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951.
Pieters G Cazzolaro A Bonomi R Prins LJ 《Chemical communications (Cambridge, England)》2012,48(13):1916-1918
Self-assembled monolayers on Au nanoparticles terminating with TACN·Zn(II) head groups are attractive scaffolds for the formation of multivalent supramolecular structures at submicromolar concentrations in water. 相似文献
952.
Scholten E Visser JE Sagis LM van der Linden E 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2292-2297
Many protein/polysaccharide mixtures phase separate when the concentrations ofthese biopolymers are sufficiently high. One of the properties involved in this phenomenon is the interfacial tension. Here we present measurements of the interfacial tension of two different protein/polysaccharide mixtures. The protein gelatin was mixed with either dextran or gum arabic, all used in a variety of food products. The phase diagrams were constructed using optical rotation. Although both polysaccharides have the same molecular weight, the phase diagrams differed. The interfacial tension of samples, varying in the distance from the critical point, was determined using the spinning drop method. The interfacial tension was found to be in the range of 1-15 microN/m. For both systems, the scaling behavior of the interfacial tension was investigated. The investigated gelatin/dextran system gave critical exponents of 2.5+/-0.1 and 1.4+/-0.1, in reasonable agreement with the mean-field values 3 and 1.5, respectively. The gelatin/gum arabic system did not show critical behavior. For this system, the interfacial tension shows a logarithmic dependence on the distribution of the gelatin and the gum arabic molecules in the separated phases. 相似文献
953.
Physicochemical evaluation of PLA nanoparticles stabilized by water-soluble MPEO-PLA block copolymers 总被引:4,自引:0,他引:4
Chognot D Six JL Leonard M Bonneaux F Vigneron C Dellacherie E 《Journal of colloid and interface science》2003,268(2):441-447
Different water-soluble MPEO-PLA diblock copolymers with various alpha-methoxy-omega-hydroxyl polyethylene (MPEO) and poly(lactic acid) (PLA) block lengths have been synthesized. Their surface-active properties were evidenced by surface tension (water/air) measurements. In each case the surface tension leveled down above a critical polymer concentration, which was attributed to the formation of a dense polymer layer at the liquid-air interface. The applicability of copolymers as emulsion stabilizers in the preparation of PLA nanospheres by an o/w emulsion/evaporation technique was then investigated. Four copolymers presenting sufficient water solubility and good surfactive properties were used to prepare PLA nanospheres with MPEO chains firmly anchored at the particle surface. The effect of polymer concentration in emulsion on particle size and surface coverage was examined. Whatever the copolymer characteristics, it was found that the optimal concentration to obtain a large amount of MPEO at the particle surface was similar (around 2 g/l). The effect of the copolymer composition on MPEO layer characteristics and on colloidal stability was also evaluated. The conformation of MPEO blocks at the PLA particle surface is discussed in relation to the layer thickness and the surface area occupied per molecule. 相似文献
954.
Leonard C. Pasqualini Dr. Oliver Janka Dr. Selina Olthof Prof. Dr. Hubert Huppertz Prof. Dr. Klaus R. Liedl Prof. Dr. Rainer Pöttgen Dr. Maren Podewitz Dr. Jörn Bruns 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17405-17415
Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex-linked (SO4)- and (BO4)-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B2(SO4)4] and Co[B2(SO4)4], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: NiII is located between the borosulfate layers, while CoII—in contrast—is embedded within the layer. Detailed analysis of these two structures based on single-crystal X-ray diffraction, magnetochemical investigations, X-ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species. 相似文献
955.
Dr. Aigui Zhang Dr. Peter Leonard Prof. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202103872
Anomeric base pairs in heterochiral DNA with strands in the α-d and β-d configurations and homochiral DNA with both strands in α-d configuration were functionalized. The α-d anomers of 2′-deoxyuridine and 7-deaza-2′-deoxyadenosine were synthesized and functionalized with clickable octadiynyl side chains. Nucleosides were protected and converted to phosphoramidites. Solid-phase synthesis furnished 12-mer oligonucleotides, which were hybridized. Pyrene click adducts display fluorescence, a few of them with excimer emission. Tm values and thermodynamic data revealed the following order of duplex stability α/α-d ≫β/β-d ≥α/β-d . CD spectra disclosed that conformational changes occur during hybridization. Functionalized DNAs were modeled and energy minimized. Clickable side chains and bulky click adducts are well accommodated in the grooves of anomeric DNA. The investigation shows for the first time that anomeric DNAs can be functionalized in the same way as canonical DNA for potential applications in nucleic acid chemistry, chemical biology, and DNA material science. 相似文献
956.
