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排序方式: 共有391条查询结果,搜索用时 281 毫秒
51.
Kim J Jung C Rhee CK Lim TH 《Langmuir : the ACS journal of surfaces and colloids》2007,23(21):10831-10836
This work presents characteristics of Pt deposits on Au(111) obtained by the use of spontaneous deposition and investigated by electrochemical scanning tunneling microscopy (EC-STM). On such prepared and STM characterized Au(111)/Pt surfaces, we studied electrocatalytic oxidation of formic acid and methanol. We show that the first monatomic layer of Pt displays a (square root 3 x square root 3)R30 degrees surface structure, while the second layer is (1 x 1). After prolonged deposition, multilayer Pt deposits are formed selectively on Au(111) surface steps and are 1-20 nm wide and one to five layers thick. On the optimized Au(111)/Pt surface, formic acid oxidation rates are enhanced by a factor of 20 compared to those of pure Pt(111). The (square root 3 x square root 3)R30 degrees-Pt yields very low methanol oxidation rates, but the rates increase significantly with further Pt growth. 相似文献
52.
Presented are sequential images of CO on Pt(111), observed with electrochemical scanning tunneling microscopy, during its electrochemical preoxidation process. In the course of the well-known phase transition from the (2 x 2)-3CO-alpha structure to the (radical 19 x radical 19)R23.4 degrees-13CO structure, various structures were observed: (2 x 2)-3CO-beta (Chem. Comm. 2006, 2191-2193), (1 x 1)-CO, and (radical 13 x radical 13)R46.1 degrees-9CO. Based on an analysis of the populations of the structures averaged over imaging time and imaged location at the preoxidation potential range (0-0.25 V vs Ag/AgCl), the structures of CO domains changed sequentially in the order of (2 x 2)-3CO-alpha, (2 x 2)-3CO-beta, (1 x 1)-CO, (radical 13 x radical 13)R46.1 degrees-9CO, and (radical 19 x radical 19)R23.4 degrees-13CO as the potential shifted from 0 to 0.25 V. Such a sequential structural change demonstrates that the structures of (2 x 2)-3CO-beta, (1 x 1)-CO, and (radical 13 x radical 13)R46.1 degrees-9CO are transient ones during the preoxidation of CO on Pt(111). Discussed are the transient structures in terms of various aspects, such as the absence of CO in solution and the origin of compressed structures. 相似文献
53.
In order to enhance the flexibility of the robotic welding, it is necessary to generate the robot path automatically. In this paper, the automatic teaching of the welding robot for free-formed seam was implemented through the range data acquired by the laser vision sensor. The geometric modeling of objects such as the worktable and weld joint were performed from sequential range data. The orientation as well as the position of the torch was determined by the geometric models, and the path of the welding robot was automatically generated. Experiments for the free-formed seam showed that the proposed method performed sucessfully. 相似文献
54.
SangNyon Kim SangChul Shim DoYoung Kim YoungHa Rhee YoungBaek Kim 《Macromolecular rapid communications》2001,22(13):1066-1071
Biodegradable poly(3‐hydroxyundecenoate) (PHU) films on silicon wafers were crosslinked with UV light under patterned masks. The films were crosslinked most efficiently when irradiated in the presence of diphenyl(2,4,6‐trimethylbenzoylphosphane oxide) as the initiator. Crosslinked patterns were developed with depolymerase solution because crosslinked PHU was degraded much more slowly than natural PHU. Patterned images with thicknesses of as low as 2.5 μm were obtained showing the potential application of PHU in microlithography as a photosensitive material, which is friendly to the environment. 相似文献
55.
The medium formulation and robust process modeling for anti-HIV peptide (T-20) production by recombinant Escherichia coli overexpression were studied by employing a crossed experimental design. The crossed design, a mixture design combined with process factor (induction duration), was used to find the optimal medium formulation and process time. The optimal settings for three major components (7.75 mL of NPK sources, 5.5 mL of glucose, and 11.75 mL of MgSO4) characterized by %T-20 (14.45%), the proportion of peptide to the total protein, were observed in a total of 100 mL of medium inducted at an optical density of 0.67 with 0.7 mM isopropyl-beta-D-thiogalactopyranoside) for a 3-h induction duration at shake-flask scale. These conditions were further investigated to find robust process conditions (8.2 mL of NPK sources, 5.6 mL of glucose, and 11.3 mL of MgSO4, and a 3.5-h induction duration time) for T-20 production (13.9%) by applying propagation of error. 相似文献
56.
