全文获取类型
收费全文 | 902篇 |
免费 | 52篇 |
国内免费 | 11篇 |
专业分类
化学 | 590篇 |
力学 | 26篇 |
数学 | 209篇 |
物理学 | 140篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 22篇 |
2021年 | 43篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 21篇 |
2017年 | 23篇 |
2016年 | 44篇 |
2015年 | 44篇 |
2014年 | 43篇 |
2013年 | 77篇 |
2012年 | 65篇 |
2011年 | 73篇 |
2010年 | 53篇 |
2009年 | 46篇 |
2008年 | 49篇 |
2007年 | 68篇 |
2006年 | 46篇 |
2005年 | 57篇 |
2004年 | 39篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1942年 | 1篇 |
排序方式: 共有965条查询结果,搜索用时 31 毫秒
781.
Dr. Naveen Kumar Allampally Prof. Dr. Michael Bredol Dr. Cristian A. Strassert Prof. Luisa De Cola 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16863-16868
We have synthesised a neutral, water‐soluble, PtII complex able to aggregate more efficiently in aqueous solutions than in organic solvents. The aggregates are luminescent and are not quenched by molecular oxygen. Further, we have prepared phosphorescent hydrogels utilising host–guest interactions between cyclodextrins and the tetraethylene glycol tails of the PtII complex. The soft assemblies feature host‐dependent emission properties. 相似文献
782.
Sunil Choudhary Cristian Gozalvez Alexander Higelin Prof. Ingo Krossing Prof. Manuel Melle‐Franco Prof. Aurelio Mateo‐Alonso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1525-1528
A synthetic strategy that allows the induction of twist angles of different sizes in 5,6,11,12,17,18‐hexaazatrinaphthylene (HATNA) chromophores is reported. The different twist angles are accompanied by measurable changes in the emission and electrochemical characteristics of HATNA. 相似文献
783.
Cristian Rodríguez 《合成通讯》2014,44(6):772-778
A convenient methodology for the synthesis of 3-sustituted-2,3-dihydrobenzofurans was developed based on the tandem intramolecular carbolithiation–cyclization of 2-bromophenyl-3-phenylprop-2-enyl ether, followed by trapping of the new lithiated intermediate by suitable electrophiles. Several electrophiles were tested, affording good to excellent yields. Alkyl bromides show better results than chlorides and when doubly halogenated alkyl chains are used as electrophiles only one position reacts, affording substituted benzofurans conveniently functionalized to undergo further reactions. The performance of both butyl and phenyllithium as lithiating agents was examined.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
784.
RhIII‐Catalyzed CH Activation with Pyridotriazoles: Direct Access to Fluorophores for Metal‐Ion Detection
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Ju Hyun Kim Tobias Gensch Dr. Dongbing Zhao Linda Stegemann Priv.‐Doz. Dr. Cristian A. Strassert Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2015,54(37):10975-10979
The first C? H bond activation with pyridotriazoles as coupling partners is presented using a RhIII catalyst. The pyridotriazoles can be used as new carbene precursors in C? H activation for direct access to novel fluorescent scaffolds. These tunable fluorophores can be applied for the detection of metal ions. 相似文献
785.
Organoantimony(III)‐Containing Tungstoarsenates(III): From Controlled Assembly to Biological Activity
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Peng Yang Dr. Bassem S. Bassil Dr. Zhengguo Lin Dr. Ali Haider Dr. Gabriela Alfaro‐Espinoza Prof. Matthias S. Ullrich Prof. Cristian Silvestru Prof. Ulrich Kortz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15600-15606
A family of three sandwich‐type, phenylantimony(III)‐containing tungstoarsenates(III), [(PhSbIII){Na(H2O)}AsIII2W19O67(H2O)]11? ( 1 ), [(PhSbIII)2AsIII2W19O67(H2O)]10? ( 2 ), and [(PhSbIII)3(B‐α‐AsIIIW9O33)2]12? ( 3 ), have been synthesized by one‐pot procedures and isolated as hydrated alkali metal salts, Cs3K3.5Na4.5[(PhSbIII){Na(H2O)}AsIII2W19O67(H2O)]?41H2O ( CsKNa ‐ 1 ), Cs4.5K5.5[(PhSbIII)2AsIII2W19O67(H2O)]?35H2O ( CsK‐2 ), and Cs4.5Na7.5[(PhSbIII)3(B‐α‐AsIIIW9O33)2]?42H2O ( CsNa ‐ 3 ). The number of incorporated {PhSbIII} units could be selectively tuned from one to three by careful control of the reaction parameters. The three compounds were characterized in the solid state by single‐crystal XRD, IR spectroscopy, and thermogravimetric analysis. The aqueous solution stability of sandwich polyanions 1 – 3 was also studied by multinuclear (1H, 13C, 183W) NMR spectroscopy. Effective inhibitory activity against six different kinds of bacteria was identified for all three polyanions, for which the activity increased with the number of incorporated {PhSbIII} groups. 相似文献
786.
