全文获取类型
收费全文 | 206137篇 |
免费 | 19754篇 |
国内免费 | 13522篇 |
专业分类
电工技术 | 32658篇 |
技术理论 | 8篇 |
综合类 | 19024篇 |
化学工业 | 17521篇 |
金属工艺 | 10756篇 |
机械仪表 | 16992篇 |
建筑科学 | 15503篇 |
矿业工程 | 7363篇 |
能源动力 | 5927篇 |
轻工业 | 6474篇 |
水利工程 | 5703篇 |
石油天然气 | 7106篇 |
武器工业 | 2977篇 |
无线电 | 19161篇 |
一般工业技术 | 13038篇 |
冶金工业 | 9523篇 |
原子能技术 | 1613篇 |
自动化技术 | 48066篇 |
出版年
2024年 | 295篇 |
2023年 | 2549篇 |
2022年 | 3994篇 |
2021年 | 5089篇 |
2020年 | 5971篇 |
2019年 | 4822篇 |
2018年 | 4126篇 |
2017年 | 5984篇 |
2016年 | 6375篇 |
2015年 | 7124篇 |
2014年 | 13290篇 |
2013年 | 11875篇 |
2012年 | 14991篇 |
2011年 | 15937篇 |
2010年 | 11884篇 |
2009年 | 12464篇 |
2008年 | 12275篇 |
2007年 | 15230篇 |
2006年 | 13756篇 |
2005年 | 11935篇 |
2004年 | 9893篇 |
2003年 | 8916篇 |
2002年 | 7218篇 |
2001年 | 6079篇 |
2000年 | 5178篇 |
1999年 | 4111篇 |
1998年 | 3230篇 |
1997年 | 2827篇 |
1996年 | 2289篇 |
1995年 | 1993篇 |
1994年 | 1707篇 |
1993年 | 1189篇 |
1992年 | 1018篇 |
1991年 | 773篇 |
1990年 | 624篇 |
1989年 | 567篇 |
1988年 | 349篇 |
1987年 | 206篇 |
1986年 | 159篇 |
1985年 | 151篇 |
1984年 | 199篇 |
1983年 | 144篇 |
1982年 | 144篇 |
1981年 | 101篇 |
1980年 | 76篇 |
1979年 | 69篇 |
1978年 | 54篇 |
1977年 | 54篇 |
1959年 | 16篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《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
2.
高面板坝的变形对面板的安全运行有着特别重要的影响,国内外已建的高面板坝工程中,因坝体变形大导致防渗面板挤压破损,坝体渗漏量大的实例较多,不得不降低水库水位进行修复处理,造成较大的经济损失乃至给大坝的长期运行留下安全隐患。通过发生挤压破损的实例分析,发现变形控制缺乏系统性是发生面板挤压破损的主要因素,为预防面板破损,系统提出了“控制坝体总变形,转化有害变形,适应纵向变形”的坝体变形控制方法,并在使用软硬岩混合料筑坝的董箐面板堆石坝中得到的应用,取得了良好效果,该工程运行至今达十余年,未见面板有挤压破损迹象,该方法对建设200 m以上乃至300 m级超高面板坝具有重要借鉴意义。 相似文献
3.
Guishang Pei Junyi Xiang Qingyun Huang Xuewei Lv 《Journal of the American Ceramic Society》2022,105(10):6359-6369
A double pyrovanadate CaMgV2O7 sample was synthesized via a facile solid-state route under an air atmosphere. The nonequilibrium formation pathways of the CaMgV2O7 were investigated via powder X-ray diffraction. A multistep reactions path (metavanadates–pyrovanadates–double pyrovanadate CaMgV2O7) was proposed to describe the formation of the CaMgV2O7 considering the thermodynamic and kinetic factors. The cell unit parameters of the CaMgV2O7 sample indicated the crystallization according to a monoclinic system with space group P12/c1(14), and the lattice parameters of a = 6.756 Å, b = 14.495 Å, c = 11.253 Å, β = 99.12, and V = 108.806 Å3. X-ray photoelectron spectroscopy also confirmed the +5 oxidation state vanadium in CaMgV2O7. The endothermic effects at 1033 and 1143 K were related to the incongruent melting and liquidus temperatures of CaMgV2O7, respectively. The comprehensive thermodynamic properties of CaMgV2O7 were established in both low- and high-temperature regions, utilizing a physical property measurement system and multi-high-temperature calorimetry (96 lines). The heat capacity (200 J mol K−1) and entropy (198 J mol K−1) at 298.15 K were computed based on the low-temperature heat capacity values, and the enthalpy of formation at 298.15 K was also estimated. The fitted high-temperature capacity can be used to obtain the changes in the enthalpy, entropy, and Gibbs free energy. This study is part of building a reliable thermodynamic database of the CaO–MgO–V2O5 system. 相似文献
4.
