全文获取类型
收费全文 | 2308870篇 |
免费 | 130905篇 |
国内免费 | 81086篇 |
专业分类
电工技术 | 116510篇 |
技术理论 | 1篇 |
综合类 | 108814篇 |
化学工业 | 372136篇 |
金属工艺 | 125453篇 |
机械仪表 | 105081篇 |
建筑科学 | 116217篇 |
矿业工程 | 51349篇 |
能源动力 | 73010篇 |
轻工业 | 196679篇 |
水利工程 | 46558篇 |
石油天然气 | 66625篇 |
武器工业 | 14291篇 |
无线电 | 287926篇 |
一般工业技术 | 337762篇 |
冶金工业 | 151764篇 |
原子能技术 | 48237篇 |
自动化技术 | 302448篇 |
出版年
2023年 | 17178篇 |
2022年 | 42459篇 |
2021年 | 59084篇 |
2020年 | 42554篇 |
2019年 | 35359篇 |
2018年 | 35861篇 |
2017年 | 38598篇 |
2016年 | 43355篇 |
2015年 | 56275篇 |
2014年 | 78313篇 |
2013年 | 147023篇 |
2012年 | 109441篇 |
2011年 | 122947篇 |
2010年 | 117076篇 |
2009年 | 123247篇 |
2008年 | 118030篇 |
2007年 | 112914篇 |
2006年 | 107075篇 |
2005年 | 89633篇 |
2004年 | 77305篇 |
2003年 | 64099篇 |
2002年 | 61842篇 |
2001年 | 56029篇 |
2000年 | 50625篇 |
1999年 | 38252篇 |
1998年 | 31468篇 |
1997年 | 31353篇 |
1996年 | 30420篇 |
1995年 | 28018篇 |
1994年 | 26645篇 |
1993年 | 26598篇 |
1992年 | 25893篇 |
1991年 | 22603篇 |
1990年 | 23026篇 |
1989年 | 22117篇 |
1988年 | 20402篇 |
1987年 | 18784篇 |
1986年 | 18028篇 |
1985年 | 21357篇 |
1984年 | 21941篇 |
1983年 | 19918篇 |
1982年 | 19016篇 |
1981年 | 19136篇 |
1980年 | 17788篇 |
1979年 | 18328篇 |
1978年 | 17431篇 |
1977年 | 16534篇 |
1976年 | 16372篇 |
1975年 | 15759篇 |
1973年 | 15362篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
本文通过对巡检仪进行示值稳定性、重复性的试验,探讨热电偶的选择与巡检仪示值之间的关系,以确定校准方法,指导使其有效溯源. 相似文献
92.
Optimization and Engineering - 相似文献
93.
Ahmed Fathy Mohammad Ali Abdelkareem A.G. Olabi Hegazy Rezk 《International Journal of Hydrogen Energy》2021,46(8):6087-6099
Cell temperature and water content of the membrane have a significant effect on the performance of fuel cells. The current-power curve of the fuel cell has a maximum power point (MPP) that is needed to be tracked. This study presents a novel strategy based on a salp swarm algorithm (SSA) for extracting the maximum power of proton-exchange membrane fuel cell (PEMFC). At first, a new formula is derived to estimate the optimal voltage of PEMFC corresponding to MPP. Then the error between the estimated voltage at MPP and the actual terminal voltage of the fuel cell is fed to a proportional-integral-derivative controller (PID). The output of the PID controller tunes the duty cycle of a boost converter to maximize the harvested power from the PEMFC. SSA determines the optimal gains of PID. Sensitivity analysis is performed with the operating fuel cell at different cell temperature and water content of the membrane. The obtained results through the proposed strategy are compared with other programmed approaches of incremental resistance method, Fuzzy-Logic, grey antlion optimizer, wolf optimizer, and mine-blast algorithm. The obtained results demonstrated high reliability and efficiency of the proposed strategy in extracting the maximum power of the PEMFC. 相似文献
94.
S. Sarika S. Abhilash V.S. Sumi S. Rijith 《International Journal of Hydrogen Energy》2021,46(30):16387-16403
A promising electrocatalyst containing variable percentage of V2O5–TiO2 mixed oxide in graphene oxide support was prepared by embedding the catalyst on Cu substrate through facile electroless Ni–Co–P plating for hydrogen evolution reaction. The solvothermal decomposition method was opted for tuning the crystalline characteristics of prepared material. The optimized mixed oxide was well characterized, active sites centres were identified and explained by X-ray diffraction, high resolution tunnelling electron microscopy, scanning electron microscopy coupled with energy dispersive X-ray and X-ray photon spectroscopy analysis. The structural and electronic characteristics of material was done by fourier transform infrared spectroscopy and the electrochemical behaviour of the prepared material was evaluated by using Tafel plot, electrochemical impedance analysis, linear sweep voltammetry, open circuit analysis and chronoamperometry measurements. The results show the enhanced catalytic activity of Ni–Co–P than pure Ni–P plate, due to synergic effect. Moreover, the prepared mixed oxide incorporated Ni–Co–P plate has a high activity towards HER with low over potential of 101 mV, low Tafel slope of 36 mVdec?1, high exchange current density of 9.90 × 10?2 Acm?2. 相似文献
95.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
96.
97.
目的建立超高效液相色谱-串联质谱法同时测定糕点中6种常用合成甜味剂的分析方法。方法选用超纯水作为提取溶剂,涡旋和超声提取后,低温离心,取部分上清液加入正己烷除脂,Waters Atlantis■T3色谱柱、甲醇-5 mmol/L甲酸铵(含0.1%甲酸)作为流动相、亲水亲脂平衡型固相萃取柱HLB(hydrophile-lipophile balance)净化。结果6种甜味剂在质量浓度为10~200 ng/mL的曲线范围内呈良好线性关系,相关系数r均大于0.999,平均加标回收率在85.0%-98.2%之间,相对平均偏差(relative standard deviation,RSD)为1.3%~6.7%。结论该方法具有前处理简单、灵敏度高、检测速度快等优点,适合糖精钠、甜蜜素、三氯蔗糖、阿斯巴甜、阿力甜、纽甜的检测,但不适用于安赛蜜的检测。 相似文献
98.
Elli Ntakou Ralph Masiello Farnaz Farzan Shay Bahramirad Aleksi Paaso M.A. Nayeem Maigha Maigha Daniel Kushner 《The Electricity Journal》2019,32(4):45-49
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal. 相似文献
99.
Gordenchuk A. D. Kudryashova O. S. 《Theoretical Foundations of Chemical Engineering》2019,53(4):591-595
Theoretical Foundations of Chemical Engineering - Calcium formate is widely used in construction, tanning, and textile manufacture and as an E238 biological additive in cosmetology and the food... 相似文献
100.
简要介绍某化工厂污水处理装置日常运行管理,通过技术改造及优化调整运行参数,在装置开停工或装置工况异常产生的高负荷冲击下,确保污水生化处理系统稳定运行. 相似文献