全文获取类型
收费全文 | 800篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
化学 | 538篇 |
晶体学 | 17篇 |
力学 | 12篇 |
数学 | 34篇 |
物理学 | 227篇 |
出版年
2023年 | 5篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 15篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 47篇 |
2012年 | 45篇 |
2011年 | 38篇 |
2010年 | 27篇 |
2009年 | 33篇 |
2008年 | 36篇 |
2007年 | 55篇 |
2006年 | 47篇 |
2005年 | 31篇 |
2004年 | 38篇 |
2003年 | 27篇 |
2002年 | 30篇 |
2001年 | 33篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1967年 | 4篇 |
排序方式: 共有828条查询结果,搜索用时 15 毫秒
821.
The transmissivity and the optical absorption of a WO3 film with oxygen deficiencies introduced were characterized and compared with those of an electrochromically colored WO3 upon injecting a proton (H+). The WO3 film with oxygen deficiencies introduced was clearly colored blue. It was shown that the wavelength regions of optical absorption of both films almost overlapped each other. 相似文献
822.
Katsunori Kawamura 《Letters in Mathematical Physics》2010,93(3):229-241
The direct sum \({{\mathcal O}_{*}}\) of all Cuntz algebras has a non-cocommutative comultiplication \({\Delta_{\varphi}}\) such that there exists no antipode of any dense subbialgebra of the C*-bialgebra \({({\mathcal O}_{*},\Delta_{\varphi})}\). From states equations of \({{\mathcal O}_{*}}\) with respect to the tensor product, we construct an operator W for \({({\mathcal O}_{*},\Delta_{\varphi})}\) such that W* is an isometry, \({W(x\otimes I)W^{*}=\Delta_{\varphi}(x)}\) for each \({x\in {\mathcal O}_{*}}\) and W satisfies the pentagon equation. 相似文献
823.
The reaction of tris(2‐pyridyl)phosphine oxides with benzeneselenenyl chloride in methanol gave the corresponding 5‐phenylseleno‐2,2′‐bipyridyls together with a small amount of 2,2′‐bipyridyls. Similarly, the reaction with arenesulfenyl chlorides in aqueous acetonitrile afforded two kinds of coupling products, 5‐phenylthio‐2,2′‐bipyridyls and 2,2′‐bipyridyls. While in the reaction with arenesulfinyl chlorides in aqueous acetonitrile, four corresponding bipyridyl derivatives, 2,2′‐bipyridyls, 5‐arylthio‐2,2′‐bipyridyls, 5‐arylsulfinyl‐2,2′‐bipyridyls, and 5‐arylsulfonyl‐2,2′‐bipyridyls, were formed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:72–81, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10085 相似文献
824.
Vitor A. Fernandes Rafaely N. Lima Yoisel B. Broterson Meire Y. Kawamura Radell Echemendía Alexander F. de la Torre Marco A. B. Ferreira Daniel G. Rivera Marcio W. Paixo 《Chemical science》2021,12(48):15862
An efficient strategy combining the stereocontrol of organocatalysis with the diversity-generating character of multicomponent reactions is described to produce structurally unique, tetrasubstituted cyclopentenyl frameworks. An asymmetric Michael addition–hemiacetalization between α-cyanoketones and α,β-unsaturated aliphatic aldehydes was performed for constructing cyclic hemiacetals, which were next employed as chiral bifunctional substrates in a new diastereoselective intramolecular isocyanide-based multicomponent reaction. This approach furnished a diversity of structurally complex compounds – including peptidomimetics and natural product hybrids in high stereoselectivity (up to >99% ee and up to >99 : 1 dr) and in moderate to high yields.Simple and available reagents are combined in this new three-component isocyanide-based multicomponent reaction providing an interesting and straightforward way to prepare complex and highly functionalized cyclopentenyl rings. 相似文献
825.
826.
827.
Yusuke Hioki Dr. Tatsuya Sato Dr. Toyoki Iwao Junya Ikuma Dr. Atsushi Kawamura Dr. Takayuki Ohyoshi Dr. Yuta Tsunematsu Dr. Masaki Kita 《European journal of organic chemistry》2023,26(12):e202300084
The shell-less herbivorous marine mollusk (sea hare) Aplysia kurodai is known to contain a variety of bioactive substances. While these compounds have been thought to originate from sea algae or their associated microbes, most of their origin and acquisition pathways are still unclear. Six new cytotoxic aplaminone derivatives, bromodopamine-terpenoid hybrid molecules, were isolated from A. kurodai. Among them, isoaplaminone had a reverse prenyl group at the C15 aliphatic chain, which is a rare structural feature from the viewpoint of terpenoid biosynthesis. Investigation for chemical components in A. kurodai and the sea algae collected at several different locations revealed that two major aplaminones were contained in the Laurencia complex species at specific sites. Our chemical and ecological studies provide new insights into the origin of marine alkaloid toxins and their dynamism through the food chain. 相似文献
828.
Fengniu Lu Akira Shinohara Izuru Kawamura Akinori Saeki Tomohisa Takaya Koichi Iwata Takashi Nakanishi 《Helvetica chimica acta》2023,106(8):e202300050
Achieving the lowest phase transition temperature with minimal chemical modification in highly crystalline π-conjugated molecules is a universal problem in related research fields. This paper reports room-temperature liquefication of diphenylpyrene isomers by introducing bulky yet flexible branched alkyl chains through molecular desymmetrization. Six isomers with different symmetries depending on the positions of the phenyl groups and alkyl groups were synthesized, and three of the isomers were found to be liquids at 25 °C, a state in which they have remained for more than five years. Although it is generally believed that the lower the symmetry of a molecule, the less likely it is to crystallize, one molecule with a relatively high molecular symmetry unexpectedly did not crystallize, which was evidenced by the kinetic inhomogeneity of this amorphous material (practically stable liquid) assessed by rheological analysis. 相似文献