全文获取类型
收费全文 | 177篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 147篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 4篇 |
物理学 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 14篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 13篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 9篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有186条查询结果,搜索用时 31 毫秒
81.
Alexopoulos T Allen C Anderson EW Areti H Banerjee S Beery PD Biswas NN Bujak A Carmony DD Carter T Cole P Choi Y De Bonte R Erwin A Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Kenney VP Koltick D Lindsey CS LoSecco JM McMahon T McManus AP Morgan N Nelson K Oh SH Piekarz J Porile NT Reeves D Scharenberg RP Stringfellow BC Stampke SR Thompson M Turkot F Walker WD Wang CH Wesson DK 《Physical review letters》1988,60(16):1622-1625
82.
83.
The speed of sound in (heptane + dodecane) mixtures was measured over the whole concentration range at pressures up to 101 MPa and within the temperature range from (293 to 318) K. The density of (heptane + dodecane) was measured in the whole composition range under atmospheric pressure and at temperatures from (293 to 318) K. The densities and heat capacities of these binaries at the same temperatures were calculated for pressures up to 100 MPa from the speeds of sound under elevated pressures together with the densities and heat capacities at atmospheric pressure. The effects of pressure and temperature on the excess molar volume and the excess molar heat capacity are discussed. 相似文献
84.
Chiral liquid crystals with three-ring rigid core were examined. The method based on the selectively reflected light was used to determine the helical pitch. The helical twist sense was worked out using the polarimetry method. 1H and 13C NMR measurements were performed. The influence of three molecular structure parameters: the type of chiral centre, the length of non-chiral chain and substitution of benzene ring by fluorine atoms, on helical pitch, handedness of helical structure and values of chemical shift in proton and carbon spectra was determined. The change of the length of non-chiral terminal chain has the most significant influence on the temperature dependence of helical pitch. All tested parameters have the biggest influence on the values of chemical shift of atoms in the chiral centre. 相似文献
85.
Alexopoulos T Allen C Anderson EW Balamurali V Banerjee S Beery PD Bhat P Bishop JM Biswas NN Bujak A Carmony DD Carter T Choi Y Cole P DeBonte R DeCarlo V Erwin AR Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Jennings JR Kenney VP Lindsey CS Loomis C LoSecco JM McMahon T McManus AP Morgan N Nelson K Oh SH Porile NT Reeves D Rimai A Robertson WJ Scharenberg RP Stampke SR Stringfellow BC Thompson M Turkot F Walker WD Wang CH Warchol J Wesson DK Zhan Y 《Physical review letters》1993,71(10):1490-1493
86.
Maciej Bujak 《Journal of solid state chemistry》2004,177(9):3202-3211
The dependence of molar ratio of reactants on the formula, crystal structure and physicochemical properties of chloroantimonates(III) with different organic cations was studied. It was proved, that the compounds show preferences in crystallization of one product. The changes of the molar ratio of substrates lead to the corresponding changes of these components in crystallized products. The structure of ferroelectric chloroantimonate(III), [(CH3)3NH]3[Sb2Cl9], was determined at 165 and 95 K. It crystallizes in monoclinic space group Pc: a=9.9612(11), b=9.0714(8), c=15.1807(14) Å, β=90.086(8)°, R1=0.0202, wR2=0.0405 and a=9.9138(10), b=9.0783(7), c=15.1299(14) Å, β=90.026(8)°, R1=0.0163, wR2=0.0356 at 165 and 95 K, respectively. At both temperatures the crystal is built of polyanionic layers and trimethylammonium cations. They are bound together by the system of hydrogen bonds. The molecular motions of the organic cations are gradually frozen with decreasing temperature. At 165 K all cations are ordered. The non-structural ferro-ferroelectric phase transition at 125 K is associated with changes in the dynamics of trimethylammonium cations. 相似文献
87.
Marzena Jankowska Teobald Kupka Leszek Stobiński Rasmus Faber Evanildo G. Lacerda Jr. Stephan P. A. Sauer 《Journal of computational chemistry》2016,37(4):395-403
Hartree–Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange‐correlation functionals were used for nonrelativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton, and xenon dimers and free atoms. Relativistic corrections were calculated with the scalar and spin‐orbit zeroth‐order regular approximation Hamiltonian in combination with the large Slater‐type basis set QZ4P as well as with the four‐component Dirac–Coulomb Hamiltonian using Dyall's acv4z basis sets. The relativistic corrections to the nuclear magnetic shieldings and chemical shifts are combined with nonrelativistic coupled cluster singles and doubles with noniterative triple excitations [CCSD(T)] calculations using the very large polarization‐consistent basis sets aug‐pcSseg‐4 for He, Ne and Ar, aug‐pcSseg‐3 for Kr, and the AQZP basis set for Xe. For the dimers also, zero‐point vibrational (ZPV) corrections are obtained at the CCSD(T) level with the same basis sets were added. Best estimates of the dimer chemical shifts are generated from these nuclear magnetic shieldings and the relative importance of electron correlation, ZPV, and relativistic corrections for the shieldings and chemical shifts is analyzed. © 2015 Wiley Periodicals, Inc. 相似文献
88.
89.
Marzena BiaŁek Anna GarŁowska Ozanna Liboska 《Journal of polymer science. Part A, Polymer chemistry》2009,47(18):4811-4821
A titanium complex with [O,N,N,O]‐type tetradentate Schiff base (LTiCl2), never used before in polymerization of olefins, was immobilized on silica‐ and magnesium‐type carriers, and it was used in ethylene polymerization. The conducted research revealed that the catalytic properties of the complex LTiCl2 supported on those carriers were different for both the catalytic systems studied, and simultaneously they turned out different from those of the unsupported system. The supported catalysts require the use of Me3Al, Et3Al, or MAO as the activator to be able to offer high catalytic activities, whereas Et2AlCl is needed for the nonsupported catalyst. This finding, together with considerable changes in polymerization yields and in properties of polymers versus composition of the catalytic system, suggest that there are different types of active sites in the studied catalysts. The catalyst anchored on the carrier produced in the reaction of MgCl2·3.4EtOH with Et2AlCl is definitely the most active one within the support systems tested. Its activity remarkably increases with the increasing reaction temperature. Moreover, that catalyst does not undergo deactivation over the studied period of time, irrespective of the type of the activator used and of the process temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4811–4821, 2009 相似文献
90.
Marzena Białek Anna Pietruszka 《Journal of polymer science. Part A, Polymer chemistry》2009,47(14):3480-3489
Ethylenebis(5‐chlorosalicylideneiminato)vanadium dichloride supported on MgCl2(THF)2 or on the same carrier modified by EtnAlCl3?n, where n = 1–3, was used in ethylene polymerization in the presence of MAO or a common alkylaluminium compounds as a cocatalyst. The support type alter vanadium loading and also change the characteristic of the catalytic active sites. Et2AlCl is the best activator for a catalyst which has been immobilized on a nonmodified support, whereas the systems which contain a carrier which has been modified by an organoaluminium compound reveal the highest activity in conjunction with MAO. That difference, together with different temperature effects on polymerization efficiency (i.e., decrease and increase of catalytic activity for increasing temperatures, respectively) suggest the formation of different types of active sites in the catalytic systems supported on modified and nonmodified magnesium carrier. However, all supported precatalysts possess a long lifetime, still being active towards ethylene polymerization after 2 h. All the systems yield wide MWD polyethylene, while bimodal MWD is found for some part of analyzed samples. Polyethylene with bimodal particle size distribution is formed with the system which contain modified carriers at higher temperatures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3480–3489, 2009 相似文献