全文获取类型
收费全文 | 1041篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
化学 | 742篇 |
晶体学 | 14篇 |
力学 | 10篇 |
数学 | 74篇 |
物理学 | 221篇 |
出版年
2023年 | 6篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 44篇 |
2012年 | 35篇 |
2011年 | 51篇 |
2010年 | 24篇 |
2009年 | 33篇 |
2008年 | 43篇 |
2007年 | 59篇 |
2006年 | 78篇 |
2005年 | 70篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 20篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 24篇 |
1991年 | 9篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1061条查询结果,搜索用时 31 毫秒
31.
John J. Lenhart Linda A. Figueroa Bruce D. Honeyman David Kaneko 《Colloids and surfaces. A, Physicochemical and engineering aspects》1997,120(1-3):243-254
This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l−1 chitin. 相似文献
32.
Motohisa Kaneko Akio Matsuyama Chikayoshi Nagata 《Photochemistry and photobiology》1978,27(3):359-361
Abstract. Photodimerization of thymine in aqueous solution in the presence of tyrosine was studied with monochromatic UV irradiation. The total dimer formation was sensitized in the presence of tyrosine. The action spectrum of sensitized total dimer formation has a peak near 280 nm corresponding to the absorption maximum of tyrosine. Triplet quenchers reduced the sensitization substantially. It seems probable that tyrosine-sensitized photodimerization of thymine occurred via triplet-triplet energy transfer from tyrosine to thymine. 相似文献
33.
Monolayer properties of irisresorcinol [5-(cis-10-heptadecenyl) resorcinol] were measured at the air/water interface. TheA-T isobars of the monolayers at 10 and 15 mN/m gave two-dimensional thermal expansivities of 1.4 × 10–4/K and 1.3 × 10–4/K at a temperature span from 7–40 C, respectively. The- A isotherms of the material showed only a little dependence on temperature from 5–35 C and onpH except at highpH, where monolayers expanded by ionization of resorcinol headgroups. Some types of saccharose in the subphase exhibited a characteristic interaction with irisresorcinol in monolayers, and there is a possibility that this material will be used for molecular recognition of some saccharoses. 相似文献
34.
Nitrogen adsorption isotherms for fluorinated activated carbon fiber (F-ACF) and fluorinated carbon black (F-CB) were measured at 77 K. Surface structures of F-ACF and F-CB were examined by
s
-plot analysis using the adsorption data on the nonporous carbon black (CB) and F-CB. The surface energy of F-ACF was lower than that of ACF. The micropore structure of ACF was preserved even after fluorination, although the limiting adsorption amount and the micropore width decreased with fluorination. 相似文献
35.
Ikuyo Kaneko 《Mathematical Programming》1977,12(1):48-59
The parametric linear complementarity problem is given by the conditions:q + p + Mz 0, 0,z 0,z
T
(q + p + Mz) = 0. Under the assumption thatM is a P-matrix, Cottle proved that the solution mapz() of the above problem is montonically nondecreasing in the parameter for every nonnegativeq and everyp if and only ifM is a Minkowski matrix. This paper examines whether a similar result holds in various other settings including a nonlinear case. 相似文献
36.
Polymeric pendant Ru(bpy)_3~(2+) complexes were prepared from homopolymer and copolymers of 4-methyl-4'-vinyl-2,2'-bipyridine (Vbpy). Vbpy was prepared from 4-methylpyridine. The comonomers were styrene (St), acrylic acid (AA), N-vinylpyrrolidone (Pyr), 4-vinylpyridine (Vpy), methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), acrylonitrile (AN) and N-ethyl-4-vinylpyridium bromide (EQ-Vpy). The fraction of the pendant Ru(bpy)_3~(2+) repeating unit in the polymeric complex was 0.022 to 0.052. Absorption maximum, molar extinction coefficient, emission maximum and relative emission intensity of the polymeric complexes were studied. 相似文献
37.
Yuichi Yoshimura Tetsuya Kuze Fumiko Komiya Hiromichi Tanaka Kohei Yamada Nobuaki Kaneko 《Tetrahedron letters》2006,47(4):591-594
A practical synthesis of 4′-thioribonucleosides starting from inexpensive l-arabinose is described. 1,4-Anhydro-2,3-O-isopropylidene-4-thioribitol, which was prepared by using a novel reductive ring-contraction reaction, was converted to the 5-O-silylated sulfoxides. The Pummerer-type thioglycosylation of the sulfoxides gave the 4′-thioribonucleosides stereoselectively. 相似文献
38.
The interaction of water with hydrophobic surfaces is quite important in a variety of chemical and biochemical phenomena. The coexistence of water and oil can be realized by introduction of surfactants. In the case of water vapor adsorption on graphitic nanopores, plenty of water can be adsorbed in graphitic nanopores without surfactants, although the graphitic surface is not hydrophilic. Why are water molecules adsorbed in hydrophobic nanopores remarkably? This work can give an explicit insight to water adsorption in hydrophobic graphite nanopores using experimental and theoretical approaches. Water molecules are associated with each other to form the cluster of 1 nm in size, leading to a significant stabilization of the cluster in the graphitic nanopores. This mechanism can be widely applied to interfacial phenomena relating to coexistence of water and nanostructural materials of hydrophobicity. 相似文献
39.
The adsorption isotherms of Xe vapor at 196 K and supercritical Xe at 300 K on activated carbon fibers of different pore widths were gravimetrically measured. The adsorption isotherms of Xe vapor were compared with the N(2) adsorption isotherms. A Dubinin-Radushkevich (DR) plot of the adsorption isotherms of Xe vapor showed a good linearity, indicating that Xe vapor is adsorbed by the representative micropore filling mechanism. The adsorption isotherms of supercritical Xe were approximated by the Langmuir equation. The saturated adsorption amounts of supercritical Xe, W(L), were in the range of 0.14 to 0.22 ml g(-1). The adsorption isotherms of supercritical Xe were described by the supercritical DR equation, which provides the quasisaturated vapor pressure P(0q). Both P(0q) and W(L) lead to the reduced isotherm, which can describe three isotherms. The obtained reduced isotherm derived from the isotherms of supercritical Xe could describe even those of Xe vapor. Hence, both Xe vapor and supercritical Xe should be adsorbed by the same mechanism. The isosteric heat of Xe adsorption was greater than the enthalpy of vaporization of Xe by more than 12 kJ mol(-1). These results suggest that Xe molecules are stabilized in the form of a cluster in micropores even at 300 K. Copyright 2000 Academic Press. 相似文献
40.
In this paper, we investigate the effect of the solid surface on the fluid-fluid intermolecular potential energy. This modified fluid-fluid interaction energy due to the inducement of a solid surface is used in the grand canonical Monte Carlo (GCMC) simulation of various noble gases, nitrogen, and methane on graphitized thermal carbon black. This effect is such that the effective interaction potential energy between two particles close to surface is less than the potential energy if the solid substrate is not present. With this modification the GCMC simulation results agree extremely well with the experimental data over a wide range of pressures while the simulation results with the unmodified potential energy give rise to a shoulder near the neighborhood of monolayer coverage and the significant overprediction of the second and higher layer coverages. In particular the unmodified GCMC results exhibit very sharp change in those higher layers while the experimental data have a much gradual change in the uptake. We will illustrate this theory with adsorption data of argon, xenon, neon, nitrogen, and methane on graphitized thermal carbon black. 相似文献