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991.
Dominique Collin Günter K. Auernhammer Odile Gavat Philippe Martinoty Helmut R. Brand 《Macromolecular rapid communications》2003,24(12):737-741
We describe the preparation and characterization of uniaxial magnetic gels. Fibril formation of the embedded magnetic particles generates easily detectable magnetic and optical anisotropies. A finite magnetization is frozen‐in and leads to a ferromagnetic‐like response in small homogeneous external magnetic fields. We present, for the first time, frequency dependent measurements of the shear modulus G′. Despite their optical and magnetic anisotropy, the gels are mechanically isotropic.
992.
Philippe Mongondry Chantal Bonnans‐Plaisance Martine Jean Jean Franois Tassin 《Macromolecular rapid communications》2003,24(11):681-685
The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido‐PEGs gave the amino compounds in high yields. Quaternization of the amino groups leads to hydrophilic polymer chains bearing a positive charge on one or two ends, depending on the chosen PEG. Such products can be used to protect sterically, negatively charged particles such as clays.
993.
Bénédicte Lepoittevin Nadège Pantoustier Michael Alexandre Cédric Calberg Robert Jérôme Philippe Dubois 《Macromolecular Symposia》2002,183(1):95-102
In this study, layered silicate/aliphatic polyester nanohybrids were synthesized by ring-opening polymerization of ϵ-caprolactone as promoted by the so-called coordination-insertion mechanism. These nanocomposites were formed in presence of montmorillonite surface-modified by ammonium cations bearing hydroxyl group(s), such as bis(2-hydroxyethyl)methyl (hydrogenated tallow alkyl) ammonium. The lactone polymerization could be initiated by all the hydroxyl functions available at the clay surface, after activation into either tin(II) or Al(III) alkoxide active species. Hybrid nanocomposites were accordingly generated through the covalent grafting of every polyester chain onto the filler surface. Surface-grafted polycaprolactone (PCL) chains were untied and isolated by ionic exchange reaction with LiCl in THF solution and molar masses were measured by size exclusion chromatography. The PCL molar masses could be controlled and readily tuned by the content of hydroxyl groups available at the clay surface. Interestingly, initiation reaction by aluminum trialkoxide active species yielded grafted PCL chains characterized by very narrow molecular weight distribution (Mw/Mn∼1.2). These polyester-grafted layered silicate nanohybrids displayed complete exfoliation of silicate sheets as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM). 相似文献
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996.
Nafaa Mekhilef Pierre J. Carreau Basil D. Favis Philippe Martin Abdelhak Ouhlal 《Journal of Polymer Science.Polymer Physics》2000,38(10):1359-1368
The linear viscoelastic properties of polystyrene polyethylene (PS/PE) blends have been investigated in the molten state. For concentrations of the dispersed phase equal to 30 vol %, the blends exhibited a droplet‐matrix morphology with a volume‐average diameter of 5.5 μm for a 70/30 PS/PE blend at 200 °C and 14.7 μm for a 30/70 PS/PE blend at 230 °C. Enhanced elasticity (G′) for both blends, in the terminal zone, compared to the modulus of the matrix (PS and PE, respectively) was observed. This is related to the deformation of the droplets in the matrix phase and hence to the interfacial forces between the blend components. The results for these uncompatibilized blends are shown to be in agreement with the predictions of the emulsion model of Palierne. These predictions were used to obtain the interfacial tension between PS and PE, which was found to be between 2 and 5 mN/m at 200 °C and 4 ± 1 mN/m at 230 °C. Independent interfacial tension measurements using the breaking‐thread method resulted in a value of 4.7 mN/m and 4.1 mN/m at 200 °C and 230 °C for the respective blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1359–1368, 2000 相似文献
997.
Walter Mühlecker Bernhard Krutler Daniel Moser Philippe Matile Stefan Hrtensteiner 《Helvetica chimica acta》2000,83(1):278-286
The primary fluorescent chlorophyll catabolite 1 (Ca‐FCC‐2) from sweet pepper (Capsicum annuum) has similar optical properties, but is slightly less polar than the primary FCC (pFCC; 2 ) from senescent cotyledons of oilseed rape (Brassica napus). Ca‐FCC‐2 was prepared from pheophorbide a using an enzyme extract from ripe C. annuum chromoplasts. The catabolite Ca‐FCC‐2 ( 1 ) could be determined from fast‐atom‐bombardment (FAB) mass spectra to be an isomer of pFCC ( 2 ). The constitution of Ca‐FCC‐2 was determined by homo‐ and heteronuclear magnetic‐resonance experiments and was found to be identical to that of pFCC. Further 2D‐homonuclear spectra of Ca‐FCC‐2 revealed it to differ from pFCC by the configuration at the methine atom C(1), whose configuration results from the action of red chlorophyll catabolite reductase (RCCR). The occurrence of two primary FCCs that are epimeric at C(1) provides a structural basis for the recent observation of two types of RCCRs among higher plants. 相似文献
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1000.
Judith C. Gallucci Sbastien Gentil Nadine Pirio Philippe Meunier Fabrice Gallou Leo A. Paquette 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):m67-m69
Transmetallation of the dilithium salt of (3,5‐dimethyphenylamino)(isodicyclopentadienyl)dimethylsilane by treatment with zirconium tetrachloride in a 2:1 ratio leads to the substitution of all four chloride ligands. With the applied stoichiometry, the title complex, [Zr(C20H25NSi)2]·C4H10O, was obtained and crystallized from diethyl ether. X‐ray diffraction characterization showed that both isodicyclopentadienyl ligands (alternatively called 4,5,6,7‐tetrahydro‐4,7‐methano‐1H‐indene) are complexed to the metal on their exo face in a completely stereoselective manner and that they are η5‐bonded to the Zr atom. 相似文献