全文获取类型
收费全文 | 1082篇 |
免费 | 22篇 |
国内免费 | 243篇 |
专业分类
化学 | 1051篇 |
晶体学 | 1篇 |
力学 | 5篇 |
综合类 | 2篇 |
物理学 | 221篇 |
综合类 | 67篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 13篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 27篇 |
2017年 | 29篇 |
2016年 | 22篇 |
2015年 | 28篇 |
2014年 | 56篇 |
2013年 | 96篇 |
2012年 | 55篇 |
2011年 | 68篇 |
2010年 | 59篇 |
2009年 | 75篇 |
2008年 | 61篇 |
2007年 | 81篇 |
2006年 | 74篇 |
2005年 | 86篇 |
2004年 | 83篇 |
2003年 | 50篇 |
2002年 | 38篇 |
2001年 | 30篇 |
2000年 | 32篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 30篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1347条查询结果,搜索用时 15 毫秒
1.
2.
The content of residual monomers is one of the most important characteristics of polymer dispersions. As a result of the similar physicochemical parameters of ethyl acrylate and methyl methacrylate, it is very difficult to determine the residual monomers in acrylate dispersions obtained by emulsion polymerization of both monomers. Gas chromatography with capillary columns, however, permits separation of these monomers and their quantitative determination in acrylate dispersions. 相似文献
3.
High-resolution Fourier transform spectra of CH3OH have been investigated in the infrared region from 930 to 1450 cm−1 in order to map the torsion-rotation energy manifolds associated with the ν7 in-plane CH3 rock, the ν11 out-of-plane CH3 rock, and the ν6 OH bend. Upper-state term values have been determined from the assigned spectral subbands, and have been fitted to power-series expansions to obtain substate origins and effective B-values for the three modes. The substate origins have been grouped into related families according to systematic trends observed in the torsion-vibration energy map, but there are substantial differences from the traditional torsional patterns. There appears to be significant torsion-mediated spectral mixing, and a variety of “forbidden” torsional combination subbands with |Δυt|>1 have been observed, where υt denotes the torsional quantum number (equivalent to υ12). For example, coupling of the (υ6,υt)=(1,0) OH bend to nearby torsionally excited (υ7,υt)=(1,1) CH3-rock and (υ8,υt)=(1,1) CO-stretch states introduces (υ6,υt)=(1,0)←(0,1) subbands into the spectrum and makes the ν7+ν12−ν12 torsional hot band stronger than the ν7 fundamental. The results suggest a picture of strong coupling among the OH-bending, CH3-rocking, and CO-stretching modes that significantly modifies the traditional energy structure and raises interesting and provocative questions about the torsion-vibration identity of a number of the observed states. 相似文献
4.
Jean-Marcel Colmont François Rohart Jean-Pierre Bouanich 《Journal of Molecular Spectroscopy》2006,238(1):98-107
Extensive experiments on the K = 3 component of the J = 12-11 rotational transition of acetonitrile CH3C14N, located near 220.7 GHz, were performed at different temperatures in the range 235-350 K. They allow determining the N2-, H2-, and He-broadening coefficients, as well as their temperature dependences. More specific measurements on all the K-components of the involved transition perturbed by N2 at 303 K allow to point out a clear decreasing of the broadening coefficient with increasing K. Narrowing effects are clearly observed, and experimental lines were analysed both with Voigt and speed dependent Voigt profiles; but no exhaustive lineshape study was carried out. All the experimental parameters are compared with results derived from a semiclassical calculation of collisional interactions, including electrostatic, induction, and dispersion energy contributions. 相似文献
5.
基于超分子结构共掺杂纳米复合薄膜的制备与荧光特性 总被引:5,自引:0,他引:5
为改善功能分了的特性,提出一种基于金属纳米粒子-偶氮染料复合物共掺杂超分子结构功能材料的设计新方法.并依照此方法制备出复合材料,观测了其显微结构,测量了其紫外-可见光吸收,研究了该超分子结构复合体系的荧光特性.实验发现,由于金属银纳米粒子的掺杂,使得超分子结构复合体系中功能分子甲基橙在溶液态体系的荧光强度增强近5倍,而在两种不同结构(共混结构和包覆结构)的薄膜态超分子结构体系中,其荧光强度分别被猝灭15%和20%.研究结果表明,复合膜中采用超分子结构完全能够改善功能分子的特性. 相似文献
6.
本文研究了在油酸钠存在下醋酸乙烯酯──甲基丙烯酸甲酯的无乳化剂乳液共聚。发现油酸钠加速聚合反应,并测定了胶乳粒子。 相似文献
7.
Igor V. Bliznets Grigory G. Aleksandrov Sergey M. Lukyanov 《Tetrahedron letters》2004,45(49):9127-9130
2-Methyl-3-cyanopyridines were converted into the corresponding 2-azidomethyl derivatives, which then underwent an intramolecular cycloaddition reaction. A novel heterocyclic system containing a 3-(tetrazol-5-yl)pyridine unit was obtained in this way. 相似文献
8.
在pH为2~3的硫酸介质中,缓慢加入稀硫化钠溶液,可以将甲基紫染料中的铜含量降至1000ug/g以下.本方法工艺简单,设备投资低,试剂用量少,经济效益高,是理想的甲基紫染料生产工艺改进方法.讨论了工业生产中的废料利用及治理环境污染等问题.对该方法已成功进行了工业放大实验. 相似文献
9.
本文报道四甲基膦酸二甲庚酸萃淋树脂(CL-P_(350)从硝酸溶液中吸附鳞的性能和机理研究。实验结果表明,吸附平衡服从Langmuir经验等温式。测得吸附物分子中P(350)与Re(Ⅶ)的摩尔比为2:1。Re(Ⅶ)是以形式被树脂吸附,其吸附机理属于综合反应:并测定了吸附过程的热力学函数。 相似文献
10.
The study of the partitioning mechanism of methyl orange in an aqueous two-phase system 总被引:2,自引:0,他引:2
An aqueous two-phase system of dodecyl triethylammonium bromide (C12NE, cationic surfactant) and sodium dodecyl sulfate (SDS, anionic surfactant) mixture is proposed for the extraction of some dyes and porphyrin compounds. Transparent two phase-systems are formed when the surfactant concentrations and C12NE/SDS ratios are in certain regions. In this study, the aqueous two phase-systems were prepared by mixing 0.1 mol l−1 C12NE and SDS with a molar ratio of 1.7:1.0. The results showed that negatively charged chlorophyll (sodium copper chlorophyllin) and positively charged dye (methyl violet) were efficiently extracted into the upper phase. The negatively charged methyl orange (pH>7) was moved into the upper phase mostly while amphoteric methyl orange (pH<3) was distributed in the two phases uniformly. Except for hydrophobic force, charge interaction between solute and surfactant also play an important role in the extraction process. 相似文献