全文获取类型
收费全文 | 25篇 |
免费 | 111篇 |
国内免费 | 18篇 |
专业分类
化学 | 28篇 |
数学 | 6篇 |
物理学 | 120篇 |
出版年
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2011年 | 7篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 12篇 |
2001年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 31 毫秒
81.
运用生物电子等排及拼合设计原理,设计并合成了14个新型的噻吩并四氢吡啶芳酸醚类化合物(4a~4j和8a~8d),其结构经1H NMR,13C NMR和ESI-MS表征。采用Bron比浊法测定了4a~8d对腺苷二磷酸(ADP)和花生四烯酸(AA)诱导的血小板聚集抑制活性。结果表明:4-【3-{6,7-二氢噻吩并[3,2-c]吡啶-5(4H)-基}丙氧基】-苯甲酸对AA诱导的血小板聚集和4-【3-{6,7-二氢噻吩并[3,2-c]吡啶-5(4H)-基}丙氧基】-3,5-二甲氧基苯甲酸对ADP诱导的血小板聚集均显示出较强的抑制活性,其IC50分别为0.020 mmol·L-1和0.018 mmol·L-1。 相似文献
82.
Theoretical Study of Photoabsorption Spectra near Si 2p Edges of Silanes: to Determine Orientations of Adsorbed Silanes 下载免费PDF全文
In the frame work of quantum defect theory, photoabsorption spectra near Si 219 edges of silane have been studied. When silanes are adsorbed on a physical surface and excited by polarized x-ray photons, relative intensities of the spectra will be different from that of free molecules. Such features can be used to determine orientations of adsorbed silanes based on selection rules. 相似文献
83.
根据骨架迁跃原理,设计并合成了一系列具有酪氨酸激酶抑制剂拉帕替尼(Lapatinib)和诺拉替尼(Neratinib)结构片段的水杨酰芳胺类化合物,其结构均经IR,1H NMR,13C NMR和MS确证.采用四甲基偶氮唑盐(MTT)法考察所合成化合物的体外抗肿瘤细胞(A549,MCF-7,SGC-7901,Bel-7402)活性.结果表明,所合成的化合物对4种肿瘤细胞增殖均有一定的抑制活性,部分化合物的活性强于阳性对照药吉非替尼(Gefitinib). 相似文献
84.
Effect of Electron Correlations and Breit Interactions on Ground-State Fine-Structures along the Nitrogen-Like Isoelectronic Sequence 下载免费PDF全文
The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections oi1 the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addition to spin-orbit interactions for precise calculations. 相似文献
85.
86.
为了研究HIV-1 Tat/PCAF BRD抑制剂的构效关系, 合成了6个3-芳氧基-1-丙胺类化合物. 以取代的2-硝基苯酚为起始原料, 在常规加热和微波辐射加热下与1,3-二溴丙烷反应合成3-(2-硝基芳氧基)-1-溴丙烷(3), 结果显示, 微波辐射加热比常规加热下的反应速度明显加快, 收率有所提高. 3和邻苯二甲酰亚胺钾进行N-烷基化反应合成了2-[3-(芳氧基)-丙基]二氢异吲哚-1,3-二酮, 再经肼解得到了目标化合物, 所有化合物的结构均经FTIR, 1H NMR, 13C NMR及HRMS确证. ELISA检测法测定了它们体外抑制HIV-1 Tat/PCAF BRD的活性, 并对影响活性的因素进行了讨论. 相似文献
87.
L—shell absorption measurement and simulation of x—ray—heated constrained material 总被引:1,自引:0,他引:1 下载免费PDF全文
Using the newly-designed multi-layered target, we obtain a homogeneous Al sample plasma at high density, low electron temperature, and in near local thermodynamic equilibrium. L-shell resonance absorption lines of Li-like and Be-like ions, as well as satellites are clearly observed. Transition arrays such as 2s-3p, 2s2-2s3p and 2s2p-2p3p are identified. We present the calculation method based on the unresolved transition array model, and we compare the measured transmission spectrum with the calculated results. The electron temperature of the constrained sample plasma is determined to be 34eV with a variation of ±2eV. 相似文献
88.
Experimental and theoretical investigations of absolute optical oscillator strengths for valence excitations of nitric oxide 下载免费PDF全文
The absolute optical oscillator strength density spectra of nitric oxide in the energy region of 5.0-22.0 eV have been measured by a high-resolution fast-electron energy loss spectrometer. With the calculated results obtained by the multiscattering self-consistent-field method and channel characteristics, the strongly overlapped spectra in the energy region of 7.5-9.3 eV have been analysed and the corresponding partially vibrationally resolved optical oscillator strengths have been estimated from the experimental spectra. 相似文献
89.
90.
利用相对论性多通道量子亏损理论计算了Sc的原子里德堡态能级 .计算结果显示 ,由于通道间的相互作用 ,使得光谱非常复杂 ,这与实验测量结果是一致的. The energy levels of Rydberg series of Sc atom have been calculated by Relativistic Multichannel Theory (RMCT). The calculations reveal that the Rydberg spectra are complex due to the channel interactions, which is consistent with the experimental spectra. 相似文献