全文获取类型
收费全文 | 20603篇 |
免费 | 1613篇 |
国内免费 | 772篇 |
专业分类
电工技术 | 333篇 |
技术理论 | 1篇 |
综合类 | 955篇 |
化学工业 | 10098篇 |
金属工艺 | 341篇 |
机械仪表 | 332篇 |
建筑科学 | 929篇 |
矿业工程 | 135篇 |
能源动力 | 463篇 |
轻工业 | 644篇 |
水利工程 | 69篇 |
石油天然气 | 2178篇 |
武器工业 | 243篇 |
无线电 | 1557篇 |
一般工业技术 | 4155篇 |
冶金工业 | 255篇 |
原子能技术 | 70篇 |
自动化技术 | 230篇 |
出版年
2024年 | 99篇 |
2023年 | 327篇 |
2022年 | 324篇 |
2021年 | 507篇 |
2020年 | 554篇 |
2019年 | 563篇 |
2018年 | 504篇 |
2017年 | 681篇 |
2016年 | 680篇 |
2015年 | 669篇 |
2014年 | 1026篇 |
2013年 | 1144篇 |
2012年 | 1266篇 |
2011年 | 1429篇 |
2010年 | 1057篇 |
2009年 | 1125篇 |
2008年 | 1005篇 |
2007年 | 1284篇 |
2006年 | 1339篇 |
2005年 | 1054篇 |
2004年 | 943篇 |
2003年 | 872篇 |
2002年 | 790篇 |
2001年 | 709篇 |
2000年 | 577篇 |
1999年 | 488篇 |
1998年 | 445篇 |
1997年 | 300篇 |
1996年 | 213篇 |
1995年 | 169篇 |
1994年 | 179篇 |
1993年 | 152篇 |
1992年 | 117篇 |
1991年 | 87篇 |
1990年 | 42篇 |
1989年 | 36篇 |
1988年 | 31篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 51篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
T. Cotgreave 《Polymer》1985,26(9):1419-1422
A milled fibre reinforced epoxy resin composite (MFRE) has been developed for low temperature use. It is resistant to fracture at temperatures down to at least 77 K in direct contact with liquefied gases. It can be used as an adhesive, a gap-filling mastic or a moulding compound for difficult cryogenic applications. The characteristics of the material and some applications are described. 相似文献
52.
Yong Min Lee 《Electrochimica acta》2006,52(4):1582-1587
Highly ion-conductive solid polymer electrolyte (SPE) based on polyethylene (PE) non-woven matrix is prepared by filling poly(ethylene glycol) (PEG)-based crosslinked electrolyte inside the pores of the non-woven matrix. The PE non-woven matrix not only shows good mechanical strength for SPE to be a free-standing film, but also has very porous structure for high ion conductivity. The ion conductivity of SPE based on PE non-woven matrix can be enhanced by adding sufficient non-volatile plasticizer such as poly(ethylene glycol) dimethyl ether (PEGDME) into ion conduction phase without sacrificing mechanical strength. SPE with 20 wt.% crosslinking agent and 80 wt.% non-volatile plasticizer shows 3.1 × 10−4 S cm−1 at room temperature (20 °C), to our knowledge, which is the highest level for SPEs. It is also electrochemically stable up to 5.2 V and has high transference number about 0.52 due to the introduction of anion receptor as an additive. The interfacial resistance between Li electrode and SPE is low enough to perform charge/discharge test of unit cell consisting of LiCoO2/SPE/Li at room temperature. The discharge capacity of the unit cell shows 87% of theoretical value with 86% Coulombic efficiency. 相似文献
53.
It is proposed that the twist in polyethylene chains that can result from crystallization and subsequent deformation aggregates at boundaries and becomes a template for further reorganization that results in the long period observed in polyethylene fibres. The observed lower density at the boundaries requires the transport of free volume to the twist boundaries. Dispirations, disclinations and dislocations are crystallographic defects that are involved in the necessary transport mechanism. Twist and bend, derived from the Eulerian angles which are computed from the sets of chain internal coordinates, relate the orientation of different segments of a chain. Twist and bend are useful for the characterization of both crystallographic defects and arbitrary conformations of polymer chains. Defects, along with folds, chain ends, and ordinary edge and screw dislocations provide a basis for interpretation of structure-property relationships in solid polyethylene. 相似文献
54.
