全文获取类型
收费全文 | 170篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
化学 | 76篇 |
晶体学 | 1篇 |
力学 | 2篇 |
综合类 | 1篇 |
数学 | 37篇 |
物理学 | 88篇 |
出版年
2018年 | 1篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 5篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1974年 | 7篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 140 毫秒
181.
The sample-drying procedure described improves the precision, decreases the time needed and reduces the expense of the solid-surface room-temperature phosphorescence technique. Samples are dried in a glovebg apparatus interfaced to the sample compartment of the spectrophotophosphorimeter. The samples are treated with sodium citrate to prevent moisture quenching the phosphorescence emission The relative standard deviations of measurements are reduced to less than 2% for large sets of samples. The total time required for 37 samples is only 5.5 h compared to 20 h by a conventional technique. 相似文献
182.
Using classical trajectory calculations, we show that photodissociation involving a transition from a linear ground state to a bent excited state can account for the gross structure in the rotational distributions of the CN fragment from ClCN and ICN. If one excited state dominates in the ICN spectrum, its potential energy surface must be characterized by a bending angle near but not equal to the linear configuration. 相似文献
183.
Systematics of hyperfine parameters from 237Np Mössbauer resonance data of compounds with Np in a high formal charge state are discussed with respect to electronic structure properties. In neptunyl(VI) species, we find a linear correlation between the isomer shift and the strength of quadrupole interaction. Both scale linearly with the actinide-oxygen bond length, stressing the central role of this parameter. Some compounds show paramagnetic relaxation spectra which makes their analysis difficult. The hyperfine interactions are often not rotational symmetric indicating a deviation from the simple linear O-Np-O configuration. Mössbauer spectra of NpO3·2H2O reveal that this compound should be described as a neptunyl. A comparison of hyperfine parameter systematics indicates that the Np valence electron properties in Np(VII) species are basically similar to those in Np(VI) neptunyls. 相似文献
184.
WANG Xing qiao GAO Shuang CA Chang sheng YU Lian xiang GUO Jing fu SHUN Shu ju CAO Xi zhang 《高等学校化学研究》1998,(2)
AStudyofSynthesis,ImmobilizationandCatalyticCapabilityofMetaloporphyrin*WANGXing-qiao**,GAOShuang,CAChang-shengYULian-xiang,G... 相似文献
185.
Nawrocki J Dunlap C Li J Zhao J McNeffe CV McCormick A Carr PW 《Journal of chromatography. A》2004,1028(1):31-62
In this part of the review authors discuss methods used for modification of metal oxide surfaces. On the basis of literature data it is shown, that silanization of the surfaces do not form stable supports for chromatography. On the other hand, the success of polymer modified surfaces such as polybutadiene (PBD) and polystyrene (PS) is emphasized. Permanent modification of metal oxide surfaces with Lewis bases is also widely discussed. Chromatographic properties of polymer modified surfaces of zirconia are discussed in details. The perspectives of carbon-coated metal oxide surfaces in HPLC and high temperature separations are described. 相似文献
186.
Childs SL Chyall LJ Dunlap JT Smolenskaya VN Stahly BC Stahly GP 《Journal of the American Chemical Society》2004,126(41):13335-13342
A crystal engineering strategy for designing cocrystals of pharmaceuticals is presented. The strategy increases the probability of discovering useful cocrystals and decreases the number of experiments that are needed by selecting API:guest combinations that have the greatest potential of forming energetically and structurally robust interactions. Our approach involves multicomponent cocrystallization of hydrochloride salts, wherein strong hydrogen bond donors are introduced to interact with chloride ions that are underutilized as hydrogen bond acceptors. The strategy is particularly effective in producing cocrystals of amine hydrochlorides with neutral organic acid guests. As an example of the approach, we report the discovery of three cocrystals containing fluoxetine hydrochloride (1), which is the active ingredient in the popular antidepressant Prozac. A 1:1 cocrystal was prepared with 1 and benzoic acid (2), while succinic acid and fumaric acid were each cocrystallized with 1 to provide 2:1 cocrystals of fluoxetine hydrochloride:succinic acid (3) and fluoxetine hydrochloride:fumaric acid (4). The presence of a guest molecule along with fluoxetine hydrochloride in the same crystal structure results in a solid phase with altered physical properties when compared to the known crystalline form of fluoxetine hydrochloride. On the basis of intrinsic dissolution rate experiments, cocrystals 2 and 4 dissolve more slowly than 1, and 3 dissolves more quickly than 1. Powder dissolution experiments demonstrated that the solid present at equilibrium corresponds to the cocrystal for 2 and 4, while 3 completely converted to 1 upon prolonged slurry in water. 相似文献
187.
The LCAO -X α method is used to compute the X α rotational barrier for ethane both in the rigid-rotor approximation and for optimized staggered and eclipsed geometries. The problem of how to pick points and weights in three dimensions for fitting the nonanalytic exchange and correlation functionals of local density-functional theory is examined; a variational weighting procedure is developed which greatly reduces the size of errors due to the 3-D grid as compared to simple volume-element weighting. The accuracy of the X α results for the optimized geometries and the barrier height of ethane is found to be comparable to that of large-basis Hartree–Fock calculations. 相似文献
188.
Peggy M. Dunlap Wilson Carl F. Brandner 《Journal of colloid and interface science》1977,60(3):473-479
Ultra-low values of the tension at an oil-aqueous electrolyte solution interface can be developed by the addition of water-soluble surfactants of the petroleum sulfonate type. Interfacial tensions in the range of 10−3 dyne/cm or lower are readily achieved with surfactant concentrations of the order of 0.1 wt%. For a given oil and aqueous solution, the minimum interfacial tension resulting from the addition of a petroleum sulfonate depends markedly on the average equivalent weight of the sulfonate. Sulfonates having average equivalent weights higher and lower than a previously determined optimum weight, when mixed so as to yield this particular average weight, will also produce ultra-low interfacial tensions. For a given oil, additional control of this unusual type of interfacial activity is accomplished by adjustment of the electrolyte concentration of the aqueous phase. 相似文献
189.
190.