Tagir A. Yangirov Akhnef A. Fatykhov Elvira A. Sedova Leonard M. Khalilov Ekaterina S. Meshcheryakova Sergey P. Ivanov Sergey N. Salazkin Vladimir A. Kraikin 《Tetrahedron》2019,75(9):1282-1292
A wide range of diastereomeric pairs of biaryl-3,3′-diphthalides with aromatic (heteroaromatic) substituents of polyphenylene series (including halogen substituted) was synthesized. All of them were separated and characterized by the methods of X-ray analysis, HPLC, IR-, 1H and 13C NMR spectroscopy. It was determined that solubility, tendency to adsorption and related to it retention times, chemical shifts of equivalent hydrogen and carbon atoms of biaryl-3,3′-diphthalides diastereoisomers are determined firstly by the stereo-electronic effects of two adjacent strongly polar phthalide groups. It was shown that both in crystalline phase and in solution all the diphthalides, regardless of the chemical structure of their substituents, are existing as stable rotamers with cis or synperiplanar (chiral forms) and trans or antiperiplanar (meso-forms) conformation. 相似文献
957.
Yingying Chai Peter Leonard Xiurong Guo Prof. Dr. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(72):16639-16651
Isolated and consecutive heterochiral α-dC– base pairs have been incorporated into 12-mer oligonucleotide duplexes at various positions, thereby replacing Watson–Crick pairs. To this end, a new synthesis of the α-d anomer of dC has been developed, and oligonucleotides containing α-dC residues have been synthesized. Silver-mediated base pairs were formed upon the addition of silver ions. Furthermore, we have established that heterochiral α-dC–dC base pairs can approach the stability of a Watson–Crick pair, whereas homochiral dC–dC pairs are significantly less stable. A positional change of the silver-mediated base pairs affects the duplex stability and reveals the nearest-neighbor influence. When the number of silver ions was equivalent to the number of duplex base pairs (12), non-melting silver-rich complexes were formed. Structural changes have been supported by circular dichroism (CD) spectra, which showed that the B-DNA structure was maintained whilst the silver ion concentration was low. At high silver ion concentration, silver-rich complexes displaying different CD spectra were formed. 相似文献
958.
Robert P. Young Corbin R. Lewis Chen Yang Luther Wang James K. Harper Leonard J. Mueller 《Magnetic resonance in chemistry : MRC》2019,57(5):211-223
The representation of nuclear magnetic resonance (NMR) tensors as surfaces on three-dimensional molecular models is an information-rich presentation that highlights the geometric relationship between tensor principal components and the underlying molecular and electronic structure. Here, we describe a new computational tool, TensorView, for depicting NMR tensors on the molecular framework. This package makes use of the graphical interface and built-in molecular display functionality present within the Mathematica programming environment and is robust for displaying tensor properties from a broad range of commercial and user-specific computational chemistry packages. Two mathematical forms for representing tensor interaction surfaces are presented, the popular ellipsoidal construct and the more technically correct “ovaloid” form. Examples are provided for chemical shielding and shift tensors, dipole–dipole and quadrupolar couplings, and atomic anisotropic displacement parameters (thermal ellipsoids) derived from NMR crystallography. 相似文献
959.
Lyudmila V. Parfenova Alexandr V. Balaev Irek M. Gubaidullin Liya R. Abzalilova Svetlana V. Pechatkina Leonard M. Khalilov Semyon I. Spivak Usein M. Dzhemilev 《国际化学动力学杂志》2007,39(6):333-339
The mechanism of α‐olefin hydroalumination by HAlBui2, ClAlBui2, and AlBui3 in the presence of Cp2ZrCl2 catalyst has been studied. It was established that the key intermediate of the reaction is a bimetallic complex [Cp2ZrH2 · ClAlBui2]2, which reacts with olefins and yields higher diisobutylalkylalanes. In parallel with this stage, the key complex can readily react with XAlBui2 (X = H, Cl, Bui) and form a stable trihydride complex Cp2ZrH2 · ClAlBui2 · HAlBui2, which does not exhibit reactivity in olefin hydroalumination. A kinetic model of α‐olefin hydroalumination with HAlBui2 and AlBui3 has been developed. The model explains the causes of the low stability of the key intermediate [Cp2ZrH2 · ClAlBui2]2 and of the different activities of organoaluminum compounds (OACs) in the olefin hydroalumination reaction. Moreover, the model gives information about the limit stages of the reaction and explains the influence of the length of the initial olefins on the rate of the whole catalytic process. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 333–339, 2007 相似文献