全文获取类型
收费全文 | 2671篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
化学 | 1887篇 |
晶体学 | 8篇 |
力学 | 44篇 |
综合类 | 1篇 |
数学 | 452篇 |
物理学 | 320篇 |
出版年
2016年 | 33篇 |
2015年 | 31篇 |
2014年 | 37篇 |
2013年 | 98篇 |
2012年 | 76篇 |
2011年 | 72篇 |
2010年 | 50篇 |
2009年 | 47篇 |
2008年 | 72篇 |
2007年 | 83篇 |
2006年 | 65篇 |
2005年 | 69篇 |
2004年 | 52篇 |
2003年 | 55篇 |
2002年 | 27篇 |
2001年 | 19篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 27篇 |
1994年 | 42篇 |
1993年 | 29篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 28篇 |
1989年 | 36篇 |
1988年 | 29篇 |
1987年 | 37篇 |
1986年 | 32篇 |
1985年 | 51篇 |
1984年 | 56篇 |
1983年 | 26篇 |
1982年 | 52篇 |
1981年 | 49篇 |
1980年 | 41篇 |
1979年 | 36篇 |
1978年 | 61篇 |
1977年 | 60篇 |
1976年 | 43篇 |
1975年 | 38篇 |
1974年 | 34篇 |
1973年 | 46篇 |
1972年 | 30篇 |
1971年 | 46篇 |
1970年 | 30篇 |
1969年 | 20篇 |
1966年 | 24篇 |
1932年 | 18篇 |
1931年 | 17篇 |
1927年 | 17篇 |
1923年 | 18篇 |
排序方式: 共有2712条查询结果,搜索用时 15 毫秒
1.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate 下载免费PDF全文
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
2.
Prof. Dr. Antonín Klásek Assoc. Prof. Dr. Stanislav Kafka Dr. Ondřej Rudolf Prof. Dr. Antonín Lyčka Dr. Michal Rouchal Lukáš Bednář 《ChemistryOpen》2021,10(6):645-652
3-Chloroquinoline-2,4-diones react with cyanide ions in dimethyl formamide to give 3-cyanoquinoline-2,4-diones in small yields due to the strong hindrance of the substituent at the C-3 atom. Good yields can be achieved if the substituent at this position is the methyl group. In the methanol solution, the reaction proceeds by an addition mechanism to form 2-oxo-1a,2,3,7b-tetrahydrooxireno[2,3-c]quinoline-7b-carbonitriles, from which 4-hydroxy-3-methoxy-2-oxo-1,2,3,4-tetrahydroquinoline-4-carbonitriles are subsequently formed by opening of the epoxide ring with methanol. Some minor products of these reactions have also been isolated. The 1H, 13C and 15N NMR spectra of the prepared compounds were measured, and all resonances were assigned using appropriate two-dimensional spectra. 相似文献
3.
A cheap synthesis of the so‐called ‘decalin‐1,8‐diones’ started with the conjugate (1,4‐) addition of cyclohex‐2‐en‐1‐one derivatives to the γ‐position of the dilithium derivative (buta‐1,3‐diene‐1,1‐bis(olate)) of crotonic acid. Hydrogenation of these ‘1,4‐γ’ adducts and final cyclization afforded the enol tautomers of decalin‐1,8‐diones. Nucleophilic substitutions at these 3‐oxoenols by NH3 or primary amines created only monoamino products (namely, 3‐oxoenamines) whose reactions with OPCl3 yielded dihydro(1,3,2)oxazaphosphinin‐2‐one derivatives. The two regioisomers of a trimethyl‐3‐oxoenamine served as models for the constitutional assignments of the two rapidly interconverting (hence, individually NMR‐invisible), tautomeric trimethyl‐3‐oxoenols. Such methyl substitutions served to break the ‘pretended’ symmetry of ‘decalin‐1,8‐dione’. Hydrazine and 3‐oxoenols furnished oxygen‐free indazole derivatives whose N?H bonds exchanged with t1/2=ca. 0.00035 s at ca. ?58(9) °C. 相似文献
4.
Martin Scherer Patrick Scheibe Jérôme Schoenhentz Anja Hoffmann-Röder Rudolf Zentel 《Colloid and polymer science》2014,292(8):1803-1815
This paper deals with pattern formation in Langmuir monolayers of two sets of lipid mixtures that include (1) a fluorinated lipid for phase separation, (2) a polymerizable lipid for stabilization of the patterned structure, and (3) a unit for the presentation of biological recognition units. Differences in the distribution of these functionalities allow a polymerization of dispersed or continuous phase and a placement of the recognition units in crystalline or solid analogue phase. Also, a ternary mixture including a lipid modified with the tandem repeat domain of MUC1 plus a TN-antigen was studied. Based on the biphasic pattern obtained (starlike crystals of up to 50 μm with a fine structure of some micrometers), we also verified the potential of the laterally patterned monolayer to stimulate the immune system (quartz crystal microbalance). The second set of lipids combines a highly fluorinated itaconic ester (polymerizable unit) with the natural phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine. 相似文献
5.
6.
Rudolf Holze 《Journal of Solid State Electrochemistry》2017,21(9):2601-2607
Terminology of electrodes and electrode materials used in supercapacitors as well as naming of electrode processes and devices prepared with these electrodes is confusing and rather unregulated. Consequently, misunderstanding in communication about research and development is somehow matched with an incomplete understanding of the reasons of the observed capacitive, pseudocapacitive, or Faradaic behavior. Observed and investigated phenomena relevant for supercapacitor electrodes are briefly reviewed and explained in terms of electrode processes and interfacial phenomena. Further research possibly useful in more fundamental understanding and rational improvement of materials is proposed. 相似文献
7.
Based on the proposed states of the Metropolis-Hastings (MH) algorithm we construct a MH Importance Sampling estimator for the approximation of expectations. The new approximation scheme is asymptotically correct and numerical experiments indicate that it can outperform the classical MH Markov chain Monte Carlo estimator. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Theodosis Giousis Georgia Potsi Antonios Kouloumpis Konstantinos Spyrou Yiannis Georgantas Nikolaos Chalmpes Konstantinos Dimos Myrsini‐Kiriaki Antoniou Georgios Papavassiliou Athanasios B. Bourlinos Hae Jin Kim Vijay Kumar Shankarayya Wadi Saeed Alhassan Majid Ahmadi Bart J. Kooi Graeme Blake Daniel M. Balazs Maria A. Loi Dimitrios Gournis Petra Rudolf 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2021,133(1):364-369
Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a β‐CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (Eg) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells. 相似文献
9.
Thomas D. Hettich Richard Rudolf Dr. Christoph M. Feil Nicholas Birchall Dr. Martin Nieger Prof. Dr. Dr. h. c. Dietrich Gudat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(17):5412-5416
Unprecedented metalated phosphonite boranes were prepared from PH-substituted precursors and silyl amides. Although potassium derivatives were thermally stable and could even be isolated and structurally characterised, lithiated analogues proved to be unstable towards self-condensation under cleavage of LiOR at ambient temperature. Reaction studies revealed that the metalated phosphonite boranes exhibit ambiphilic character. Their synthetic potential as nucleophilic building blocks was demonstrated in the synthesis of the first stannylated phosphonite representing a new structural motif in phosphine chemistry. 相似文献
10.
Journal of Solid State Electrochemistry - 相似文献