全文获取类型
收费全文 | 6607篇 |
免费 | 102篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 94篇 |
综合类 | 15篇 |
化学工业 | 1302篇 |
金属工艺 | 128篇 |
机械仪表 | 185篇 |
建筑科学 | 151篇 |
矿业工程 | 30篇 |
能源动力 | 353篇 |
轻工业 | 607篇 |
水利工程 | 67篇 |
石油天然气 | 46篇 |
无线电 | 732篇 |
一般工业技术 | 1446篇 |
冶金工业 | 557篇 |
原子能技术 | 74篇 |
自动化技术 | 953篇 |
出版年
2024年 | 164篇 |
2023年 | 143篇 |
2022年 | 326篇 |
2021年 | 529篇 |
2020年 | 359篇 |
2019年 | 376篇 |
2018年 | 343篇 |
2017年 | 294篇 |
2016年 | 283篇 |
2015年 | 195篇 |
2014年 | 242篇 |
2013年 | 476篇 |
2012年 | 282篇 |
2011年 | 310篇 |
2010年 | 207篇 |
2009年 | 177篇 |
2008年 | 176篇 |
2007年 | 148篇 |
2006年 | 128篇 |
2005年 | 91篇 |
2004年 | 71篇 |
2003年 | 86篇 |
2002年 | 70篇 |
2001年 | 67篇 |
2000年 | 50篇 |
1999年 | 66篇 |
1998年 | 157篇 |
1997年 | 133篇 |
1996年 | 101篇 |
1995年 | 74篇 |
1994年 | 63篇 |
1993年 | 57篇 |
1992年 | 37篇 |
1991年 | 43篇 |
1990年 | 39篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 23篇 |
1973年 | 8篇 |
1972年 | 9篇 |
排序方式: 共有6740条查询结果,搜索用时 0 毫秒
71.
Zia-ur-Rehman Sakhawat Ali A D Khan F H Shah 《Journal of the science of food and agriculture》1994,65(4):381-383
Improvement in egg production and egg size was noted when dietary rice polishing was replaced by carrot residue at 80 g kg?1 diet. The layers fed on a diet containing orange waste or mango peels showed results comparable with the control. Egg production and egg size were adversely affected when mango stone was added to the layers' diet. 相似文献
72.
Sakina Khatoon Mohammad I. Khan Thangaraj Jeyarani 《International Journal of Food Science & Technology》2012,47(11):2259-2265
Hard fractions of palm oil and coconut oil, blended in the ratios of 90:10, 85:15, 80:20 and 75:25, were interesterified for 8 h using Lipozyme TL IM. Major fatty acids in the blends were palmitic acid (41.7–48.4%) and oleic acid (26.2–30.8%). Medium‐chain fatty acids accounted for 4.5–13.1% of the blends. After interesterification (IE), slip melting point was found to decrease from 44.8–46.8 °C to 28.5–34.0 °C owing to reduction in solids content at all temperatures. At 37.5 °C, the blends containing 25% coconut stearins had 17.4–19% solids, which reduced to 0.4–1.5% on IE, and the slip melting point (28.6 and 28.8 °C) indicated their suitability as margarine base. The reduction in solid fat index of the interesterified fats is attributed to the decrease in high‐melting triacylglycerols in palm oil (GS3 and GS2U type) and increase in triolein (GU3) content from 1 to 9.2%. Retention of tocopherols and β‐carotene during IE was 76 and 60.1%, respectively, in 75:25 palm stearin and coconut stearin blend. 相似文献
73.
Ahmad A Anjum FM Zahoor T Nawaz H Dilshad SM 《Critical reviews in food science and nutrition》2012,52(3):201-212
β-Glucan is a valuable functional ingredient and various extraction techniques are available for its extraction. Choice of an appropriate extraction technique is important as it may affect the quality, structure, rheological properties, molecular weight, and other functional properties of the extracted β-glucan. These properties lead to the use of β-glucan into various food systems and have important implications in human health. This review focuses on the extraction, synthesis, structure, molecular weight, and rheology of β-glucan. Furthermore, health implications and utilization of β-glucan in food products is also discussed. 相似文献
74.
75.
Ishrat M. Khan 《Polymer Bulletin》1990,24(3):305-308
Summary A criterion (°) for testing stereoblock and heterotactic polymers is developed. The criterion takes values between 1 and-1,
a value of 1 is indicative of a pure stereoblock polymer and a value of-1 indicates a pure heterotactic polymer. The criterion
(°) is compared with persistence ratio (ρ) and average stereochemical sequence length. The importance of δ as an aid in the
synthesis of stereoblock polymers is discussed. 相似文献
76.
