全文获取类型
收费全文 | 12459篇 |
免费 | 1491篇 |
国内免费 | 381篇 |
专业分类
电工技术 | 5377篇 |
综合类 | 523篇 |
化学工业 | 2042篇 |
金属工艺 | 569篇 |
机械仪表 | 382篇 |
建筑科学 | 130篇 |
矿业工程 | 300篇 |
能源动力 | 1984篇 |
轻工业 | 78篇 |
水利工程 | 13篇 |
石油天然气 | 29篇 |
武器工业 | 62篇 |
无线电 | 755篇 |
一般工业技术 | 1259篇 |
冶金工业 | 345篇 |
原子能技术 | 26篇 |
自动化技术 | 457篇 |
出版年
2024年 | 49篇 |
2023年 | 241篇 |
2022年 | 501篇 |
2021年 | 526篇 |
2020年 | 647篇 |
2019年 | 485篇 |
2018年 | 407篇 |
2017年 | 633篇 |
2016年 | 691篇 |
2015年 | 542篇 |
2014年 | 814篇 |
2013年 | 589篇 |
2012年 | 754篇 |
2011年 | 1102篇 |
2010年 | 762篇 |
2009年 | 712篇 |
2008年 | 682篇 |
2007年 | 833篇 |
2006年 | 661篇 |
2005年 | 530篇 |
2004年 | 457篇 |
2003年 | 433篇 |
2002年 | 325篇 |
2001年 | 284篇 |
2000年 | 228篇 |
1999年 | 127篇 |
1998年 | 86篇 |
1997年 | 51篇 |
1996年 | 66篇 |
1995年 | 39篇 |
1994年 | 28篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1964年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
镉镍电池电解液中锂含量的测定 总被引:2,自引:0,他引:2
研究与应用氧化亚氮———乙炔火焰原子吸收法测定镉镍电池电解液中的锂含量。介绍了锂的最佳测定条件及呈良好线性范围的浓度 ,该方法具有很高的灵敏度 ,选择性和重现性好、干扰小 ,并具有操作简便、易掌握、分析周期短等特点。相对标准偏差RSD<1.00 %(n=10) ,标准加入回收率均在97.00 %~102.00 %(n=4)范围内(回收率要求符合课题指标)。方法的精确度和准确度均能满足镉镍电池研制工作的要求 ,结果令人满意。 相似文献
992.
993.
大容量方型Cd-Ni,MH-Ni碱性蓄电池在充电过程中存在严重的“涨肚”,导致电池使用寿命缩短。大量的试验工作证明,在真空条件下实现电池封口,是降低电池内压的一种方法。该方法能有效地降低电池内压,减少电池在充电过程中发生“涨肚”及防爆气塞启动泄气的机会,减缓电液量的损失,延长电池使用寿命。 相似文献
994.
《Journal of Nuclear Science and Technology》2013,50(12):1056-1062
Mesocarbon microbeads (MCMBs) heat-treated at 1,273 and 3,073 K were irradiated with an electron beam current density ~1.34μA/cm2 of 0.5–1.5 MeV for 0–600 s, and the irradiated MCMBs were examined as anode materials for secondary lithium-ion batteries. Charge capacity of both materials irradiated for short time within 100 s became larger than that before irradiation. Improvement of discharge capacity of MCMB annealed at 3,073 K was achieved by irradiation with 0.5 and 1.5 MeV electrons for 600 s. Good performance of cyclical discharge of MCMB annealed at 3,073 K was also attained by the irradiation with 0.5–1.5 MeV electrons for 600 s. 相似文献
995.
Mehmet Önder Efe 《Asian journal of control》2012,14(2):413-425
This work considers the fractional order control of a lightweight quadrotor under loss in the battery voltage. Since the outdoor brushless motors are driven via a pulse width modulation (pwm) scheme, handshaking between the dynamic model and controller is established at the pwm level and this constitutes a major contribution of the paper. The attitude control is achieved via fractional order sliding mode control (FSMC) scheme. Necessary stability considerations are presented and it is seen that FSMC is a good alternative for the control of unmanned aerial vehicles. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
996.
Andrew M. Colclasure 《Electrochimica acta》2010,55(28):8960-8973
This paper is particularly concerned with the elementary reactions and transport processes that are responsible for Li-ion battery performance. The model generally follows the widely practiced approach developed by Newman and co-workers (e.g., Doyle et al., J. Electrochem. Soc. 140 (1993) 1526 [1]). However, there are significant departures, especially in modeling electrochemical charge transfer. The present approach introduces systems of microscopically reversible reactions, including both heterogeneous thermal reactions and electrochemical charge-transfer reactions. All reaction rates are evaluated in elementary form, providing a powerful alternative to a Butler-Volmer formalism for the charge-transfer reactions. The paper is particularly concerned with the influence of non-ideal thermodynamics for evaluating reversible potentials as well as charge-transfer rates. The theory and modeling approach establishes a framework for extending chemistry models to incorporate detailed reaction mechanisms that represent multiple competitive reaction pathways. 相似文献
997.
