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71.
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Cocquyt J Olsson U Olofsson G Van der Meeren P 《Langmuir : the ACS journal of surfaces and colloids》2004,20(10):3906-3912
Dilute dispersions of the synthetic bilayer forming double-chained cationic lipid dioctadecyldimethylammonium bromide (DODAB) were investigated. In dispersions sonicated above the chain melting temperature Tm (approximately 45 degrees C) it was found by H NMR that about 50% of the surfactant chains remained fluid when the samples were cooled to room temperature, which is 20 degrees C below Tm. In contrast, there was no sign of a fluid fraction in unsonicated samples at room temperature. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) to DODAB dispersions at room temperature resulted in the formation of an essentially stoichiometric DODA-DS complex with frozen chains, as seen by titration calorimetry and H NMR experiments. For sonicated samples, turbidity experiments demonstrated that, after a fast complexation reaction, the system remains colloidally stable unless the SDS-to-DODAB mixing ratio is too close to unity. H NMR experiments also showed that in the unreacted DODAB the fraction of fluid chains remained close to 50%, indicating either that SDS reacts equally fast with fluid and frozen DODAB or that there is a relaxation of the fluid fraction after the complexation. The melting enthalpy and the melting temperature of the alkyl chains rise gradually as the mixing ratio increases. We observed with cryo-TEM that the fraction of large unilamellar vesicles was significantly larger after addition of SDS. This indicates vesicle fusion. Based on both wide- and small-angle X-ray scattering patterns, the structure of the equimolar SDS-DODAB complex at 25 degress C was proposed to be lamellar. 相似文献
74.
Following an approach to density functional theory calculations based on the matrix representation of operators, we implemented
a scheme as an alternative to traditional grid-based methods. These techniques allow integrals over exchange-correlation operators
to be evaluated through matrix manipulations. Both local and gradient-corrected functionals can be treated in a similar way.
After deriving all the required expressions, selected examples with various functionals are given.
Received: 7 March 1998 / Accepted: 21 May 1998 / Published on line: 6 August 1998 相似文献
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76.
Anna Grünberg Dr. Xu Yeping Dr. Hergen Breitzke Dr. Gerd Buntkowsky Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(23):6993-6998
The Wilkinson’s catalyst [RhCl(PPh3)3] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA‐3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid‐state NMR methods. The successful modification of the silica surface was confirmed by 29Si CP‐MAS NMR experiments. The presence of the Tn peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. 31P‐31P J‐resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable 31P‐31P J‐coupling, well resolvable in 2D MAS NMR experiments. This J‐coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable 31P‐31P J‐coupling in off‐magic‐angle‐spinning experiments, as well as slow‐spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules. 相似文献
77.
Thomas Schwarze Wulfhard Mickler Dr. Carsten Dosche Dr. Roman Flehr Tillmann Klamroth Dr. Hans‐Gerd Löhmannsröben Prof. Dr. Peter Saalfrank Prof. Dr. Hans‐Jürgen Holdt Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(6):1819-1825
Fluoroionophores of fluorophore–spacer–receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1 – 13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1 – 3 ) revealed a dominant through‐space pathway for oxidative photoinduced electron transfer (PET) in CH2‐bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4 – 9 containing two anthracene or pyrene fragments connected through CH2 bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (EOx) through electron‐withdrawing or ‐donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (ΔGPET) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Φf), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl2 were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10 – 13 were synthesized. 相似文献
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79.
Christian M. Schurz Monika Meyer Gerd Meyer Prof. Dr. Thomas Schleid Prof. Dr. 《无机化学与普通化学杂志》2010,636(7):1169-1171
First single crystals of Na2[{(ON)Ce4}Cl9] were obtained during synthesis attempts for the cerium nitride chloride Ce2NCl3(= {N2Ce4}Cl6). With a molar ratio of 8:10:3 for Ce, CeCl3 and NaN3 along with an excess of the flux NaCl, the mixture obviously contained a small amount of CeOCl that led to the formation of quinary Na2[{(ON)Ce4}Cl9]. It crystallizes in the monoclinic space group P21/m(no. 11) with two formula units in the unit cell with dimensions of a = 813.21(6) pm, b = 1146.13(9) pm, c = 942.86(7) pm and β = 107.504(5) °. As the dominating structural feature {ZCe4}9.5+ tetrahedra are fused through trans‐oriented edges to generate chains (Z = 1/2 O + 1/2 N) just as in the structurally isotypic compounds A2[{Z2R4}X9] (A = Na, K; R = Pr, Nd, Gd; X = Cl, Br; Z = O, O/N). 相似文献
80.
Christine Walbaum Ingo Pantenburg Peter Junk Glen B. Deacon Gerd Meyer Prof. Dr. 《无机化学与普通化学杂志》2010,636(8):1444-1446
Black single crystals of [Lu(Db18c6)(H2O)3(thf)6]4(I3)2(I5)6(I8)(I12) were obtained from lutetium, I2 and Db18c6 (dibenzo‐18‐crown‐6) in THF solution. In the bulky cation, Lu3+ is surrounded by nine oxygen atoms, six of Db18c6 and three of water molecules to which two THF molecules are attached each. Meanwhile, four polyiodide anions, (I3)–, (I5)–, (I8)2– and (I12)2–, in a 2:6:1:1 ratio form a three‐dimensional network and leave space for the bulky cations. 相似文献