全文获取类型
收费全文 | 4327篇 |
免费 | 101篇 |
国内免费 | 5篇 |
专业分类
化学 | 2797篇 |
晶体学 | 56篇 |
力学 | 58篇 |
数学 | 433篇 |
物理学 | 1089篇 |
出版年
2021年 | 33篇 |
2020年 | 35篇 |
2019年 | 38篇 |
2016年 | 58篇 |
2015年 | 66篇 |
2014年 | 73篇 |
2013年 | 142篇 |
2012年 | 137篇 |
2011年 | 163篇 |
2010年 | 111篇 |
2009年 | 83篇 |
2008年 | 143篇 |
2007年 | 135篇 |
2006年 | 144篇 |
2005年 | 141篇 |
2004年 | 130篇 |
2003年 | 129篇 |
2002年 | 120篇 |
2001年 | 117篇 |
2000年 | 115篇 |
1999年 | 60篇 |
1998年 | 42篇 |
1997年 | 47篇 |
1996年 | 86篇 |
1995年 | 62篇 |
1994年 | 81篇 |
1993年 | 62篇 |
1992年 | 62篇 |
1991年 | 59篇 |
1990年 | 58篇 |
1989年 | 46篇 |
1988年 | 50篇 |
1987年 | 64篇 |
1986年 | 58篇 |
1985年 | 58篇 |
1984年 | 63篇 |
1983年 | 48篇 |
1982年 | 52篇 |
1981年 | 60篇 |
1980年 | 42篇 |
1979年 | 46篇 |
1978年 | 53篇 |
1977年 | 56篇 |
1976年 | 58篇 |
1975年 | 57篇 |
1974年 | 57篇 |
1973年 | 42篇 |
1968年 | 27篇 |
1967年 | 24篇 |
1957年 | 30篇 |
排序方式: 共有4433条查询结果,搜索用时 15 毫秒
21.
Various combinations of polyurethane (PUR) and poly(methyl methacrylate) (PMMA) were prepared as interpenetrating polymer networks (IPN) or semi-IPNs. In the latter, either the PUR or the PMMA component was crosslinked. The optical transmissions of these materials were measured as a function of the crosslink degrees of both phases. The role of the PUR chain extender, poly(oxypropylene) glycol, is discussed. It is concluded that any means which increases the degree of phase dispersion favours the transparency of PUR/PMMA based IPNs and semi-IPNs. 相似文献
22.
23.
24.
25.
Abachi S Baringer P Bylsma BG DeBonte R Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Rangan LK Shibata EI Derrick M Gan KK Kooijman P Loos JS Musgrave B Price LE Repond J Sugano K Weiss JM Wood DE Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Kesten P Meyer DI Nitz D Seidl AA Thun R Willutzky M Cork B 《Physical review letters》1986,57(16):1990-1993
26.
27.
28.
T. Al Adlouni F. Meyer C. Meyer A. Fayt 《International Journal of Infrared and Millimeter Waves》1986,7(3):405-419
The perpendicularv
8 band lying in the 1000–1100 cm–1 region has been studied from infrared and laser Stark, spectra. We were interested in the part of spectrum corresponding to the spectral range of the 9 m CO2 laser lines. Assignments of rovibrational lines with J'<40 and K'<6 have been made. About 100 Stark resonances have been assigned to 12 rovibrational transitions. Effective molecular constants and dipole moment have been determined with high accuracy. A list of close resonances with CO2 laser lines is given and may be used for optical pumping experiments. 相似文献
29.
G. Lhersonneau D. Weiler P. Kohl H. Ohm K. Sistemich R. A. Meyer 《Zeitschrift für Physik A Hadrons and Nuclei》1986,323(1):59-67
An isomeric state at 3,523 keV excitation energy in97Y with a half-life of 144(10) ms has been discovered with the fission-product separator JOSEF. This isomer is depopulated through aγ transition of 162 keV. AnE3 multipolarity for this transition is consistent with the measured conversion coefficients ofα K =0.98(20) andα T =1.00(19). Subsequent electromagnetic transitions populate several new97Y levels which have high spins. For the isomer the three-quasiparticle configuration [πg 9/2?ν(h 11/2,g 7/2)]27/2? is proposed. TheE3 transition with a strength about 2 single-particle units is supposed to be of the typeh 11 2/+1 →d 5 2/?1 . These findings provide evidence for the rapid shape transition atA?100 since they indicate shell-model character of 39 97 Y58 even at high excitation energies while the immediate neighbour 39 98 Y59 contains a rotational band based on a level at 495 keV. 相似文献
30.
In contrast to the classical method where a single molecule is designed to extract metal cations under specific conditions, dynamic covalent chemistry provides an approach based on the implementation of an adaptive dynamic covalent library for inducing the generation of the extractant species. This approach has been applied to the liquid–liquid extraction of copper(ii) nitrate based on a dynamic library of acylhydrazones constituents that self-build and distribute through the interface of a biphasic system. The addition of copper(ii) cations to this library triggers a modification of its composition and the up-regulation of the ligand molecules driven by coordination to the metal cations. Among these, one species has proven to be sufficiently lipophilic to play the role of carrier agent and its formation by component exchange enables the partial extraction of the copper(ii). The study of different pathways to generate the dynamic covalent library demonstrates the complete reversibility and the adaptability of the system. The detailed analytical investigation of the system provides a means to assess the mechanism of the dynamic extraction process.Phase transfer of Cu(ii) cations is achieved by component exchange in a dynamic covalent library of acylhydrazone ligands. B1/B2 component exchange leads to the generation of a lipophilic carrier agent that extracts Cu(ii) into chloroform. 相似文献