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排序方式: 共有275条查询结果,搜索用时 15 毫秒
81.
82.
Roy Sourav Singha Sarkar Sriparna Chakraborty Debashis 《Journal of inclusion phenomena and macrocyclic chemistry》2021,100(1-2):1-36
Journal of Inclusion Phenomena and Macrocyclic Chemistry - In the twenty-first century, one of the central focus of polymer research in academia and industries is directed towards the design of... 相似文献
83.
The template 2‐deoxy‐1‐thio‐α‐hexopyranosid‐3‐ulose was synthesized in quantitative yield and high diastereoselectivity by 1,4‐addition of aryl and alkyl thiols to hex‐1‐en‐3‐ulose promoted by cesium carbonate in THF. 相似文献
84.
The catalytic role of cucurbit[n]urils on the reactivity and stereoselectivity of the [4+2] cycloaddition reaction between cyclopentadiene and methyl acrylate has been examined with density functional calculations. 相似文献
85.
S.K. Barik 《Solid State Communications》2011,151(24):1986-1989
We report the ac electrical response of La0.7Sr0.3Mn1−xFexO3(x=0.05) as a function of temperature, magnetic field (H) and frequency of radio frequency (rf) current (). The ac impedance (Z) was measured while rf current directly passes through the sample as well as in a coil surrounding the sample. It is found that with increasing frequency of the rf current, Z(T) shows an abrupt increase accompanied by a peak at the ferromagnetic Curie temperature. The peak decreases in magnitude and shifts down with increasing value of H. We find a magnetoimpedance of for at around room temperature when the rf current flows directly through the sample and when the rf current flows through a coil surrounding the sample. It is suggested that the magnetoimpedance observed is a consequence of suppression of transverse permeability which enhances skin depth for current flow. Our results indicate that the magnetic field control of high frequency impedance of manganites is more useful than direct current magnetoresistance for low-field applications. 相似文献
86.
Somnath Roy Tarak Nath Mandal Anil Kumar Barik Samik Gupta Ray J. Butcher Munirathinam Nethaji Susanta Kumar Kar 《Polyhedron》2008
Two pyrimidine based NNS tridentate Schiff base ligands S-methyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL1] and S-benzyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL2] have been synthesised by 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and S-methyl/S-benzyl dithiocarbazate. One Co(III) and one Mn(II) complex of HL1 and one Mn(II) complex of HL2 have been prepared and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and spectroscopic studies. All the bis-chelate complexes have a distorted octahedral arrangement with an N4S2 chromophore around the central metal ion. Each ligand molecule binds the metal ion using pyrimidyl nitrogen, azomethine nitrogen and the thiolato sulfur atoms. In the free ligand moieties, the pyrimidine nitrogen atoms, azomethine nitrogen atoms and thione sulfur atoms are in EEE orientation to each other. During chelation, all the donor sites of the ligands are reoriented to ZEZ configuration in order to facilitate the chelation process. In all the complexes, the respective ligand molecule functions as the monoanionic tridentate one. All complexes were analyzed by single crystal X-ray diffraction and significant differences concerning the distortion from octahedral geometry of the coordination environment were observed. 相似文献
87.
88.
Debashis Das 《Journal of solution chemistry》2008,37(7):947-955
Accurate measurements of electrical conductivities and laser Raman spectra of solutions of lithium chloride (LiCl), lithium
bromide (LiBr), lithium tetrafluoroborate (LiBF4) and lithium perchlorate (LiClO4) in tetrahydrofuran are reported. The conductivity data have been analyzed by the Fuoss-Krauss theory, yielding values for
the ion-pair and triple-ion formation constants. The Raman spectra suggest the presence of a new signal of perchlorate ClO4− ions in solution, whereas there is no such evidence for the other investigated anions. The observed processes have been interpreted
by an Eigen multistep mechanism. For each salt, the predominant portion is found to remain in the form of ion pairs, leaving
only a small fraction of triple ions. 相似文献
89.
Adhikari D Mossin S Basuli F Huffman JC Szilagyi RK Meyer K Mindiola DJ 《Journal of the American Chemical Society》2008,130(11):3676-3682
Pincer-type ligands are believed to be very robust scaffolds that can support multifarious functionalities as well as highly reactive metal motifs applied in organometallic chemistry, especially in the realm of catalysis. In this paper, we describe the redox and, therefore, noninnocent behavior of a PNP (PNP- = N[2-P(CHMe2)2-4-methylphenyl]2) pincer ancillary bound to nickel. A combination of structural, spectroscopic, and theoretical techniques suggests that this type of framework can house an electron hole when coordinated to Ni(II). 相似文献
90.
Sikdar D Pradhan SM Katti DR Katti KS Mohanty B 《Langmuir : the ACS journal of surfaces and colloids》2008,24(10):5599-5607
This paper describes a multiscale approach used to model polymer clay nanocomposites (PCNs) based on a new altered phase concept. Constant-force steered molecular dynamics (SMD) is used to evaluate nanomechanical properties of the constituents of intercalated clay units in PCNs, which were used in the finite element model. Atomic force microscopy and nanoindentation techniques provided additional input to the finite element method (FEM) model. FEM is used to construct a representative PCN model that simulates the composite response of intercalated clay units and the surrounding polymer matrix. From our simulations we conclude that, in order to accurately predict mechanical response of PCNs, it is necessary to take into account the molecular-level interactions between constituents of PCN, which are responsible for the enhanced nanomechanical properties of PCNs. This conclusion is supported by our previous finding that there is a change in crystallinity of polymeric phase due to the influence of intercalated clay units. The extent of altered polymeric phase is obtained from observations of a zone of the altered polymeric phase surrounding intercalated clay units in the "phase image" of PCN surface, obtained using an atomic force microscope (AFM). An accurate FEM model of PCN is constructed that incorporates the zone of the altered polymer. This model is used to estimate elastic modulus of the altered polymer. The estimated elastic modulus for the altered polymer is 4 to 5 times greater than that of pure polymer. This study indicates that it is necessary to take into account molecular interactions between constituents in nanocomposites due to the presence of altered phases, and furthermore provides us with a new direction for the modeling and design of nanocomposites. 相似文献