全文获取类型
收费全文 | 3060篇 |
免费 | 561篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 37篇 |
综合类 | 76篇 |
化学工业 | 2760篇 |
金属工艺 | 7篇 |
机械仪表 | 6篇 |
建筑科学 | 16篇 |
矿业工程 | 6篇 |
能源动力 | 16篇 |
轻工业 | 177篇 |
石油天然气 | 153篇 |
武器工业 | 5篇 |
无线电 | 51篇 |
一般工业技术 | 241篇 |
冶金工业 | 3篇 |
原子能技术 | 91篇 |
自动化技术 | 2篇 |
出版年
2024年 | 15篇 |
2023年 | 31篇 |
2022年 | 42篇 |
2021年 | 141篇 |
2020年 | 135篇 |
2019年 | 71篇 |
2018年 | 89篇 |
2017年 | 126篇 |
2016年 | 152篇 |
2015年 | 160篇 |
2014年 | 200篇 |
2013年 | 223篇 |
2012年 | 164篇 |
2011年 | 170篇 |
2010年 | 132篇 |
2009年 | 136篇 |
2008年 | 121篇 |
2007年 | 154篇 |
2006年 | 168篇 |
2005年 | 178篇 |
2004年 | 166篇 |
2003年 | 169篇 |
2002年 | 116篇 |
2001年 | 91篇 |
2000年 | 86篇 |
1999年 | 69篇 |
1998年 | 67篇 |
1997年 | 51篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1951年 | 1篇 |
排序方式: 共有3647条查询结果,搜索用时 15 毫秒
131.
Characteristics of hemicelluloses obtained from sweet sorghum based on successive extractions 下载免费PDF全文
Hemicelluloses were successively extracted from sweet sorghum by hot water, dioxane, DMSO, and different concentrations of NaOH between 0.5% and 6.0%. The yields of the seven fractions together accounted for 88.6% of the original hemicelluloses. The obtained hemicellulosic subfractions were comprehensively investigated by both destructive methods such as alkaline nitrobenzene oxidation and acid hydrolysis and nondestructive techniques such as gel permeation chromatography, Fourier‐transform infrared, 13C‐nuclear magnetic resonance, and 2D‐heteronuclear singular quantum correlation. Sugar composition studies showed that the water‐soluble polysaccharides consisted mainly of glucose, while xylose, arabinose, and glucuronic acid were the major sugars in other hemicellulosic fractions. It was found that the hemicelluloses from sweet sorghum were l‐ arabino‐(4‐O‐methyl‐d‐ glucurono)‐xylans. Comparison with the hemicellulosic fractions dissolved by the alkali treatment, the hemicellulosic fraction extracted by DMSO had lower molecular weight. In addition, it was also found that the hemicelluloses prepared by dioxane and DMSO were more branched since that they had higher nonxylose/xylose ratios than those extracted by the alkali treatment, which were more linear and contained higher amounts xylose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42790. 相似文献
132.
Nantharak Rodkate Boonjira Rutnakornpituk Uthai Wichai Gareth Ross Metha Rutnakornpituk 《应用聚合物科学杂志》2015,132(8)
Thermo‐responsive poly(N‐isopropylacrylamide) (poly(NIPAAm)) and pH‐responsive poly(N,N′‐diethylaminoethyl methacrylate) (poly(DEAEMA)) polymers were grafted to carboxymethylchitosan (CMC) via radical polymerization to form highly water swellable hydrogels with dual responsive properties. Ratios of CMC, NIPAAm to DEAEMA used in the reactions were finely adjusted such that the thermo and pH responsiveness of the hydrogels was retained. Scanning electron microscopy (SEM) indicated the formation of an internal porous structure for the swollen CMC hydrogels upon incorporation of poly(NIPAAm) and poly(DEAEMA). Effect of temperature and pH changes on water swelling properties of the hydrogels was investigated. It was found that the water swelling of the hydrogels was enhanced when the solution pH was under basic conditions (pH 11) or the temperature was below its lower critical solution temperature (LCST). These responsive properties can be used to regulate releasing rate of an entrapped drug from the hydrogels, a model drug, indomethacin was used to demonstrate the release. These smart and nontoxic CMC‐based hydrogels show great potential for use in controlled drug release applications with controllable on‐off switch properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41505. 相似文献
133.
134.
