全文获取类型
收费全文 | 490篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 339篇 |
晶体学 | 9篇 |
力学 | 43篇 |
数学 | 30篇 |
物理学 | 88篇 |
出版年
2024年 | 6篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 29篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 17篇 |
2015年 | 22篇 |
2014年 | 16篇 |
2013年 | 47篇 |
2012年 | 41篇 |
2011年 | 41篇 |
2010年 | 14篇 |
2009年 | 24篇 |
2008年 | 17篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1969年 | 3篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1959年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有509条查询结果,搜索用时 46 毫秒
61.
Neelam?Kumari D.?R.?Prabhu P.?N.?PathakEmail author A.?S.?Kanekar V.?K.?Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):835-843
Extraction behavior of 1 × 10−2–0.1 M U(VI) from aqueous phases containing 0.86 M Th(IV) at 4 M HNO3 in 1.1 M tributyl phosphate (TBP) and 1.1 M N,N-dihexyl octanamide (DHOA) solutions in different diluents viz. n-dodecane, 10% 1-octanol + n-dodecane, and decahydronaphthalene (decalin) was studied. Third-phase formation was observed in both the extractants using
n-dodecane as diluent. There was a gradual decrease in Th(IV) concentration in the third-phase (heavy organic phase, HOP) with
increased aqueous U(VI) concentration [0.71 M (no U(VI))–0.61 M (0.1 M U(VI)) for TBP; 0.27 M (no U(VI))–0.22 M (0.1 M U(VI))
for DHOA]. The HOP volume in case of DHOA was ~2.2 times of that of TBP. Uranium concentration in HOP increased with its initial
concentration in the aqueous phase [from 1.8 × 10−2 M (0.01 M U(VI))–0.162 M (0.1 M U(VI)) for TBP; from 1.4 × 10−2 M (0.01 M U(VI))–0.14 M (0.1 M U(VI)) for DHOA] suggesting that Th(IV) was being replaced by U(VI). An empirical correlation
was developed for predicting the concentrations of uranium and thorium in HOP for both the extractants. No third-phase appeared
during the extraction of uranium and thorium from the aqueous phases employing 10% 1-octanol + n-dodecane, or decalin as diluents, and therefore, were better choices as diluent for alleviating the third-phase formation
during the reprocessing of spent thorium based fuels, and for the recovery of thorium from high-level waste solutions. 相似文献
62.
63.
The structural characterization of different kinds of zigzag and chiral single-walled carbon nanotubes (SWNTs) has been investigated theoretically using (19)F NMR spectroscopy. The chemical shift anisotropy (CSA) tensor is computed at different levels of theory for the (19)F nuclei in different forms of functionalized fluorinated carbon nanotubes (CNT). A set of fluorine CSA parameters comprising the span, skew, and isotropic chemical shift is computed for each form of the fluoronanotubes and multidimensional CSA parameter correlation maps are constructed. We show that these correlations are able to clearly distinguish between the chiral and zigzag forms of fluorinated carbon nanotubes (F-SWNTs). Implications for solid-state and liquid-state NMR experiments are discussed. 相似文献
64.
Kumari H Kline SR Schuster NJ Atwood JL 《Chemical communications (Cambridge, England)》2011,47(45):12298-12300
The stability of copper-seamed C-alkylpyrogallol[4]arene hexamers with varying chain lengths in solution has been studied using small-angle neutron scattering (SANS). The progression in diameter of spherical capsules with increasing alkyl chain lengths of copper-seamed hexamers in solution suggests both robustness as well as a close correlation between the solid phase and solution phase structures. 相似文献
65.
Singh P Kumar P Kumari K Sharma P Mozumdar S Chandra R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):909-912
In the present work, we report a novel method for the synthesis of palladium and lead nanoparticles by the reduction method in tetrazolium ring based ionic liquid. Palladium and lead nanoparticles so-prepared were well characterized by powder X-ray diffraction measurements (pXRD), transmission electron microscopy (TEM) and quasi elastic light scattering (QELS) techniques. Powder X-ray diffraction (pXRD) analysis revealed all relevant Bragg's reflection for crystal structure of palladium and lead. Powder X-ray diffraction plots also revealed no oxidized material of palladium and lead nanoparticles. TEM showed nearly uniform distribution of the particles in methanol and confirmed by QELS. Typical applications of palladium nanoparticles include in vitro use and sensor design applications. Palladium nanoparticles is also ideal for spin coating, self-assembly and monolayer formation. Palladium nanoparticles can also be considered as potential new catalysts. 相似文献
66.
The essential oil of Eucalyptus cinerea is reported to possess a higher 1,8-cineole content than other Eucalyptus species. Variations in the quantitative and qualitative characteristics of E. cinerea oil produced by hydrodistillation (HD) and supercritical carbon dioxide extraction (SCE) techniques and a comparison between glycoside-bound and free volatile constituents produced by HD have been studied. It was found that HD produced higher oil (free volatiles) content (3.1%) as compared with SCE (1.1%), whereas bound volatiles constituted only about 0.4%. Gas chromatographic (GC) analysis of the oil samples revealed significant difference in their chemical composition. The essential oil (free volatiles) produced by HD contained 1,8-cineole (85.1%) as the major constituent, followed by a-terpineol (7.2%) and limonene (4.4%). In the bound volatile fraction produced by HD, 1,8 cineole (20.6%), alpha-terpineol (7.6%), p-cymene (6.3%), and limonene (4.5%) were found as major constituents. The extract produced by SCE was dominated by 1,8-cineole (70.4%), a-terpineol (8.6%), globulol (3.1%), aromadendrene (2%), citronellal (1.7%), viridiflorol (1.3%), phytol (1.1%) and terpinen-4-ol (1%). Although HD produced higher oil yields, SCE produced better extract in terms of the number of components detected. 相似文献
67.
The thermosolutal convection in a layer of Maxwellian viscoelastic fluid heated and soluted from below in porous medium is considered. The effects of uniform magnetic field and uniform rotation on the thermosolutal convection are also considered. For stationary convection, the Maxwellian viscoelastic fluid behaves like a Newtonian fluid. The sufficient conditions for the nonexistence of overstability are obtained. The critical Rayleigh number is found to increase with the increase in magnetic field, rotation and stable solute gradient. 相似文献
68.
69.
70.
Manisha Bajpai Kusum Kumari Ritu Srivastava M.N. Kamalasanan R.S. Tiwari Suresh Chand 《Solid State Communications》2010,150(13-14):581-584
The current density–voltage () behavior of polymer PDY 132 thin films has been investigated in hole-only device configuration, viz., ITO/poly(ethylene-dioxthiophene):polystyrenesulphonate (PEDOT:PSS)/PDY 132/Au, as a function of polymer (PDY) film thickness (150 nm and 200 nm) and temperature (290–90 K). Hole current density was found to follow two distinct modes of conduction, (i) low electric field region I: ohmic conduction where slope , and (ii) intermediate and high electric field region II: non ohmic conduction where slope . Region I has been attributed to the transport of intrinsic background charge carriers while region II has been found to be governed by space charge limited currents (SCLC) with hole mobility strongly dependent on electric field and temperature. The respective hole transport parameters determined from the SCLC regime, is , is , and zero field activation energy () of 0.48 eV is obtained. 相似文献