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排序方式: 共有651条查询结果,搜索用时 15 毫秒
101.
Paola Acosta Braulio Insuasty Rodrigo Abonia Margarita Gutierrez Jairo Quiroga 《Molecular diversity》2017,21(4):943-955
An efficient route for the synthesis of novel 7-aryl and 7-spiropyrazolo[4\(^{\prime }\),3\(^{\prime }\):5,6]pyrido[2,3-d]pyrimidine derivatives is described. These compounds were obtained by a cyclocondensation reaction between pyrazolopyridinediamines 4 and aldehydes 5 or cyclic ketones 6 in the presence of acetic acid as catalyst. This procedure provides the desired compounds in good yields under a simple two-step methodology. The obtained compounds were evaluated as AChE inhibitors and showed weak AChe inhibition with \(\hbox {IC}_{50} = 115{-}470 \, \upmu \hbox {M}\). 相似文献
102.
We present here a novel quartz cell for monitoring H/D exchange in biomolecules using Raman spectroscopy. This cell is combined with a syringe to pump heavy water through a hollow microdialysis fibre, which is inserted into the cell. The deuterium efflux into the sample has been studied as a function of the molecular weight cut‐off of the microdialysis fibre and compared with other microcell systems comprising conventional glass capillaries. The fastest D2O efflux that we have obtained (kd = 0.38 ± 0.008 min−1) permits to measure exchange rates of 2.5 min−1 or less. Application of this cell to deuterium exchange in glyceraldehyde‐3‐phosphate dehydrogenase reveals a class of H‐atoms highly resistant to deuteration, which is consistent with a previous infrared study on this protein. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
103.
J.?G.?Due?as N.?Gutierrez R.?Martínez F.?Ochoa 《The European Physical Journal C - Particles and Fields》2009,60(4):653-659
We analyse the possibilities to detect a new Z
′ boson in di-electron events at Tevatron and LHC in the framework of the 331 model with right-handed neutrinos. We also study
other fermions and Higgs events as final state at LHC. Using
collision data collected by the CDF II detector at Fermilab Tevatron, we find that the 331 Z
′ boson is excluded with masses below 920 GeV. For an integrated luminosity of 100 fb−1 at LHC, and considering a central value
GeV, we obtain the invariant-mass distribution in the process pp→Z
′→e
+
e
−, where a huge peak, corresponding to 800 signal events/(20 GeV), is found above the SM background. The number of di-electron
events vary from 50000 to 2400 in the mass range of
–2000 GeV. We also obtain branching ratios and cross sections in other fermion and Higgs channels at LHC, where a heavy top
quark T exhibits the biggest ratio with m
T
=300 GeV. 相似文献
104.
Rafael Fernández Dr. Abdessamad Grirrane Dr. Irene Resa Dr. Amor Rodríguez Dr. Ernesto Carmona Prof. Eleuterio Álvarez Dr. Enrique Gutiérrez‐Puebla Prof. Ángeles Monge Prof. Juan Miguel López del Amo Dr. Hans‐Heinrich Limbach Agustí Lledós Prof. Feliu Maseras Prof. Diego del Río Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):924-935
New zincocenes [ZnCp′2] ( 2 – 5 ) with substituted cyclopentadienyl ligands C5Me4H, C5Me4tBu, C5Me4SiMe2tBu and C5Me4SiMe3, respectively, have been prepared by the reaction of ZnCl2 with the appropriate Cp′‐transfer reagent. For a comparative structural study, the known [Zn(C5H4SiMe3)2] ( 1 ), has also been investigated, along with the mixed‐ring zincocenes [Zn(C5Me5)(C5Me4SiMe3)] ( 6 ) and [Zn(C5Me5)(C5H4SiMe3)] ( 7 ), the last two obtained by conproportionation of [Zn(C5Me5)2] with 5 or 1 , as appropriate. All new compounds were characterised by NMR spectroscopy, and by X‐ray methods, with the exception of 7 , which yields a side‐product ( C ) upon attempted crystallisation. Compounds 5 and 6 were also investigated by 13C CPMAS NMR spectroscopy. Zincocenes 1 and 2 have infinite chain structures with bridging Cp′ ligands, while 3 and 4 exhibit slipped‐sandwich geometries. Compounds 5 and 6 have rigid, η5/η1(σ) structures, in which the monohapto C5Me4SiMe3 ligand is bound to zinc through the silyl‐bearing carbon atom, forming a Zn? C bond of comparable strength to the Zn? Me bond in ZnMe2. Zincocene 5 has dynamic behaviour in solution, but a rigid η5/η1(σ) structure in the solid state, as revealed by 13C CPMAS NMR studies, whereas for 6 the different nature of the Cp′ ligands and of the ring substituents of the η1‐Cp′ group (Me and SiMe3) have permitted observation for the first time of the rigid η5/η1 solution structure. Iminoacyl compounds of composition [Zn(η5‐C5Me4R)(η1‐C(NXyl)C5Me4R)] resulting from the reactions of some of the above zincocenes and CNXyl (Xyl=2,6‐dimethylphenylisocyanide) have also been obtained and characterised. 相似文献
105.
