全文获取类型
收费全文 | 2797篇 |
免费 | 91篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 958篇 |
金属工艺 | 59篇 |
机械仪表 | 65篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 161篇 |
轻工业 | 210篇 |
水利工程 | 10篇 |
石油天然气 | 6篇 |
无线电 | 195篇 |
一般工业技术 | 561篇 |
冶金工业 | 197篇 |
原子能技术 | 21篇 |
自动化技术 | 396篇 |
出版年
2023年 | 39篇 |
2022年 | 108篇 |
2021年 | 122篇 |
2020年 | 102篇 |
2019年 | 92篇 |
2018年 | 107篇 |
2017年 | 99篇 |
2016年 | 70篇 |
2015年 | 60篇 |
2014年 | 114篇 |
2013年 | 365篇 |
2012年 | 140篇 |
2011年 | 118篇 |
2010年 | 123篇 |
2009年 | 127篇 |
2008年 | 105篇 |
2007年 | 82篇 |
2006年 | 86篇 |
2005年 | 71篇 |
2004年 | 40篇 |
2003年 | 51篇 |
2002年 | 43篇 |
2001年 | 32篇 |
2000年 | 34篇 |
1999年 | 31篇 |
1998年 | 43篇 |
1997年 | 27篇 |
1996年 | 35篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 33篇 |
1992年 | 36篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 38篇 |
1988年 | 14篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 26篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有2900条查询结果,搜索用时 15 毫秒
111.
A 2D model for the potential distribution in silicon film is derived for a symmetrical double gate MOSFET in weak inversion. This 2D potential distribution model is used to analytically derive an expression for the subthreshold slope and threshold voltage. A drain current model for lightly doped symmetrical DG MOSFETs is then presented by considering weak and strong inversion regions including short channel effects, series source to drain resistance and channel length modulation parameters. These derived models are compared with the simulation results of the SILVACO (Atlas) tool for different channel lengths and silicon film thicknesses. Lastly, the effect of the fixed oxide charge on the drain current model has been studied through simulation. It is observed that the obtained analytical models of symmetrical double gate MOSFETs are in good agreement with the simulated results for a channel length to silicon film thickness ratio greater than or equal to 2. 相似文献
112.
Low‐temperature plasma processing for the enhancement of surface properties and dyeability of wool fabric
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In the present investigation, wool fabric was treated with a low‐temperature air plasma. The plasma discharge power and treatment time were varied. The effect of plasma treatment on various fabric properties such as wettability, wickability, dyeability, crease recovery angle, breaking strength, and elongation at break was investigated. Surface morphology was studied using SEM micrographs. The fabric became substantially hydrophilic even with a short duration of air plasma treatment of 30 s with improvement in dye uptake and in the rate of dyeing when dyed at a lower temperature. Under these treatment conditions, aging was almost nil in a dry environment, even after 45 days, whereas some aging was observed in a humid (75% relative humidity) environment. A 20% increase in the breaking strength and 24% increase in the elongation at break were observed with reduction in wrinkle recovery angle to 133–144° from 169° for untreated fabric. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43097. 相似文献
113.
Naira V. Margaryan Alina Gilgur Elisabeth A. Seftor Chad Purnell Nicoleta C. Arva Arun K. Gosain Mary J. C. Hendrix Luigi Strizzi 《International journal of molecular sciences》2016,17(3)
Expression of Nodal, a Transforming Growth Factor-beta (TGF-β) related growth factor, is associated with aggressive melanoma. Nodal expression in adult dysplastic nevi may predict the development of aggressive melanoma in some patients. A subset of pediatric patients diagnosed with giant or large congenital melanocytic nevi (LCMN) has shown increased risk for development of melanoma. Here, we investigate whether Nodal expression can help identify the rare cases of LCMN that develop melanoma and shed light on why the majority of these patients do not. Immunohistochemistry (IHC) staining results show varying degree of Nodal expression in pediatric dysplastic nevi and LCMN. Moreover, median scores from Nodal IHC expression analysis were not significantly different between these two groups. Additionally, none of the LCMN patients in this study developed melanoma, regardless of Nodal IHC levels. Co-culture experiments revealed reduced tumor growth and lower levels of Nodal and its signaling molecules P-SMAD2 and P-ERK1/2 when melanoma cells were grown in vivo or in vitro with normal melanocytes. The same was observed in melanoma cells cultured with melanocyte conditioned media containing pigmented melanocyte derived melanosomes (MDM). Since MDM contain molecules capable of inactivating radical oxygen species, to investigate potential anti-oxidant effect of MDM on Nodal expression and signaling in melanoma, melanoma cells were treated with either N-acetyl-l-cysteine (NAC), a component of the anti-oxidant glutathione or synthetic melanin, which in addition to providing pigmentation can also exert free radical scavenging activity. Melanoma cells treated with NAC or synthetic melanin showed reduced levels of Nodal, P-SMAD2 and P-ERK1/2 compared to untreated melanoma cells. Thus, the potential role for Nodal in melanoma development in LCMN is less evident than in adult dysplastic nevi possibly due to melanocyte cross-talk in LCMN capable of offsetting or delaying the pro-melanoma effects of Nodal via anti-oxidant effects of MDM. 相似文献
114.
