全文获取类型
收费全文 | 14292篇 |
免费 | 1064篇 |
国内免费 | 228篇 |
专业分类
电工技术 | 68篇 |
综合类 | 663篇 |
化学工业 | 10529篇 |
金属工艺 | 107篇 |
机械仪表 | 39篇 |
建筑科学 | 112篇 |
矿业工程 | 53篇 |
能源动力 | 68篇 |
轻工业 | 677篇 |
水利工程 | 9篇 |
石油天然气 | 985篇 |
武器工业 | 25篇 |
无线电 | 212篇 |
一般工业技术 | 1769篇 |
冶金工业 | 64篇 |
原子能技术 | 108篇 |
自动化技术 | 96篇 |
出版年
2024年 | 32篇 |
2023年 | 145篇 |
2022年 | 115篇 |
2021年 | 239篇 |
2020年 | 240篇 |
2019年 | 265篇 |
2018年 | 238篇 |
2017年 | 317篇 |
2016年 | 361篇 |
2015年 | 419篇 |
2014年 | 665篇 |
2013年 | 660篇 |
2012年 | 943篇 |
2011年 | 974篇 |
2010年 | 749篇 |
2009年 | 856篇 |
2008年 | 789篇 |
2007年 | 959篇 |
2006年 | 1057篇 |
2005年 | 878篇 |
2004年 | 765篇 |
2003年 | 682篇 |
2002年 | 538篇 |
2001年 | 474篇 |
2000年 | 384篇 |
1999年 | 374篇 |
1998年 | 275篇 |
1997年 | 237篇 |
1996年 | 146篇 |
1995年 | 138篇 |
1994年 | 129篇 |
1993年 | 135篇 |
1992年 | 106篇 |
1991年 | 69篇 |
1990年 | 38篇 |
1989年 | 45篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
41.
42.
43.
用乳液聚合法合成了聚丙烯酸酯/醇酸树脂复合乳液,研究了醇酸树脂组成和用量及聚合条件对动力学和复合乳液性能的影响。结果表明,醇酸树脂对乳液聚合有明显的阻聚作用,而且这种阻聚作用随醇酸树脂中马来酸酐含量的增加而加剧。升高聚合温度和增加引发剂用量均有利于改善乳液的机械稳定性。随着醇酸树脂用量的增加,复合乳液的机械稳定性和涂膜的耐水性逐渐提高;醇酸树脂中马来酸酐含量增加,乳液机械稳定性提高,当醇酸树脂中马来酸酐质量分数为2 4%时,涂膜具有最佳的耐水性。 相似文献
44.
45.
Aimin Xiang Zhongjie Du Qinghua Zeng Chen Zhang Hangquan Li 《Polymer International》2005,54(10):1366-1370
This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry 相似文献
46.
Microcellular polymeric materials can be obtained by the polymerization of a high‐internal‐phase emulsion. These materials are good candidates as targets toward inertial confinement fusion. This application requires severe specifications, including a very low density and a small cell size. In this study, we examined the influence of parameters such as emulsification conditions, surfactant nature, and the presence of a porogen on the obtainment of those requirements. It was possible to obtain microcellular polymeric foams with apparent densities as low as 0.0126 g/cm3. However, it was difficult to obtain very low material density and still maintain a small average pore size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2053–2063, 2005 相似文献
47.
Todd M. Alam Joshua U. Otaigbe Dave Rhoades Gregory P. Holland Brian R. Cherry Paul G. Kotula 《Polymer》2005,46(26):12468-12479
Nanostructured polymer blends prepared via anionic ring opening polymerizations of cyclic monomers in the presence of a pre-made polymer melt exhibit a number of special properties over traditional polymer blends and homopolymers. Here, we report on a simple and versatile method of in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride polypropylene (mPP) matrix and a surface-active compatibilizer (i.e. PC grafted onto a mPP backbone generated in situ) to yield a micro- and nanostructured polymer blends consisting of a polycarbonate (PC) minor phase, and a polypropylene (PP) major phase. By varying the processing conditions and concentration of the macrocyclic carbonate it was possible to reduce the size of the PC dispersions to an average minor diameter of 150 nm. NMR and TEM characterizations indicate that the PC dispersions do not influence crystal content in the PP phase. Overall, the results point to a simple strategy and versatile route to new polymeric materials with enhanced benefits. 相似文献
48.
CuMgAl类水滑石的制备和表征 总被引:5,自引:0,他引:5
用盐-碱制备法合成了CuMgAl三元类水滑石化合物。探讨了原料配比、合成方式、水热处理温度和时间对合成过程的影响,筛选出合成HTLcs的适宜条件,并对HTLcs结构的热稳定性进行初步研究。结果表明,制备HTLcs主要取决于pH值,同时由于Cu2+的姜-太勒效应,合成结构单一的CuMgAl类水滑石要求原料配比中n(Cu)∶n(Mg)不得超过1.0,CuMgAl-HTLcs热稳定性较差,300℃焙烧2h结构破坏,600℃开始烧结,在300~500℃之间,随焙烧温度提高所得复合氧化物比表面积增大,最高可达200 m2/g。 相似文献
49.
Photoluminescence features in a commercial grade cured DGEBA-based epoxy resin have been investigated with as objective to determine which of the material compounds are responsible for cured resin emissions. The origin of the bands has been approached by considering photoluminescence of base resin and hardener taken separately, of their mixture, and in the course of curing. Most of the bands observed in the cured resin could be interpreted based on those found in the components taken separately. Fluorescence of the cured resin appears dominated by two broad bands that are characteristic of the hardener and exhibits a blue shift by up to 30 nm in the course of curing which could be used for cure monitoring purpose of the investigated system. Fluorescence of the base resin is clearly detected in the resin cured with tertiary amine as catalyser. However, it is very weak if the catalyser is not added. Two phosphorescence processes have been isolated in the cured resin, one of them being related to the base resin. Finally, a chemiluminescence spectrum has been recorded in the course of curing, which has been related to either curing-related reactions or to an oxidation process. 相似文献
50.