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931.
Marian Vargas Robert M. Kriegel David M. Collard David A. Schiraldi 《Journal of polymer science. Part A, Polymer chemistry》2002,40(19):3256-3263
Dimethyl 2,6‐anthracene dicarboxylate is used as a comonomer in the synthesis of functional copolymers that are subject to modification with Diels–Alder reactions. The formation of poly(ethylene terephthalate‐co‐2,6‐anthracenate), containing less than 20 mol % of the anthracene‐2,6‐dicarboxylate structural units, provides materials that are tractable and soluble. The anthracene units of the copolymers undergo Diels–Alder reactions with N‐substituted maleimides. The grafting of N‐alkylmaleimides affords soluble, hydrophobic polymers, whereas grafting with maleimide‐terminated poly(ethylene glycol) affords hydrophilic polymers. Because this reaction proceeds below the melting point of the copolymers, the procedure can be applied to thin films, whereby the surface properties are modified. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3256–3263, 2002 相似文献
932.
Summary We compute the potential energy surfaces of 12 electronic states of OsH2 (four quintet, four triplet, and four singlet) arising from5
D ground state of the Os atom as well as triplet and singlet excited states using the complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by multireference configuration interaction (MRCI) and relativistic CI (RCI) calculation which include up to 430,000 configurations. We find that the5
D ground state of Os atom does not insert into H2 while the excited3
F state of Os does. The3
B
1 ground state of OsH2 (there are two other nearly degenerate states) in the absence of spin-orbit coupling was found to be 22 kcal/mol more stable than Os(5
D)+H2. The spin-orbit mixing of3
B
1,3
B
2,3
A
2, and1
A
1 states was so strong that it induces significant change in bond angles (up to 10°) for OsH2.Dedicated to Prof. Klaus RuedenbergCamille and Henry Dreyfus Teacher-Scholar 相似文献
933.
Tetsuo Okada 《Analytica chimica acta》2005,540(1):139-145
The interaction and separation of ions with zwitterionic layers are reviewed principally based on a series of the author's work. An electrostatic model has allowed us to discuss the chromatographic retention of ions on the zwitterionic stationary phase, and has revealed the ionic interaction occurring at the zwitterionic interface. Similar consideration is applicable to the ionic partition into zwitterionic micelles having the spherical dimension. In the electrostatic models, ion association and solvation changes of ions have been assumed to explain the selectivity in ion recognition. Both assumptions are applicable to polarizable large ions, whereas the former cannot account for the results obtained for small and well-hydrated ions (Cl− and Br−). A special X-ray absorption finestructure (XAFS) measurement, which allows selective access to ions interacting with surface monolayers, has been developed, and applied to ions attracted by a zwitterionic monolayer. The X-ray absorption spectra suggest that Zn2+ attracted by the zwitterionic monolayer is still hydrated. In contrast, the direct interaction of Br− has been confirmed, indicating that the electrostatic model involving either ion association or the solvation change of an ion does not properly explain the observed phenomena but both effects should be taken into consideration. 相似文献
934.
Surfaces of poly(vinyl methyl ether) (PVME), poly(vinyl methyl ketone) (PVMK), and poly(methyl methacrylate) (PMMA) were covered with different thicknesses of nickel with a metal‐vapor‐condensation method, and the metal–polymer interfaces were analyzed by X‐ray photoelectron spectroscopy. In the very first steps of the metalization, it was found that a systematic degradation of the polymer surface occurs through CO or CO2 losses, depending on the polymer functionalities. Then, at the interface with the polymer, the condensed metal reacts by oxidization with the oxygen atoms that are still available after the surface degradation. Nickel oxide is then formed at the interface, whatever the nature of the initial polymer functional group. These new oxide species are not chemically bonded to the polymer structure, and their formation is not affected by the type of bond existing between oxygen and carbon atoms in the original polymer. Finally, the accumulation of metal on the substrate induces an amorphization of the polymer carbon structure because thermal energy is transferred from the metal coating to the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 82–94, 2002 相似文献
935.
Petter Persson Sten Lunell Lars Ojame 《International journal of quantum chemistry》2002,89(3):172-180
Results from ab initio Hartree–Fock and gradient‐corrected density functional theory calculations of formic acid interactions with ZnO (101 0) surfaces are reported. Surface relaxation is found to affect equilibrium geometries and adsorption energies significantly. Large variations in adsorption energy with coverage and ordering of the adsorbates are revealed and explained in terms of strong and highly anisotropic electrostatic adsorbate–adsorbate interactions. The results are compared to published experimental and theoretical results, and differences in suggested binding geometries from the different studies are discussed. Dynamic properties of the adsorption, surface mobility, and surface reactivity are inferred from key elements of the potential energy surface obtained from the quantum chemical computations and supported by ab initio molecular dynamics simulations. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
936.