Patricia Lara Margarita Paneque Prof. Dr. Manuel L. Poveda Prof. Dr. Laura L. Santos Dr. José E. V. Valpuesta Verónica Salazar Dr. Ernesto Carmona Prof. Dr. Salvador Moncho Gregori Ujaque Dr. Agustí Lledós Prof. Dr. Celia Maya Dr. Kurt Mereiter Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9046-9057
Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(TpMe2)Ir(H){?C(CH2R)ArO }] (TpMe2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C6H4 group), and their corresponding hydride olefin isomers, [(TpMe2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(TpMe2)Ir(C6H5)2] with o‐C6H4(OH)CH2R, or with the substituted anisoles 2,6‐Me2C6H3OMe, 2,4,6‐Me3C6H2OMe, and 4‐Br‐2,6‐Me2C6H2OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by 13C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers. 相似文献
106.
107.
Pedro Carmona Arantxa Rodríguez-Casado Marina Molina 《Analytical and bioanalytical chemistry》2009,393(4):1289-1295
We describe the improvement of a novel approach to investigating hydrogen/deuterium (H/D) exchange kinetics in biomolecules
using transmission infrared spectroscopy. The method makes use of a Fourier transform infrared spectrometer coupled with a
microdialysis flow cell to determine exchange rates of labile hydrogens. With this cell system, the monitoring of exchange
reactions has been studied here as a function of some cell characteristics such as: (a) dialysis membrane surface contacting
both the H2O and D2O compartments; (b) molecular cutoff of dialysis membrane; and (c) distance between the cell-filling holes. The best improvement
has been obtained by increasing the dialysis membrane surface followed by increase of molecular cutoff. However, not significant
differences were found using various distances between filling holes. The fastest exchange rate which can be measured with
the cell system used here is found to be k = 0.41 ± 0.02 min−1, that is, about threefold greater than the one got in a previous work. This microdialysis flow cell has been used here for
the study of H/D exchange in nucleic acids with subsequent structural analysis by 2D correlation spectroscopy. 相似文献
108.
Gutierrez JA Pan YX Koroniak L Hiratake J Kilberg MS Richards NG 《Chemistry & biology》2006,13(12):1339-1347
Drug resistance in lymphoblastic and myeloblastic leukemia cells is poorly understood, with several lines of evidence suggesting that resistance can be correlated with upregulation of human asparagine synthetase (hASNS) expression, although this hypothesis is controversial. New tools are needed to investigate this clinically important question, including potent hASNS inhibitors. In vitro experiments show an adenylated sulfoximine to be a slow-onset, tight-binding inhibitor of hASNS with nanomolar affinity. This binding affinity represents a 10-fold improvement over that reported for the only other well-characterized hASNS inhibitor. The adenylated sulfoximine has a cytostatic effect on L-asparaginase-resistant MOLT-4 cells cultured in the presence of L-asparaginase, an enzyme that depletes L-asparagine in the growth medium. These observations represent direct evidence that potent hASNS inhibitors may prove to be effective agents for the clinical treatment of acute lymphoblastic leukemia. 相似文献
109.
Barba C Carmona D García JI Lamata MP Mayoral JA Salvatella L Viguri F 《The Journal of organic chemistry》2006,71(26):9831-9840
A B3LYP/6-31G* study has been carried out for the reactions of methacrolein with cyclopentadiene, parent nitrone, 1-pyrroline-1-oxide, and (Z)-C,N-diphenylnitrone, in which the coordination of a Lewis acid (borane) and the solvent polarity (dichloromethane) have been taken into account. Calculated activation parameters, regioselectivities (for 1,3-dipolar cycloaddition reactions), and endo/exo stereoselectivities show good agreement with available experimental data. Gas-phase calculations show a varied behavior of the s-cis/s-trans TS stability for noncatalyzed reactions (from the systematic s-cis preference for the cyclopentadiene reaction to the systematic s-trans predilection encountered in the diphenylnitrone cycloaddition). BH3 coordination leads to a preferential stabilization of s-trans TSs in the reactions of cyclopentadiene (exo approach) and diphenylnitrone but a larger stabilization of s-cis structures in the processes involving the parent nitrone or 1-pyrroline-1-oxide. Additionally, a rather systematic preferential stabilization of s-trans structures is induced by solvent polarity in most reactions. As a consequence, an s-trans preference is predicted in solution for both thermal and catalyzed types of reactions in most approaches. Such a conclusion is consistent with some experimental results suggesting a preference for a particular conformation of the methacrolein-Lewis acid complexes. 相似文献
110.
O Gutierrez JG Harrison RP Pemberton DJ Tantillo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(35):11029-11035
DFT (both B3LYP and M06-2X), CASSCF, and CASPT2 calculations were used to investigate competing [3,?3] and [3,?5] sigmatropic shifts and intramolecular [4+2] cycloaddition of 1,3,7-octatriene. In accord with previous results on 1,5-hexadiene, CASSCF calculations found both stepwise and concerted pathways for the [3,?3] rearrangement. For the competing [3,?5] sigmatropic rearrangement, CASSCF and CASPT2 calculations revealed three stepwise pathways with similar barriers. UB3LYP and UM06-2X calculations predicted a different potential energy landscape: no stepwise [3,?3] pathway, only two competing [3,?5] sigmatropic shifts, and an intramolecular Diels-Alder cycloaddition/homolytic ring-opening pathway. Significant lowering of barriers for all rearrangements was predicted for some 1,3,7-octatrienes with substituents at the 4- and 7-positions. 相似文献