全文获取类型
收费全文 | 556篇 |
免费 | 33篇 |
国内免费 | 6篇 |
专业分类
化学 | 385篇 |
晶体学 | 3篇 |
力学 | 22篇 |
数学 | 72篇 |
物理学 | 113篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 13篇 |
2013年 | 31篇 |
2012年 | 27篇 |
2011年 | 36篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 27篇 |
2007年 | 39篇 |
2006年 | 18篇 |
2005年 | 41篇 |
2004年 | 27篇 |
2003年 | 21篇 |
2002年 | 23篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1992年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1969年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有595条查询结果,搜索用时 15 毫秒
91.
Jos Enrique Gmez lex Cristfol Arjan W. Kleij 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3943-3947
Tertiary propargylic sulfones are of significant importance in organic synthesis and medicinal chemistry, but to date no general asymmetric synthesis approach has been developed. We disclose a versatile copper‐catalyzed sulfonylation of propargylic cyclic carbonates using sodium sulfinates that allows the construction of propargylic sulfones featuring elusive quaternary stereocenters. This method provides the first successful example of such an enantioselective propargylic sulfonylation, features high asymmetric induction, wide functional group tolerance, and scalability, and enables attractive product diversification. 相似文献
92.
Peng Teng Geoffrey M. Gray Mengmeng Zheng Sylvia Singh Xiaopeng Li Lukasz Wojtas Arjan vanderVaart Jianfeng Cai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(23):7860-7864
Peptide‐mediated self‐assembly is a prevalent method for creating highly ordered supramolecular architectures. Herein, we report the first example of orthogonal C?X???X?C/C?X???π halogen bonding and hydrogen bonding driven crystalline architectures based on synthetic helical peptides bearing hybrids of l ‐sulfono‐γ‐AApeptides and natural amino acids. The combination of halogen bonding, intra‐/intermolecular hydrogen bonding, and intermolecular hydrophobic interactions enabled novel 3D supramolecular assembly. The orthogonal halogen bonding in the supramolecular architecture exerts a novel mechanism for the self‐assembly of synthetic peptide foldamers and gives new insights into molecular recognition, supramolecular design, and rational design of biomimetic structures. 相似文献
93.
Kumar Niraj Rodriguez Jassiel R. Pol Vilas G. Sen Arijit 《Journal of Solid State Electrochemistry》2019,23(5):1443-1454
Journal of Solid State Electrochemistry - Here, we present a unique morphology comprising a blend of ultrafine 1D MnO2 and graphene oxide as an efficient anode material to overcome the issue of... 相似文献
94.
AlIII‐Catalysed Formation of Poly(limonene)carbonate: DFT Analysis of the Origin of Stereoregularity 下载免费PDF全文
Leticia Peña Carrodeguas Joan González‐Fabra Dr. Fernando Castro‐Gómez Prof. Dr. Carles Bo Prof. Dr. Arjan W. Kleij 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6115-6122
Amino‐triphenolate derived AlIII complexes combined with suitable nucleophiles have been investigated as binary catalysts for the coupling of limonene oxide and carbon dioxide to afford alternating polycarbonates. These catalysts are able to produce stereoregular, perfectly alternating trans‐polymers from cis‐limonene oxide, whereas the pure trans isomer and cis/trans mixture give rise to lower degrees of stereoregularity. The best AlIII catalyst shows the potential to mediate the conversion of both stereoisomers of limonene oxide with high conversion levels of up to 71 % under neat conditions, indicating the high degree of robustness and atom‐efficiency of this catalytic process. Computational studies have revealed unique features of the binary catalyst system, among which is the preferred nucleophilic attack on the quaternary carbon centre in the limonene oxide substrate. 相似文献
95.
96.
97.
98.
Organocatalyzed Domino [3+2] Cycloaddition/Payne‐Type Rearrangement using Carbon Dioxide and Epoxy Alcohols 下载免费PDF全文
Sergio Sopeña Mariachiara Cozzolino Cristina Maquilón Dr. Eduardo C. Escudero‐Adán Dr. Marta Martínez Belmonte Prof. Dr. Arjan W. Kleij 《Angewandte Chemie (International ed. in English)》2018,57(35):11203-11207
An unprecedented organocatalytic approach towards highly substituted cyclic carbonates from tri‐ and tetrasubstituted oxiranes and carbon dioxide has been developed. The protocol involves the use of a simple and cheap superbase under mild, additive‐ and metal‐free conditions towards the initial formation of a less substituted carbonate product that equilibrates to a tri‐ or even tetrasubstituted cyclic carbonate under thermodynamic control. The latter are conveniently trapped in situ, providing overall a new domino process for synthetically elusive heterocyclic scaffolds. Control experiments provide a rationale for the observed cascade reactions, which demonstrate similarity to the well‐known Payne rearrangement of epoxy alcohols. 相似文献
99.
Dr. Robert Lizatović Marvin Assent Arjan Barendregt Jonathan Dahlin Dr. Anna Bille Katharina Satzinger Dagnija Tupina Prof. Albert J. R. Heck Dr. Stefan Wennmalm Dr. Ingemar André 《Angewandte Chemie (International ed. in English)》2018,57(35):11334-11338
Protein‐based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitis B virus capsid in which an engineered high‐affinity interaction between cargo and capsid proteins can be modulated by Ca2+. Cargo proteins are loaded into capsids in the presence of Ca2+, while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with β‐glucosidase activity. 相似文献
100.
J. Málek R. A. Evarestov A. N. Ermoshkin B. Hejda K. Polák 《Czechoslovak Journal of Physics》1975,25(11):1201-1207
One-electron energy levels of NiF
6
4–
cluster, effective charges qNi and qF, parameters 10Dq,
crys
,,f
s
,f
andf
were calculated using four alternative models of population analysis. The influence of the size of basis set was also investigated. Based on comparison of results it was shown that all evaluated quantities are dependent on the manner of division of overlap charge made up by virtual 4s and 4p nickel orbitals. To remove this discrepancy it was suggested to assign the whole 4s and 4p population to ligands. In this case all calculated parameters are nearly independent of a model of population analysis and the size of basis set and their values correspond better to experimental data. 相似文献