In this paper, the electrochemical behavior of the reduction products in solution for Li/S cell is studied by UV-visual spectroscopy and electrochemical impedance spectroscopy (EIS). The results tell that the redox process of the polysulfide intermediate contains five charge-transfer steps in the practical Li/S cell. The formation of final reduction product of Li2S and the final re-oxidation product of S8 is completely irreversible. The transform between polysulfide and Li2S2 is electrochemical sluggish. The peaks corresponding to transformation Li2Sx ↔ Li2Sy (2 < x < y ≤ 6) are still symmetrical in spite of an increasing polarization with the proceeding of CV scan. While the redox process corresponding to Li2Sm ↔ Li2Sn (4 < m < n ≤ 8) is reversible. The dissolution long-chain polysulfide and deposition of short-chain polysulfide contribute mostly to the electrode deterioration even electrode blockage. Therefore, homogeneous mixing element sulfur with conductive components and alleviating the polysulfide dissolution are equally important to improving the active material utilization and rechargeability for rechargeable Li/S battery. 相似文献
998.
Erwan Dumont-Botto Carole BourbonSébastien Patoux Patrick Rozier Mickaël Dolle 《Journal of power sources》2011,196(4):2274-2278
In the search of high-performance materials for lithium ion batteries, Li2CoPO4F offers many advantages like high theoretical capacity and high operating potential. The synthesis of Li2CoPO4F has been reinvestigated considering a conventional solid state reaction and an unconventional way. Due to the long heat-treatments required by the conventional approach, a beginning of grains coalescence is observed. Limiting particles growth has been allowed by a shorter reaction done by SPS (Spark Plasma Sintering). By this method, the synthesis of Li2CoPO4F was greatly shortened (from 10 h to 9 min), which favours the getting of submicrometric particles. The comparison of the electrochemical properties of the Li2CoPO4F obtained by the different ways confirms the advantages of SPS synthesis in performance enhancement. 相似文献
999.
S. Schaeck A.O. StoermerF. Kaiser L. KoehlerJ. Albers H. Kabza 《Journal of power sources》2011,196(3):1541-1554
Micro-hybrid electric vehicles were launched by BMW in March 2007. These are equipped with brake energy regeneration (BER) and the automatic start and stop function (ASSF) of the internal combustion engine. These functions are based on common 14 V series components and lead-acid (LA) batteries. The novelty is given by the intelligent onboard energy management, which upgrades the conventional electric system to the micro-hybrid power system (MHPS). In part I of this publication the key factors for the operation of LA batteries in the MHPS are discussed. Especially for BER one is high dynamic charge acceptance (DCA) for effective boost charging. Vehicle rest time is identified as a particular negative parameter for DCA. It can be refreshed by regular fully charging at elevated charge voltage. Thus, the batteries have to be outstandingly robust against overcharge and water loss. This can be accomplished for valve-regulated lead-acid (VRLA) batteries at least if they are mounted in the trunk. ASSF goes along with frequent high-rate loads for warm cranking. The internal resistance determines the drop of the power net voltage during cranking and is preferably low for reasons of power net stability even after years of operation. Investigations have to be done with aged 90 Ah VRLA-absorbent glass mat (AGM) batteries. Battery operation at partial state-of-charge gives a higher risk of deep discharging (overdischarging). Subsequent re-charging then is likely to lead to the formation of micro-short circuits in the absorbent glass mat separator. 相似文献
1000.
To improve the cycling performance of LiNi0.8Co0.15Al0.05O2 at 55 °C, a thin Ni3(PO4) layer was homogeneously coated onto the cathode particle via simple ball milling. The morphology of the Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 particle was characterized using SEM and TEM analysis, and the coating thickness was found to be approximately 10-20 nm. The Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 cell showed improved lithium intercalation stability and rate capability especially at high C rates. This improved cycling performance was ascribed to the presence of Ni3(PO4)2 on the LiNi0.8Co0.15Al0.05O2 particle, which protected the cathode from chemical attack by HF and thus suppressed an increase in charge transfer resistance. Transmission electron microscopy of extensively cycled particles confirmed that the particle surface of the Ni3(PO4)2-coated LiNi0.8Co0.15Al0.05O2 remained almost undamaged, whereas pristine particles were severely serrated. The stabilization of the host structure by Ni3(PO4)2 coating was also verified using X-ray diffraction. 相似文献