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31.
The enhancement of teleportation fidelity by weak measurement or quantum measurement reversal is investigated. One qubit of a maximally entangled state undergoes the amplitude damping, and the subsequent application of weak measurement or quantum measurement reversal could improve the teleportation fidelity beyond the classical region. The improvement could not be attributed to the increasing of entanglement, quantum discord, classical correlation or total correlation. We declare that it should be owed to the probabilistic nature of the method. 相似文献
32.
Chemical differences of the extractives revealed by FTIR methods can be further confirmed by 1H NMR and 13C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS 相似文献
33.
Xiaoqin Liang Xuemei Pu Xianwei Liao Ning-Bew Wong Anmin Tian 《Journal of Molecular Structure》2008,860(1-3):86-94
B3LYP/aug-cc-pvDZ level of theory is applied to study the geometric structures, electronic topologies, heats of formation, hyperconjugations and steric repulsions of 27 kinds of compounds obtained by successive replacement of CH groups with nitrogen atoms in cyclobutadiene, cyclopentadiene and benzene. The results reveal that the total energy linearly decreases along with the replacement of CH groups by nitrogen atoms for the three systems. To estimate the potential of high nitrogen content high energy materials (HNC–HEMs), heats of formation are calculated by G3 method. With the increase of the number of nitrogen atoms in ring, heats of formation increase substantially. The four-membered ring system is found to have the greatest heat of formations, followed by the six-membered ring system, and then by the five-membered ring system. Especially, hexazine and tetraazacyclobutadiene have great heats of formation relative to the other compounds, which implies that they should be applicable as HNC–HEMs. In addition, our studies indicate that the relationship between the total energy or heats of formation of isomers and the position of nitrogen atoms is (ortho) meta < (ortho) para < ortho. NBO analysis shows that it is hyperconjugation, not steric repulsion that plays a key role in the relative stability of isomers. 相似文献
34.
31P chemical shift of adsorbed trialkylphosphine oxides for acidity characterization of solid acids catalysts 总被引:1,自引:0,他引:1
Zheng A Huang SJ Chen WH Wu PH Zhang H Lee HK de Ménorval LC Deng F Liu SB 《The journal of physical chemistry. A》2008,112(32):7349-7356
A comprehensive study has been made to predict the adsorption structures and (31)P NMR chemical shifts of various trialkylphosphine oxides (R3PO) probe molecules, viz., trimethylphosphine oxide (TMPO), triethylphosphine oxide (TEPO), tributylphosphine oxide (TBPO), and trioctylphosphine oxide (TOPO), by density functional theory (DFT) calculations based on 8T zeolite cluster models with varied Si-H bond lengths. A linear correlation between the (31)P chemical shifts and proton affinity (PA) was observed for each of the homologous R3PO probe molecules examined. It is found that the differences in (31)P chemical shifts of the R3POH(+) adsorption complexes, when referring to the corresponding chemical shifts in their crystalline phase, may be used not only in identifying Br?nsted acid sites with varied acid strengths but also in correlating the (31)P NMR data obtained from various R3PO probes. Such a chemical shift difference therefore can serve as a quantitative measure during acidity characterization of solid acid catalysts when utilizing (31)P NMR of various adsorbed R3PO, as proposed in our earlier report (Zhao; et al. J. Phys. Chem. B 2002, 106, 4462) and also illustrated herein by using a mesoporous H-MCM-41 aluminosilicate (Si/Al = 25) test adsorbent. It is indicative that, with the exception of (TMPO), variations in the alkyl chain length of the R3PO (R = C(n)H(2n+1); n > or = 2) probe molecules have only negligible effect on the (31)P chemical shifts (within experimental error of ca. 1-2 ppm) either in their crystalline bulk or in their corresponding R3POH(+) adsorption complexes. Consequently, an average offset of 8 +/- 2 ppm was observed for (31)P chemical shifts of adsorbed R3PO with n > or = 2 relative to TMPO (n = 1). Moreover, by taking the value of 86 ppm predicted for TMPO adsorbed on 8T cluster models as a threshold for superacidity (Zheng; et al. J. Phys. Chem. B 2008, 112, 4496), a similar threshold (31)P chemical shift of ca. 92-94 ppm was deduced for TEPO, TBPO, and TOPO. 相似文献
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36.
分子的自旋轨道耦合常数对分析分子光谱的精细结构有重要意义。Richards等[1]自七十年代起利用Hartree-Fock波函数,非经验地计算了一些分子的旋轨耦合常数,获得了与实验值吻合的结果。本文报导利用我们发展的计算程序,对两个基态分子NS(X2Π),SiF(X2Π)进行了旋轨耦合常数的计算,其结果与实验符合良好。 相似文献
37.
Ming Li Rugang Xie Changwei Hu Xin Wang Anmin Tian 《International journal of quantum chemistry》2000,78(4):245-251
The ab initio molecular orbital method is employed to study the structures and properties of chiral cyclic sulfur‐containing oxazaborolidine, as a catalyst, and its borane adducts. All the structures are optimized completely by means of the Hartree–Fock method at 6‐31g* basis sets. The catalyst is a twisted chair structure and reacts with borane to form four plausible catalyst–borane adducts. Borane–sulfur adducts may be formed, but they barely react with aromatic ketone to form catalyst–borane–ketone adducts, because they are repulsed greatly by the atoms arising from the chair rear of the catalyst with a twisted chair structure. Borane–N adduct has the largest formation energy and is predicted to react easily with aromatic ketone to form catalyst–borane–ketone adducts. The formation of the catalyst–borane adducts causes the BBH3 HBH3 bond lengths of the BH3 moiety to be increased and thus enhances the activity of the enantioselective catalytic reduction. The borane–N adduct is of great advantage to hydride transfer. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 245–251, 2000 相似文献
38.
采用密度泛函方法(DFT)研究了2-(氟代己酰胺基)-苯甲醛与NH3的微观反应机理. 在B3LYP/6-31G*水平上优化了反应物、过渡态、中间体及产物的几何构型, 通过振动分析确认了过渡态的结构, 并用内禀反应坐标方法(IRC)确认反应途径. 应用分子中的原子理论(AIM)分析了这些物质的成键特征. 报道了可能的反应通道, 其中Re→TS1→ IM1→TS2→IM2→TS3→IM3→TS4→IM7→TS11→IM9→TS12→IM10→TS13→IM11→TS14→P1具有相对较低的活化能, 是反应的主要通道, 理论预测的主要产物与实验吻合. 采用连续介质模型(PCM)方法研究了反应体系的溶剂化效应, 结果表明反应过程中各物质的能量比气相要低. 溶剂化效应使转化能垒有一定程度的升高. 相似文献
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40.
Based on new deformation theorems concerning strongly indefinite functionals, we give some new min-max theorems which are useful in looking for critical points of functionals which are strongly indefinite and satisfy Cerami condition instead of Palais-Smale condition. As one application of abstract results, we study existence of multiple periodic solutions for a class of non-autonomous first order Hamiltonian system