Multilayer‐coated NPK compound fertilizer hydrogel with controlled nutrient release and water absorbency 下载免费PDF全文
A novel trilayered controlled‐release nitrogen, phosphorous, and potassium (NPK) fertilizer hydrogel was prepared by dipping the NPK fertilizer granules sequentially in 7% w v?1 poly(vinyl alcohol) (PVA) and 2% w v?1 chitosan (CS) solutions and then cross‐linking the CS layer (cross‐CS) via glutaraldehyde vapor deposition. Different NPK fertilizer hydrogels were then synthesized by inverse suspension polymerization of the dried PVA/cross‐CS bilayer‐coated fertilizer granules in various molar ratios of acrylamide (AM) and acrylic acid (AA) monomers, and polymerization with varying molar ratios of ammonium persulfate, N,N,N′,N′‐tetramethylethylenediamine and N,N′‐methylenebisacrylamide (N‐MBA). The water dissolution time of the obtained PVA/cross‐CS/poly (AA‐co‐AM) trilayer‐coated NPK fertilizer hydrogel granules was prolonged, while the water absorbency increased with increasing AA contents, and decreased with increasing N‐MBA contents in the outer poly(AA‐co‐AM) coating. The optimal trilayer‐coated NPK fertilizer hydrogel obtained released 84 ± 18, 63 ± 12, and 36 ± 15% of the N, P, and K nutrients, respectively, after a 30‐day immersion in water. The release phenomena of the N, P, and K nutrients of the fertilizer hydrogel obeyed both the Korsmeyer‐Peppas and Ritger‐Peppas models with a pseudo‐Fickian diffusion mechanism. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41249. 相似文献
135.
Hydrogels are being prepared for use in a wide variety of applications ranging from medicines, tissue engineering, superabsorbents, controlled release of drugs & fertilizers, and oil absorbers etc. This review highlights hydrogel structure and their different classifications under various heads. It also discusses various routes to obtain tailormade hydrogels by polymerizing a combination of two or more monomers with proper type of crosslinks in order to obtain desired properties in the resulting hydrogel. Novel hydrogel configurations like microgels and nanogels, slide ring gels, double network hydrogels and nanocomposite gels have also been reviewed. 相似文献
136.
Influence of 1,2‐polybutadiene on properties of dicumyl peroxide cured brominated butyl rubber 下载免费PDF全文
Peroxide curing of brominated butyl rubber (BIIR) is an attractive topic, but the degradation of BIIR during the curing is a drawback needed to be overcome. Coagent assisted peroxide curing system is an attractive and effective choice in order to increase the crosslink density of rubbers. 1,2‐polybutadiene (1,2‐PB) is used as a crosslinking coagent for the curing of BIIR by dicumyl peroxide (DCP), and the effect of 1,2‐PB on the curing characteristics, crosslink density, and mechanical properties is investigated. The addition of 1,2‐PB affects the curing characteristics of BIIR compound and significantly increases the crosslink density of BIIR vulcanizates. With increasing 1,2‐PB content, the tensile strength and stresses at a given extension of BIIR vulcanizates increase, but the elongation at break decreases. A stress‐softening effect of the carbon black filled BIIR vulcanizates is observed and becomes more pronounced with increasing 1,2‐PB content. The addition of 1,2‐PB increases the stress relaxation index of BIIR. GPC and 13C‐NMR results indicate 1,2‐PB participates in the crosslinking reaction, and the existence of 1,2‐PB component in the insoluble fraction of BIIR/1,2‐PB vulcanizates is confirmed by solid‐state 13C‐NMR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43280. 相似文献
137.
Aspects of varying crosslinker and catalyst concentrations on tear strength of silicone polymer networks: Comparison of tear strengths using samples of different geometries 下载免费PDF全文
Gul Bali Shah 《应用聚合物科学杂志》2016,133(15)
Crosslinker and catalyst concentrations have been varied to prepare different hydroxyfunctional poly(dimethylsiloxane) (HOPDMS) polymer network compositions. The tear strengths of these silicone polymer networks have been measured using different geometries, as trouser, crescent, and Graves (angled) specimens. It has been observed that the results of tear strength of Graves and crescent‐shaped specimens do not show a constant ratio with the concentration of crosslinker used for curing of HOPDMS networks. Instead, it has been observed and reported for the first time that the tear strengths of Graves and crescent‐shaped samples show a crossover at about 1.2% crosslinker. The observation of this crossover pattern for different compositions of silicone networks show that it is difficult to compare the results of the tear test of the same polymer performed on samples of different geometries with one another. The crossover pattern of the tear energy results for the test specimens of two different geometries has been explained in the light of essential work facture theory based on the geometry of the testing sample, crosslinking, and testing that alters the distribution of force over the width of the specimen. It was shown that the change in composition of the HOPDMS networks changes the order of ranking of Graves and crescent tear tests. With varying catalyst concentration in the silicone network composition, the tear property differences between the Graves and crescent‐shaped specimens are not significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43115. 相似文献
138.
