全文获取类型
收费全文 | 18885篇 |
免费 | 3133篇 |
国内免费 | 1968篇 |
专业分类
电工技术 | 2514篇 |
综合类 | 2046篇 |
化学工业 | 469篇 |
金属工艺 | 867篇 |
机械仪表 | 2302篇 |
建筑科学 | 601篇 |
矿业工程 | 395篇 |
能源动力 | 413篇 |
轻工业 | 243篇 |
水利工程 | 158篇 |
石油天然气 | 241篇 |
武器工业 | 616篇 |
无线电 | 3834篇 |
一般工业技术 | 1193篇 |
冶金工业 | 591篇 |
原子能技术 | 204篇 |
自动化技术 | 7299篇 |
出版年
2024年 | 42篇 |
2023年 | 361篇 |
2022年 | 576篇 |
2021年 | 668篇 |
2020年 | 754篇 |
2019年 | 665篇 |
2018年 | 614篇 |
2017年 | 853篇 |
2016年 | 965篇 |
2015年 | 1126篇 |
2014年 | 1450篇 |
2013年 | 1338篇 |
2012年 | 1714篇 |
2011年 | 1735篇 |
2010年 | 1314篇 |
2009年 | 1192篇 |
2008年 | 1205篇 |
2007年 | 1364篇 |
2006年 | 1159篇 |
2005年 | 897篇 |
2004年 | 714篇 |
2003年 | 657篇 |
2002年 | 561篇 |
2001年 | 410篇 |
2000年 | 321篇 |
1999年 | 238篇 |
1998年 | 207篇 |
1997年 | 163篇 |
1996年 | 136篇 |
1995年 | 111篇 |
1994年 | 99篇 |
1993年 | 67篇 |
1992年 | 65篇 |
1991年 | 37篇 |
1990年 | 40篇 |
1989年 | 30篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1978年 | 4篇 |
1965年 | 4篇 |
1964年 | 7篇 |
1963年 | 6篇 |
1961年 | 5篇 |
1959年 | 8篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
在受到陀螺效应、动框架效应等影响后产生的磁力非线性问题是磁悬浮控制力矩陀螺(MSCMG)高速转子位置精度下降的主要因素。为解决以上问题,提高转子位置精度,本文分析了转子所受磁力的特性,建立了转子系统非线性动力学模型,提出了神经网络滑模控制方法。设计滑模控制律,采用径向基函数神经网络逼近控制律中的非线性模型,自适应算法根据误差在线调整神经网络的权值,同时可以保证整个系统的稳定性。仿真和实验结果表明,所提出方法的转子位置精度达到99%,稳态误差为0.000 2 mm。神经网络滑模控制可以实现MSCMG转子系统的高精度位置控制。 相似文献
72.
Sobha Karuthedom George Lucia Laukov Ren Weiss Vladislav Semak Birgit Fendl Victor U. Weiss Stephanie Steinberger Günter Allmaier Carla Tripisciano Viktoria Weber 《International journal of molecular sciences》2021,22(8)
Growing interest in extracellular vesicles (EVs) has prompted the advancements of protocols for improved EV characterization. As a high-throughput, multi-parameter, and single particle technique, flow cytometry is widely used for EV characterization. The comparison of data on EV concentration, however, is hindered by the lack of standardization between different protocols and instruments. Here, we quantified EV counts of platelet-derived EVs, using two flow cytometers (Gallios and CytoFLEX LX) and nanoparticle tracking analysis (NTA). Phosphatidylserine-exposing EVs were identified by labelling with lactadherin (LA). Calibration with silica-based fluorescent beads showed detection limits of 300 nm and 150 nm for Gallios and CytoFLEX LX, respectively. Accordingly, CytoFLEX LX yielded 40-fold higher EV counts and 13-fold higher counts of LA+CD41+ EVs compared to Gallios. NTA in fluorescence mode (F-NTA) demonstrated that only 9.5% of all vesicles detected in scatter mode exposed phosphatidylserine, resulting in good agreement of LA+ EVs for CytoFLEX LX and F-NTA. Since certain functional characteristics, such as the exposure of pro-coagulant phosphatidylserine, are not equally displayed across the entire EV size range, our study highlights the necessity of indicating the size range of EVs detected with a given approach along with the EV concentration to support the comparability between different studies. 相似文献
73.