Identification and structural characterization of novel O‐ and N‐glycoforms in the urine of a Schindler disease patient by Orbitrap mass spectrometry
下载免费PDF全文
![点击此处可从《Journal of mass spectrometry : JMS》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mirela Sarbu Cristian V. A. Munteanu Liana Dehelean Andrei J. Petrescu Jasna Peter‐Katalinic Alina D. Zamfir 《Journal of mass spectrometry : JMS》2015,50(9):1044-1056
Schindler disease is an inherited metabolic disorder caused by the deficient activity of α‐N‐acetylgalactosaminidase enzyme. An accurate diagnosis requires, besides clinical examination, complex and costly biochemical and molecular genetic tests. In the last years, mass spectrometry (MS) based on nanofluidics and high‐resolution instruments has become a successful alternative for disease diagnosis based on the investigation of O‐glycopeptides in patient urine. A complex mixture of glycoforms extracted from the urine of a 3‐year‐old patient was investigated by Orbitrap MS equipped with Nanospray Flex Ion Source in the negative ion mode. For structural characterization of several molecular species, collision‐induced dissociation MS2–MS3 was carried out using collision energy values within 20–60 eV range. By our approach, 39 novel species associated to this condition were identified, among which O‐glycopeptides, free O‐glycans and one structure corresponding to an N‐glycan never characterized in the context of Schindler disease. The experiments conducted at a resolution of 60 000 allowed the discrimination and identification of a total number of 69 different species with an average mass accuracy of 9.87 ppm, an in‐run reproducibility of almost 100%, an experiment‐to‐experiment and day‐to‐day reproducibility of about 95%. This study brings contributions in the diagnosis of Schindler disease through the elucidation of potential biomarker species in urine. Our multistage MS results completed with 39 new glycoforms the inventory of potential biomarker structures associated to Schindler disease. For the first time, an N‐glycan was identified and structurally characterized in Schindler patient urine, which opens new research directions in the field. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
787.
This paper presents the results of an experiment in which fourth to sixth graders with above-average mathematical abilities modified a given problem. The experiment found evidence of links between problem posing and cognitive flexibility. Emerging from organizational theory, cognitive flexibility is conceptualized through three primary constructs: cognitive variety, cognitive novelty, and changes in cognitive framing. Among these components, changes in cognitive framing could be effectively detected in problem-posing situations, giving a relevant indication of students’ creative potential. The students’ capacity to generate coherent and consistent problems in the context of problem modification may indicate the existence of a strategy of functional type for generalizations, which seems to be specific to mathematical creativity. 相似文献
788.
Virgil Percec Cristian Grigoras 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5283-5299
Metal‐catalyzed living radical polymerization of methyl methacrylate initiated with N‐chloro amides (N‐chloro N‐ethyl propionamide, N‐chloro benzanilide, N‐chloro methylbenzamide, and N‐chloro acetanilide), lactams (N‐chloro caprolactam and N‐chloro 2‐pyrrolidinone), carbamates or urethanes (N‐chloro ethylcarbamate or N‐chlorourethane), imides (N‐chloro phtalimide, N‐chloro succinimide, trichloroisocyanuric acid, and N‐chloro saccharin) and catalyzed with the self‐regulated catalytic system Cu2S/2,2′‐bipyridine is reported. The initiation efficiency of these initiators is determined by their structure. Regardless of the initiator efficiency, in all cases, poly (methyl methacrylate) with narrow molecular weight distribution and functionalized chain‐ends was obtained. These new classes of initiators open new strategies for the functionalization of polymer chain‐ends and for the synthesis of complex architectures by graft copolymerization initiated from N‐chloro proteins, aliphatic, aromatic and semiaromatic polyamides, and polyurethanes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5283–5299, 2005 相似文献
789.
Cristian A. Strassert Josefina Awruch 《Monatshefte für Chemie / Chemical Monthly》2006,137(12):1499-1503
Summary. Reduction of N-alkylsubstituted phthalimides to the corresponding isoindolines by means of diborane is herein described. 相似文献
790.