Affinity‐tuned peroxidase‐like activity of hydrogel‐supported Fe3O4 nanozyme through alteration of crosslinking concentration 下载免费PDF全文
In this work, we evaluated the effect of crosslinking concentration on the affinity of poly (2‐acrylamido‐2‐methyl‐1‐propansulfonic acid) (PAMPS) hydrogel‐supported Fe3O4 nanozyme towards substrates (tetramethylbenzidine (TMB) and H2O2). The peroxidase‐like catalytic activity of PAMPS/Fe3O4 nanozyme was discussed with respect to crosslinking concentration of PAMPS hydrogel for the oxidation of TMB in the presence of H2O2 at room temperature. High catalytic activity was achieved due to good dispersion of Fe3O4 nanozyme in the hydrogel network and strong affinity of PAMPS hydrogel‐supported Fe3O4 nanozyme towards substrates. The affinity between the hydrogel‐supported Fe3O4 nanozyme and substrates can be improved by regulating the crosslinking concentration of PAMPS hydrogel without other trenchant experimental conditions. In addition, the result indicated that H2O2 can be detected even at a concentration as low as 1.5 × 10?6 mol L?1 with a linear detection range of 1.5–9.8 × 10?6 mol L?1. Such investigations not only showed a new approach to improve the affinity and peroxidase‐like activity of Fe3O4 nanozyme, but also verified its potential application in bio‐detection and environmental chemistry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43065. 相似文献
139.
Replacement of styrene with acrylated epoxidized soybean oil in an unsaturated polyester resin from propylene glycol,isophthalic acid,and maleic anhydride 下载免费PDF全文
Commercial unsaturated polyester (UPE) resins typically contain a high amount of volatile toxic styrene. A non‐volatile acrylated epoxidized soybean oil (AESO) was found to be an excellent replacement of styrene in a commercially available UPE resin [designated as Styrene‐(PG‐IPA‐MA)] that is derived from propylene glycol (PG), isophthalic acid (IPA), and maleic anhydride (MA) in terms of the mechanical properties of the resulting kenaf fiber‐reinforced composites. The AESO‐(PG‐IPA‐MA) resins had low viscosity and long pot life below 70°C for a typical fiber‐reinforced composite application. AESO and PG‐IPA‐MA were not able to form a strong polymer matrix individually for fiber‐reinforced composites. However, a combination of AESO and PG‐IPA‐MA saw strong synergistic effects between them. The flexural, tensile, and water absorption properties of kenaf fiber‐reinforced composites made from AESO‐(PG‐IPA‐MA) resins were comparable with or even superior to those from the Styrene‐(PG‐IPA‐MA) resin. The AESO/(PG‐IPA‐MA) weight ratio was investigated for maximizing the mechanical properties of the kenaf fiber‐reinforced composites. The curing mechanism of the AESO‐(PG‐IPA‐MA) resins is discussed in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43052. 相似文献
140.
Csilla Lakatos Katalin Czifrák József Karger‐Kocsis Lajos Daróczi Miklós Zsuga Sándor Kéki 《应用聚合物科学杂志》2016,133(43)
Crosslinked polyurethanes (PUs) containing irreversible (allophanate) and reversible Diels‐Alder chemical bonds were synthesized using various diisocyanates (methylene diphenyl diisocyanate MDI, 1,6‐hexamethylenediisocyanate HDI) and poly(?‐caprolactone) ((PCL) with different molecular weights (Mn = 10 kg/mol, 25 kg/mol, 50 kg/mol) as diol component. The melting/crystallization of PCL and the reversible DA bonds acted as temperature‐activated switches for shape memory performances, while allophanate network provided the permanent crosslinks for these PUs. The reversible DA bonds were obtained by the reaction of diisocyanate‐ended prepolymers with furfurylamine (FA) followed by the addition of bismaleimide (BMI). The permanent crosslinks between the linear chains containing DA bonds were achieved using additional amounts of diisocyanates (MDI or HDI). The above reaction path was supported by infrared spectroscopic results and swelling experiments. Tensile mechanical and shape memory properties in tension of the PUs were determined and discussed as a function of composition and crosslink densities deduced from swelling and dynamic mechanical analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44145. 相似文献