全文获取类型
收费全文 | 1312篇 |
免费 | 84篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 27篇 |
综合类 | 4篇 |
化学工业 | 295篇 |
金属工艺 | 31篇 |
机械仪表 | 40篇 |
建筑科学 | 34篇 |
能源动力 | 91篇 |
轻工业 | 135篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 140篇 |
一般工业技术 | 318篇 |
冶金工业 | 66篇 |
原子能技术 | 23篇 |
自动化技术 | 199篇 |
出版年
2024年 | 5篇 |
2023年 | 34篇 |
2022年 | 89篇 |
2021年 | 109篇 |
2020年 | 81篇 |
2019年 | 81篇 |
2018年 | 95篇 |
2017年 | 62篇 |
2016年 | 92篇 |
2015年 | 51篇 |
2014年 | 68篇 |
2013年 | 102篇 |
2012年 | 64篇 |
2011年 | 74篇 |
2010年 | 36篇 |
2009年 | 44篇 |
2008年 | 36篇 |
2007年 | 41篇 |
2006年 | 25篇 |
2005年 | 28篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1966年 | 1篇 |
排序方式: 共有1411条查询结果,搜索用时 15 毫秒
991.
El Mostafa Benchafia Chi Yu Marek Sosnowski N. M. Ravindra Zafar Iqbal 《JOM Journal of the Minerals, Metals and Materials Society》2014,66(4):608-615
The radio frequency plasma synthesis of nitrogen clusters stabilized on carbon nanotube sheets has been demonstrated under various conditions. Characterization of the samples produced has been carried out using micro-Raman and attenuated total reflectance-Fourier transform infrared spectroscopy. Initial investigations of the sample morphologies and compositions have also been performed using scanning electron microscopy combined with energy-dispersive x-ray analysis and transmission electron microscopy. The spectroscopic results, together with density functional theory calculations, suggest that a linear chain nitrogen cluster is formed under the plasma conditions employed and is stabilized most likely inside the walls of the carbon nanotubes that are used as substrates during the synthesis. 相似文献
992.
M. Hassan Farooq Xiao-Guang Xu Hai-Ling Yang Cong-Jun Ran Jun Miao M. Zubair Iqbal Yong Jiang 《稀有金属(英文版)》2013,32(3):264-268
In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparticles have hexagonal wurtzite structure. Field emission scanning electron microscopy observations show that the nanoparticles have a diameter of 50 nm. The room temperature ferromagnetism increases monotonically with increasing B concentration to the ZnO nanoparticles and reaches the maximum value of saturation magnetization 0.0178 A·m2 ·kg-1 for 5 % B-doped ZnO nanoparticles. Moreover, photoluminescence spectra reveal that B doping causes to produce Zn vacancies (VZn ). Magnetic moment of oxygen atoms nearest to the B-VZn vacancy pairs can be considered as a source of ferromagnetism for B-doped ZnO nanoparticles. 相似文献
993.
Asghar Ali Frieder Hadlich Muhammad W. Abbas Muhammad A. Iqbal Dawit Tesfaye Gerrit J. Bouma Quinton A. Winger Siriluck Ponsuksili 《International journal of molecular sciences》2021,22(5)
Pregnancy complications are a major cause of fetal and maternal morbidity and mortality in humans. The majority of pregnancy complications initiate due to abnormal placental development and function. During the last decade, the role of microRNAs (miRNAs) in regulating placental and fetal development has become evident. Dysregulation of miRNAs in the placenta not only affects placental development and function, but these miRNAs can also be exported to both maternal and fetal compartments and affect maternal physiology and fetal growth and development. Due to their differential expression in the placenta and maternal circulation during pregnancy complications, miRNAs can be used as diagnostic biomarkers. However, the differential expression of a miRNA in the placenta may not always be reflected in maternal circulation, which makes it difficult to find a reliable biomarker for placental dysfunction. In this review, we provide an overview of differentially expressed miRNAs in the placenta and/or maternal circulation during preeclampsia (PE) and intrauterine growth restriction (IUGR), which can potentially serve as biomarkers for prediction or diagnosis of pregnancy complications. Using different bioinformatics tools, we also identified potential target genes of miRNAs associated with PE and IUGR, and the role of miRNA-mRNA networks in the regulation of important signaling pathways and biological processes. 相似文献
994.
Poling of Lead Zirconate Titanate Ceramics and Flexible Piezoelectric Composites by the Corona Discharge Technique 总被引:1,自引:0,他引:1
In the conventional poling method, piezoelectric ceramics and composites are poled by applying a large dc voltage. Poling of composites having a polymer matrix with 0–3 connectivity is especially difficult because the electric field within the high-dielectricconstant grains is far smaller than in the low-dielectric-constant polymer matrix. Therefore, very large electric fields are required to pole these types of composites. However, large electric fields often cause dielectric breakdown of the samples. In this study for improved poling, the corona discharge technique was used to pole piezoelectric ceramics, fired PZT composites, and 0.5PbTiO3 · 0.5BiFeO3 0–3 polymer composites. An experimental setup for corona poling is described. The dielectric and piezoelectric properties of materials poled by the corona discharge technique were comparable to those obtained with the conventional poling method. 相似文献
995.
