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111.
112.
Tailor-made hexaethylene glycolic ionic liquids as organic catalysts for specific chemical reactions
Hexaethylene glycol substituted imidazolium based ionic liquids (hexaEGILs) were designed and prepared well-tailored to a specific organic reaction using alkali-metal fluorides (MFs) as multifunctional organic catalysts. These hexaEGIL catalysts could significantly enhance the reactivity of MF, even KF. Furthermore, the hexaEGIL systems showed tremendous efficiency in the nucleophilic fluorination of base-sensitive substrates. 相似文献
113.
Technology evaluation has played a crucial role in selecting and supporting companies with innovative technology. Previous studies have focused on developing technology evaluation methods such as scorecard. However, technology credit rating is rarely applied, despite its convenient usage for technology financing. In this paper, we propose a technology credit rating system, called cross matrix, based on empirical data obtained from the technology scoring model and examine their properties. The proposed rating system is expected to provide valuable information for effective management of the technology credit fund. 相似文献
114.
115.
Sohn EH Ahn J Kim BG Lee JC 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1811-1820
The influence of side chain length and sulfonyl moiety on the molecular structures and wettability behavior of poly(oxyethylene)s with alkyl sulfonyl side chains (CH(3)-nSE, n = 1, 2, 3, 4, 5, 6, 8, 10), where n is the number of the carbon atom in the n-alkyl side group, was investigated. CH(3)-nSEs having shorter side chains (n < 5) do not have ordered structures, and their surfaces were found to be more polar than those of CH(3)-nSEs having longer side chains (n ≥ 5). The CH(3)-nSEs having longer side chains show double-layered lamellar structures (n ≥ 5) with well-aligned side chains and low surface energies in the range 21.2-25.8 mN/m. Interestingly, stick-slip behavior was observed only on the surfaces of CH(3)-3SE and CH(3)-4SE when water was used as the test liquid. The surface deformation at the three-phase line was generated from interactions between water and sulfonyl groups, and the optimum side chain lengths were believed to cause the stick-slip behavior. 相似文献
116.
Vinod H. Jadhav Sang Bong Lee Hwan-Jeong Jeong Seok Tae Lim Myung-Hee Sohn Dong Wook Kim 《Tetrahedron letters》2012,53(16):2051-2053
Phenolic tert-butyldimethylsilyl (TBDMS) ethers can be deprotected to yield phenols in excellent yield using tailor-made ionic liquid [dihexaEGim][OMs] (dihexaEGim = dihexaethylene glycolic imidazolium salt) as an organic catalyst with alkali-metal fluoride in tert-amyl alcohol. On the contrary, all TBDMS protecting groups can be cleaved cleanly from the bis-TBDMS ether using the same reaction in CH3CN solvent instead of tert-alcohol at 100 °C. This [dihexaEGim][OMs]/tert-amyl alcohol media system allows the highly selective phenolic deprotection reaction of various bis-TBDMS ethers containing both phenolic and aliphatic TBDMS ethers to provide the corresponding phenols in high yield. 相似文献
117.
Dyson BS Burton JW Sohn TI Kim B Bae H Kim D 《Journal of the American Chemical Society》2012,134(28):11781-11790
Elatenyne is a small dibrominated natural product first isolated from Laurencia elata. The structure of elatenyne was originally assigned as a pyrano[3,2-b]pyran on the basis of NMR methods. Total synthesis of the originally proposed pyrano[3,2-b]pyran structure of elatenyne led to the gross structure of the natural product being reassigned as a 2,2'-bifuranyl. The full stereostructure of this highly flexible small molecule was subsequently predicted by Boltzmann-weighted DFT calculations of (13)C NMR chemical shifts for all 32 potential diastereomers, with the predicted structure being in accord with the proposed biogenesis outlined below. Herein we report two complementary total syntheses of elatenyne, which confirm the computer-predicted stereostructure. Additionally, the total syntheses of (E)-elatenyne and a related 2,2'-bifuranyl, laurendecumenyne B, are reported. This work has not only allowed the full structure determination of all of these natural products but also provides excellent supporting evidence for their proposed biogenesis. The total synthesis of elatenyne demonstrates that DFT calculations of (13)C NMR chemical shifts coupled with biosynthetic postulates, comprise a very useful method for distinguishing among large numbers of highly flexible, closely related molecules. 相似文献
118.
119.
Yuri Sohn 《Applied Surface Science》2009,256(4):1078-1081
GaN nanorods were grown on c-plane sapphire substrates by using catalyst-free hydride vapor phase epitaxy (HVPE). The effects of substrate temperature, Ga boat temperature, and Ga pretreatment on the surface morphology of GaN nanorods were investigated. From the dependence of a radial and axial growth rate on the substrate temperature, the kinetically limited process was found to be a rate determining step in the growth of GaN nanorods in HVPE. In addition, the activation energy of the growth along the both axial and radial directions were estimated. The dependence of a Ga boat temperature and the Ga pretreatment effect revealed that the density of nanorods were dependent on the flux of Ga species on the substrate. 相似文献
120.
Jin Sun Sohn Yu-Hau Tseng Shuwang Li Axel Voigt John S. Lowengrub 《Journal of computational physics》2010,229(1):119-144
We develop and investigate numerically a thermodynamically consistent model of two-dimensional multicomponent vesicles in an incompressible viscous fluid. The model is derived using an energy variation approach that accounts for different lipid surface phases, the excess energy (line energy) associated with surface phase domain boundaries, bending energy, spontaneous curvature, local inextensibility and fluid flow via the Stokes equations. The equations are high-order (fourth order) nonlinear and nonlocal due to incompressibility of the fluid and the local inextensibility of the vesicle membrane. To solve the equations numerically, we develop a nonstiff, pseudo-spectral boundary integral method that relies on an analysis of the equations at small scales. The algorithm is closely related to that developed very recently by Veerapaneni et al. [81] for homogeneous vesicles although we use a different and more efficient time stepping algorithm and a reformulation of the inextensibility equation. We present simulations of multicomponent vesicles in an initially quiescent fluid and investigate the effect of varying the average surface concentration of an initially unstable mixture of lipid phases. The phases then redistribute and alter the morphology of the vesicle and its dynamics. When an applied shear is introduced, an initially elliptical vesicle tank-treads and attains a steady shape and surface phase distribution. A sufficiently elongated vesicle tumbles and the presence of different surface phases with different bending stiffnesses and spontaneous curvatures yields a complex evolution of the vesicle morphology as the vesicle bends in regions where the bending stiffness and spontaneous curvature are small. 相似文献