This paper describes the shear imposed interfacial segregation of release systems for the facilitated attenuation of polyurethane (PU) adhesion to metal coun-terfaces using a RI-RIM system. It is shown that the migration rate of the dispersed release additives due to a shear imposed stress in the resin fluid is much greater than that arising from Fickian diffusion, thereby removing a vital constraint from conventional practice. The novel rotary injection RIM system is presented to simulate the on-line injection and shear induced interfacial segregation in model PU/abherent systems. A wide range of recipes comprising single (liquids or solids) and multicomponent (liquid-liquid and solid-liquid) release materials were injected into the polymerizing resin mixture to provide cohesively weak and friable “particle” boundary layer assemblies at the PU/metal interface. An instrumented Blister Test was employed to evaluate the quality of the molded interfaces in terms of adhesion and the concentration distribution of the injected species in the final cured moldings was determined through high pressure liquid chromatography (HPLC). A comparison of the results on the shear modified and the compounded interfaces confirm an accentuated lateral migration of the additives to the interface resulting in an appreciable diminution in the adhesion of the system. Finally, transport models are suggested to account for the observed augmented transport. 相似文献
77.
M. Y. Raie D. Muhammad S. A. Khan 《European Journal of Lipid Science and Technology》1985,87(7):282-283
Three varieties of Safflower cultivated in Pakistan have been studied. These contain 29.7–32.0% oils on the basis of dried and undecorticated seeds. Their fatty acid composition as determined by GLC is myristic (0.9–3.1%), palmitic (9.4–12.0%), stearic (2.3–5.5%), oleic (14.0–15.7%) and linoleic (65.9–73.4%). 相似文献
78.
M. Rashid Khan 《Fuel》1989,68(12):1522-1531
Coal devolatilization studies to maximize the yield of condensable products by operating at elevated temperatures and heating rates have been published. The objectives of this study were to investigate the influences of relatively mild operating conditions (e.g. relatively low temperature and pressure) on product quality, by comparing devolatilized products obtained at various temperatures and heating rates. Fixed bed, fluid bed, and entrained flow reactor units were used to obtain pyrolysis products. In addition, literature data on tar yields in various reactor units at a range of temperatures and residence times were surveyed and compared with experimental data. The liquids were characterized by a number of techniques, including field ionization mass spectroscopy (f.i.m.s.), sequential elution solvent chromatography (s.e.s.c.) and elemental analysis. The results demonstrate that the quality and yield of liquids obtained at a rapid heating rate are functions of peak pyrolysis temperature. It was shown that at a rapid heating rate, the yields of heavier polyfunctional groups (i.e. hydrocarbons with greater mean molecular weight) are greater than those obtained in the fixed bed slow heating rate reactor. The liquids generated at a slow heating rate are of lower molecular weight, viscosity, and sulphur content, and of higher H/C atomic ratios compared with the liquids obtained in a rapid heating rate unit. The effect of increasing the maximum pyrolysis temperature (at a constant slow heating rate) was to increase the yield of light gases (mainly H) at the expense of char hydrogen content and char reactivity. The tar yield is not markedly influenced when the peak devolatilization temperature is increased at a relatively slow heating rate. However, the quality (as defined by the H/C (atomic) ratio) of the liquids, and the reactivity (in air) of char, was reduced when the peak pyrolysis temperature was increased. At a rapid heating rate, the primary products, which have many structural characteristics of the parent coal, are devolatilized. The quality of the liquids obtained at a rapid heating rate is, therefore, determined by the devolatilized primary coal fragments evolved at the devolatilization temperature. In a slow heating rate fixed bed unit, however, the primary coal fragments undergo additional cracking reactions which involve stabilization of free radicals by donatable hydrogen. This leads to the formation of low molecular weight hydrocarbons of relatively higher quality. In-situ (both intraparticle or extraparticle) stabilization of reactive coal fragments by donatable hydrogen may lead to a significant improvement in the overall quality of the pyrolysis liquids in a fixed bed system in which time-temperature history is conducive for such reactions. 相似文献
79.
Mohammad Maududul Huq Md. Robiur Rahman Masnun Naher Mohammad Mizanur Rahman Khan Mostafa Kamal Masud Golam Mohammad Golzar Hossain Nianyong Zhu Yih Hsing Lo Muhammad Younus Wai-Yeung Wong 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(6):1243-1252
Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (1H, 13C and 31P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh3, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S1 → S0) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts. 相似文献
80.
In this article, polymer microspheres and silica nanoparticles have been discussed as important filler in polymer composites. Their synthesis methods, properties, and application were particularly stressed. Silica is usually used as nucleating agent, surface enhancement mediator, and as templates and cores. Among polymer/silica composites, various categories including polyaniline, polypyrrole, polystyrene, epoxy, rubber, and acrylate polymer were discussed in detail. It was observed that silica nanoparticles enhanced mechanical strength and overall performance of composites. Furthermore, composites having carbon nanotube along with silica particles possess high electrical and mechanical performance. These composites are important in nanoelectronic devices, nanomedicines, and defense-related applications. 相似文献