全文获取类型
收费全文 | 399篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 293篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 46篇 |
物理学 | 68篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 16篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 24篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1990年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 2篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1963年 | 1篇 |
1952年 | 1篇 |
1904年 | 1篇 |
排序方式: 共有410条查询结果,搜索用时 46 毫秒
131.
Szentiamide (1) a new cyclic hexadepsipeptide was isolated from the culture broth of the entomopathogenic bacterium Xenorhabdus szentirmaii DSM 16338T. The structure was elucidated by analysis of one- and two-dimensional NMR spectra and high resolution mass spectrometry. The amino acids were determined to be D-leucine, L-threonine, D-phenylalanine, D-valine, L-tyrosine and L-tryptophane after hydrolysis and derivatization with D-FDVA [Nalpha-(2,4-dinitro-5-fluorophenyl)-D-valinamide]. 相似文献
132.
Jutta KocklerAuthor VitaeMichael OelgemöllerAuthor Vitae Sherryl RobertsonAuthor VitaeBeverley D. GlassAuthor Vitae 《Journal of Photochemistry and Photobiology, C: Photochemistry Reviews》2012,13(1):91-110
Sunscreens were originally designed to include mainly UVB-filters. Because of the deeper penetration of UVA light, causing photoaging and DNA damage, there has been a shift towards broad spectrum sunscreens. These broad spectrum sunscreens now include both UVA- and UVB-filters and other ingredients which possess antioxidant activity. Although sunscreens are regulated in most countries, photostability testing is not mandatory. Because of the ability of sunscreen ingredients to absorb UV-light and the complexity of most of these formulations, which may include more than one UV-filter, antioxidants and other formulation excipients, it is important that their photostability in combination is determined. 相似文献
133.
A Horatscheck S Wagner J Ortwein BG Kim M Lisurek S Beligny A Schütz J Rademann 《Angewandte Chemie (International ed. in English)》2012,51(37):9441-9447
A light switch for phosphotyrosine- recognizing proteins: Irradiation of the bioisosteric benzoylphosphonate suffices to "turn off" the activity of target proteins and to label them covalently. Photoactive bioisosters may find applications in functional cell biology, bioanalytics, and proteome research. 相似文献
134.
135.
Kristof Seubert Dominik Böhme Jutta Kösters Wei‐Zheng Shen Eva Freisinger Prof. Dr. Jens Müller 《无机化学与普通化学杂志》2012,638(11):1761-1767
Metal‐mediated base pairs can be used to insert metal ions into nucleic acids at precisely defined positions. As structural data on the resulting metal‐modified DNA are scarce, appropriate model complexes need to be synthesized and structurally characterized. Accordingly, the molecular structures of nine transition metal complexes of N‐methyl‐2, 2'‐dipicolylamine (dipic) are reported. In combination with an azole‐containing artificial nucleoside, this tridentate ligand had recently been used to generate metal‐mediated base pairs (Chem. Commun. 2011 , 47, 11041–11043). The PdII and PtII complexes reported here confirm that the formation of planar complexes (as required for a metal‐mediated base pair) comprising N‐methyl‐2, 2'‐dipicolylamine is possible. Two HgII complexes with differing stoichiometry indicate that a planar structure might also be formed with this metal ion, even though it is not favored. In the complex [Ag2(dipic)2](ClO4)2, the two AgI ions are located close to one another with an Ag ··· Ag distance of 2.9152(3) Å, suggesting the presence of a strong argentophilic interaction. 相似文献
136.
We propose a general framework for the numerical study of balanced black rings for any spacetime dimensions d?5. Numerical solutions are constructed in a systematic way for d=6, by solving the Einstein field equations with suitable boundary conditions. These black rings have a regular event horizon with S1×S3 topology, and they approach the Minkowski background asymptotically. We analyze their global and horizon properties. 相似文献
137.
Jutta Ellermann Wen Ling Mikko J. Nissi Elizabeth Arendt Cathy S. Carlson Michael Garwood Shalom Michaeli Silvia Mangia 《Magnetic resonance imaging》2013
In the present work we introduced two MRI rotating frame relaxation methods, namely adiabatic T1ρ and Relaxation Along a Fictitious Field (RAFF), along with an inversion-prepared Magnetization Transfer (MT) protocol for assessment of articular cartilage. Given the inherent sensitivity of rotating frame relaxation methods to slow molecular motions that are relevant in cartilage, we hypothesized that adiabatic T1ρ and RAFF would have higher sensitivity to articular cartilage degradation as compared to laboratory frame T2 and MT. To test this hypothesis, a proteoglycan depletion model was used. Relaxation time measurements were performed at 0 and 48 h in 10 bovine patellar specimens, 5 of which were treated with trypsin and 5 untreated controls were stored under identical conditions in isotonic saline for 48 h. Relaxation times measured at 48 h were longer than those measured at 0 h in both groups. The changes in T2 and MT relaxation times after 48 h were approximately 3 times larger in the trypsin treated specimens as compared to the untreated group, whereas increases of adiabatic T1ρ and RAFF were 4 to 5 fold larger. Overall, these findings demonstrate a higher sensitivity of adiabatic T1ρ and RAFF to the trypsin-induced changes in bovine patellar cartilage as compared to the commonly used T2 and MT. Since adiabatic T1ρ and RAFF are advantageous for human applications as compared to standard continuous-wave T1ρ methods, adiabatic T1ρ and RAFF are promising tools for assessing cartilage degradation in clinical settings. 相似文献
138.
We show that, at finite weak mixing angle the sphaleron solution of Weinberg–Salam theory can be endowed with angular momentum proportional to the electric charge. Carrying baryon number 1/2 these sphalerons with spin and charge may contribute to baryon number violating processes. 相似文献
139.
The addition of RMgX or R2Mg to nicotinic acid esters, activated with triisopropylsilyl triflate, was investigated. The regioselectivity of this reaction, where 4-unsubstituted and 4-substituted pyridine derivatives were employed as starting materials, was examined. Depending on the structure of the organomagnesium reagent varying ratios of 1,2-, 1,4-, and 1,6-regioisomers were obtained but in any case the 1,4-addition products were clearly predominating. Desilylation of the isomeric pure addition products with LiOH provided stable 4,4-disubstituted dihydropyridines, which could be easily N-alkylated with alkylhalides in high yield. Furthermore, it was shown that the silyl protecting group of the obtained dihydropyridines can be easily replaced by an acyl group. 相似文献
140.
Gaëlle Mellot Jean‐Michel Guigner Laurent Bouteiller Franois Stoffelbach Jutta Rieger 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(10):3205-3209
Dispersions of block copolymer fibres in water have many potential applications and can be obtained by polymerization‐induced self‐assembly (PISA), but only under very restricted experimental conditions. In order to enlarge this experimental window, we introduced a supramolecular moiety, a hydrogen‐bonded bis‐urea sticker, in the macromolecular reversible addition fragmentation chain transfer (RAFT) agent to drive the morphology of the nano‐objects produced by RAFT‐mediated PISA towards the fibre morphology. This novel concept is tested in the synthesis of a series of poly(N,N‐dimethylacrylamide)‐b‐poly(2‐methoxyethyl acrylate) (PDMAc‐b‐PMEA) diblock copolymers prepared by dispersion polymerization in water. The results prove that the introduction of the templating bis‐urea stickers into PISA greatly promotes the formation of fibres in a large experimental window. 相似文献