全文获取类型
收费全文 | 925篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 833篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 63篇 |
物理学 | 41篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 24篇 |
2012年 | 29篇 |
2011年 | 33篇 |
2010年 | 13篇 |
2009年 | 22篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 25篇 |
2005年 | 22篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1966年 | 36篇 |
1965年 | 85篇 |
1964年 | 117篇 |
1963年 | 4篇 |
1956年 | 85篇 |
1955年 | 91篇 |
1954年 | 16篇 |
排序方式: 共有946条查询结果,搜索用时 604 毫秒
751.
Fabio Mazzotta Georg Zitzer Prof. Dr. Bernd Speiser Prof. Dr. Doris Kunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16291-16305
The synthesis of electron-poor mono-, di- and tri(imidazolium)-substituted Cp-ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X-ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH3CN)3Cp*](PF6). With mono- and di(imidazolium)-substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X-ray), whereas tri(imidazolium) cyclopentadienides are too electron-poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron-withdrawing imidazolium substituent at the Cp ligand by 0.53–0.55 V in an electrolyte based on a weakly coordinating anion. A reversible oxidation can be observed for the free 1,3-disubstituted ligand as well. 相似文献
752.
The coordination chemistry of an electron-rich macrocyclic CNC pincer-ligand consisting of two pentamethylene tethered N-heterocyclic carbene moieties on a carbazole backbone (bimcaC5) is investigated by mainly NMR spectroscopy and X-ray crystal structure analysis. A bridging coordination mode is found for the lithium complex. With the larger and softer potassium ion, the ligand adopts a facial coordination mode and a polymeric structure by intermolecular potassium nitrogen interactions. The facial coordination is also confirmed at a Cp*Ru fragment, while C-H activation under dehydrogenation at the alkyl chain is observed upon reaction with [Ru(PPh3)3Cl2]. In contrast, Pd(OAc)2 reacts under C-H activation at the central carbon atom of the pentamethylene tether to an alkyl-pincer macrocycle. 相似文献
753.
Fernanda Pilaquinga Sofía Crdenas Doris Vela Eliza Jara Jeroni Morey Jos Luis Gutirrez-Coronado Alexis Debut María de las Nieves Pia 《Molecules (Basel, Switzerland)》2021,26(9)
Research on nanomaterial exposure-related health risks is still quite limited; this includes standardizing methods for measuring metals in living organisms. Thus, this study validated an atomic absorption spectrophotometry method to determine fertility and bioaccumulated iron content in Drosophila melanogaster flies after feeding them magnetite nanoparticles (Fe3O4NPs) dosed in a culture medium (100, 250, 500, and 1000 mg kg−1). Some NPs were also coated with chitosan to compare iron assimilation. Considering both accuracy and precision, results showed the method was optimal for concentrations greater than 20 mg L−1. Recovery values were considered optimum within the 95–105% range. Regarding fertility, offspring for each coated and non-coated NPs concentration decreased in relation to the control group. Flies exposed to 100 mg L−1 of coated NPs presented the lowest fertility level and highest bioaccumulation factor. Despite an association between iron bioaccumulation and NPs concentration, the 500 mg L−1 dose of coated and non-coated NPs showed similar iron concentrations to those of the control group. Thus, Drosophila flies’ fertility decreased after NPs exposure, while iron bioaccumulation was related to NPs concentration and coating. We determined this method can overcome sample limitations and biological matrix-associated heterogeneity, thus allowing for bioaccumulated iron detection regardless of exposure to coated or non-coated magnetite NPs, meaning this protocol could be applicable with any type of iron NPs. 相似文献
754.
Jonte' C. Taylor Karen L. Rizzo Jiwon Hwang Doris Hill 《School science and mathematics》2020,120(2):116-125
Understanding science concepts and phenomena is important for an increasingly complex global society. For students with disabilities, there continue to be huge achievement disparities in science achievement when compared to their peers without disabilities. This includes students with autism spectrum disorder (ASD). The current study examines and analyzes published research on science and science-related achievement for students with ASD. The authors reviewed characteristics of the research related to science achievement for students with ASD from 2000 through 2018 and analyzed included data to evaluate the effectiveness of the interventions included in the studies. Implications for research and teaching are discussed. 相似文献
755.
Karine Porte Brigitte Renoux Elodie Praudeau Jonathan Clarhaut Balkis Eddhif Pauline Poinot Edmond Gravel Eric Doris Anne Wijkhuisen Davide Audisio Sbastien Papot Frdric Taran 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6432-6436
A bioorthogonal approach is explored to release the content of nanoparticles on demand. Exploiting our recently described click‐and‐release technology, we developed a new generation of cleavable micelles able to disassemble through a sequential enzymatic and bioorthogonal activation process. Proof‐of‐concept experiments showed that this new approach could be successfully used to deliver the substances encapsulated into micelles in living cells as well as in mice by two complementary targeted strategies. 相似文献
756.
Emteborg Håkan Florian Doris Choquette Steven Ellison Stephen L. R. Fernandes-Whaley Maria Mackay Lindsey McCarron Pearse Panne Ulrich Sander Sylvia G. Kim Sook-Kyung Held Andrea Linsinger Thomas Trapmann Stefanie 《Accreditation and quality assurance》2018,23(6):371-377
Accreditation and Quality Assurance - 相似文献
757.
Doris Kunz 《Nachrichten aus der Chemie》2005,53(9):951-951
Zum dritten Mal nach 2001 und 2003 fand Anfang Juli das „Heidelberg Forum of Molecular Catalyis”︁ (HFMC} mit drei Gastrednern aus den USA und der Verleihung des „BASF Catalysis Award”︁ statt. Das Symposium organisiert der SFB 623 „Molekulare Katalyse: Struktur und Funktionsdesign”︁ ( www.sfb623.uni‐hd.de ) an der Universität Heidelberg; die BASF finanziert. Über 500 Teilnehmer aus Deutschland und den angrenzenden Nachbarländern waren der Einladung gefolgt. 相似文献
758.
Taurino R Fabbri E Messori M Pilati F Pospiech D Synytska A 《Journal of colloid and interface science》2008,325(1):149-156
Different organic/inorganic compositions and deposition methods were used to prepare superhydrophobic surfaces using metal alkoxides and the sol-gel process. Both surface roughness and composition had to be adjusted in order to obtain very high contact angles and low contact angle hysteresis as a necessary requirement for superhydrophobicity. Multilayer samples with a fluorinated organic-inorganic top layer showed water contact angles of about 157 degrees with low hysteresis (2 degrees ). Water drops rolled easily off their surface at a tilt angle as low as 4 degrees . 相似文献
759.
760.
Yakai Feng Jens Knüfermann Doris Klee Hartwig Hcker 《Macromolecular rapid communications》1999,20(2):88-90
The enzymatic ring‐opening polymerization of a 6‐membered cyclic depsipeptide, 3(S)‐isopropylmorpholine‐2,5‐dione in the bulk, was investigated by using lipases as catalysts at 100 and 130°C. Unchanged monomer was recovered in the absence of the enzyme or using an inactivated enzyme, indicating that the present polymerization proceeds through enzymatic catalysis. Poly(3‐isopropylmorpholine‐2,5‐dione) has a carboxylic acid group at one end and a hydroxy group at the other end. 相似文献