全文获取类型
收费全文 | 1270篇 |
免费 | 45篇 |
国内免费 | 254篇 |
专业分类
化学 | 1310篇 |
晶体学 | 10篇 |
力学 | 33篇 |
综合类 | 4篇 |
数学 | 16篇 |
物理学 | 196篇 |
出版年
2024年 | 1篇 |
2023年 | 44篇 |
2022年 | 38篇 |
2021年 | 36篇 |
2020年 | 48篇 |
2019年 | 32篇 |
2018年 | 19篇 |
2017年 | 50篇 |
2016年 | 42篇 |
2015年 | 31篇 |
2014年 | 44篇 |
2013年 | 107篇 |
2012年 | 53篇 |
2011年 | 78篇 |
2010年 | 59篇 |
2009年 | 74篇 |
2008年 | 87篇 |
2007年 | 93篇 |
2006年 | 95篇 |
2005年 | 62篇 |
2004年 | 66篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 34篇 |
2000年 | 38篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 33篇 |
1995年 | 25篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有1569条查询结果,搜索用时 421 毫秒
21.
As a kind of special functional microspheres, fluorescent polymer microspheres could be used in cell label and separation, blood flow assay, flow cytometer marking, chemical reaction assay,and in analyst of the transform and diffusion of particles in soil 1. However, one of the most important applications of fluorescent microspheres is in the high-throughput screening of drugs (HTS) 2. Through affinity interaction, radioactive ligands (latent drugs) are bound to fluorescent microspheres covered by receptor, and luminescence is produced by radioactivity, so ligands can be assayed and screened.In this study, we developed a technique for preparing micron-size fluorescent microspheres with different functional groups. The methods included the synthesis of micron-size polystyrene microspheres through the dispersion polymerization of styrene in different media such as ethanol,ethanol-water, and isopropanol; the functional polystyrene microspheres were prepared by introduction of functional monomers into the reaction system of styrene; the functional fluorescent microspheres were obtained by the way of dying functional microspheres in the fluorescent material's ethanol solvent.The average diameter of microspheres was in the range of 1~10 μm, and the distribution was normal distribution. The functional groups included -OH, -CHO, -COOH, -CONH2, and SO3H. The absorbing spectrum and exciting spectrum were tested, the results showed that the maximal absorbance of fluorescent microsphere was near 306.5 nm, and its maximal excitation was near 362 nm. The excitation spectrum of fluorescent material (DPO) and fluorescent microspheres were shown in figure 1, and it indicated that the developed fluorescent microspheres showed the same excitation behavior like DPO, which related to the fluorescent microspheres had stable luminescence property. 相似文献
22.
本文研究了以正丁基锂为引发剂,四氢呋喃为添加剂,环己烷为溶剂中的α-甲基苯乙烯阴离子平衡聚合动力学。讨论了体系中的反应活性种;提出了聚合机理;得到了聚合温度为20℃时的平衡单体浓度与活性种速率常数及添加剂浓度之间的关系式。 相似文献
23.
Highly reactive zinc was readily prepared by electrolysis of a DMF solution containing pyrene as a mediator with a platinum cathode and a zinc anode. Preferential reduction of pyrene occurred to generate the corresponding radical anion, which reduced zinc ions generated from anodic dissolution to give zero valent zinc with high reactivity. The reactive zinc was successfully used for an efficient transformation of bromoalkanes into the corresponding organozinc bromides. Organozinc bromides obtained were further used successfully in Pd-catalyzed cross-coupling reaction with various aryl iodides and bromides. 相似文献
24.
The synthesis and cationic photopolymerization of different cationically polymerizable monomers containing electroactive groups are reviewed with 98 references. The preparation of various compounds containing electron‐donor or electron‐acceptor moieties and photopolymerizable functional groups is described. After a short discussion of basic principles of cationic polymerization, photoinduced cationic polymerizations of various cationically polymerizable monomers containing both electron‐donor or electron‐acceptor chromophores and the functional groups such as epoxy, vinyl, thiiranyl, oxetanyl and others are reviewed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
25.