Trimerization of the HIV Transmembrane Domain in Lipid Bilayers Modulates Broadly Neutralizing Antibody Binding 下载免费PDF全文
Dr. Timothy M. Reichart Dr. Michael M. Baksh Dr. Jin‐Kyu Rhee Dr. Jason D. Fiedler Prof. Dr. Stephen G. Sligar Prof. Dr. M. G. Finn Prof. Dr. Michael B. Zwick Prof. Dr. Philip E. Dawson 《Angewandte Chemie (International ed. in English)》2016,55(8):2688-2692
The membrane‐proximal external region (MPER) of HIV gp41 is an established target of antibodies that neutralize a broad range of HIV isolates. To evaluate the role of the transmembrane (TM) domain, synthetic MPER‐derived peptides were incorporated into lipid nanoparticles using natural and designed TM domains, and antibody affinity was measured using immobilized and solution‐based techniques. Peptides incorporating the native HIV TM domain exhibit significantly stronger interactions with neutralizing antibodies than peptides with a monomeric TM domain. Furthermore, a peptide with a trimeric, three‐helix bundle TM domain recapitulates the binding profile of the native sequence. These studies suggest that neutralizing antibodies can bind the MPER when the TM domain is a three‐helix bundle and this presentation could influence the binding of neutralizing antibodies to the virus. Lipid‐bilayer presentation of viral antigens in Nanodiscs is a new platform for evaluating neutralizing antibodies. 相似文献
57.
Obtaining accurate and wiggle free Large Eddy Simulation (LES) results of high Re configurations with obstacles is a challenge, especially when the resolution is moderate. This study focusses on LES of buoyant jet in crossflow (JICF). The zone in front of the jet is sensitive for wiggle formation because the jet acts as an obstacle. Only 10 grid cells over the diameter of the jet at outflow are used in order to be able to simulate very large mixing areas with limited CPU power. The resolution increases rapidly to 30–50 cells over the diameter of the bend over jet further downstream. This study tests an artificial viscosity advection scheme with sixth order dissipation, called AV6, which dissipates wiggles adequately with almost no dissipation on physical relevant scales. This desirable behaviour is demonstrated by a Fourier analysis of the Advection-Diffusion equation and turbulent flow simulations. AV6 is a mix of, and improvement over, the artificial viscosity scheme of Jameson et al. (1981) with fourth order dissipation, here called AV4, and a fifth order upwind scheme (UPW5) of Wicker and Skamarock (Mon Weather Rev 130:2088, 2002). AV6 is a robust, simple and easy to implement advection scheme and the total computational time of a simulation with AV6 is only a few percent more than with the second order central scheme (CDS2). Three realistic turbulent flow problems, relevant for buoyant JICF, are used to compare the performance of AV6 with CDS2, AV4 and UPW5 with each other and with experiments. Different grid resolutions and sub-grid scale models are used. The three test cases are a non-buoyant JICF, a buoyant jet in weak coflow, and a buoyant JICF. Of all tested advection schemes, AV6 produces best results and is preferred for LES of buoyant JICF. 相似文献
58.
Tanveer AhmadHongsub Bae Ilsu Rhee Yongmin ChangJaejun Lee Sungwook Hong 《Current Applied Physics》2012,12(3):969-974
We investigate the particle size dependence of the relaxivity of hydrogen protons in an aqueous solution of iron oxide (Fe3O4) nanoparticles coated in silica for biocompatibility. The T1 and T2 relaxation times for various concentrations of silica-coated nanoparticles were determined by a magnetic resonance scanner. We find that the relaxivity increased linearly with increasing particle size. The T2 relaxivity (R2) is more than 50 times larger than the T1 relaxivity (R1) for the nanoparticle contrast agent, which reflects the fact that the T2 relaxation is mainly influenced by outer sphere processes. The high R2/R1 ratio demonstrates that silica-coated iron oxide nanoparticles may serve as a T2 contrast agents in magnetic resonance imaging with high efficacy. 相似文献
59.
Facile and efficient procedures for the N-acylation reaction of amide derivatives with various acid anhydrides and the cyclization reaction of N-acylated amide derivatives with various hydrazine hydrochlorides were described. The reactions were carried out under microwave irradiation to give products in good yields in a few minutes. The synthesis of 1,3,5-trisubstituted-1,2,4-triazoles from benzamides can also be accomplished in a simple one-pot sequential reaction. 相似文献
60.
Porous carbon-based electrodes were prepared by carbonization with poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composites to further increase the specific capacitance for supercapacitors. The specific capacitance, pore size distribution, and surface area of the PVDF/CNT composites were measured, and the effect of the carbonization temperatures was examined. The electrochemical properties were examined by cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge performance using a two-electrode system in TEABF(4) (tetraethylammonium tetrafluoroborate)/acetonitrile as a non-aqueous electrolyte. The highest specific capacitance of ~101 Fg(-1) was obtained for the samples carbonized at 600 °C. The pore size of the samples could be controlled to below 7 nm through the carbonization process. This suggests that micropores make a significant contribution to the specific capacitance due to improved charge transfer between the pores of the electrode materials and the electrolyte. 相似文献