全文获取类型
收费全文 | 15652篇 |
免费 | 1174篇 |
国内免费 | 288篇 |
专业分类
电工技术 | 73篇 |
综合类 | 768篇 |
化学工业 | 11137篇 |
金属工艺 | 122篇 |
机械仪表 | 41篇 |
建筑科学 | 121篇 |
矿业工程 | 72篇 |
能源动力 | 65篇 |
轻工业 | 1249篇 |
水利工程 | 10篇 |
石油天然气 | 1075篇 |
武器工业 | 25篇 |
无线电 | 218篇 |
一般工业技术 | 1860篇 |
冶金工业 | 71篇 |
原子能技术 | 114篇 |
自动化技术 | 93篇 |
出版年
2024年 | 53篇 |
2023年 | 149篇 |
2022年 | 149篇 |
2021年 | 263篇 |
2020年 | 275篇 |
2019年 | 289篇 |
2018年 | 250篇 |
2017年 | 358篇 |
2016年 | 394篇 |
2015年 | 459篇 |
2014年 | 719篇 |
2013年 | 751篇 |
2012年 | 1044篇 |
2011年 | 1089篇 |
2010年 | 828篇 |
2009年 | 929篇 |
2008年 | 835篇 |
2007年 | 1082篇 |
2006年 | 1168篇 |
2005年 | 989篇 |
2004年 | 831篇 |
2003年 | 754篇 |
2002年 | 592篇 |
2001年 | 516篇 |
2000年 | 407篇 |
1999年 | 403篇 |
1998年 | 292篇 |
1997年 | 252篇 |
1996年 | 157篇 |
1995年 | 144篇 |
1994年 | 135篇 |
1993年 | 141篇 |
1992年 | 105篇 |
1991年 | 70篇 |
1990年 | 43篇 |
1989年 | 47篇 |
1988年 | 24篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 21篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1980年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The polymerization of α‐methylstyrene (AMS) catalyzed by Maghnite‐H+ (Mag‐H) was investigated. Mag‐H is a montmorillonite sheet silicate clay, exchanged with protons. It was found that the cationic polymerization of AMS is initiated by Mag‐H at ambient temperature in bulk and in solution. The effect of the amount of Mag‐H, the temperature, and the solvent was studied. The polymerization rate increased with increase in the temperature and the proportion of catalyst, and it was larger in nonpolar solvents. These results indicated the cationic nature of the polymerization. It may be suggested that the polymerization is initiated by proton addition to monomer from Mag‐H. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
102.
Raquel Rodríguez 《Polymer》2008,49(3):691-696
The limiting conversion phenomenon observed in high solid content silicone-modified acrylic miniemulsion polymerizations was investigated. It was found that the limiting conversion was mainly due to the formation of inactive radicals upon propagation of butyl acrylate radicals with the vinyl end groups of the polydimethylsiloxane. Polymerization strategies that allowed overcoming this problem and achieving high monomer conversion were implemented. 相似文献
103.
104.
Heather J. Avens 《Polymer》2008,49(22):4762-4768
Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eightfold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from fivefold lower eosin surface densities (2.8 versus 14 eosins/μm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. 相似文献
105.
106.
详细研究了以乙酸乙酯和环己烷为溶剂,丙烯酸为单体,BPO,LPO,AIBN为引发剂,聚烯基多醚为交联剂,合成增稠能力强、透明度高的聚丙烯酸树脂。于混和溶剂存在下制得的聚合物,消除了以往由二氯甲烷为溶剂的反应介质中所得产品的毒性,可广泛应用于医药及日用化工等行业。 相似文献
107.
水溶性聚偶氮酯的研究 总被引:1,自引:0,他引:1
用Pinner合成方法制备了用PEG400封端的水溶性聚偶氮酯,并表征了其结构;研究了热分解反应动力学及用于乳液聚合的动力学。结果表明,该种引发剂具有引发速度快、热分解机理简单和具有辅助乳化作用等优点。 相似文献
108.
W. Harmon Ray 《加拿大化工杂志》1991,69(3):626-629
A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free-radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes. 相似文献
109.
The effects of temperature, initiator, and accelerator levels on the curing of an epoxy bisphenol‐A vinyl ester resin Derakane® 411‐45 (formulated with styrene) were investigated by gel‐time and exotherm‐peak measurements on bulk samples. It was observed that the gel time was reduced as the initiator or accelerator ratio increased. Except at higher contents of the accelerator, a small kinetic plateau was seen in the gel curve and a shift of the maximum exotherm toward high temperatures in the DSC curves. This was explained by the dual role played by the accelerator species. A regression analysis of all gel‐time data showed a dependence of 3/2 order in the accelerator and first order in the initiator concentrations. Thus, for this polymerization initiation system, the gel time can be predicted for any initiator and cobalt levels and at any temperature within the ranges studied. The effect of the initiator on the unreacted styrene and vinyl ester was also examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1146–1154, 2002; DOI 10.1002/app.10403 相似文献
110.
Radiation polymerization of acrylonitrile in a viscous system with styrene was performed at ambient temperature by using γ‐rays. It is found that the overall rate of polymerization was accelerated after critical conversion due to the gel effect. As the molar fraction of styrene in monomer feed (fSt) is increased, both the total polymer conversion and molar fraction of acrylonitrile in the copolymer feed (FAN) were decreased. The monomer reactivity ratios for acrylonitrile and styerne were determined to be r1 (AN) = 0.25 and r2 (St) = 2.0, respectively. The copolymers obtained were characterized by Fourier transformed infrared spectra (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), 1H‐NMR, and pyrolysis mass spectrometry (PMS). It was found that the slight addition of styrene to acrylonitrile strongly changes crystallinity, morphology, and thermal decomposition of the resulting polymer. 1H‐NMR measurment of AN/St copolymer showed the appearance of aromatic proton signals and shifted the resonance of the methylene proton to lower chemical shifts. The mass spectra of AN/St copolymers showed fragments of pyrolysates corresponding to oligonitriles with styrene end groups. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 268–275, 2002; DOI 10.1002/app.10324 相似文献