多羟甲基酚多丙烯酸酯的合成及其耐温性能研究 总被引:5,自引:0,他引:5
本文合成了新型耐温活性预聚体多羟甲基酚多丙烯酸酯,并考察了pH值,丙烯酸量,反应时间、反应温度、催化剂用量等因素对反应产率的影响。测试了固化物的TCA和DTA及力学性能,并用红外光谱确认主产物。 相似文献
55.
不同功能单体对分子印迹聚合物识别性能的模拟 总被引:1,自引:0,他引:1
以槲皮素为模板分子,以甲基丙烯酸(MAA)、三氟甲基丙烯酸(TFMAA)、丙烯酰胺(AM)、N-乙烯基吡咯烷酮(NVP)、2-乙烯基吡啶(2-VP)、4-乙烯基吡啶(4-VP)六种物质分别作为功能单体,运用量子化学方法模拟模板分子与不同功能单体的分子印迹聚合物预组装体系的构型、能量及复合反应的结合能△E,以讨论不同功能单体对分子印迹聚合物识别性能的影响,结果4-VP的印迹效应最好.通过模拟,有助于解释实验现象以及选择印迹效应更好的功能单体. 相似文献
56.
氯化聚乙烯双亲性接枝聚合物的合成与表征(Ⅰ) 总被引:4,自引:0,他引:4
采用“架桥剂”法,以马来酸酐(MAN)为“架桥剂”,使氯化聚乙烯(CPE)主链上接上一定数量的酸酐基团,然后利用接上去的酸酐基团与PMMA-OH、PEG、PPG、PTMG等反应合成了主链疏水、支链亲水或疏水的双亲性聚合物,并用IR、TG-DTA进行了表征。 相似文献
57.
Moritz Tebbe Elizabeth Galati Gilbert C. Walker Eugenia Kumacheva 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(37)
Future progress in nanoscience and nanotechnology necessitates further development of versatile, labor‐, and cost‐efficient surface patterning strategies. A new approach to nanopatterning is reported, which utilizes surface segregation of a smooth layer of an end‐grafted homopolymer in a poor solvent. The variation in polymer grafting density yields a range of surface nanostructures, including randomly organized pinned spherical micelles, worm‐like structures, networks, and porous films. The capability to use the polymer patterns for site‐specific deposition of small molecules, polymers, or nanoparticles is shown. This versatile strategy enables patterning of curved surfaces with direct access to the substrate and no need in changing polymer composition to realize different surface patterns. 相似文献
58.
Bhim Bali Prasad Deepak Kumar Rashmi Madhuri Mahavir Prasad TiwariAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):418
A new kind of molecularly imprinted polymer-modified graphite electrode was fabricated by “grafting-to” approach, incorporating sol–gel technique, for the detection of acute deficiency in serum ascorbic acid level (SAAL), manifesting hypovitaminosis C. The modified electrode exhibited ascorbic acid (AA) oxidation at less positive potential (0.0 V) than the earlier reported methods, resulting in a limit of detection as low as 6.13 ng mL−1 (RSD = 1.2%, S/N = 3). The diffusion coefficient (1.096 × 10−5 cm2 s−1), rate constant (7.308 s−1), and Gibb's free energy change (−12.59 kJ mol−1) due to analyte adsorption, were also calculated to explore the kinetics of AA oxidation. The proposed sensor was found to enhance sensitivity substantially so as to detect ultra trace level of AA in the presence of other biologically important compounds (dopamine, uric acid, etc.), without any cross interference and matrix complications from biological fluids and pharmaceutical samples. 相似文献
59.
This paper presents a novel signal processing technique for a square wave temperature modulated carbon black/polymer composite sensor. The technique consists of only two mathematical operations: summing the off- and on-transients of the conductance signals, and subtracting the steady-state conductance signal. The technique has been verified through its application to a carbon black/polyvinylpyrrolidone composite chemoresistor. Identification of water, methanol and ethanol vapours was successfully demonstrated using the peak time of the resultant curves. Furthermore, quantification of those vapours was found to be possible using the height of the peak heights, which was linearly proportional to concentration. The technique does not require zero-gas calibration and thus is superior to previously reported techniques. 相似文献
60.