全文获取类型
收费全文 | 188篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 84篇 |
力学 | 5篇 |
数学 | 21篇 |
物理学 | 81篇 |
出版年
2021年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1937年 | 1篇 |
1930年 | 4篇 |
排序方式: 共有191条查询结果,搜索用时 15 毫秒
31.
Michael R. Smith Clare B. Martin Sonia Arumuganainar Ari Gilman Bruce E. Koel Michele L. Sarazen 《Angewandte Chemie (International ed. in English)》2023,62(8):e202218208
Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO2 electroreduction. Herein, well-dispersed iron-porphyrin-based MOF (PCN-222(Fe)) on carbon-based electrodes revealed optimal turnover frequencies for CO2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO2 mass transport limitations. In situ Raman suggested that PCN-222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer-proton transfer mechanism for CO2 electroreduction on PCN-222(Fe) electrodes, which followed a shift from a rate-limiting electron transfer to CO2 mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO2 electroreduction mechanisms on PCN-222(Fe) MOFs. 相似文献
32.
Haggenmueller R Rahatekar SS Fagan JA Chun J Becker ML Naik RR Krauss T Carlson L Kadla JF Trulove PC Fox DF Delong HC Fang Z Kelley SO Gilman JW 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):5070-5078
The use of single wall carbon nanotubes (SWCNTs) in current and future applications depends on the ability to process SWCNTs in a solvent to yield high-quality dispersions characterized by individual SWCNTs and possessing a minimum of SWCNT bundles. Many approaches for the dispersion of SWCNTs have been reported. However, there is no general assessment which compares the relative quality and dispersion efficiency of the respective methods. Herein we report a quantitative comparison of the relative ability of "wrapping polymers" including oligonucleotides, peptides, lignin, chitosan, and cellulose and surfactants such as cholates, ionic liquids, and organosulfates to disperse SWCNTs in water. Optical absorption and fluorescence spectroscopy provide quantitative characterization (amount of SWCNTs that can be suspended by a given surfactant and its ability to debundle SWCNTs) of these suspensions. Sodium deoxy cholate (SDOCO), oligonucleotides (GT)(15), (GT)(10), (AC)(15), (AC)(10), C(10-30), and carboxymethylcellulose (CBMC-250K) exhibited the highest quality suspensions of the various systems studied in this work. The information presented here provides a good framework for further study of SWCNT purification and applications. 相似文献
33.
Separation and detection of individual submicron particles by capillary electrophoresis with laser-light-scattering detection 总被引:1,自引:0,他引:1
Separation and detection of individual submicron polystyrene spheres using capillary electrophoresis with laser-light-scattering detection has been demonstrated. Electrophoretically separated particles were passed through a focused laser beam and light scattered from individual particles was collected at 90 degrees. Each diameter of polystyrene spheres injected (from 110 to 992 nm) resulted in the observation of a well-defined migration window containing multiple peaks, each arising from the light scattered by an individual particle. The migration time window for individual particles of a particular size corresponded well to the migration time of a peak from a population of particles of the same size detected using a UV absorbance detector. The electrophoretic mobility and scattered light intensity were determined for each particle detected. The average scattered light intensity for each particle size was consistent with Mie scattering theory. Particles as small as 110 nm in diameter were detected individually using this method, but particles with a diameter of 57 nm could not be individually detected. The number of single particle scattering events was counted and compared to the theoretical number of particles injected electrokinetically, and the detection efficiency determined ranged from 38 to 57% for polystyrene spheres of different sizes. The laser-light-scattering detection method was directly compared to laser-induced fluorescence detection using fluorescent polystyrene microspheres. The number of particles detected individually by each method was in agreement. 相似文献
34.
35.
Significant changes in the formation and retention of magnetic bead plugs in a capillary during electrophoresis were studied, and it was demonstrated that these effects were due to the type of biological molecule immobilized on the surface of these beads. Three biological molecules, an antibody, an oligonucleotide, and alkaline phosphatase (AP), were attached to otherwise identical streptavidin-coated magnetic beads through biotin-avidin binding in order to isolate differences in bead immobilization in a magnetic field resulting from the type of biological molecule immobilized on the bead surface. AP was also attached to the magnetic beads using epoxy groups on the bead surfaces (instead of avidin-biotin binding) to study the impact of immobilization chemistry. The formation and retention of magnetic bead plugs were studied quantitatively using light scattering detection of magnetic particles eluting from the bead plugs and qualitatively using microscopy. Both the types of biomolecule immobilized on the magnetic bead surface and the chemistry used to link the biomolecule to the magnetic bead impacted the formation and retention of the bead plugs. 相似文献
36.
Migration of salts in the unsaturated zone caused by heating 总被引:3,自引:0,他引:3
Heat-transfer phenomena as well as moisture movement in unsaturated soils due to thermal gradients, have been extensively studied during the last four decades. Less attention has been devoted to the transport and redistribution of solutes caused by heating.Solar radiation, radioactive waste repositories, underground energy storage, buried electric cables and steam pipes, disposal of waste heat from power plants are examples of heat sources in the soil.Soil-water properties, such as surface tension, viscosity, density, as well as the equilibrium composition of phases, depend on temperature. Hence, nonuniform heating of a soil partially saturated by saline water has an effect on such processes as water flow under capillary and gravitational forces, evaporation, condensation and diffusion of vapor and transport and precipitation of salts.A mathematical model is presented for the migration of salts in the vadoze zone in the soil under nonisothermal conditions, taking into account the above-mentioned phenomena. The physical assumptions underlying the model are briefly discussed.The study of a particular case shows that under certain conditions, a heat source may attract dissolved salts, and cause their precipitation in the hot area. 相似文献
37.
R. Gilman L.C. Bland Peter A. Seidl C.Fred Moore C.L. Morris Steven J. Greene H.T. Fortune 《Nuclear Physics A》1985,432(3):610-618
An earlier model developed to fit the DCX excitation function of 18O has been extended to account for the angular distribution in terms of that for 16O and a double-isobaric-analog transition. 相似文献
38.
39.
40.
Cumberland RW Weinberger MB Gilman JJ Clark SM Tolbert SH Kaner RB 《Journal of the American Chemical Society》2005,127(20):7264-7265
The need for wear- and scratch-resistant materials drives the quest for new superhard materials. In this work, we apply two design parameters to identify ultra-incompressible, superhard materials-high valence electron density and high bond covalency. Our first example of such a material is OsB2. The bulk modulus of OsB2 was measured using in situ high-pressure X-ray diffraction and was determined to be in the range of 365-395 GPa. While this value is slightly less than that of the bulk modulus of diamond, due to the anisotropic crystal structure of OsB2, the axis compressibility in the orthorhombic c-direction is less than the axis compressibility found in diamond. OsB2 also scratches the surface of a sapphire window, indicating that the hardness of OsB2 exceeds 2000 kg/mm2. 相似文献