全文获取类型
收费全文 | 493篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 135篇 |
金属工艺 | 17篇 |
机械仪表 | 9篇 |
建筑科学 | 16篇 |
矿业工程 | 1篇 |
能源动力 | 26篇 |
轻工业 | 47篇 |
水利工程 | 9篇 |
石油天然气 | 4篇 |
无线电 | 67篇 |
一般工业技术 | 65篇 |
冶金工业 | 26篇 |
原子能技术 | 7篇 |
自动化技术 | 84篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 26篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 37篇 |
2016年 | 28篇 |
2015年 | 11篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 31篇 |
2011年 | 22篇 |
2010年 | 34篇 |
2009年 | 20篇 |
2008年 | 22篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有529条查询结果,搜索用时 22 毫秒
21.
Ahmad Zamani Gharaghooshi Akbarinezhad Esmaeil Esmaeili Naser Neshati Jaber 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(1):153-167
Protection of Metals and Physical Chemistry of Surfaces - In this study, the inhibitive performance of 2-mercaptobenzothiazole (2MBT) and 2-aminobenzothiazole (2ABT) were investigated on API-5L X60... 相似文献
22.
Polyacrylonitrile (PAN) in dimethylformamide solution containing 0.25 or 1 wt% graphene oxide (GO) was gel spun to tapes. Scanning electron microscopy of tapes showed compact staircase cross-sections hallmarking the gel spun products. Low shear rate rheometry of the tape precursors revealed a viscosity increase, while the structural viscosity indexes of dispersions dropped to 40 and 70% at high shear rates by 0.25 and 1 wt% GO inclusion, respectively. Furthermore, the sol–gel transition temperature of PAN solution was enhanced by about 2.5 and 10 °C with 0.25 and 1 wt% GO inclusion, respectively. Strain sweep test implied a gel-to-sol transition from 9 to 28% by 1 wt% GO inclusion. The experimental reinforcement coefficient corresponded the aligned Halpin–Tsai model confirming the suitable dispersion preparation route namely master batch dilution implementing strong interphase formation among the PAN chains and GO platelets. Molecular evolution analysis during air stabilization through a combined second derivative of FTIR spectra, Gaussian peak fitting represented by Isd index, indicated the initial cyclization at 290 °C followed by its enhanced rate. Final Isd was noticed to be 48% higher for the tapes containing GO nanosheets. GO inclusion not only enhanced the tape heat of stabilizations but also differentiated its proportional Isd and toughness dependency based on the heat of stabilization. 相似文献
23.
A. Nadjafi Maryam Negari R. S. Mamoory A. Simchi N. Ehsani 《Powder Metallurgy and Metal Ceramics》2007,46(9-10):423-428
Microwave energy is highly efficient for heating and processing different materials. In recent years, this type of heat transfer has been used in sintering process. Rapid and highly efficient heating, time and energy saving, and improved properties of sintered materials are advantages of microwave sintering. In this paper, Fe and Fe-Cu powder compact samples (cylindrical and bone shapes) are sintered both in microwave and electrical tube furnaces. The microwave generator has 2.45 GHz frequency and 1 KW power. Times are selected in the range of 5–25 min for microwave sintering and 5–40 min for electrical heating. The sintering temperature is set at 1120°C. Samples are sintered in the reducing atmosphere of 95% N2 + 5% H2 mixture. The density, hardness, and tensile strength of the samples are measured. The results are compared. The results show that the microwave-sintered materials have a finer microstructure. The microwave-sintered materials have 6–8% higher density, 5–10 HV5 higher hardness, and about 10% higher tensile strength than conventionally sintered materials. 相似文献
24.
Saleh Jahanshah Najafi Nosratollah Oustan Shahin Ghasemi-Golezani Kazem Aliasghrzad Naser 《SILICON》2019,11(6):2659-2667
Silicon - Silicon (Si) application shows beneficial effects on growth and salt tolerance of plants; however, its effects on the rice (Oryza sativa L. var. Hashemi) growth, superoxide dismutase... 相似文献
25.
