全文获取类型
收费全文 | 1995篇 |
免费 | 132篇 |
国内免费 | 18篇 |
专业分类
化学 | 1560篇 |
晶体学 | 6篇 |
力学 | 21篇 |
数学 | 348篇 |
物理学 | 210篇 |
出版年
2024年 | 3篇 |
2023年 | 20篇 |
2022年 | 16篇 |
2021年 | 34篇 |
2020年 | 57篇 |
2019年 | 69篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 70篇 |
2015年 | 55篇 |
2014年 | 69篇 |
2013年 | 97篇 |
2012年 | 129篇 |
2011年 | 136篇 |
2010年 | 66篇 |
2009年 | 77篇 |
2008年 | 137篇 |
2007年 | 143篇 |
2006年 | 130篇 |
2005年 | 131篇 |
2004年 | 107篇 |
2003年 | 88篇 |
2002年 | 92篇 |
2001年 | 37篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 19篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 24篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 7篇 |
1991年 | 20篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有2145条查询结果,搜索用时 0 毫秒
41.
[reaction: see text] Rhodium-catalyzed oxygen transfer was used to generate benzyl 2-silyl-2-oxoacetates in good yields. The hydrogenation of these compounds led to chiral alpha-silyl-substituted alpha-hydroxyacetic acids. Resolution by means of HPLC using a chiral stationary phase afforded an enantiomerically pure representative of this class of compounds, which was successfully applied as a chiral ligand in an asymmetric aldol-type reaction. 相似文献
42.
A polymeric malonato-bridged copper(II) complex, {[Cu(H2O)3][Cu(MAL)2]· 2H2O}, and a mononuclear malonato-copper(II) complex with triethanolamine, [Cu(MAL)(TEA)]·H2O, have been prepared and characterized by elemental analyses, i.r., u.v.–vis, magnetic measurements and single crystal X-ray diffraction. The polymeric complex consists of one-dimensional chains containing the MAL bridged [Cu(H2O)3]2+ and [Cu(MAL)2]2– ions and each MAL ligand simultaneously exhibits chelating bidentate (at one copper atom) and bridging (at the adjacent copper atom) coordination modes. The intrachain Cu1...Cu2 separation is 4.963 Å and the polymeric complex exhibits antiferromagnetic behaviour. In the mononuclear complex, the copper(II) ion is octahedrally coordinated by one bidentate MAL and one tetradentate neutral TEA ligands. The i.r. spectra and thermal decompositions of both complexes are described. 相似文献
43.
Johannes Karthuser Vladimirs Biziks Carsten Mai Holger Militz 《Molecules (Basel, Switzerland)》2021,26(9)
Improving the environmental performance of resins in wood treatment by using renewable chemicals has been a topic of interest for a long time. At the same time, lignin, the second most abundant biomass on earth, is produced in large scale as a side product and mainly used energetically. The use of lignin in wood adhesives or for wood modification has received a lot of scientific attention. Despite this, there are only few lignin-derived wood products commercially available. This review provides a summary of the research on lignin application in wood adhesives, as well as for wood modification. The research on the use of uncleaved lignin and of cleavage products of lignin is reviewed. Finally, the current state of the art of commercialization of lignin-derived wood products is presented. 相似文献
44.
Carsten Jaeschke Marta Padilla Johannes Glckler Inese Polaka Martins Leja Viktors Veliks Jan Mitrovics Marcis Leja Boris Mizaikoff 《Molecules (Basel, Switzerland)》2021,26(12)
Exhaled breath analysis for early disease detection may provide a convenient method for painless and non-invasive diagnosis. In this work, a novel, compact and easy-to-use breath analyzer platform with a modular sensing chamber and direct breath sampling unit is presented. The developed analyzer system comprises a compact, low volume, temperature-controlled sensing chamber in three modules that can host any type of resistive gas sensor arrays. Furthermore, in this study three modular breath analyzers are explicitly tested for reproducibility in a real-life breath analysis experiment with several calibration transfer (CT) techniques using transfer samples from the experiment. The experiment consists of classifying breath samples from 15 subjects before and after eating a specific meal using three instruments. We investigate the possibility to transfer calibration models across instruments using transfer samples from the experiment under study, since representative samples of human breath at some conditions are difficult to simulate in a laboratory. For example, exhaled breath from subjects suffering from a disease for which the biomarkers are mostly unknown. Results show that many transfer samples of all the classes under study (in our case meal/no meal) are needed, although some CT methods present reasonably good results with only one class. 相似文献
45.
Afshin Nabiyan Johannes Bernhard Max Dr. Christof Neumann Magdalena Heiland Prof. Dr. Andrey Turchanin Prof. Dr. Carsten Streb Prof. Dr. Felix Helmut Schacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16924-16929
An effective strategy to enhance the performance of inorganic semiconductors is moving towards organic-inorganic hybrid materials. Here, we report the design of core–shell hybrid materials based on a TiO2 core functionalized with a polyampholytic (poly(dehydroalanine)-graft-(n-propyl phosphonic acid acrylamide) shell (PDha-g-PAA@TiO2). The PDha-g-PAA shell facilitates the efficient immobilization of the photosensitizer Eosin Y (EY) and enables electronic interactions between EY and the TiO2 core. This resulted in high visible-light-driven H2 generation. The enhanced light-driven catalytic activity is attributed to the unique core–shell design with the graft copolymer acting as bridge and facilitating electron and proton transfer, thereby also preventing the degradation of EY. Further catalytic enhancement of PDha-g-PAA@TiO2 was possible by introducing [Mo3S13]2− cluster anions as hydrogen-evolution cocatalyst. This novel design approach is an example for a multi-component system in which reactivity can in future be independently tuned by selection of the desired molecular or polymeric species. 相似文献
46.
47.
Kerstin Zab Detlev Joachimi Eva Novotna Siegmar Diele Carsten Tschierske 《Liquid crystals》2013,40(4):631-637
Abstract Various trimeric co-oligomers combining 2-phenyl-1,3,4-thiadiazole mesogenic moieties with a biphenyl mesogenic moiety were synthesized and their mesomorphic behaviour investigated by polarizing microscopy, calorimetry and X-ray scattering. Such co-oligomeric structures provide an opportunity to combine different mesogenic units. Thus readily accessible homochiral biphenyl mesogenic units were connected with thiadiazole mesogenic units leading to an oligomeric liquid crystal material with ferroelectric properties. 相似文献
48.
49.
50.
Markus Balmer Dr. Florian Weigend Prof. Dr. Carsten von Hänisch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4914-4919
The N-heterocyclic carbene (NHC)-stabilized phosphinidenide, SIMesPK [SIMes=1,3-bis(2,4,6-trimethylphenyl)imidazolidine-2-ylidene], was used as an (NHC)P-transfer reagent for the synthesis of the low-valent Group 14 ate complexes K[(SIMesP)3E] (E=Ge: 2 , Sn: 3 , Pb: 4 ), which were characterized by 1H NMR, 31P NMR, IR spectroscopy as well as elemental and X-ray analysis. Furthermore, SIMesPK was used in reactions with potassium amides and alkoxides to form the molecular phosphorus–potassium clusters [K4(SIMesP)2(hmds)2] [ 5 , hmds=N(SiMe3)2] and [K6(SIMesP)2(OtBu)4] ( 6 ). Finally, the reaction of SIMesPK with Li[Al(OC4F9)4] led to the potassium-rich ionic compound [(SIMesP)4K5][Al(OC4F9)4] ( 7 ). 相似文献