《Ceramics International》2022,48(1):754-759
Thermal control coatings (TCCs) are an essential part of the thermal control systems in the spacecraft. Solar absorptance and emittance are the key performance parameters of TCCs. To develop an ultra-low solar absorption and stable inorganic TCCs for surface radiator, different TCCs were prepared by co-sintering ZnO and SiO2 nanoparticles to form Zn2SiO4/SiO2 pigment in this work, and the optical properties and radiation stability were systematically studied. It is found that the coating based on composite pigment has high reflectivity in the ultraviolet band and excellent optical performance possessing the low solar absorption of 0.06. In addition, the Zn2SiO4/SiO2 coating demonstrates the highest proton and electron radiation stability because that SiO2 between Zn2SiO4 particles acts as the relaxation center of the defects caused by radiation. 相似文献
5.
《Ceramics International》2022,48(11):14987-14992
The ceramic compound CaMoO4 is synthesized via a solid-state reaction technique. Rietveld refinement studies were done on the powder X-ray diffraction data of CaMoO4 and revealed that the compound is crystallized in the tetragonal Scheelite structure with I41/a space group. The differential scanning calorimetry (DSC) studies on CaMoO4 divulged an anomaly around 440 °C. This anomaly is further probed using the temperature-dependent Raman and dielectric spectroscopic measurements and are corroborating with the results obtained from DSC. A detailed investigation on the temperature-dependent Raman spectroscopic data revealed that the A1g mode of CaMoO4 showed a soft phonon behavior up to the phase transition temperature. It is observed that the A1g mode displayed phonon hardening behavior with further increasing the temperature. The anomaly is attributed to an isostructural phase transition (IPT), a rarely observed phenomenon in the compounds with Scheelite structure. The IPT in CaMoO4 is elucidated with a phonon softening mechanism. 相似文献
6.
5G蜂窝网络发展迅猛,其覆盖面积将逐渐增大,因此使用5G蜂窝网络进行定位是有研究潜力的研究方向。本文提出一种新的深度学习技术来实现高效、高精度和低占用的定位,以代替传统指纹定位过程中繁重的指纹库生成以及距离计算。该方法建立了一个特殊的卷积神经网络,并根据5G天线信号的接收信号强度指示、相位和到达角等特征量,选择合适的输入数据格式构造样本组建训练集,对该卷积神经网络进行训练。训练得到的卷积神经网络可以替代指纹定位中的庞大指纹库,非常有利于直接在5G移动设备端实现定位。虽然卷积神经网络在训练过程中需要大量时间,但在训练完毕后直接进行分类定位的速度非常快,可以保障定位实现的实时性。本文所实现的卷积神经网络权重与偏置所占内存不到0.5 MB,且能够在实际应用环境中以95%的定位准确率以及0.1 m的平均定位精度实现高精度定位。 相似文献
7.
8.
随着社会的进步和发展,计算机网络通信技术已被应用到实际生活、生产的各个方面,对人们的生活、生产等产生了深刻的影响。为此,文章就计算机通信及网络远程控制技术在实际生活中的应用问题进行了探究,旨在借助先进科技促进社会实现更优质发展。 相似文献
9.
10.
《Advanced Powder Technology》2022,33(12):103879
Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ~ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity. 相似文献