M. Manickam P. Iqbal M. Belloni S. Kumar Jon A. Preece 《Israel journal of chemistry》2012,52(10):917-934
Liquid crystals are commonplace in technological devices, such as watch and computer displays and temperature and pressure monitors. Such materials are central to our technological lifestyles. Classically, liquid crystalline materials are based on a structural motif which could be classed as rod-like (e.g. biphenyl derivatives) and in more recent times as disc-like (e.g. triphenylene derivatives). The rod-like materials are very attractive in terms of their chemical stability and their response to electric fields, both of which are a prerequisite for display devices, whereas disc-like materials show promise as one-dimensional conducting materials. Increasing scientific and technological requirements mean that new materials are continually sought to surpass the liquid crystalline materials which are presently known. Carbazole derivatives are well-known interesting natural products. Several methods have been developed and reported in the literature for the synthesis of carbazole derivatives. There are several review articles published on the photorefractive properties of carbazole-based materials. Chemical modification of the carbazole moiety to create a new class of discotic, calamitic and banana-shaped liquid crystalline materials, which will have novel and enhanced photorefractive properties over the amorphous carbazole derivatives, will be discussed in this mini review. 相似文献
996.
Z. Iqbal A. Ali A. Rauf A. ul Haq S. Tajammul Hussain M. H. Asghar 《Protection of Metals and Physical Chemistry of Surfaces》2011,47(4):512-516
Di-titanium nitride coatings were synthesized on commercial AISI 304 stainless steel using a Cathodic Arc Plasma Deposition
(CAPD) technique. The effect of substrate bias voltage on the formation of coatings was studied keeping other parameters constant.
The study revealed that 120 volts of substrate bias voltage is the most suitable for formation of Ti2N on the substrate. The thickness of the Ti2N coating was 0.70 to 0.80 μm for all the experiments. The hardness of the thin Ti2N coatings, determined by using Johnson and Hogmark relation was 2000 Hv. The structure of the coatings was studied by XRD.
The surface roughness and texture was also studied which are important parameters for the given films. The case studies for
high energy magnets and fertilizer industry are also discussed to show the worthiness of the work for industrial applications. 相似文献
997.
This article investigates the viscosity behavior of new membrane dope solutions of poly(ether sulfone) (PES) and dimethylformamide with low‐molecular‐weight halogenated lithium bromide (LiBr) additives prepared with two different techniques: (1) a microwave (MW) technique and (2) a conventional heating (CH) technique. In addition, the influence of different concentrations of anhydrous halogenated LiBr additives (0–5 wt %) on the viscosity behavior is analyzed. The viscosity of the dope solutions was assessed with a conical rheometer equipped with a high‐viscosity adapter. The results revealed that the pure PES solutions prepared by the MW and CH techniques exhibited pseudoplastic and Newtonian behavior, respectively. Both the MW and CH PES solutions containing the LiBr additives exhibited dilatant behavior, which obeyed the power law. The apparent viscosity of all the dope solutions prepared with the MW technique was lower than that of those prepared with the CH technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
998.
A simple empirical model to calculate solar spectral diffuse and global irradiance under cloudless skies is presented here. This formulation takes into account absorption of radiation by molecules such as O3, H2O and the uniformly-mixed gases. Attenuation by Rayleigh scattering and aerosol extinction are included. Aerosol attenuation is calculated through Ångström's turbidity parameters α and β. The diffuse radiation is assumed to be composed of three parts: (1) Rayleigh-scattered diffuse irradiance; (2) aerosol-scattered diffuse irradiance; and (3) irradiance arising out of multiple reflections between the atmosphere and the ground. The global irradiance is the sum of these three components of diffuse irradiance plus the direct irradiance. The input parameters include an extraterrestrial spectrum, zenith angle, turbidity coefficient β, wavelength exponent α, ground albedo g, water vapor content and ozone content. The model is shown to yield very good results up to air mass two when compared to accurate theoretical calculations. No comparisons with measured spectra are presented because of a lack of accurate specifications of input parameters. Results are presented to show the effect of variation of certain of the input parameters. 相似文献
999.
Plateau B. Atif K. 《IEEE transactions on pattern analysis and machine intelligence》1991,17(10):1093-1108
A methodology for modeling a system composed of parallel activities with synchronization points is proposed. Specifically, an approach based on a modular state-transition representation of a parallel system called the stochastic automata network (SAN) is developed. The state-space explosion is handled by a decomposition technique. The dynamic behavior of the algorithm is analyzed under Markovian assumptions. The transition matrix of the chain is automatically derived using tensor algebra operators, under a format which involves a very limited storage cost 相似文献
1000.