全文获取类型
收费全文 | 2075篇 |
免费 | 88篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 24篇 |
综合类 | 7篇 |
化学工业 | 575篇 |
金属工艺 | 73篇 |
机械仪表 | 95篇 |
建筑科学 | 27篇 |
矿业工程 | 2篇 |
能源动力 | 157篇 |
轻工业 | 152篇 |
水利工程 | 8篇 |
石油天然气 | 10篇 |
无线电 | 117篇 |
一般工业技术 | 532篇 |
冶金工业 | 159篇 |
原子能技术 | 14篇 |
自动化技术 | 214篇 |
出版年
2024年 | 5篇 |
2023年 | 26篇 |
2022年 | 53篇 |
2021年 | 55篇 |
2020年 | 69篇 |
2019年 | 52篇 |
2018年 | 80篇 |
2017年 | 73篇 |
2016年 | 72篇 |
2015年 | 70篇 |
2014年 | 83篇 |
2013年 | 176篇 |
2012年 | 114篇 |
2011年 | 165篇 |
2010年 | 98篇 |
2009年 | 94篇 |
2008年 | 93篇 |
2007年 | 89篇 |
2006年 | 59篇 |
2005年 | 54篇 |
2004年 | 39篇 |
2003年 | 47篇 |
2002年 | 37篇 |
2001年 | 15篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 43篇 |
1997年 | 30篇 |
1996年 | 25篇 |
1995年 | 27篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 13篇 |
1971年 | 4篇 |
排序方式: 共有2166条查询结果,搜索用时 15 毫秒
61.
B. T. Raut M. A. Chougule A. A. Ghanwat R. C. Pawar C. S. Lee V. B. Patil 《Journal of Materials Science: Materials in Electronics》2012,23(12):2104-2109
Nanocomposites of CdS nanocrystals with conducting polyaniline doped with camphor sulfonic acid (CSA) have been prepared by spin coating technique and investigated by X-ray diffraction, field emission scanning electron microscopy (FESEM), fourier transform infra red spectroscopy (FTIR), UV–visible spectroscopy and electrical transport method. The X-ray diffraction patterns showed broad peaks due to formation of nanoparticles of CdS in polyaniline matrix. FESEM showed that the transformation of morphology from agglomeration to nanopetals. The FTIR spectra confirmed the interaction between CSA and polyaniline (PANi)–CdS nanocomposite. The UV–visible spectrums revealed the enhancement of doping level for the PANi–CdS nanocomposites which is assigned to the existence of greater number of charges on the polymer backbone. DC electrical conductivity studies showed an increase in conductivity of PANi–CdS nanocomposites from 6.9?×?10?6 to 3.14?×?10?4 due to addition of CSA (10–50?%). 相似文献
62.
Kil Sun Yoo Eun Jin Lee Daniel Leskovar Bhimanagouda S. Patil 《Journal of food science》2012,77(12):C1279-C1284
Abstract: We developed a system to run the Folin‐Ciocalteu (F‐C) total phenolic assay, in artichoke extract samples, which is fully automatic, consistent, and fast. The system uses 2 high performance liquid chromatography (HPLC) pumps, an autosampler, a column heater, a UV/Vis detector, and a data collection system. To test the system, a pump delivered 10‐fold diluted F‐C reagent solution at a rate of 0.7 mL/min, and 0.4 g/mL sodium carbonate at a rate of 2.1 mL/min. The autosampler injected 10 μL per 1.2 min, which was mixed with the F‐C reagent and heated to 65 °C while it passed through the column heater. The heated reactant was mixed with sodium carbonate and color intensity was measured by the detector at 600 nm. The data collection system recorded the color intensity, and peak area of each sample was calculated as the concentration of the total phenolic content, expressed in μg/mL as either chlorogenic acid or gallic acid. This new method had superb repeatability (0.7% CV) and a high correlation with both the manual method (r2= 0.93) and the HPLC method (r2= 0.78). Ascorbic acid and quercetin showed variable antioxidant activity, but sugars did not. This method can be efficiently applied to research that needs to test many numbers of antioxidant capacity samples with speed and accuracy. 相似文献
63.
64.
