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101.
对-叔丁基杯[8]芳烃键合硅胶制备及其毛细管电色谱性能研究 总被引:1,自引:0,他引:1
以γ-(环氧丙氧)丙基键合硅胶为前体,于硅胶表面键合环氧基,在催化剂存在下以杯芳烃钠盐开环制备杯芳烃键合硅胶固定相.该方法反应条件温和,适用性强.将这个新方法首次用于制备对-叔丁基杯[8]芳烃电色谱键合固定相(C8BS),采用加压电色谱初步评价其电色谱性能.研究结果表明,C8BS电渗流(Electrosmoticflow,EOF)较小,但通过控制键合反应及使用压力辅助电色谱可部分弥补上述不足.该固定相的EOF受流动相pH影响小(pH=3-8),同时大环配体屏蔽效应能有效地克服硅羟基引起的碱性化合物拖尾现象,这对电色谱分离具有重要意义.通过分步封尾研究EOF的来源发现,杯芳烃酚羟基对EOF有弱的贡献,这与报道的杯芳烃涂层具有径向电渗流调控能力相一致. 相似文献
102.
103.
Shirley H. Lomeli Sheng Yin Rachel R. Ogorzalek Loo Joseph A. Loo 《Journal of the American Society for Mass Spectrometry》2009,20(4):593-596
Increased multiple charging of native proteins and noncovalent protein complexes is observed in electrospray ionization (ESI)
mass spectra obtained from nondenaturing protein solutions containing up to 1% (vol/vol) m-nitrobenzyl alcohol (m-NBA). The increases in charge ranged from 8% for the 690 kDa α7β7β7α7 20S proteasome complex to 48% additional charge for the zinc-bound 29 kDa carbonic anhydrase-II protein. No dissociation
of the noncovalently bound ligands/subunits was observed upon the addition of m-NBA. It is not clear if the enhanced charging is related to altered surface tension as proposed in the “supercharging” model
of Iavarone and Williams (Iavarone, A. T.; Williams, E. R. J. Am. Chem. Soc.
2003, 125, 2319–2327). However, more highly charged noncovalent protein complexes have utility in relaxing slightly the mass-to-charge
(m/z) requirements of the mass spectrometer for detection and will be effective for enhancing the efficiency for tandem mass spectrometry
studies of protein complexes. 相似文献
104.
Silvana T. Castaman Shirley Nakagaki Ronny R. Ribeiro Ktia J. Ciuffi Sueli M. Drechsel 《Journal of molecular catalysis. A, Chemical》2009,300(1-2):89-97
The synthesis and characterization of a binuclear carboxylated bridged manganese complex containing the heptadentate ligand N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)-2-ol-1,3-propanediamine (H3bbppnol) is reported. This complex was characterized by elemental analysis; infrared, electronic (UV–vis) and EPR spectroscopy; and conductivity measurements. The complex was immobilized on silica by either adsorption or entrapment via a sol–gel route. The obtained solids were characterized by thermogravimetric analyses (TG and DSC), UV–vis and infrared spectroscopy, and X-ray diffraction. The catalytic performance of the binuclear manganese complex in epoxidation reactions was evaluated for both homogeneous and heterogeneous systems. The catalytic investigation revealed that the complex performs well as an epoxidation catalyst for the substrates cyclohexene (26–39%) and cyclooctene (29–74%). The solids containing the immobilized complex can be recovered from the reaction medium and reused, maintaining good catalytic activity. 相似文献
105.
Matilte Halma Kelly Aparecida Dias de Freitas Castro Vanessa Prvot Claude Forano Fernando Wypych Shirley Nakagaki 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):42-50
The first generation anionic iron(III) porphyrin [Fe(TSPP)] and the second generation anionic complexes [Fe(TDFSPP)], [Fe(TCFSPP)], and [Fe(TDCSPP)] were immobilized into three-dimensionally macroporous layered double hydroxide (3DM-LDH), using the direct reconstruction of 3DM-LDH from macroporous mixed oxides MOX or the anionic exchange on DDS intercalated 3DM-LDH. The macroporous layered double hydroxides were obtained at the surface of nanometric polystyrene spheres, which were synthesized by an inverse opal method. Polystyrene was removed after calcination in oxidizing atmosphere, nanostructured mixed oxides (3DM-MOX) were obtained, which after reconstruction give origin to macroporous layered double hydroxide (3DM-LDH). Following metalloporphyrin immobilization, the resulting materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), UV–vis (glycerin mull) spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR), and electron paramagnetic resonance (EPR). Results revealed that the complexes are either immobilized at the surface of the macroporous layered double hydroxide or intercalated between the layers, displacing some dodecylsufate anions. The obtained materials were investigated as catalysts for oxidation reactions, to find out whether they function as cytochrome P-450 models. 相似文献
106.
Imaging and manipulation of biological structures with the AFM 总被引:11,自引:0,他引:11
Fotiadis D Scheuring S Müller SA Engel A Müller DJ 《Micron (Oxford, England : 1993)》2002,33(4):385-397
Many biologists have dreamt of physically touching and manipulating the biomolecules they were investigating. With the invention of the atomic force microscope (AFM), this dream has come true. Here, recent applications of the AFM to image and to manipulate biological systems at the nanometer scale are reviewed. Macromolecular biological assemblies as well as individual biomolecules can be subjected to controlled nanomanipulation. Examples of AFM application in imaging and nanomanipulation include the extraction of chromosomal DNA for genetic analysis, the disruption of antibody--antigen bonds, the dissection of biological membranes, the nanodissection of protein complexes, and the controlled modulation of protein conformations. Also reviewed is the novel combination of single molecule imaging and force spectroscopy which allows biomolecules to be imaged, and inter- and intramolecular forces to be measured. Future application of these nanotechniques will reveal new information on the structure, function and assembly of biomolecules. 相似文献
107.
Shirley M.M. Rodrigues Viviani NardiniMauricio G. Constantino Gil Valdo J. da Silva 《Tetrahedron letters》2012,53(45):6136-6137
The treatment of cerium metal with ethyl bromosuccinate (1) forms the stabilized organolanthanoid intermediate (2), which reacts with carbonyl compounds in a Reformatsky-type reaction, under mild conditions, to produce functionalized γ-substituted paraconic acids (4) in good yields. 相似文献
108.
A family of anionic iron(III) porphyrins (FePor) was immobilized onto zinc oxide (ZnO) obtained by the in situ hydrothermal decomposition of zinc hydroxide nitrate, a layered hydroxide salt. The immobilization probably occurred via the interaction between the anionic charges on the porphyrins and the positively charged surface of the ZnO, in slightly acidic to neutral pH. The resulting solids were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRDP), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and ultraviolet-visible spectroscopy (UV-Vis) (solid samples), which confirmed the formation of ZnO and the immobilization of the FePor. The prepared materials were employed as catalysts for the heterogeneous catalytic oxidation of cyclooctene, cyclohexane, and n-heptane, using iodosylbenzene as the oxygen donor. Good catalytic results were achieved for all the substrates, and selectivity for the alcohol was verified during the oxidation of alkanes. The reuse capacity of the solid catalyst was also investigated. 相似文献
109.
An improved, tandem acid activation/aldol-lactonization process is described. This more practical protocol shortens reaction times for the construction of bicyclic β-lactones from ketoacids and implements the use of commercially available reagents p-toluenesulfonyl chloride (p-TsCl) as activator and 4-dimethylaminopyridine (4-DMAP) as nucleophilic promoter (Lewis base). Substrates with β-substituents, with respect to the carboxylic acid, consistently showed excellent levels of diastereoselectivity during the bis-cyclization event. 相似文献
110.