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991.
Julian C. Kwok 《Supramolecular chemistry》2014,26(3-4):182-191
The 1:1 and 2:1 host–guest complexation of a series of 1,n-bis(isoquinolinium)alkane dications (Iq(CH2)nIq2+, n = 2, 4, 5, 6, 8, 9, 10 and 12, and Iq(p-xylene)Iq2+) by cucurbit[7]uril (CB[7]) in aqueous solution has been investigated by 1H NMR spectroscopy and ESI mass spectrometry. The site of binding of the first CB[7] is dependent on the nature of the central linker group, with encapsulation of the p-xylene group or the polymethylene chain when n = 6–10.With shorter (n = 2–5) or longer (n = 12) chains, the first CB[7] binds over an isoquinolinium group. With a second CB[7], the binding of the central group is abandoned in favour of the CB[7] hosts encapsulating the two cationic isoquinolinium termini. The 1:1 and 2:1 host–guest stability constants are related to modes of binding and the nature of the central linkers, and are compared with dicationic guests bearing different terminal groups. 相似文献
992.
M. Sc. Hans A. Laub Prof. Dr. Gwilherm Evano Prof. Dr. Herbert Mayr 《Angewandte Chemie (International ed. in English)》2014,53(19):4968-4971
Donor‐substituted diarylcarbenium ions Ar2CH+ react with ynamides to give 1‐amido‐substituted allyl cations (α,β‐unsaturated iminium ions). Kinetic studies show that these adducts, which correspond to the addition of a C? H bond across the C?C bond, are formed stepwise with initial formation of keteniminium ions and subsequent 1,3‐hydride shifts. The linear correlations between the second‐order rate constants (lg k2, 20 °C) with the electrophilicity parameters E of the diarylcarbenium ions allow us to include ynamides in our comprehensive nucleophilicity scale and thus predict potential electrophilic reaction partners. 相似文献
993.
Self‐Assembly of Three‐Dimensional Supramolecular Polymers through Cooperative Tetrathiafulvalene Radical Cation Dimerization
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Jia Tian Yu‐Di Ding Tian‐You Zhou Dr. Kang‐Da Zhang Prof. Xin Zhao Dr. Hui Wang Prof. Dan‐Wei Zhang Prof. Yi Liu Prof. Zhan‐Ting Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):575-584
The self‐assembly of a new type of three‐dimensional (3D) supramolecular polymers from tetrahedral monomers in both organic and aqueous media is described. We have designed and synthesized two tetraphenylmethane derivatives T1 and T2 , both of which bear four tetrathiafulvalene (TTF) units. When the TTF units were oxidized to the radical cation TTF.+, their pre‐organized tetrahedral arrangement remarkably enhanced their intermolecular dimerization, leading to the formation of new 3D spherical supramolecular polymers. The structure of the supramolecular polymers has been inferred on the basis of UV/Vis absorption, electron paramagnetic resonance, cyclic voltammetry, and dynamic light scattering (DLS) analysis, as well as by comparing these properties with those of the self‐assembled structures of mono‐, di‐, and tritopic control compounds. DLS experiments revealed that the spherical supramolecular polymers had hydrodynamic diameters of 68 nm for T1 (75 μM ) in acetonitrile and 105 nm for T2 (75 μM ) in water/acetonitrile (1:1). The 3D spherical structures of the supramolecular polymers formed in different solvents were also supported by SEM and AFM experiments. 相似文献
994.
Cationic Bis‐N‐Heterocyclic Carbene (NHC) Ruthenium Complex: Structure and Application as Latent Catalyst in Olefin Metathesis
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Dr. Mathieu Rouen Dr. Pierre Queval Laura Falivene Jessica Allard Loïc Toupet Dr. Christophe Crévisy Frédéric Caijo Dr. Olivier Baslé Prof. Luigi Cavallo Dr. Marc Mauduit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13716-13721
An unexpected cationic bis‐N‐heterocyclic carbene (NHC) benzylidene ether based ruthenium complex ( 2 a ) was prepared through the double incorporation of an unsymmetrical unsaturated N‐heterocyclic carbene (U2‐NHC) ligand that bore an N‐substituted cyclododecyl side chain. The isolation and full characterization (including X‐ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring‐closing metathesis, which could be “switched on” under acidic conditions. 相似文献
995.
