visible light. 相似文献
4.
5.
《International Journal of Hydrogen Energy》2022,47(85):36216-36231
The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB. 相似文献
6.
《International Journal of Hydrogen Energy》2022,47(67):28782-28793
Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass-derived biochar has been considered as promising carbon material because of its advantages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni2P–Fe2P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni2P–Fe2P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni0.75Fe0.25)2P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm2 in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production. 相似文献
7.
通过对崔庄煤矿煤炭自然发火规律的研究及气体分析法在该矿自然发火预测预报中的实际应用,阐述了正确布置监测取样点,并采用多种指标进行综合分析的必要性。提出了预测发火的范围、分析漏风点位置、在火区治理过程中验证灭火效果等,也是气体分析法预测预报的重要组成部分。 相似文献
8.
为提高跨临界CO2空气源热泵热水系统运行性能,对不同压缩机频率、电子膨胀阀开度和水流量下的系统及部件运行特性进行了实验研究,并对循环加热模式下的调节方式进行了优化。结果表明:当阀开度减小时,系统性能系数COP和制热量随过热度的增大而减小;压缩机存在最大电效率点,并且电效率极值点会随着运行频率的增大而向低过热度段发生移动;与电子膨胀阀调节方式相比,水流量调节方案下系统COP提升了13.22%;在循环加热模式下不同加热时期的最优阀开度并不相同,根据最优高压理论对其调节方式进行了优化,最大优化率为15.96%。 相似文献
9.
为了提高燃气轮机性能数字孪生体求解过程的鲁棒性,提出了一种基于改进广义牛顿法的燃气轮机性能数字孪生体构建方法。首先,选择广义牛顿法作为性能数字孪生体的求解方法;其次,在广义牛顿迭代法的基础上,调整隐式非线性方程对应曲线切线的斜率,改进广义牛顿法的初值设置方法;最后,构建性能数字孪生体,将改进广义牛顿法嵌入性能数字孪生体。通过PGT25+型燃气轮机实测数据验证提出的方法,结果表明:扩大初值范围后,基于改进广义牛顿法的性能数字孪生体的仿真精度仍与原始方法一致,该方法能够提高性能数字孪生体的鲁棒性,扩大性能数字孪生体的适用范围。 相似文献
10.