全文获取类型
收费全文 | 4303篇 |
免费 | 110篇 |
国内免费 | 40篇 |
专业分类
电工技术 | 22篇 |
综合类 | 213篇 |
化学工业 | 2724篇 |
金属工艺 | 84篇 |
机械仪表 | 163篇 |
建筑科学 | 130篇 |
矿业工程 | 41篇 |
能源动力 | 32篇 |
轻工业 | 229篇 |
水利工程 | 3篇 |
石油天然气 | 230篇 |
武器工业 | 23篇 |
无线电 | 18篇 |
一般工业技术 | 430篇 |
冶金工业 | 36篇 |
原子能技术 | 34篇 |
自动化技术 | 41篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 22篇 |
2021年 | 43篇 |
2020年 | 50篇 |
2019年 | 59篇 |
2018年 | 32篇 |
2017年 | 53篇 |
2016年 | 64篇 |
2015年 | 77篇 |
2014年 | 115篇 |
2013年 | 156篇 |
2012年 | 219篇 |
2011年 | 229篇 |
2010年 | 217篇 |
2009年 | 235篇 |
2008年 | 228篇 |
2007年 | 270篇 |
2006年 | 334篇 |
2005年 | 270篇 |
2004年 | 249篇 |
2003年 | 241篇 |
2002年 | 191篇 |
2001年 | 162篇 |
2000年 | 164篇 |
1999年 | 161篇 |
1998年 | 117篇 |
1997年 | 116篇 |
1996年 | 52篇 |
1995年 | 52篇 |
1994年 | 43篇 |
1993年 | 55篇 |
1992年 | 29篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 16篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有4453条查询结果,搜索用时 31 毫秒
91.
92.
以过硫酸铵为引发剂,十二烷基硫酸钠为乳化剂,采用种子聚合工艺,合成了偏氯乙烯质量分数为23%~43%的羧基偏氯乙烯丁苯胶乳。通过电镜观察到所合成的胶乳粒子具有核-壳结构。通过测定胶闰子表面层的羧基数量,研究了羧基的分布,结果表明,羧酸种类对羧基在胶乳粒子中及在聚合体系中的分布有重要影响,该胶乳作为地毯背衬粘合剂,具有粘合力高,极限氧指数高的特点,是一种较好的阻燃性粘合剂。 相似文献
93.
In the copolymerization of phenylacetylene with various acetylenes catalysed by WCl6·Ph4Sn, the relative reactivity of monomer decreased with increasing steric effect of monomer, e.g. HC Cn-Bu, HC Cn-Hex > HC CPh, HC Cs-Bu > HC Ct-Bu, MeCCPh, CICCPh. While 1-chloro-2-phenylacetylene (a disubstituted acetylene) showed high reactivity in the homopolymerization by Mobased catalysts, the reactivity was remarkably depressed in the presence of phenylacetylene as comonomer. Based on these results, the relative reactivity of the acetylenic monomers in copolymerization was explained in terms of competitive coordination of monomers to the propagating end. 相似文献
94.
95.
固相接枝共聚法制备PP—g—PS 总被引:4,自引:0,他引:4
用固相接枝共聚方法制备了聚丙烯接枝苯乙烯(PP-g-PS),详细地考察了聚丙烯与引发剂的品种、反应温度、苯乙烯及引发剂的浓度等因素对接枝率和接枝效率的影响。研究结果表明:PP-g-PS具有较高的接技率,应用于聚丙烯/聚苯乙烯(PP/PS)共混物中,能降低分散相PS的粒径,提高PP/PS的相容性。 相似文献
96.
97.
We report the graft copolymerization of acrylic acid onto the polypropylene (PP) melt‐blown nonwovens induced by electron beam (EB) preirradiation in this article. The occurrence of the graft copolymerization was confirmed by means of XPS, FTIR, and SEM. The effects of preirradiation dose, monomer concentration, bath ratio, reaction time, and temperature on the graft ratio were investigated. The water conservation, water absorption rate, and K+ exchange capacity were also determined on the grafted PP melt‐blown nonwovens, which showed that EB preirradiation‐induced grafting was an effective way to improve the hydrophicility of PP melt‐blown nonwovens. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4971–4977, 2006 相似文献
98.