R. WinterP.G. Nixon R.J. TerjesonJ. Mohtasham N.R. HolcombD.W. Grainger D. GrahamD.G. Castner G.L. Gard 《Journal of fluorine chemistry》2002,115(2):107-113
A new perfluorinated acrylate monomer containing the SF5(CF2)6-perfluorinated side chain was synthesized and polymerized into films. Bulk monomer characterization is consistent with the molecular structure based on FTIR, mass spectrometry and NMR analyses. The surface properties of polymer coatings were studied with aqueous wetting (contact angle) and X-ray photoelectron spectroscopy (XPS) methods. The surface composition is shown to be highly enriched in the terminal side chain SF5-chemistry and exhibits properties consistent with a highly apolar, non-wetting perfluorinated polymer surface. Depth-dependent XPS studies using angular-resolved methods (ADXPS) confirmed a non-stoichiometric enrichment of sulfur and fluorine at the film ambient interface, consistent with a surface presence of the terminal SF5-group and possibly film structural anisotropy in the surface zone. Time-of-flight (TOF) secondary ion mass spectrometry (SIMS) analysis supplements the XPS data by showing the presence of all expected SF5-acrylate chemistry components in the outer 15 Å of the film surface. 相似文献
26.
Marta Gonzlez‐lvarez Gloria Alzuet Jos Luis García‐Gimnez Benigno Macías Joaquín Borrs 《无机化学与普通化学杂志》2005,631(11):2181-2187
Three flavonoid copper(II) complexes Cu2(quercetin)(CH3COO)3(CH3OH) ( 1 ), Cu(anthrarufin)(CH3COO)·1/2H2O ( 2 ) and Cu(naringin)(OCH3)(CH3OH)2 ( 3 ) have been synthesized and characterized by elemental analysis, IR, electronic absorption and EPR (X‐band) spectroscopy. The complexes have a strong protective action over the Δsod1 mutant of S. cerevisiae against reactive oxygen radicals generated by an external source of free radicals (H2O2 or the superoxide‐generating, menadione). On the other hand, the complexes cleave DNA efficiently even in the absence of reducing agents. The main reactive oxygen species responsible for the DNA strand cleavage have been determined using radical scavengers. A probably mechanism of the DNA damage is proposed. 相似文献
27.
28.
聚丙烯共混物反应挤出过程中的降解抑制 总被引:4,自引:0,他引:4
聚丙烯/(丙烯腈-苯乙烯)共聚物在过氧化二异丙苯存在下反应共混挤出时,加入亚油酸三甘酯可以有效地抑制过程的降解,从挤出物中分离出聚丙烯组分测试熔体流动速率表明,加入亚油酸三甘酯后,其熔体流动速率有很大下降,扫描电子显微镜的观察表明,调节过氧化二异丙苯和亚油酸三甘酯的加入量,可有效控制降解并生成较多的接枝物相容性,显著改善相形态。 相似文献
29.
硝酸根离子介质中偏钛酸钡的水热合成 总被引:1,自引:0,他引:1
以硝酸和钛酸四丁酯为原料,在240℃的碱液中成功地制备了四方相BaTiO3运用XRD、DSC和IR等技术碱度、硝酸根离子、钛源活性、填充度等因素对BaTiO3形成、粒度和物相的作用,KOH最适宜浓度为1.0mol/L,碱液中BaTiO3是BaO-TiO2体系中最稳定的物相,硝酸根离子参与了BaTiO3晶体的成核和生长,钛源的高活性和高填充度有利于四方BaTiO3的形成。 相似文献
30.
Chaowei Yuan Wen Cui Yanjuan Sun Jiadong Wang Ruimin Chen Jin Zhang Yuxin Zhang Fan Dong 《中国化学快报》2020,31(3):751-754
It is of a great challenge to develop semiconductor photocatalysts with potential possibilities to simultaneously enhance photocatalytic efficiency and inhibit generation of toxic intermediates.In this study,we developed a facile method to induce the La doping and cationic vacancie(V(Zn))on ZnO for the highly efficient complete NO oxidation.The photocatalytic NO removal efficiency increases from 36.2%to 53,6%.Most importantly,a significant suppressed NO2 production also has been realized.According to the DFT calculations,ESR spectra and in situ FTIR spectra,the introduction of La^3+induce the redistribution of charge carriers in La-ZnO,which promote the production of·O2^- and lead to the formation of V(Zn)for the formation of·OH,contributing to the complete oxidation of NO to nitrate.Besides,the conversion pathway of photocatalytic NO oxidation has been elaborated,This work paves a new way to simultaneously realize the photocatalytic pollutants removal and the inhibition of toxic intermediates generation for efficient and safe air purification. 相似文献