115.
Silicon - Tunnel Field Effect Transistor can be introduced as an emerging alternate to MOSFET which is energy efficient and can be used in low power applications. Due to the challenge involved in... 相似文献
116.
Thin film composite sodium alginate membranes for dehydration of acetic acid and isobutanol
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dehydration of widely used organic solvents such as acetic acid (AA) and isobutanol (IB) is challenging tasks, which form close boiling mixtures with water. Sodium alginate (SA) thin film composite membranes were prepared and crosslinked with 2,4‐toluene diisocyanate (TDI) and glutaraldehyde for dehydration of IB and AA/water mixtures through pervaporation (PV). The crosslinked and uncrosslinked SA composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and universal testing machine for intermolecular interactions, crystalline nature, thermal stability, surface morphology, and tensile strength, respectively. At a feed composition of 98 wt % IB and 95 wt % AA aqueous solutions, the TDI crosslinked SA composite membrane exhibited separation factors of 3229 and 708 with reasonable fluxes of 0.021 and 0.012 kg m?2 h?1, respectively. The results obtained in the study for IB and AA systems were compared with other SA membranes reported in the literature. The membranes appeared to have potential for commercial PV ability to dehydrate the solvents up to desirable purity levels (>99%) and feasibility of preparing them in a composite form which would enable scale‐up into modular configurations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40018. 相似文献
117.
Three alternate dying methods—vacuum drying (VD), vacuum microwave drying (VMD), and pulse-spouted vacuum–microwave drying (PSVMD)—were examined experimentally for their potential as an industrial scale technology to produce granules of fish. Drying kinetics as well as key quality parameters such as expansion ratio, texture, color, sensory characteristics, and microstructure of crispy granules produced by these drying techniques were examined. Results showed that the drying time is reduced with an increase in microwave power level and with reduced pressure as expected. The quality of the granules is affected by the drying method and the operating parameters employed. Granules obtained using PSVMD at a microwave power density of 6.0 W/g displayed optimal quality required for the commercial product accepted by consumers. 相似文献
118.
Non-uniform heating is a major issue in microwave applications, mainly due to inherently uneven distribution of electromagnetic energy in the microwave applicator. In this work, our aim is to improve electric field distribution uniformity by utilizing microwave reflection from electrically conductive beads placed in the microwave oven. The effects of position, size, and number of electrically conductive beads on the electric field distribution were numerically investigated, and validated through water-load experiments in the cavity. It is found that uniform electric field distribution was realized to some extent by appropriate placement of electrically conductive beads; meanwhile, average electric field intensity in the microwave oven was increased. 相似文献
119.
The drying homogeneity of the microwave–pulsed spouted bed drying (MPSBD) method was studied via preparing tubers granules by MPSBD under different predefined conditions. The effects of three parameters (microwave power, moisture content transition point, and loading) on the homogeneity of prepared tubers granules were studied. Based on response surface analysis results, it was concluded that the optimum conditions for tuber granules prepared by MPSBD method is 1.10 W/g microwave power, 80% moisture content transition point, and 90 g material loading. It was proven that the experimental result from the predicted optimal condition agreed with the model-predicted results, which evidenced the accuracy of the response surface analysis. Furthermore, the brighter color and higher rehydration capacity of samples prepared by MPSBD indicates that MPSBD is a promising method that can be applied in the food dehydration industry. 相似文献
120.
Ruhi H. Pathan Chetan K. Modi Arun G. Basrur 《Journal of the American Ceramic Society》2020,103(11):6615-6629
Zirconia was deposition precipitated on γ-alumina in pH range 7-10 from zirconium oxy-nitrate and soda ash. Zirconium formed its hydroxycarbonate as deduced from ICP-EOS, CHN, and TGA-MS. Higher pH favored formation of carbonate species of zirconium over its hydroxide. TGA-MS indicated formation of three different types of carbonate species. FTIR results corroborated this. Monodentate metal carbonate was observed irrespective of pH of preparation. In addition, bridged bidentate species formed at pH ≤ 8 which changed to chelating bidentate at pH > 8. XRD indicated that all the samples formed tetragonal-zirconia upon calcination irrespective of pH of preparation. Higher pH resulted in smaller crystallites of t-ZrO2. Changes in chemical moiety with pH reflected on acidity and the deactivation rate for 2-methyl-3-butyn-2-ol which decreased by two orders of magnitude in samples prepared at higher pH. Surface area and pore volume benefited from deposition precipitation. SEM-EDAX showed reasonable distribution of zirconia over γ-Al2O3. 相似文献