Sachin Patil Yi Yang Tay Farzad Baratzadeh Hamid Lankarani 《Journal of Mechanical Science and Technology》2017,31(7):3225-3232
Ever increasing requirements regarding vehicle safety have led to rapid developments in various joining process. Among FSW widely used for Aluminum alloy welded structure of car body because of their remarkable performance in welding. For a better understanding of this performance, it is necessary to determine the behavior of butt weld in service conditions. In earlier phase of this study, thermo mechanical simulations and analysis are performed to understand the thermal behavior in the FSW weld zones. The developed models are correlated against published experimental results in terms of temperature profile of the weld zone. The objectives of the second part of this work is to develop and demonstrate an FE model of bumper and crash box assembly that would improve on the current modeling techniques for the mechanical response of welds in structural problems. 相似文献
65.
66.
Chia‐Che Chang Sin‐Ren Li Hung‐Lung Chou Yi‐Cheng Lee Shivaraj Patil Ying‐Sheng Lin Chun‐Chih Chang Yuan Jay Chang Di‐Yan Wang 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(49)
The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO2 emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth‐abundant iron pyrite (FeS2) nanocrystals grown on carbon fiber paper (FeS2/CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS2/CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH3 yield rate of ≈0.096 µg min?1 at ?0.6 V versus RHE electrode in 0.25 m LiClO4. During the electrochemical catalytic reaction, the crystal structure of FeS2/CFP remains in the cubic pyrite phase, as analyzed by in situ X‐ray diffraction measurements. With near‐infrared laser irradiation (808 nm), the NH3 yield rate of the FeS2/CFP catalyst can be slightly improved to 0.1 µg min?1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N2 molecule has strong chemical adsorption energy on the iron atom of FeS2. Overall, iron pyrite‐based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications. 相似文献
67.
P. P. Hankare N. M. Patil R. P. Patil D. R. Patil S. D. Delekar 《Journal of Materials Science: Materials in Electronics》2013,24(10):4028-4032
Optimum composition (x = 0.0–0.75) of copper substituted Zn0.25Mn0.75?xCuxFe2O4 ferrites system have been synthesized by simple chemical co-precipitation method. X-ray diffraction pattern of all samples shows characteristic features of nanocrystalline cubic spinel structure of ferrites. The average grain size of the samples was measured using scanning electron micrographs. The saturation magnetization, coercivity and remanance were studied as a function of copper content in the host ferrite materials. Electrical resistivity of the samples was measured by two probe method. The semiconducting nature of the samples was noted from variation of electrical resistivity with temperature. The effect of copper substitution in ferrites was studied through the measurements of structural, electrical and magnetic properties. 相似文献
68.
69.
There is growing interest in the role and contribution of e-government to the levels of corruption, economic prosperity and environmental degradation of nation states. In this paper, we use publicly available archival data to explore the relationships among them. Results substantiate a significant relationship between (1) e-government maturity and corruption; and (2) e-government maturity, economic prosperity and environmental degradation through the mediating effects of corruption. The findings suggest that while e-government maturity did not contribute to economic prosperity and environmental degradation, its value could be realized indirectly via its impacts on corruption. Our findings contribute to the theoretical discourse on e-government impact by identifying the role of e-government in a country and provide indications to practice on enhancing its economic prosperity and lowering its environmental degradation by managing the levels of e-government maturity and corruption. 相似文献
70.
Satish Kumar Amanpreet Singh Hemant Kumar 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(24):2967-2973
Presently, fly ash–water slurry is transported to ash disposal site at very low solid concentration of approximately 15–20% (by weight), resulting in huge water and energy wastage which leads to several environmental and health problem. The production of a large amount of the toxic metal elements in the ash disposal system of the thermal power plants can pose negative environmental effects on human health and on plants. In the present study, an attempt has been made to investigate the leaching characteristics of fly ash at higher concentrations. The bottom ash was taken as an additive in the proportion of 10, 20, and 30% (by weight) to enhance the leaching characteristics of fly ash. The solid concentration of fly ash suspension was taken in the range of 40 to 60% (by weight). The addition of additive helps to reduce the tracing metal concentration of fly ash. Leaching experiment data show that leachate concentration of all tracing elements present in fly ash reduced maximum with 20% addition of bottom ash (by weight). The present study helps to improve the ash disposal system of the thermal power plant and to minimize the environmental impact. 相似文献