全文获取类型
收费全文 | 114篇 |
免费 | 14篇 |
国内免费 | 32篇 |
专业分类
化学 | 69篇 |
晶体学 | 1篇 |
力学 | 6篇 |
综合类 | 1篇 |
数学 | 14篇 |
物理学 | 69篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 3篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2010年 | 4篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有160条查询结果,搜索用时 46 毫秒
11.
Ultrasound in organic electrosynthesis 总被引:2,自引:0,他引:2
Mechanical effects induced by ultrasonication can be very helpful for the activation of electrochemical reactions. The continuous cleaning of the electrodes by ultrasound irradiation of the electrochemical cell or the enhancement of mass transfer at the electrodes are examples of such activation. Finally, ultrasonication can play an important part for the orientation of reactions whose selectivities are very sensitive to stirring. Two very different examples have been chosen to illustrate these phenomena: the indirect electrooxidation of di-ketone-L-sorbose into the corresponding ketogulonic acid and the direct electroreduction of acetophenone into pinacol. 相似文献
12.
Non-relativistic configuration interaction (CI) ab initio calculations using large basis sets have been carried out to determine the potential curves of the first electronic states of Ne2 +, Ar2 + and Kr2 +. The spin—orbit interaction was treated assuming that the spin—orbit coupling constant is independent of the internuclear separation (R). For Ar2 +, calculated dissociation energies and equilibrium separations are in good agreement with experimental results. The calculations for Ne2 + suggest that the lowest vibrational level of the I(1/2u) ground state observed by threshold photoelectron spectroscopy by Hall et al. [1995, J. Phys. B: At. molec. opt. Phys., 28, 2435] and assigned to either ν = 0 or ν = 2 actually corresponds to ν = 4. The calculations also predict the I(1/2g) state of Ne2 + and Ar2 + to possess a double-well potential and that of Kr2 + to be repulsive at short range and to only possess a single shallow well at large internuclear separation. The ab initio calculations provide an explanation for the observation made by Yoshii et al. [2002, J. chem. Phys., 117, 1517] that Kr2 + and Xe2 + dissociate after photoemission from the II(1/2u) state to the I(1/2g) state whereas Ar2 + does not. 相似文献
13.
14.
Azzouzi F Ait Lyazidi S Haddad M Lamotte M Essassi EM Hnach M Zenkouar M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(5):1263-1269
Room temperature UV-vis absorption and emission spectra of the 1,4-diallylquinoxaline-2,3-dione (DAQX) are measured in solution at different concentrations. Even at very low concentration (approximately 10(-7)M), DAQX is shown to form ground state van der Waals dimers and excited dimers. These later species do not seem to rearrange into an excimer geometry. The theoretical simulation of the dimer, performed using the analytical atom-atom pair potential described below, predicts a non sandwich face-to-reverse slipped structure with head-to-tail orientation. The allowed absorption transitions, calculated using ZINDO/S package, reproduce satisfactory the experimental spectrum for both the monomer and the simulated dimer. 相似文献
15.
16.
17.
At weak force range the two-well Duffing equation has a closed bifurcation region in theparameter plane, inside which there are many different periodic windows. By means ofone-dimensional and two-dimensional symbolic dynamics, these periodic windows and thedynamical behavior of chaotic attractors are analyzed systematically. 相似文献
18.
19.
低地球轨道上的航天器易受到微流星体及空间碎片的超高速撞击,导致其严重的损伤甚至灾难性的失效。撞击损伤特性研究是航天器防护设计的一个重要问题。通过铝球弹丸超高速正撞击薄铝板的实验研究和数值模拟,证明了AUTODYN-2D软件数值模拟预测薄铝板超高速撞击穿孔直径的有效性。通过对弹丸直径、弹丸撞击速度和薄铝板厚度影响薄铝板超高速撞击穿孔直径的数值模拟,以及利用实验结果和数值模拟结果拟合的曲线,得到了铝球弹丸超高速撞击薄铝板的穿孔规律以及影响薄铝板超高速撞击穿孔直径的主要因素。 相似文献
20.
采用分光光度法 ,测定了蒙药卷柏中总黄酮的含量 ,检测波长为 5 0 0 nm,校准曲线相关系数为 0 .9996 ,相对标准偏差为 1 .0 1 %,平均加样回收率为 1 0 1 .6 1 %。此法准确度较高 ,为卷柏中黄酮含量测定提供了一种切实可行的方法。 相似文献