The effect of the reaction conditions on the grafting parameters during grafting of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto sodium carboxymethylcellulose using H2O2/Fe+2 redox pair are studied at 30°C. The grafting ratio, add on, and conversion initially increase with the H2O2 concentration in the range of (10.0–15.0) × 10?2 mol dm?3. Thereafter, these parameters decrease with the H2O2 concentration. The grafting ratio, add on, and conversion increase when increasing the ferrous ion concentration from (0.5 to 4.0) × 10?2 mol dm?3 and decrease with a further increase in the concentration. It is observed that the grafting ratio and add on increase with the monomer concentration, whereas the conversion decrease. The hydrogen ions seem to be facilitating the grafting reaction up to a certain concentration and after this concentration seem to be retarding the process. The grafting ratio, add on, and conversion decrease with the sodium carboxymethylcellulose concentration. When increasing the time period from 60 to 90 min, the grafting parameters increase but decrease thereafter. Similarly, when increasing the temperature from 25 to 30°C, the grafting parameters increase and decrease thereafter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4819–4825, 2006 相似文献
99.
Jing Zhang 《Polymer》2007,48(5):1269-1275
A copolymer, poly(aniline-co-m-aminophenol), was synthesized chemically. The monomer concentration ratio strongly affects the copolymerization rate and the properties of the copolymer. A solution consisting 0.34 M aniline, 0.012 M m-aminophenol, 0.47 M ammonium peroxydisulfate and 2 M H2SO4 was found to be an optimum mixture for the chemical copolymerization. The visible spectra show that a high concentration ratio of m-aminophenol/aniline in the mixture inhibits the chain growth of the copolymer. The spectra of IR and 1H NMR demonstrate that m-aminophenol units are included in the copolymer chain, which play a key role in extending usable pH region of the copolymer. The result of cyclic voltammograms in a wide potential region of −0.20-0.80 V (vs. SCE) indicates that the copolymer prepared under the optimum condition still held 52.7% of the electrochemical activity when the copolymer electrode was transferred from a solution of pH 4.0 to a solution of pH 11.0, which is much better than that of polyaniline. The X-ray diffraction spectra and images of the copolymers reveal a fact that the changes in the crystal structure and morphology of the copolymers are as a function of the monomer ratio in the mixture. The conductivity of the copolymer prepared under the optimum condition is 2.3 S cm−1 and slightly depends on the pH value. 相似文献
100.
This study concerns a comparative study of three crosslinkers, divinylbenzene (DVB), 1,2‐bis(p,p‐vinylphenyl)ethane (BVPE), and triallyl cyanurate (TAC) crosslinked poly(ethylene‐co‐tetrafluoroethylene) (ETFE)‐based radiation‐grafted membranes, which were prepared by radiation grafting of p‐methylstyrene onto ETFE films and subsequent sulfonation. The effect of the different types and contents of the crosslinkers on the grafting and sulfonation, and the properties such as water uptake, proton conductivity, and thermal/chemical stability of the resulting polymer electrolyte membranes were investigated in detail. Introducing crosslink structure into the radiation‐grafted membranes leads to a decrease in proton conductivity due to the decrease in water uptake. The thermal stability of the crosslinked radiation‐grafted membranes is also somewhat lower than that of the noncrosslinked one. However, the crosslinked radiation‐grafted membranes show significantly higher chemical stability characterized in the 3% H2O2 at 50°C. Among the three crosslinkers, the DVB shows a most pronounced efficiency on the crosslinking of the radiation‐grafted membranes, while the TAC has no significant influence; the BVPE is a mild and effective crosslinker, showing the moderate influence between the DVB and TAC crosslinkers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4565–4574, 2006 相似文献