Reactions of the Donor‐Stabilized Silylene Bis[N,N′‐diisopropyl‐benzamidinato(−)]silicon(II) with Brønsted Acids
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Konstantin Junold Katharina Sinner Johannes A. Baus Dr. Christian Burschka Dr. Célia Fonseca Guerra Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Reinhold Tacke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16462-16466
Reaction of the donor‐stabilized silylene 1 (which is three‐coordinate in the solid state and four‐coordinate in solution) with [HMCp(CO)3] (M=Mo, W; Cp=cyclopentadienyl) leads to the cationic five‐coordinate silicon(IV) complexes 2 and 3 , respectively, and reaction of 1 with CH3COOH yields the neutral six‐coordinate silicon(IV) complex 4 . Compounds 2 – 4 were structurally characterized by crystal structure analyses and multinuclear NMR spectroscopic studies in the solid state and in solution. The formation of 2 – 4 can be formally described in terms of a Brønsted acid/base reaction, coupled with a redox process (SiII→SiIV, H+→H?). 相似文献
996.
Dr. Olga Ekkert Christopher B. Caputo Conor Pranckevicius Dr. Constantin G. Daniliuc Dr. Gerald Kehr Prof. Dr. Gerhard Erker Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11287-11290
The reactions of the intramolecular frustrated Lewis pair‐adduct Ph2PC(p‐Tol)?C(C6F5)B(C6F5)2(CNtBu) with XeF2 gave Ph2P(F)C(p‐Tol)?C(C6F5)B(F)(C6F5)2 ( 3 ). This species reacts with two equivalents of Al(C6F5)3?C7H8 producing the salt, [Ph2P(F)C(p‐Tol)?C(C6F5)B(C6F5)2][F(Al(C6F5)3)2] ( 4 ), whereas reaction with HSiEt3/B(C6F5)3 gave Ph2P(F)C(p‐Tol)?C(H)B(C6F5)3 ( 5 ). The photolysis of 3 resulted in aromatization affording the phenanthralene derivative Ph2P(F)C(p‐Tol(o‐C6F4))?CB(F)(C6F5)2 ( 6 ). 相似文献
997.
西江干流梧州--肇庆段水化学特征研究 总被引:1,自引:0,他引:1
河流水化学特征可以从一定程度上反映出人类活动对水环境的影响。对西江干流梧州———肇庆段水化学参数分析表明,该段水体中阴离子以HCO3-占优势,阳离子以Ca2+为主,其矿化度为256~414 mg/L。岩石风化作用成为控制河流离子化学组成主导因素,工农业污染物输入在一定程度上改变了天然河流的离子化学组成,使NO3-、 SO2-4等呈现富集趋势。 相似文献
998.
999.
Dr. Jian‐zhi Wang Dr. Guang‐hui Zhao Dr. Yan‐feng Li Xiao‐meng Peng Yan‐tao Li 《化学:亚洲杂志》2013,8(12):3116-3122
Based on the characteristics of polycations of chitosan and glucoamylase, which are oppositely charged, they were successfully alternatingly deposited onto the surface of aldehyde‐modified Fe3O4 nanoparticles by using a layer‐by‐layer ion exchange method to form magnetic carriers to construct multilayer films (designated as Fe3O4@(CS/GA)n). The (CS/GA)n film systems were endowed with the pH‐dependent properties of chitosan as well as the catalytic activity of glucoamylase. The changes in weight loss and surface chemistry, morphology, and magnetic sensitivity were monitored and verified by UV/Vis spectroscopy, zeta potential, TEM, and a vibrating sample magnetometer. Subsequently, the influence of the number of bilayers, storage stability, pH, temperature, and reusability of Fe3O4@(CS/GA)5 biocatalysts on catalytic activity were investigated. The results from characterization and determination remarkably indicate that Fe3O4@(CS/GA)5 presents excellent catalytic activity, storage stability, pH stability, and reusability in comparison with free enzyme. Fe3O4@(CS/GA)5 retained >60 % of its initial activity at 65 °C over 6 h; the optimum temperature and pH also increased to the ranges of 45–65 °C and 2.5–3.5, respectively, and only 27 % activity was lost after 10 cycles. This new strategy simplifies the reaction protocol and improves encapsulation efficiency and catalytic activity for new potential applications in biotechnology. 相似文献
1000.
Jonas Bresien Kirill Faust Prof. Dr. Axel Schulz Dr. Alexander Villinger 《Angewandte Chemie (International ed. in English)》2015,54(23):6926-6930
The reaction of [ClP(μ‐PMes*)]2 ( 1 ) with the Lewis acid GaCl3 yielded a hitherto unknown tetraphosphabicyclo[1.1.0]butan‐2‐ium salt, [Mes*P4(Cl)Mes*][GaCl4] ( 3 [GaCl4]), which incorporates a positively charged phosphonium center within its bicyclic P4 scaffold. The formation of the title compound was studied by means of low‐temperature NMR experiments. This led to the identification of an intermediate cyclotetraphosphenium cation, which was trapped by reaction with dimethylbutadiene (dmb). All of the compounds were fully characterized by experimental and computational methods. 相似文献