The spun tapes of synthesized PAN, its copolymer with 1 wt% itaconic acid, and doped version with 1 wt% sodium dodecyl sulfate (SDS) all showed stripy, even, and compact cross-sections as the hallmark of gel forming products. PAN doping with SDS and acrylonitrile copolymerization with itaconic acid reduced its dimethylformamide (DMF) solution structural viscosity index (Δη) by 50% and 30%, respectively, at 675 s??1. In addition, the modification of synthesized PAN through doping and acrylonitrile copolymerization with itaconic acid led to severe and mild gelation temperature decrease, respectively. The stabilization peak of the synthesized PAN tape was enhanced as much as 25 °C by 900% hot drawing, decreased by about 10 °C through copolymerization, while experienced small temperature changes through doping. The second derivative of Fourier transform infrared and Gaussian fitting was used to analyze the tapes cyclization due to stabilization treatment through introducing Isd index. 10 min Isd index was raised as much as 430% and 800% in comparison with the synthesized PAN through its doping or acrylonitrile copolymerization with itaconic acid, respectively. Further 180 min of Isd index, however, showed the same proportional increase as toughness of the drawn tapes versus their heat of stabilization through their physical and chemical modifications. 相似文献
26.
Wireless Networks - In a wireless sensor network, one of the most important constraints on sensor nodes is their power source, which is a battery. Sensor nodes carry a limited and generally... 相似文献
27.
Reza Mahjub Moojan Radmehr Farid Abedin Dorkoosh Seyed Naser Ostad 《Drug development and industrial pharmacy》2014,40(12):1645-1659
Objective: The purpose of this research was the development, in vitro, ex vivo and in vivo characterization of lyophilized insulin nanoparticles prepared from quaternized N-aryl derivatives of chitosan.Methods: Insulin nanoparticles were prepared from methylated N-(4-N,N-dimethylaminobenzyl), methylated N-(4 pyridinyl) and methylated N-(benzyl). Insulin nanoparticles containing non-modified chitosan and also trimethyl chiotsan (TMC) were also prepared as control. The effects of the freeze-drying process on physico-chemical properties of nanoparticles were investigated. The release of insulin from the nanoparticles was studied in vitro. The mechanism of the release of insulin from different types of nanoparticles was determined using curve fitting. The secondary structure of the insulin released from the nanoparticles was analyzed using circular dichroism and the cell cytotoxicity of nanoparticles on a Caco-2 cell line was determined. Ex vivo studies were performed on excised rat jejunum using Frantz diffusion cells. In vivo studies were performed on diabetic male Wistar rats and blood glucose level and insulin serum concentration were determined.Results: Optimized nanoparticles with proper physico-chemical properties were obtained. The lyophilization process was found to cause a decrease in zeta potential and an increase in PdI as well as and a decrease in entrapment efficiency (EE%) and loading efficiency (LE%) but conservation in size of nanoparticles. Atomic force microscopy (AFM) images showed non-aggregated, stable and spherical to sub-spherical nanoparticles. The in vitro release study revealed higher release rates for lyophilized compared to non-lyophilized nanoparticles. Cytotoxicity studies on Caco-2 cells revealed no significant cytotoxicity for prepared nanoparticles after 3-h post-incubation but did show the concentration-dependent cytotoxicity after 24?h. The percentage of cumulative insulin determined from ex vivo studies was significantly higher in nanoparticles prepared from quaternized aromatic derivatives of chitosan. In vivo data showed significantly higher insulin intestinal absorption in nanoparticles prepared from methylated N-(4-N, N-dimethylaminobenzyl) chitosan nanoparticles compared to trimethyl chitosan.Conclusion: These data obtained demonstrated that as the result of optimized physico-chemical properties, drug release rate, cytotoxicity profile, ex vivo permeation enhancement and increased in vivo absorption, nanoparticles prepared from N-aryl derivatives of chitosan can be considered as valuable method for the oral delivery of insulin. 相似文献
28.
29.
Equilibrium data for carbon dioxide and methane adsorption on nanoporous metal organic framework Cu‐BTC powder and tablets were measured in a magnetic suspension balance in the temperature range of 308–373 K and a pressure range of 0–7 bar and fitted with Langmuir model. The tablets adsorption loading is 0.63 mol kg–1 for methane and 3.1 mol kg–1 for carbon dioxide at 1 bar and 308 K, while these values are 0.77 and 3.9 mol kg–1 for powder in the same conditions. Isosteric heats of adsorption were 22.8 and 15.0 kJ mol–1 for carbon dioxide and methane, respectively, on both adsorbents, which indicates a strong adsorption of carbon dioxide. Also, single and binary breakthrough curves were measured in the same temperature range and atmospheric pressure by using Cu‐BTC tablets as adsorbent. A complete model was used in the simulation of breakthrough curves and good agreement was observed with experimental data. 相似文献
30.