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排序方式: 共有486条查询结果,搜索用时 31 毫秒
1.
Journal of Algebraic Combinatorics - Rigid honeycombs were introduced by Knutson et al. (J Am Math Soc 17:19–48, 2004), and they were shown in Bercovici et al. (J Funct Anal... 相似文献
2.
From Spherical to Leaf‐Like Morphologies: Tunable Supramolecular Assembly of Alkynylgold(I) Complexes through Variations of the Alkyl Chain Length 下载免费PDF全文
Eugene Yau‐Hin Hong Dr. Hok‐Lai Wong Prof. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5732-5735
A series of luminescent polynuclear alkynylgold(I) complexes with different lengths of alkyl chains attached at the N‐heterocyclic carbene moieties has been synthesised and demonstrated to display intriguing self‐assembly behaviours through a cooperative growth mechanism. Variation of the alkyl chain length was found to cause drastic morphological differences in the aggregates and to strongly affect the thermodynamic parameters as revealed by the nucleation–elongation model. 相似文献
3.
Behnaz Ghaffari Jorge Mendes-Burak Ka Wing Chan Prof. Dr. Christophe Copéret 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(61):13869-13873
Manganese, the third most abundant transition-metal element after iron and titanium, has recently been demonstrated to be an effective homogeneous catalyst in numerous reactions. Herein, the preparation of silica-supported MnII sites is reported using Surface Organometallic Chemistry (SOMC), combined with tailored thermolytic molecular precursors approach based on Mn2[OSi(OtBu)3]4 and Mn{N(SiMe3)2}2⋅THF. These supported MnII sites, free of organic ligands, efficiently catalyze numerous reactions: hydroboration and hydrosilylation of ketones and aldehydes as well as the transesterification of industrially relevant substrates. 相似文献
4.
Synthesis,Electrochemistry, and Photophysical Studies of Ruthenium(II) Polypyridine Complexes with D–π–A–π–D Type Ligands and Their Application Studies as Organic Memories 下载免费PDF全文
Ming‐Yi Leung Dr. Sammual Yu‐Lut Leung Dr. Di Wu Dr. Tao Yu Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):14013-14021
A new class of ruthenium(II) polypyridine complexes with a series of D–π–A–π–D type (D=donor, A=acceptor) ligands was synthesized and characterized by 1H NMR spectroscopy, mass spectrometry, and elemental analysis. The photophysical and electrochemical properties of the complexes were also investigated. The newly synthesized ruthenium(II) polypyridine complexes were found to exhibit two intense absorption bands at both high‐energy (λ=333–369 nm) and low‐energy (λ=520–535 nm) regions. They are assigned as intraligand (IL) π→π* transitions of the bipyridine (bpy) and π‐conjugated bpy ligands, and IL charge‐transfer (CT) transitions from the donor to the acceptor moiety with mixing of dπ(RuII)→π*(bpy) and dπ(RuII)→π*(L) MLCT characters, respectively. In addition, all complexes were demonstrated to exhibit intense red emissions at approximately λ=727–744 nm in degassed dichloromethane at 298 K or in n‐butyronitrile glass at 77 K. Nanosecond transient absorption (TA) spectroscopy has also been carried out, establishing the presence of the charge‐separated state. In order to understand the electrochemical properties of the complexes, cyclic voltammetry has also been performed. Two quasi‐reversible oxidation couples and three quasi‐reversible reduction couples were observed. One of the ruthenium(II) complexes has been utilized in the fabrication of memory devices, in which an ON/OFF current ratio of over 104 was obtained. 相似文献
5.
Prof. Dr. Dengrong Sun Lok Wing Wong Hok Yin Wong Ka Hei Lai Dr. Lin Ye Xinyao Xv Prof. Dr. Thuc Hue Ly Prof. Dr. Qingming Deng Prof. Dr. Jiong Zhao 《Angewandte Chemie (International ed. in English)》2023,62(4):e202216008
The direct utilization of metal–organic frameworks (MOFs) for electrocatalytic oxygen evolution reaction (OER) has attracted increasing interests. Herein, we employ the low-dose integrated differential phase contrast-scanning transmission electron microscopy (iDPC-STEM) technique to visualize the atomic structure of multivariate MOFs (MTV-MOFs) for guiding the structural design of bulk MOFs for efficient OER. The iDPC-STEM images revealed that incorporating Fe3+ or 2-aminoterephthalate (ATA) into Ni-BDC (BDC: benzenedicarboxylate) can introduce inhomogeneous lattice strain that weaken the coordination bonds, which can be selectively cleaved via a mild heat treatment to simultaneously generate coordinatively unsaturated metal sites, conductive Ni@C and hierarchical porous structure. Thus, excellent OER activity with current densities of 10 and 100 mA cm−2 are achieved over the defective MOFs at small overpotentials of 286 mV and 365 mV, respectively, which is superior to the commercial RuO2 catalyst and most of the bulk MOFs. 相似文献
6.
