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171.
Tárkányi G Király P Varga S Vakulya B Soós T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(20):6078-6086
The impact of cooperativity between intermolecular interactions is demonstrated by the molecular self-recognition properties of highly enantioselective epi-cinchona bifunctional thiourea organocatalysts. Low-temperature NMR experiments in inert solvents have revealed two sets of nonequivalent resonances in equal population for thiourea-modified members of the epi-quinine and epi-quinidine families. In solution, the predominance of an asymmetric (C1) dimeric self-assembly with noteworthy structural motifs became evident: simultaneous intra- and intermolecular thiourea hydrogen bonding and a CH/pi interaction were observed. Both the stereochemical and the diverse conformational features of the system favor the observed quinoline T-shaped aromatic pi-pi stacking interaction. The structure findings are supported by quantitative proton-proton distance data that were available from NOE buildup curves. The 3D structure of the dimeric assembly has been modeled in agreement with the H-H distance restraints. Owing to the geometrical preference associated with the dimerization process, the self-assembled bifunctional system is interpreted as a charge-transfer complex with the potential for catalyst self-activation. 相似文献
172.
Polgar T Magyar C Simon I Keserü GM 《Journal of chemical information and modeling》2007,47(6):2366-2373
Structure-based virtual screens were carried out against beta-secretase (BACE1) to investigate the impact of ligand protonation on screening efficacy. A comparative evaluation of the performance and its dependence on ligand protonation states docking by Surflex, eHiTS, GOLD, and FlexX-Pharm was performed. Virtual screening performed by FlexX-Pharm (EF(1%)=69) and Surflex (EF(1%)=58) provided the best efficiency. Screening protocols by FlexX-Pharm and GOLD were affected by ligand protonation, while performance of Surflex did not depend on ligand protonation. 相似文献
173.
Experimental results are presented on the adsorption of sodium alkyl sulfate homologues (nC = 8-14) at the air/solution interface. The adsorption isotherms calculated from equilibrium surface-tension vs concentration data and the critical micelle concentration change regularly with the length of the alkyl chain; the odd/even effect was not observed. The isotherms were analyzed using a model-independent approach. The analysis indicates that the total driving force of adsorption reaches a plateau value and becomes constant in the function of the adsorbed amount in the case of each homologue. With the use of different electrostatic models, it was demonstrated that this behavior is consistent with a saturation-type hydrophobic driving-force contribution, which can be interpreted by the development of a liquidlike alkane environment in the adsorbed layer above a "critical" adsorbed amount. 相似文献
174.
Waerner T Girsch T Varga S Huang L Gornikiewicz A Loeber G 《Analytical and bioanalytical chemistry》2007,389(7-8):2109-2113
Over the last decade biological assays (bioassays) have gained much importance for quality control in biopharmaceutical development
and manufacturing. Here we describe the development and validation of a bioassay to determine the biological activity (potency)
of the plasmid biopharmaceutical pVGI.1 which encodes the VEGF-C (VEGF-2) protein. This assay was developed to test drug substance
and drug product for release and stability testing for phase I and II clinical trials. The main focus was on fast assay development
and easy handling of the assay, combined with valid results representing the specific therapeutic mechanism. The method includes
the expression of the VEGF-C protein in mammalian cells and its binding to the cell surface receptor VEGFR-3. The binding
activity of VEGF-C to its immobilized receptor is quantified in a colorimetric assay. IC50 values of VEGF-C expressed after transfection with sample plasmid and an in-house standard plasmid are determined. The ratio
of the IC50 value of the test article to that of the reference standard reflects the potency of the sample. The potency assay meets the
criteria generally requested by authorities for precision, linearity, accuracy, and range. Therefore the assay can be used
in pharmaceutical quality control and is a suitable basis for development of related bioassays. 相似文献
175.
Quantum chemical calculations have become an everyday tool in chemistry. There are commercial program packages and downloadable basis sets for most needs. However, many chemists rarely go beyond the routine use of these programs, rarely, if ever, checking the original references for basis sets. In this letter, we point out some of the pitfalls of such an approach. Structural parameters of the aluminum-monohalides, AlF, AlCl, AlBr, and AlI, have been calculated using the Gaussian 03 program package and different basis set combinations. 相似文献
176.
Zsolt Varga József Fehér Genovéva Filipcsei Miklós Zrínyi 《Macromolecular Symposia》2003,200(1):93-100
The combination of polymers with nanomaterials displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The magnetic polymer gel represents a new type of composites consisting of small magnetic particles, usually from the nanometer range to the micron range, dispersed in a highly elastic polymeric gel matrix. Combination of magnetic and elastic properties leads to a number of striking phenomena that are exhibited in response to impressed magnetic fields. Giant deformational effects, high elasticity, anisotropic properties, temporary reinforcement and quick response to magnetic field open new opportunities for using such materials for various applications. 相似文献
177.
The purpose of the present study was to provide a reliable value for the specific grain-boundary resistivity ρSGBR of Ni metal. New results are presented on the room-temperature electrical resistivity of nanocrystalline (nc) Ni metal samples produced by electrodeposition with various grain sizes. These resistivity data were compared with previous reports on nc-Ni and all results were analysed according to the procedure of Andrews [Phys. Lett. 19, 558 (1965)] who found that the resistivity increment due to grain boundaries is proportional to the grain-boundary surface area per unit volume which is, on the other hand, inversely proportional to the grain size. It is pointed out that the grain size directly accessible by transmission electron microscopy imaging is the relevant parameter for the evaluation of ρSGBR whereas the crystallite size deduced from X-ray diffraction line broadening leads to an underestimation of ρSGBR because coherency-breaking intragrain defects not contributing significantly to the resistivity also cause a line broadening. From the evaluation of the nc-Ni resistivity data at room temperature, we find that 4.45·10?16?Ω·m2?ρSGBR(Ni)?6.2·10?16?Ω·m2 and our upper bound agrees exactly with the most recent calculated value in the literature. 相似文献
178.
We study numerically the conductance distribution function w(T) for the one‐dimensional Anderson model with random long‐range hopping described by the Power‐law Banded Random Matrix model at criticality. We concentrate on the case of two single‐channel leads attached to the system. We observe a smooth transition from localized to delocalized behavior in the conductance distribution by increasing b, the effective bandwidth of the model. Also, for b < 1 we show that w(ln T/Ttyp) is scale invariant, where Ttyp = exp 〈 ln T 〉 is the typical value of T. Moreover, we find that for T < Ttyp, w(ln T/Ttyp) shows a universal behavior proportional to (T/Ttyp)‐1/2. 相似文献
179.
Sanjeev Gautam Shanshank N. Kane B.–G. Park J.–Y. Kim L.K. Varga J.–H. Song Keun Hwa Chae 《Journal of Non》2011,357(11-13):2228-2231
This paper reports x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies at Fe L3,2 and Co L3,2-edges to investigate the electronic structure of (Fe100 ? xCox)78Si9Nb3B9Cu1 (0 < x < 95) alloys. The influence of controlled Co addition on electronic structural and magnetic properties of (Fe100 ? xCox)78Si9Nb3B9Cu1 (x = 0, 20, 40, and 60) alloys has been investigated and it has been observed that Co exists as Co2+/Co3+, while Fe exists as a mixture of Fe0 (metallic) and Fe2+. The XMCD studies confirm these results and reveal that Co-ions are responsible for the room temperature ferromagnetism (RTFM) in the system, while at Fe L3,2-edge it shows a diamagnetic behavior. 相似文献
180.