Summary An appropriate procedure based on statistical criteria is suggested for the determination of the optimum set of model parameters
for a given chromatographic system. The criteria employed are the t-ratio test, the rate of change in the sum of squares of
residuals, the standard error of the fit, the F-test, and the CP-test. The suggested procedure has been evaluated using two different models, one based on partition and the other on adsorption
mechanisms, which describe the combined effect of pH and organic modifier content on the retention of ionogenic solutes in
reversed-phase liquid chromatography. It is shown that all the criteria give almost converged results and therefore we may
simply use the F-test, which seems to be the most sensitive and reliable criterion excluding any personal judgement. It is
also found that the retention models tested show a different behavior towards their simplification. In particular, the use
of a reduced equation of the partition model, selected on the basis of the suggested procedure, is necessary for the prediction
of meaningful retention surfaces, whereas the decrease in the number of the adjustable parameters in the adsorption model
offers only noise reduction and fitting simplicity, because no version of this model predicts abnormal retention surfaces. 相似文献
937.
利用多重散射簇(multiple scattering cluster, MSC)方法计算了N2O多层膜中氮原子的1s芯态近边X射线吸收精细结构(near edge X-ray absorption fine structure, NEXAFS)谱,首次给出N2O多层膜局域结构的模型. MSC研究显示多层膜中N2O分子以短程有序的分层错位链结构排列,并求得链中相邻分子间距为0.233 nm和相邻分子层之间距离为0.240~0.245 nm.用自洽场离散变分(discrete variation, DV)Xα方法计算的N2O多层膜电子结构支持了MSC的计算结果;阐明了NEXAFS谱中弱结构的物理起源.对N2O多层膜中分子之间相互作用的分析显示N2O多层膜的结构具有分子自组装的特性. 相似文献
938.
Irena Lj. Arsova Abdurauf R. Prusi Ljubomir D. Arsov 《Journal of Solid State Electrochemistry》2003,7(4):217-222
Anodic oxide films formed potentiostatically on niobium surfaces, from open circuit potential (OCP) to 10 V, were studied
by performing in situ and ex situ ellipsometric measurements. The kinetics of the film thickness growth in 1 M H2SO4 and complex indices of refraction of these films were determined. A strong influence of the surface preparation conditions
on the complex refractive indices of the metal substrate and anodic oxide films was shown. By steady-state measurements at
OCP, a small thickening of the natural air-formed oxide film with chemical composition Nb2O5 in 1 M H2SO4 solution was detected. With cathodic pre-treatment, only partial reduction and small thinning of the natural air-formed oxide
film was possible. The thicknesses of the natural air-formed oxide films on fine mechanically polished and electropolished
Nb surfaces were determined. The build up of the natural air-formed oxide film, at ex situ conditions, on the already formed
anodic oxide films was confirmed. It was shown that electropolishing gives more similar optical surface properties to the
bare metal than the fine mechanical polishing.
Electronic Publication 相似文献
939.
Andrzej Dąbrowski 《Monatshefte für Chemie / Chemical Monthly》1983,114(8-9):875-890
An equation for the phenomenon of competetive adsorption from binary liquid mixtures onto solids has been derived using the kinetic approach. In this equation the difference of the molecular sizes, the non-ideality of both bulk surface phases, and the energetic heterogeneity of the solid surface have been taken into account.
Theoretische Untersuchungen zur Adsorption aus nichtidealen binären Lösungsmittelgemischen an heterogene Oberflächen fester Körper unter Berücksichtigung der Unterschiede in den molekularen Größen der Komponenten
Zusammenfassung Auf Grund kinetischer Erwägungen wurde eine Gleichung, die die Konkurrenzadsorption aus binären Lösungsmittelgemischen an den Oberflächen fester Körper beschreibt, aufgestellt. In der Gleichung wurde der Größenunterschied der Teilchen, die Nichtidealität der Lösung in der Volumen- und Oberflächenphase, sowie die energetische Heterogenität der Oberfläche des festen Körpers berücksichtigt.相似文献
940.
Thomas Weis Markus M. Eisl Bernhard M. Reichl Kurt W. Brandl Herbert Störi 《Mikrochimica acta》1997,125(1-4):287-291
The analysis of segregation phenomena in bicrystals is an important step for the understanding of combined effects of the elementary diffusion processes involved in the segregation in polycristalline systems. The segregation of Si and P in a Fe-6at.%Si bicrystal with a (100) and (110) surface has been investigated by means of AES (Auger electron spectroscopy). For these experiments the technique of a linearly increased temperature has been applied. Significant differences between the segregation kinetics at the two surfaces of the sample have been found on the one hand for the maximum coverage of P and on the other hand for the high temperature behaviour of Si. Additionally, model calculations based on the KTBIM (kinetic tight binding Ising model) have been performed to qualitatively describe the experimental results. It is shown, that the striking differences between the segregation behaviour at the two differently oriented surfaces can be explained by different segregation energies of P, whereas Si plays a minor role due to its relatively small segregation energy.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献