Dr. Andrea Previtali Dr. Wei He Dr. Alessandra Forni Dr. Daniele Malpicci Dr. Elena Lucenti Dr. Daniele Marinotto Prof. Lucia Carlucci Prof. Pierluigi Mercandelli Dr. Marco Aldo Ortenzi Prof. Giancarlo Terraneo Dr. Chiara Botta Prof. Ryan Tsz Kin Kwok Dr. Jacky Wing Yip Lam Prof. Ben Zhong Tang Prof. Elena Cariati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(67):16690-16700
Organic materials with multiple emissions tunable by external stimuli represent a great challenge. TTPyr, crystallizing in different polymorphs, shows a very rich photophyisics comprising excitation-dependent fluorescence and phosphorescence at ambient conditions, and mechanochromic and thermochromic behavior. Transformation among the different species has been followed by thermal and X-ray diffraction analyses and the emissive features interpreted through structural results and DFT/TDDFT calculations. Particularly intriguing is the polymorph TTPyr(HT), serendipitously obtained at high temperature but stable also at room temperature, whose non-centrosymmetric structure guarantees an SHG efficiency 10 times higher than that of standard urea. Its crystal packing, where only the TT units are strongly rigidified by π-π stacking interactions while the Pyr moieties possess partial conformational freedom, is responsible for the observed dual fluorescence. The potentialities of TTPyr for bioimaging have been successfully established. 相似文献
7.
Antony Wing Hung Ng Samuel Kin-Man Lai Chi-Chung Yee Ho Yu Au-Yeung 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2022,134(1):e202110200
A branched [8]catenane from an efficient one-pot synthesis (72 % HPLC yield, 59 % isolated yield) featuring the simultaneous use of three kinds of templates and cucurbit[6]uril-mediated azide–alkyne cycloaddition (CBAAC) for ring-closing is reported. Design and assembly of the [8]catenane precursors are unexpectedly complex that can involve cooperating, competing and non-influencing interactions. Due to the branched structure, dynamics of the [8]catenane can be modulated in different extent by rigidifying/loosening the mechanical bonds at different regions by using solvent polarity, acid-base and metal ions as the stimuli. This work not only highlights the importance of understanding the delicate interplay of the weak and non-obvious supramolecular interactions in the synthesis of high-order [n]catenane, but also demonstrates a complex control of dynamics and flexibility for exploiting [n]catenanes applications. 相似文献
8.
Cleavage of a PN Bond in a Urea‐Containing (Ph2P(R)PPh2)‐Bridged Dinuclear Gold(I) Thiolate Complex by Fluoride and a Mechanistic Insight 下载免费PDF全文
Dr. Xiaoming He Dr. Wai Han Lam Dr. Eddie Chung‐Chin Cheng Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8447-8454
A urea‐containing, (Ph2P(R)PPh2)‐bridged, dinuclear, gold(I) thiolate complex, [Au2{Ph2PN(C6H4OMe‐4)PPh2}(SC6H4NHCONHC6H5)2] ( 1 ) was designed and synthesized and its photophysical and anion recognition properties studied. The results show that 1 has a high selectivity toward F?. Upon addition of F?, the yellow solution was decolorized, and drastic changes of emission and 1H and 31P{1H} NMR signals were observed. Interestingly, these changes are attributed to fluoride‐assisted P?N bond hydrolysis, instead of the expected hydrogen‐bonding interactions with the urea receptor. Similar changes were observed for two other basic anions, AcO? and H2PO4?, but to a much lesser extent; and these anions were found to bind to the urea receptor at the same time. On the other hand, Cl? was found to only bind to the urea moiety through hydrogen‐bonding interactions. Further studies with the control complex [Au2{Ph2PN(C6H4OMe‐4)PPh2}Cl2] ( 2 ) indicate that F? assists the hydrolysis process via cleavage of the P?N bond. DFT calculations were performed to study the reaction mechanism for the fluoride‐assisted P?N bond hydrolysis of 2 ; these provide a better insight into the role of fluoride in the hydrolysis. 相似文献
9.
Dual Esterase‐ and Steroid‐Responsive Energy Transfer Modulation of Ruthenium(II) and Rhenium(I) Complex Functionalized Gold Nanoparticles 下载免费PDF全文
Dr. Frankie Chi‐Ming Leung Dr. Vonika Ka‐Man Au Dr. Hai‐Ou Song Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16448-16454
A number of adamantane‐containing ruthenium(II) and rhenium(I) complexes have been synthesized, characterized, and noncovalently functionalized with β‐cyclodextrin‐capped gold nanoparticles (β‐CD–GNPs) through the host–guest interaction between cyclodextrin and adamantane. The resultant nanoconjugates have been characterized by transmission electron microscopy (TEM), energy‐dispersive X‐ray analysis (EDX), and 2D ROESY 1H NMR experiments. The Förster resonance energy transfer (FRET) properties of the nanoconjugates can be modulated by both esterase‐accelerated hydrolysis and competitive displacement of steroid, by monitoring the emission intensity and luminescence lifetime. The FRET efficiencies are found to vary with the nature of the chromophores and the length of the spacer between the transition metal complexes and the GNPs. This work constitutes a “proof‐of‐principle” assay method for the dual‐functional detection of important classes of biomolecules, such as enzymes and steroids. 相似文献
10.
Inside Back Cover: A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection,Naked‐Eye Recognition,and Elimination of Cyanide Ions (Chem. Eur. J. 37/2015) 下载免费PDF全文