74.
This paper aims to provide a review of the conceptual design and theoretical framework of the main control schemes proposed in the literature for unmanned underwater vehicles (UUVs). Additionally, the objective of the paper is not only to present an overview of the recent control architectures validated on UUVs but also to give detailed experimental-based comparative studies of the proposed control schemes. To this end, the main control schemes, including proportional–integral–derivative (PID) based, sliding mode control (SMC) based, adaptive based, observation-based, model predictive control (MPC) based, combined control techniques, are revisited in order to consolidate the principal efforts made in the last two decades by the automatic control community in the field. Besides implementing some key tracking control schemes from the classification mentioned above on Leonard UUV, several real-time experimental scenarios are tested, under different operating conditions, to evaluate and compare the efficiency of the selected tracking control schemes. Furthermore, we point out potential investigation gaps and future research trends at the end of this survey. 相似文献
75.
《International Journal of Hydrogen Energy》2022,47(92):39239-39254
The energy management and trajectory tracking control are crucial to realize long-endurance autonomous flight for hybrid electric UAVs. This study aims to comprehensively consider energy management and trajectory tracking for hybrid electric fixed wing UAVs with photovoltaic panel/fuel cell/battery. A double-layer fuzzy adaptive nonlinear model predictive control method (DFNMPC) is proposed. Separated by the surplus demand power, energy management and trajectory tracking problem are decoupled into the high-layer fuzzy adaptive nonlinear model predictive controll problem (H-FNMPC) and low-layer fuzzy adaptive nonlinear model predictive controll problem (L-FNMPC). H-FNMPC solves the trajectory tracking and navigation control probelm for the greatest benefit of solar energy. L-FNMPC solves the power allocation problem of hybrid energy system for minimum equivalent hydrogen consumption. A fuzzy adaptive prediction horizon adjustment method based on UAV maneuvering degree is proposed to effectively improve proposed method adaptability to different mission profiles. Analogously, a fuzzy adaptive equivalent hydrogen consumption factor adjustment method in L-FNMPC is proposed to ensure the flexible utilization of battery. In addition, an equivalent hydrogen flow rate calculation method based on the real-time current ratio is proposed for PV/FC/Battery hybrid energy system. Numerical simulation results including a spiral trajectory tracking and a quadrilateral trajectory tracking, demonstrate that DFNMPC can simultaneously handle energy management and trajectory tracking problem for hybrid electric UAVs. Compared to hierarchical fuzzy state machine strategy, DFNMPC can save 13.3% hydrogen for the spiral trajectory tracking, and 56.9% for the quadrilateral trajectory tracking. It indicates that the energy efficiency can be improved from both levels of energy management and flight motion. The proposed method prospected for exploring high-energy-efficiency autonomous flight of hybrid electric UAVs in the future. 相似文献
76.
77.
根据新登煤矿特殊的"三软"(顶板软、底板软、煤层软)地质条件,创造性地将掩护式支架的基本结构应用于放顶煤液压支架中,开发出了一种新的支架架型结构-两柱支撑掩护式低位放顶煤液压支架。该项目研究中所取得的技术成果和开发的支架产品具有较为广阔的推广应用前景。 相似文献
78.
针对MG4 0 0 /92 0 -WD型采煤机调高油缸频繁出现故障进行分析和试验,并提出切实可行的解决方法。 相似文献
79.
轻型综放开采技术在太原市西山矿区镇城底矿的较薄厚煤层中进行了推广应用,并获得了初步成功,它扩大了综放开采技术的应用范围。 相似文献
80.
应用神经网络理论建立了机床部件的BP神经网络模型 ,并在此模型上进行肋板位置的优化计算 ,在实体结构上实现了设计变量的自动搜索寻优计算。这一方法弥补了过去在实体结构上只能进行方案式比较优化而所得结果有较大随机性的缺陷 相似文献